Radiation Health & in Durham Region Report 2007

Transcription

1 Radiation & Health in Durham Region Report 2007

2 Radiation and Health in Durham Region 2007 April 2007 Acknowledgements The Durham Region Health Department would like to thank the members of the review panel and the Durham Nuclear Health Committee (listed in Appendix 1) for their invaluable comments and support of this project. The congenital anomaly data, and cancer incidence and mortality data used in this report were provided as special requests. The Health Department is grateful to Jocelyn Rouleau of the Public Health Agency of Canada, Tianhua Huang of the Genetics Program at North York General Hospital, and Cancer Care Ontario for providing their data and expertise. As well, Dave Whillans, Irv Benovich and Jane Borromeo of Ontario Power Generation were extremely helpful in answering questions and providing information about radiation and environmental monitoring. Finally, we would like to thank the Canadian Nuclear Safety Commission for providing some funding for this project. Important Web Sites Durham Region Health Department: Canadian Nuclear Safety Commission: Cancer Care Ontario: Ontario Power Generation: United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR): Citation Durham Region Health Department (2007), Radiation and Health in Durham Region Whitby, Ontario: The Regional Municipality of Durham.

3 Table of Contents Background... 1 Understanding Radiation... 2 Understanding this Report... 8 Understanding this Data...17 Results...20 Summary of Findings...76 Conclusion...78 Moving Forward...79 Glossary of Terms...80 References...85 Appendix 1: Reviewers of the Radiation and Health Draft Report...90 Appendix 2: Summary of Indicators Significantly High and Low Results...91 Table of Contents Radiation and Health in Durham Region 2007

4 Background This report is an update of Radiation and Health in Durham Region produced by the Durham Region Health Department in The 1996 report was an expansion of the Compendium of Statistical Tables for Durham, Halton, Northumberland, Ontario, a surveillance tool used to address concerns about possible health effects from the start of the Darlington Nuclear Generating Station (Darlington NGS).The Health Department, in co-operation with the Ministry of Health, produced Compendia in 1983, 1985 and 1988 using routinely collected health data on selected vital statistics, congenital anomalies, and cancer mortality. Data were presented in tables and figures with no text or interpretation. The 1996 report was much more extensive than the Compendia. It included a framework of health indicators to characterize the pattern of outcomes that would be expected in the population if radiation from the Pickering Nuclear Generating Station (Pickering NGS) or Darlington NGS were causing health effects in Durham Region. Data were provided for the municipal groupings of Ajax-Pickering, Oshawa- Whitby, Clarington, and North Durham (Scugog, Uxbridge and Brock), with Halton Region and Northumberland as comparison areas. Cancer incidence was added to the cancer mortality statistics, and more sites were included. Imprecise data (e.g. spontaneous abortion rates as measured by in-patient hospitalization) and health outcomes not associated to radiation (e.g. pancreatic cancer) were excluded. The executive summary of the 1996 report is available on Durham Region s website. The overall conclusion of the report was that the pattern of results did not suggest adverse health effects in Ajax- Pickering or Clarington from the nuclear generating stations. The 2007 report remains similar to the 1996 report but has some important differences. The framework of health indicators was updated to reflect more recent research findings. As well, indicators were no longer characterized as significant, possible, inconsistent and theoretical but were grouped as category 1, 2 or 3 indicators, which are described below. As well, Simcoe County replaced Northumberland as a comparison area. Northumberland was used in the original Compendia but was not a good comparison area; it had a small population and included the town of Port Hope which has a history of low level radiation exposure. The framework for the 2007 report was developed in 2005 prior to data analysis. It outlined the study objectives and assumptions, the geographical areas and health indicators to be included, and the categorization of the indicators. The framework was reviewed by an expert panel and also received Research and Ethics Board approval, which facilitated obtaining municipality-level cancer data from Cancer Care Ontario. The 2007 report includes eleven more years of cancer data which were grouped into two 12-year periods rather than into three five-year periods as in the 1996 report. This allowed for more stable estimates, fewer comparisons that might result in spurious results, and easier interpretation. The larger data groupings became possible with the availability of annual age and sex population estimates at the municipality level. Similarly, nine more years of congenital anomaly data were added since the 1996 report; they were grouped into two 11-year periods. New data were added on stillbirths and on congenital anomalies from the Ontario Maternal Multiple Marker Screening Database. The additional years of data in this report allowed for more extensive examination of the time period after the Darlington NGS began operating in Cancer data in the previous report went only to 1993 and congenital anomaly data to 1991, which was insufficient to examine changes in health effects in Clarington. The additional data in this report allowed investigation of leukemia, congenital anomalies and stillbirths around the Darlington NGS, as well as many more health indicators around the Pickering NGS, which has been operating for over three decades. This report has six main sections: Understanding Radiation, Understanding this Report, Results, Summary of Findings, Conclusion, and Moving Forward. Radiation and Health in Durham Region 2007 Background 1

5 Understanding Radiation What is Radiation? Radiation is a form of energy. It is classified as either ionizing or non-ionizing depending upon its effect on matter. Examples of non-ionizing radiation are heat, sunshine (ultraviolet radiation), microwaves and radio waves. Ionizing radiation, on the other hand, is characterized by its ability to remove or add electrons to the atoms or molecules it encounters, creating electrically charged atoms called ions. 2 Ionization can damage cells by disrupting chemical bonds within important molecules such as DNA. Examples of ionizing radiation are X-rays, alpha particles emitted from radon, and beta particles emitted from tritium. Throughout this report, the term radiation implies ionizing radiation. We are exposed to radiation everywhere in our daily lives it is in the earth, sky, water, and even our own bodies. People in Canada receive a total dose of about 1,800 microsieverts (µsv) a year from natural radiation, depending upon where they live. 3, 4 Actual dose depends upon such factors as soil composition, altitude, and the type of building materials used in their residence. On average, 52% of Canadians natural background radiation comes from the inhalation of radon, 18% from cosmic radiation, 12% from external sources (i.e., ground and building materials), and 17% from internal radiation as consumed in food and water. 4, 5 In addition to this natural radiation, Canadians are exposed to about 1,300 µsv per year of radiation from diagnostic medical procedures, almost all of it from medical x-rays. 6 This estimate is for countries (not only Canada) with the highest level of health care based on the number of physicians per population. Medical radiation dose varies greatly by individual, from 0 for those people who receive no x-rays or treatment to very high dose levels in those individuals receiving radiation to treat a disease such as cancer. Medical diagnostic and treatment procedures increase average radiation exposure % over natural background levels. 7 Measurement of Radiation Radiation measurement is complex, involving many different types of units; both imperial and metric units are used. A basic unit of radioactivity is the Becquerel (Bq) which corresponds to one atomic transformation per second. Radioactivity was formerly measured in curies. A Becquerel is a tiny unit so common substances often contain thousands of becquerels. Table 1 provides examples of radioactivity levels in common substances. Table 1: Examples of Radioactivity Levels Radiation Levels Average tritium concentration from Ajax Water Supply Plant in Bq/L 8 Average tritium concentration from Oshawa Water Supply Plant in Bq/L 8 Potassium 40 levels in bananas in Canada, average 128 Bq/kg 9 Wheelbarrow of earth with natural radioactive radium 1,000 Bq 10 Amount of naturally occurring Potassium 40 in a 150-lb 30-year old male 4,000 Bq 10 Maximum Allowable Concentration of tritium in drinking water 7,000 Bq/L 11 Radiation dose is expressed in three main ways. Absorbed dose is the amount of energy absorbed in a unit mass of material. It applies to any kind of radiation and any kind of matter and it is measured in grays (Gy), formerly rads. Equivalent dose is absorbed dose that takes into account the type of radiation involved since some types of radiation affect biological systems differently, e.g., alpha particles (α) have a weighting factor of 20 compared with gamma (γ) and beta (β) particles because they do more damage to cells. Equivalent dose is measured in sieverts (Sv), formerly rems. 2 Understanding Radiation Radiation and Health in Durham Region 2007

6 Because the body may not be uniformly exposed to radiation and because different body organs and tissues have different sensitivities to radiation, there is the effective dose. The effective dose is the sum of the equivalent doses to the exposed tissues and organs, multiplying by a weighting factor for each organ. The gonads (i.e., ovaries and testes), for example, have the highest weighting factor because of the effects on egg and sperm, followed by bone marrow, colon, lung and stomach which all have weighting factors of Effective dose is also measured in sieverts or often microsieverts (µsv), whereby 1 µsv = Sv or 1 millionth of a sievert. The µsv unit is more convenient because the doses are typically very small. Effective dose is the key measure that is used when determining the radiation dose to the public from NGSs and other sources. Figure 1 provides examples of common radiation doses and doses limits. Figure 1: Examples of Radiation Doses (Effective Dose) and Dose Limits 100,000 10,000 Microsievert (µsv) 50,000 Maximum dose limit for workers in a single year 12, 13 12,000 A single full-body scan by computed tomography (CT scan) 1,000 1,000 Annual dose limit for the public for anthropogenic radiation (set by Canadian Nuclear Safety Commission) Chest x-ray 8 12 Two-hour flight in an airplane Effective dose in 2005 for a resident of a correctional institution living 1 km from Pickering NGS (critical group for Pickering NGS) Effective dose in 2005 for an infant living 1 km from Darlington NGS (critical group for Darlington NGS) Ingestion of a banana (from 40 K) Ingestion of glass of milk (from 40 K) Health Effects of Radiation Since radiation has been studied for more than a hundred years, we know more about it than most other hazardous physical agents. Areas of the body most affected by radiation tend to be those with cells that divide and grow rapidly since any DNA damage will be compounded each time a cell divides. Blood cells and cells in the lining of the gut, for example, are constantly regenerating to keep a person healthy. Thus, radiation has been associated with cancers of the blood (leukemia) and of the stomach or intestine. Cells within a developing fetus are undergoing constant growth and division and are also particularly susceptible to radiation. Radiation and Health in Durham Region 2007 Understanding Radiation 3

7 Knowledge of the adverse health effects of radiation come from laboratory studies of bacteria and animals, and from four main study sources of people: atomic bomb survivors in Hiroshima and Nagasaki through the Life Span Study (LSS); people exposed to radiation to diagnose or treat specific diseases; people exposed because of events such as the Chernobyl nuclear accident; and workers with occupational exposures to radiation. Because human study populations differed with respect to the type and dose of radiation they received, how long they were studied, and their individual characteristics (family history, ethnicity, nutritional status, lifestyle behaviours, etc.) not all studies reach the same conclusions. Some health effects, such as leukemia, were consistently associated with radiation while others were not. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) summarizes information from these studies to provide key documents that form the basis of our understanding of the health effects of radiation. Radiation causes different health effects depending upon dose, dose rate, part of body exposed, and age of exposure. 2 Acute whole-body exposures of radiation, such as those from a close atomic bomb blast, can cause nausea, vomiting, eye damage, sterility, and death. 3 These effects, called deterministic, are seen only when the radiation dose is above a certain threshold. 6 A second type of damage from radiation occurs long after exposure and is the result of damage to DNA, causing cancer or hereditary disease in descendants in a proportion of those exposed. These effects are called stochastic. It is generally assumed that there is no threshold for these effects and that they can occur at low levels of radiation. While cancer effects have been measured in many studies, particularly the Life Span Study, radiation exposure has never been shown to cause hereditary effects in humans, whereby effects are passed down to offspring and subsequent generations. 14 Since experiments have shown that these genetic effects can occur in plants and animals, it makes sense to assume they may also occur in people, even if studies have not been able to demonstrate them 13, 14. Hereditary effects are not considered in this report. This report is concerned with low levels of radiation, which might be defined as 100 msv or less. 13 The long-term effects of low levels of radiation are difficult to assess because effects are generally too low to measure, years pass before an effect is seen, the same health problems are caused by other factors, and we are all constantly exposed to low levels of radiation from air, food and the earth. The main health effect of concern is cancer. Congenital anomalies or other reproductive effects have been less clearly associated with low levels of radiation, but may occur at high doses. Radiation doses received from x-rays or diagnostic procedures (often because the woman does not know she is pregnant or because the 7, 15 benefits outweigh the risks) are generally not high enough to cause anomalies or growth impairment. Doses from these procedures are much higher than what would be received from living near a nuclear station. Although radiation can cause cancers such as leukemia, and colorectal, lung, stomach and thyroid cancer 16, the vast majority of cancers are caused by other factors, such as smoking, alcohol, and diet. Only about 1-3% of cancers are attributed to radiation, most of which is from natural sources such as radon. 17, 18 This compares with 30% of cancers being attributable to tobacco use. 17 Cancers that are caused by radiation look and act the same as cancers caused by other factors, although occasionally they occur earlier than expected. The linear no-threshold hypothesis, which is most commonly used, assumes that there is a risk of cancer from exposure to radiation, no matter how small the dose. Applying Research Results to Durham Region Atomic bomb survivors and medically-exposed populations differ from Durham Region residents living near NGSs in many ways. Radiation doses are thousands of times higher among study populations than among those living near nuclear stations. As well, the study groups received one or a few large dose(s) of radiation and not low chronic exposure. Animal studies suggest that DNA is more easily repaired after many small doses than when the same dose is delivered in one short period of time, although the type of 4 Understanding Radiation Radiation and Health in Durham Region 2007

8 radiation can influence how easily the damage can be repaired. 19 Our bodies are generally efficient at repairing DNA damage because they are constantly exposed to natural sources of radiation and chemicals which damage DNA. Studies of workers exposed to radiation on the job often offer the best comparison for people living near nuclear stations, although worker exposure levels are generally higher than those received by the public. Nuclear workers wear personal dosimeters that measure radiation levels so that exposures can be closely monitored. The dosimeters are analyzed and the information is kept within the National Dose Registry of Canada. Worker doses are typically low. A recent study of nuclear power industry workers in 15 countries, including those at Ontario Power Generation, found a positive association between radiation exposure and mortality from leukemia (excluding chronic lymphocytic leukemia). 20 Most studies find that overall mortality is lower in nuclear workers than in the general population because nuclear workers are healthier to start with, a phenomenon called the healthy worker effect. 21 Nuclear Power in Durham Region Durham Region is unique in having two NGSs located only 28 km away from each other. Pickering NGS actually consists of two stations, Pickering A and Pickering B, each having four CANDU (CANadian Deuterium Uranium) reactor units, although only two of the Pickering A units are currently in operation. Darlington NGS also has four units. The CANDU technology uses natural uranium fuel and heavy water to produce energy by splitting atoms in the uranium to generate heat, which is then used to boil water to produce steam. The steam spins turbines to produce electricity. Pickering NGS produces a combined output of about 3,100 megawatts (MW) of energy and Darlington 3,500 MW. The stations in Durham Region generate about 30% of Ontario s electricity. Pickering A consists of Units 1, 2, 3 and 4. Operations began in 1971 and the units operated until 1997, when they were placed in voluntary lay-up. Unit 4 was returned to service in September 2003 and Unit 1 in November Pickering B, consisting of Units 5, 6, 7 and 8, began operating in All units remain in service. Darlington NGS similarly consists of four units. It began operating in 1990 and all remain in service. The Durham Nuclear Health Committee The Durham Nuclear Health Committee (DNHC) was formed in 1995 to act as a forum for discussing and addressing radiological emissions from nuclear facilities in Durham Region, specifically potential environmental human health impacts. DNHC is chaired by the Region's Commissioner & Medical Officer of Health and consists of nine public members from Ajax, Clarington and Pickering who are appointed by Council; two representatives of OPG; and four Provincial/Regional government representatives, including two from the Health Department. The Committee meets approximately every three months. Information about DNHC, including meeting minutes, is available on Durham Region s website. How much radiation are Durham Region residents currently exposed to? Ontario Power Generation (OPG) conducts extensive radiological monitoring of the environment in the vicinity of the Pickering and Darlington NGSs as part of its Radiological Environmental Monitoring Program (REMP). Dose models combine airborne and waterborne emission data with assessments of the radiation levels in local fish, fruits, vegetables, sediments, milk and honey to estimate the radiological dose to critical groups living around the NGSs resulting from the operation of the two stations. 4 Critical groups include individuals whose location, habits or diets may cause them to receive a higher dose (on average) than individuals in other exposed population groups. Therefore, doses to critical groups represent the maximum likely doses arising from emissions from the stations. OPG reports a radiation dose to the public on an annual basis, as specified by regulatory requirements of the Canadian Nuclear Radiation and Health in Durham Region 2007 Understanding Radiation 5

9 Safety Commission (CNSC). The Annual Summary and Assessment of Environmental Radiological Data report is available on the OPG website. The assessment of 2005 data calculated the radiation dose to eight critical groups around the Pickering NGS and nine critical groups around the Darlington NGS. The highest estimated dose to any critical group becomes the official public dose for that site. For Pickering NGS, public dose was estimated to be 6.7 µsv in 2005, as calculated from an adult at a correctional institution located 1.25 km from the station. The public dose was 0.9 µsv for Darlington NGS based on estimates for an infant living on a nearby farm. These doses are 0.7% and 0.09% of the legal limit for public radiation exposure for Pickering NGS and Darlington NGS respectively. 8 Even with exposure from the stations, the total radiation levels for critical groups in Ajax-Pickering and Clarington are lower than for Toronto and Canadian residents on average because the areas around the stations are naturally low in background radiation. This is based on assessments in Toronto, Ottawa, Montreal and Winnipeg with a vehicle-mounted gamma ray spectrometer in 2002, 5 and on an airborne gamma survey of Pickering and Darlington in Levels in Winnipeg are much higher because of inhalation of radon (see Table 2). Canadian background radiation levels are lower than the worldwide average because most of the Canadian population lives close to sea level and thus has a lower dose from cosmic radiation, and because many of the buildings are made of lower-radioactivity limestone. 5 Natural radiation sources include: cosmic radiation from space, which varies by elevation; internal radiation from food and drinking water; inhalation from radon and radon progeny; and external radiation from the ground and building materials. 5 In addition to naturally occurring radiation, the public is exposed to anthropogenic sources (i.e., of human origin) such as nuclear weapon fallout, and consumer products and services, which amounts to about 70 µsv per year. 8 Another 1,300 µsv per year comes from medical sources, almost all of it from medical x-rays. 22 In this context, 6.7 µsv and 0.9 µsv from the stations is a very small amount. Table 2: Naturally occurring annual public effective doses 8 Radiation Source Worldwide Average (µsv) Canadian Average (µsv) Toronto (µsv) Winnipeg (µsv) Ajax, Pickering, Clarington (µsv) Cosmic Internal Inhalation of Radon 1, , External Total 2,422 1,769 1,554 4,022 1,338 How much radiation have Durham Region residents been exposed to in the past? OPG is committed to reducing emissions from the stations so that the public dose (and dose to workers) is as low as reasonably achievable, a concept in radiation protection known as ALARA. As a result, radiation emissions and doses are lower now than in the past. As well, technological advances have meant that radiation levels are measured with more precision than in the past. Prior to 2003, OPG (formerly Ontario Hydro) calculated the dose to the public using a hypothetical individual who lived at the fence line of the station 100% of the time and consumed all local food and water. 4 Because very conservative estimates were used in these calculations, the actual dose to public was likely much lower than reported. At the same time, the emissions and doses were also higher than what they are now. The relationship between emissions and public dose is not straightforward since 6 Understanding Radiation Radiation and Health in Durham Region 2007

10 factors such as wind direction and weather patterns affect levels of radiation exposure. Switching methodology from hypothetical individual to critical group has resulted in more realistic estimates. Public dose estimation using the hypothetical individual was calculated for Pickering NGS from 1977 to 2002 with no estimates available for the early years of the station s operation (see Table 3). Dose estimates ranged widely from 3.6 µsv in 2000 to 57 µsv in Measurements for Darlington NGS began in 1988 although the station did not begin commercial operation until Public dose estimates for Darlington ranged from 1.2 µsv in 2001 and 2002 to 10.2 µsv in These are well below the annual dose limit of 1,000 µsv for the public. Table 3: Hypothetical doses and critical group doses for Pickering NGS and Darlington NGS (in µsv) Year Pickering Nuclear Generating Station Darlington Nuclear Generating Station Hypothetical Dose Critical Group Dose Hypothetical Dose Critical Group Dose Not calculated Radiation and Health in Durham Region 2007 Understanding Radiation 7

11 Understanding this Report Objectives The objectives of Radiation and Health in Durham Region 2007 remain essentially the same as for the 1996 report. The objectives are: To develop a framework to categorize health indicators according to their association with radiation. To compare health indicators associated with radiation for Durham Region and Ontario. To include Halton Region and Simcoe County in this comparison to provide an appreciation of how indicators vary geographically among small populations. To compare municipalities within Durham Region, grouped into Ajax-Pickering, Oshawa-Whitby, Clarington, and North Durham (Scugog, Uxbridge and Brock), to assess whether any of the indicators are significantly higher than Ontario. To suggest further areas of investigation to better understand the patterns of health outcomes described. To have our work reviewed by experts in radiation, epidemiology and public health (see Appendix 1 for the list of reviewers). Figure 2 shows a map of the study areas within Durham Region and the location of the nuclear stations. Assumptions Radiation and Health in Durham Region 2007 is a descriptive study that examines how Durham Region and municipalities within Durham Region compare with Ontario. This report describes variations in health but cannot identify why these variations exist. The assumptions are: Indicators were grouped into three categories based on the scientific literature; however, effects in scientific studies occurred at much higher radiation exposures than occurred for those living around nuclear generation stations. 1. Category 1 indicators showed consistent evidence across different studies for a statistically significant association with radiation exposure and an increasing association with radiation dose. As well, these indicators were less likely to be explained by other risk factors that were prevalent in the population. Category 1 indicators are: Leukemia (excluding chronic lymphocytic leukemia), incidence and mortality Thyroid cancer, incidence and mortality 2. Category 2 indicators showed consistent evidence across different studies for a statistically significant association with radiation exposure and an increasing association with radiation dose; however, these indicators may have been strongly influenced by other risk factors that were prevalent in the population. Category 2 indicators are: All cancer sites combined, incidence and mortality Childhood cancer (ages 0-19), incidence and mortality Childhood leukemia (ages 0-19), incidence and mortality Bladder cancer, incidence and mortality, only for incidence Breast cancer in females, incidence and mortality Colorectal cancer, incidence and mortality Lung cancer, incidence and mortality Stomach cancer, incidence and mortality Microcephaly and brain reduction congenital anomalies, birth prevalence 8 Understanding this Report Radiation and Health in Durham Region 2007

12 Figure 2: Map of Durham Region Study Areas and Nuclear Generation Stations Radiation and Health in Durham Region 2007 Understanding this Report 9

13 3. Category 3 indicators included those for which evidence was not consistent across different types of studies, may or may not have shown a statistically significant effect, and may or may not have increased with increasing dose. Category 3 indicators are: All cancer sites combined in young adults (ages 20-44), incidence and mortality Bone cancer, incidence and mortality Brain/CNS cancer, incidence and mortality Esophageal cancer, incidence and mortality Kidney cancer, incidence and mortality Multiple myeloma, incidence and mortality Non-Hodgkin lymphoma, incidence and mortality Ovarian cancer in females, incidence and mortality All congenital anomalies combined, birth prevalence Down syndrome, birth prevalence Down syndrome, incidence among pregnant women screened Other chromosomal congenital anomalies, birth prevalence Other chromosomal congenital anomalies, incidence among pregnant women screened Neural tube defects, birth prevalence Neural tube defects, incidence among pregnant women screened Stillbirths Category 1 indicators carried more weight in suggesting whether health effects from ionizing radiation were occurring than did Category 2 and Category 3 indicators. Category 2 indicators were likewise stronger than Category 3 ones. Health effects from low-level radiation, if they existed and were measurable, would be seen primarily in Ajax-Pickering and Clarington, and not likely in Oshawa-Whitby and North Durham. Radiation levels in air and water fall significantly with distance from the source. Halton Region and Simcoe County were comparison areas with no nuclear facilities. It was expected that these areas would not show patterns of health indicators consistent with a radiological effect. Health effects from low-level ionizing radiation, if they existed and were measurable, would be expected to occur after an appropriate time that was consistent with known latent periods and when the NGSs began operation (Pickering in 1971 and Darlington in 1990). Most cancers do not appear until 15 or more years after exposure to a cancer-causing agent, with the exception of leukemia which can have a 2-5 year latency. Congenital anomalies and stillbirths would appear almost immediately from exposure in utero. Based on these latencies, the following patterns would be expected if radiation was causing an effect in Durham Region based on the data available: Higher than expected rates of each of the cancers (except leukemia) in both and in Ajax-Pickering, no excess expected in Clarington. Higher than expected rates of leukemia in both and in Ajax-Pickering, and in in Clarington. Higher than expected birth prevalence rates of congenital anomalies in both and in Ajax-Pickering, and in in Clarington. Higher than expected rates of Down syndrome, other chromosomal anomalies and neural tube defects as measured in pregnant women screened from Oct 1993-Sept 2000 in both Ajax-Pickering and Clarington. Higher than expected rates of stillbirths in and in Ajax-Pickering, and in in Clarington. 10 Understanding this Report Radiation and Health in Durham Region 2007

14 All geographical areas were compared with Ontario. Cancer rates were assessed using Standardized Incidence Ratios (SIRs) and Standardized Mortality Ratios (SMRs) to control for differences in age structures between populations. A minimum of 5 cases was required for SIRs and SMRs, and 25 cases for age adjusted rates. Males and females were combined if required to increase the number of cases. Congenital anomalies were assessed using overall rates. Rates or ratios were determined to be significantly high (or low) if 95% confidence intervals did not overlap. Since all of the health indicators could be caused by factors other than ionizing radiation, any excess was not automatically attributed to the NGSs. This study did not control for important risk factors, such as smoking, alcohol, diet and occupational exposure. This study did also not control for other sources of radiation, most notably exposures from medical diagnosis and treatment, which might be different across geographical areas. Limitations The limitations of this study were discussed in the 1996 report and still apply. Many of these limitations were discussed in UNSCEAR 2000 and in BEIR VII 13 as features of epidemiologic studies. Since Radiation and Health in Durham Region 2007 is a descriptive study, we cannot make any conclusions about why rates in an area might be particularly high or low. There are many possible explanations. Specific aspects of the study limitations are described below: Ecological Study Radiation and Health in Durham Region 2007 is an ecological study it used data at the level of the community, not the individual. The study assumed that exposure was constant for all people in an area, although this was not true. People in Ajax-Pickering, for example, were not all exposed to the same amount of ionizing radiation. Individual exposure depended upon, not only emissions from an NGS, but also medical tests, occupation, air travel, housing type and location, and many other factors. People did not spend all their time in one place, and nor did they necessarily reside in an area such as Ajax-Pickering for a long time. We also do not know how many of the affected people have occupational exposures from working at the NGS. For these reasons, this study described health factors in the community but could not establish cause and effect relationships between the health patterns described and the NGS. Confounding Another limitation of this study was the presence of confounders. A confounder is a factor that is associated with both the exposure of interest and the outcome, making it difficult to know whether it is the exposure of interest or the confounder that is causing the outcome. Confounding is even more problematic with an ecological study because there are many confounders occurring at the community level. An area could have high smoking rates and high lung cancer rates as a result, which has nothing to do with living near a nuclear station. Tobacco is a more important risk factor for lung cancer than ionizing radiation and is an important confounder. Socio-economic status (i.e., income, education and occupation), lifestyle behaviours, genetic characteristics, and other environmental exposures are all important confounders. Some of these were described to provide a general overview of how the areas were different with respect to these important characteristics. While the study used using age-adjusted cancer rates and ratios to account for the different age structures of the population, the data did not control for differences in socio-economic factors, smoking and other factors among the areas. Controlling for these complex variables was beyond the scope of this study. Smoking rates from two or three decades earlier would be useful for assessing current cancer rates but this information was unavailable for the areas of interest. Data on congenital anomalies did not control for differences in maternal age because of the small numbers involved; however, stillbirth rates were adjusted for maternal age and general information about maternal age was provided for each of the areas. Radiation and Health in Durham Region 2007 Understanding this Report 11

15 Migration Durham Region, and particularly the areas of Ajax-Pickering and Clarington, experienced tremendous growth in the past twenty years. One of the assumptions of Radiation and Health in Durham Region 2007 was that health effects would be expected to occur after an appropriate time that was consistent with cancer latent periods and when the NGSs began operation. Mobility data showed that many people may not have lived in the areas of interest for more than fifteen years. Exposure to carcinogens would have occurred when they lived elsewhere. When asked in 2001, 75% of Ajax-Pickering and 74% of Clarington residents respectively had lived in the same municipality 5 years earlier in 1996 (see Figure 3), as compared to 80% for Ontario. About 23% moved within those 5 years from elsewhere in Ontario and another 3% from outside Ontario or Canada. The percentage living in the same municipality 5 years earlier decreased in 1996 to 72% in both areas, and even further to 56% and 61% in Ajax-Pickering and Clarington respectively in There was tremendous population growth between 1986 and Although the data were not available by age, the in-migration to Durham Region during this period was likely dominated by young families looking for affordable housing. Older people, who generally make up the largest proportion of cancer cases and deaths, may be less likely to move and may have remained in Durham Region for a longer period of time. While this dilutes the migration effect somewhat, this remained an important limitation of this study. Since congenital anomalies and stillbirths would appear almost immediately from exposure in utero, these indicators would not be as greatly influenced by migration as cancer. However, these are not as strongly associated with ionizing radiation as some cancers and would only be expected at high radiation doses. Comparisons with Durham Region Data were presented for Halton Region and Simcoe County to show how health indicators varied geographically. It is impossible to find a control community that is identical to Durham Region but that does not have a nuclear generating station. The rationale for choosing Halton Region and Simcoe County is described below. Complex Nature of Disease Cancer and congenital anomalies are caused by a complex combination of environmental, genetic, and lifestyle influences at both the individual and population levels. It is often impossible to determine one specific cause of a cancer, congenital anomaly or stillbirth. 12 Understanding this Report Radiation and Health in Durham Region 2007

16 Power of Detection It was difficult for this study to detect effects related to the NGSs because the number of cancers and congenital anomalies in the surrounding communities was relatively small, and because exposure to ionizing radiation was very low. Theoretically, a single exposure of radiation of 0.1 Gy or 10 rads might cause 6,000 excess cancers among one million people where we would normally expect about 250,000 cancers. This is based on a conservative model that assumes that radiation causes cancer at even very low levels and that there is no threshold at which it does not cause cancer. For this result of 256,000 to show up as statistically significant, we would need to follow 60,000 people for a lifetime in a cohort study, or 120,000 cases and 120,000 controls in a case-control study. 16 We would need even larger numbers in this case because doses to Durham Region residents are very much lower than this, and because we are studying specific types of cancers and congenital anomalies. Even when exposure levels are higher, ionizing radiation causes relatively few excess cancers. Over 9,000 deaths from solid cancers occurred in the 86,572 Japanese atomic bomb survivors from 1950 to Even with the substantial doses received from the atomic bomb blasts (doses varied considerably and did include very low levels), only 5% of deaths from solid cancer were attributable to radiation exposure. 23 Studies of low-dose chronic exposure to radiation have an inherently low ability to detect effects. 22 Because of this low power, emphasis was on looking for patterns consistent with a radiation effect. Screening and Detection Affects Incidence Ontario is fortunate in having good quality cancer incidence data; however, there are many factors that can affect cancer detection and, subsequently, incidence rates. Screening programs for breast and colorectal cancer, for example, can increase incidence because more cancers are detected. If a population in a particular area has higher screening rates, higher incidence rates are likely to result in that area. It is hoped that mortality rates for that cancer would be lower as well, although it may take years before this occurs. If physicians in a particular area are particularly vigilant or skilled at diagnosing cancer, this could increase incidence. Data for Small Geographical Areas May Be Less Accurate Radiation and Health in Durham Region 2007 featured Durham Region municipalities because it was important to examine whether there were excess health problems around Pickering NGS and Darlington NGS. However, data are less accurate for small geographical areas. Accuracy of Ontario Cancer Registry data was studied by selecting 1,194 records from and comparing them with the patient s medical record. Completeness of the patient s municipality was high at 95.7%; however, accuracy was 84.4%, suggesting that almost 16% of cases had the wrong residence information, mostly a different city, town or township. Few cases (2.1%) had the wrong county of residence recorded in the Registry data. 24 Residence information has become better over the years. Work at the Registry in 2005 raised the completeness of residence information at the level of municipality (specifically census subdivision) to over 99% 25. While completeness is high, the accuracy of this information may still be problematic for some cases. Radiation and Health in Durham Region 2007 Understanding this Report 13

17 Multiple Testing This document compared Durham Region with Ontario for many indicators, including 18 cancer groupings (incidence and mortality) and 9 perinatal outcome indicators. Because of the many comparisons, 1 out of 20 (5%) might be statistically high or low simply by chance because we used 95% confidence intervals. Comparisons by geographical area, sex and time period for 45 health indicators resulted in 966 comparisons. Forty-eight of these would theoretically be high or low just by chance. Without further study, it might be hard to explain the results. Rather than looking at as many rates as possible, it was thus more meaningful to look for patterns within known radiation-related disease and death. Over-Counting of Cancer Cases Cancer may be over-reported when cases are not actually malignant cancer but some other closely related disease. This occurs most often when the case is reported to the Ontario Cancer Registry from only one source of data, such as hospital reports. 24 Over-reporting may be more problematic with cancers such as leukemia and multiple myeloma where laboratory confirmation of cancer is lower. 26 This issue is discussed below, specifically with respect to multiple myeloma. Strengths of Radiation and Health in Durham Region 2007 While limitations in the study design prevented definitive conclusions from being made in Radiation and Health in Durham Region 2007, this report brought data and information together from many different sources to help inform the community about the issue of radiation exposure from nuclear stations in Durham Region. Descriptive studies such as this can also be used to generate new hypotheses and suggest further areas of investigation. There were a number of strengths to this study. Ionizing Radiation Well-Studied There is a prolific amount of information about the health effects of radiation that is available and has been used as background for this report. Unlike some chemicals or hazards in our environment, the health effects of radiation are well-known and have been studied for over a hundred years. Reports from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the Biological Effects of Ionizing Radiation Committee (BEIR), the International Agency for Research on Cancer (IARC), and the Committee on Medical Aspects of Radiation in the Environment (COMARE) summarized numerous scientific studies. Reports from these organizations formed the basis of the framework used in Radiation and Health in Durham Region Geographical Areas Coincided with Areas Surrounding NGSs The main geographical areas of interest in Radiation and Health in Durham Region 2007 were the municipalities of Ajax and Pickering grouped together, and the municipality of Clarington. Examining information by municipality was convenient because health data and population estimates were available at this level. Geographically, the NGSs are in the middle of the southern border of the areas of Ajax- Pickering and Clarington. About 99% of Ajax-Pickering s population was within 10 km of the Pickering NGS in 2003 and about 74% of Clarington s population was within 10 km of the Darlington NGS. The Clarington percentage was lower because the villages of Newcastle and Orono, as well as large rural areas, were outside the primary zone for Darlington. This information was based on occupant population estimates provided from the Region s Planning Department to the Durham Emergency Management Office. 14 Understanding this Report Radiation and Health in Durham Region 2007

18 Two Comparison Areas The areas of Halton Region and Simcoe County were chosen as comparison areas for Durham Region to show how health indicators varied geographically among different populations. While there is no perfect comparison area, both Halton Region and Simcoe County have been shown to be reasonably good peer groups for Durham Region as determined from four different analyses: 1) Statistics Canada analysis of all regions in Canada using the 1996 Census 28, 2) Statistics Canada analysis of all regions in Canada using the 2001 Census 29, 3) Statistics Canada analysis of Ontario public health units using the 2001 Census 30, and 4) Analysis by the Central West Health Planning Information Network (CWHPIN) of public health units in Ontario using the 2001 Census 31. All reports used socioeconomic data from the Census to determine which regions had similar characteristics. CWHPIN calculated a distance score to quantify how similar two areas were to each other based on characteristics such as population size, density, mobility, income, and unemployment rate. 31 Halton and Durham Region were consistently in the same peer group in all four analyses. Simcoe County and Durham Region were also in the same peer group, except with Statistics Canada s analysis of 2001 Census data for regions in Canada. Based on CWHPIN s distance scores, the Wellington-Dufferin-Guelph Health Unit was most similar to Durham Region, followed by Simcoe County, Waterloo Region, and then Halton Region. The health units of Wellington- Dufferin-Guelph and Waterloo were not used as comparison areas in Radiation and Health in Durham Region 2007 because they did not have sufficient data from the Rapid Risk Factor Surveillance System (RRFSS). RRFSS provided valuable background information about smoking, overweight and obesity, fruit and vegetable consumption and breast cancer screening, which are important risk or protective factors for cancer. Given all this information, Halton Region and Simcoe County proved to be the best comparison areas. Figure 4 shows a map showing Durham Region and the locations of the two comparison areas. Inclusion of Ontario Maternal Multiple Marker Screening Database Figure 4: Map of Durham Region, Halton Region and Simcoe County Data from the Canadian Congenital Anomaly Surveillance System (CCASS) captured only the birth prevalence of congenital anomalies. In some cases, a pregnant woman may undergo prenatal screening, find out that the fetus has serious congenital anomalies, and have a therapeutic abortion as a result. This congenital anomaly occurrence would not be picked up in the CCASS data. To better capture the true incidence of Down syndrome, chromosomal anomalies, and neural tube defects, data from the Ontario Maternal Multiple Marker Screening Database were added to Radiation and Health in Durham Region Radiation and Health in Durham Region 2007 Understanding this Report 15

19 Complete Cancer Incidence Data Ontario is fortunate because the Ontario Cancer Registry (OCR) is one of the largest cancer registries in North America, covering about 97% of all cancer cases in the province. 27 Many countries do not have access to high quality cancer incidence data and must rely on mortality data only. Incidence data are superior because they provide information about non-fatal cancers, which is particularly important for thyroid and breast cancer, and because there is a shorter time period between exposure and cancer diagnosis than between exposure and death from cancer. 22 Although this report emphasized incidence data, mortality data were also presented. Indicators Specific to Radiation Wherever possible, indicators were made specific to radiation based on the scientific literature. For example, chronic lymphatic leukemia was excluded from total leukemia because it is not linked to ionizing radiation. Understanding Rates: Important Information when Interpreting the Results This report presented both cancer incidence (new cases of cancer) and mortality (deaths). For each type of cancer, figures showed age-adjusted cancer incidence and mortality rates for Ontario by three-year time periods so that rates could be compared over time. Incidence data were presented for to and mortality data for to ; mortality was not presented for the last time period because the data were incomplete. When the number of cases or deaths was high enough (at least 25 total in a time period), the age-adjusted rates for Durham Region, Halton Region and Simcoe County were also presented. The age-adjusted rates controlled for age structure differences so that rates could be compared over time. Cancer rates in each of the areas of interest were also compared with Ontario using a Standardized Incidence Ratio (SIR) or Standardized Mortality Ratio (SMR). The SIR or SMR is a summary number that controls for age structure differences, allowing a small population to be compared with a larger one, such as Durham Region and Ontario. If the crude incidence rates were compared the number of cancers divided by the number of people in the population we would underestimate cancer in Durham Region. Fewer cancers occur simply because Durham Region has a younger population than Ontario. The SIR is a ratio of what was actually observed (the number of cancers in Durham Region) to what was expected given Ontario s rate. The same technique was used for cancer deaths to calculate the SMR. An SIR (or SMR) of 1.0 meant that cancer incidence (or mortality) was the same in the area of interest and Ontario. An SIR greater than 1.0 indicated that the cancer rate was higher in the area than Ontario, whereas an SIR less than 1.0 indicated that cancer was lower. Since statistical estimates could be unstable for small areas because they were based on small numbers, confidence intervals (CIs) were used to indicate the precision of the estimate and amount of natural variation. The CIs determined whether the area of interest was significantly different from Ontario. If the confidence intervals included 1.0, it meant that the rate was no different than that of Ontario. Cancers that were less common had wider confidence intervals because they were based on smaller numbers. SIRs and SMRs were presented in this report for two time periods: and If an SIR was low in the first time period and higher in the second, it did not necessarily mean that incidence increased over time, but that it was now higher relative to Ontario. Only the age-adjusted rates allowed comparisons over time. Congenital anomalies and stillbirths were presented as rates per 10,000 or per 1,000 births, respectively, with confidence intervals. Congenital anomaly data from the Ontario Multiple Marker Screening Database were presented as rates per 10,000 women screened. Congenital anomaly data were not adjusted for maternal age, but stillbirth rates were. 16 Understanding this Report Radiation and Health in Durham Region 2007

20 Understanding the Data This report used a variety of data to examine patterns of health in the study areas. Cancer Incidence and Cancer Mortality Data The Ontario Cancer Registry (OCR) of Cancer Care Ontario registers all new cases of cancer in Ontario. The Cancer Act provides the legal mandate for this data collection. All types of cancer are registered, except non-melanoma skin cancer. The system is passive and relies predominantly on administrative data. The OCR has five data sources: 1) hospital discharge summaries with cancer diagnoses, 2) pathology reports with any mention of cancer, 3) records from the Regional Cancer Centres or Princess Margaret Hospital, 4) death certificates with cancer as the underlying cause of death, and 5) hospital day surgery reports. 32 Since the OCR may receive multiple reports for the same patient, computerized probabilistic record linkage is used to identify duplicates. The OCR receives mortality data from the Office of the Registrar General, which obtains information from death certificates completed by physicians. All deaths within Ontario are registered in the office of the division registrar within which the death occurs. Because of a delay in obtaining this information, cancer mortality data was incomplete and excluded from age-adjusted rates by three-year time periods. These data were included in the SMR groupings to make them consistent with SIRs and because two years of incomplete data within a 12-year grouping was thought to make little overall difference. CCO provided municipality-level cancer data in SEERStat from 1981 to 2004 to the Durham Region Health Department as a special request. Age-adjusted rates were calculated in SEERStat while Standardized Mortality Ratios (SMRs) and Standardized Incidence Ratios (SIRs), along with their confidence intervals (CIs), were computed in Excel using counts derived from SEERStat. Equations for calculating CIs were from Armitage. 33 SIRs and SMRs based on counts less than 5 were suppressed. Ageadjusted rates based on counts less than 25 were suppressed. Canadian Congenital Anomalies Surveillance System (CCASS) The CCASS is based on hospitalization in the first year of life. Since babies with congenital anomalies are often hospitalized more than once in their first year, the CCASS attempts to identify all duplicates using sex, date of birth, province, postal code, geocode, mother s health insurance number (scrambled to protect confidentiality) and medical conditions. Because there are no unique identifiers to ensure positive identification, incomplete records make matching less accurate and may result in over-counting the number of cases. Data are influenced by factors that are unrelated to health status such as availability and accessibility of care, and administrative policies and procedures. 34 The Public Health Agency of Canada calculated the rates and confidence intervals and provided them to the Durham Region Health Department. Rates and proportions based on counts less than 5 were suppressed. Ontario Maternal Multiple Marker Screening Database (OMMMD) In 1993 the Ministry of Health and Long-Term Care established the Ontario Maternal Multiple Marker Screening Database (OMMMSD) to track all maternal serum screens done in Ontario. The OMMMSD provides information on screening results, additional testing, results of follow-up services, and pregnancy outcomes. All screening data were matched with pregnancy outcomes as they became available. OMMMSD receives data from three main sources: labs that perform screening tests; genetic counseling centres that provide follow-up results of genetic services offered to screen-positive women; and the Canadian Institute for Health Information (CIHI) which provides hospitalization data on pregnancy outcome. Radiation and Health in Durham Region 2007 Understanding the Data 17

21 OMMMSD provides a more complete picture of the number of Down syndrome and chromosomal anomaly cases than birth prevalence alone. Women in Durham Region were significantly more likely to have maternal serum screening (59.2%) in than those in Ontario (41.5%); in Halton Region and Simcoe County, 53.5% and 28.7% of pregnancies were screened respectively. 35 Increased screening could lead to increased detection of anomalies and increased rate of therapeutic abortion, with a resulting lower prevalence of congenital anomalies. Although the OMMMSD is important in capturing pregnancy information, one of its limitations is that it only includes results for women who were screened. Another limitation is that congenital anomaly cases ending in spontaneous abortion were not tracked. It is estimated that 23% of Down syndrome pregnancies will spontaneously abort after 16 weeks of gestation. 36 An area with a lower rate of screening, such as Simcoe County, may have higher rate of cases detected because only high risk women are being screened. OMMMSD, when used with birth prevalence data from CCASS, provided more complete information about congenital anomalies. The Genetics Program at North York General Hospital, which holds the OMMMSD data, calculated the rates and provided them to the Durham Region Health Department. Rates and proportions based on counts less than 5 were suppressed. Stillbirth Data Vital statistics information on stillbirths is collected by the Office of the Registrar General and is based on three forms: 1) the Statement of Stillbirth completed by parents, 2) the Physician Notice of Birth or Stillbirth (PNOB) completed by the physician, and 3) the more detailed Medical Certificate of Stillbirth completed by the physician. 32 The stillbirth data were extracted from the Provincial Health Planning Database (PHPDB) of the Ministry of Health and Long-Term Care by residence of mother. Although there were data quality concerns for 1991 and 1992, the large grouping of time period should eliminate the overcount in one year and undercount in the other. For overall stillbirth rates, stillbirths were excluded if birth weight less than 500 g or if birth weight was unknown and gestational age was less than 22 weeks. All stillbirths were included for the maternal age adjustment. Rates and proportions based on counts less than 5 were suppressed. Rapid Risk Factor Surveillance System The RRFSS is a random-digit-dialed telephone survey of adults aged 18 years and older, conducted by the Institute for Social Research at York University, on behalf of the Durham Region Health Department, Halton Region Health Department, and Simcoe Muskoka District Health Unit, as well as other health units. Since 2001, a sample of about 100 residents has been surveyed on a monthly basis in the three health units regarding health risk behaviours and characteristics such as smoking, body mass index, consumption of fruits and vegetables, frequency of screening mammography, etc (for further information, see ). RRFSS information is essential to health units for planning and evaluating programs and services as well as monitoring emerging health issues. Since RRFSS was not conducted in all health units, a provincial comparison was unavailable. RRFSS uses a two-staged sampling frame. First, there is a random selection of a household from all households with telephones. Secondly, there is a random selection of one person, 18 years and older, in the household. Because the probability of being selected is smaller in larger households than households of 1 or 2 people, a household weight was applied to all estimates to remove this bias. The weight was recalculated for grouping 2001 to 2005 data. 18 Understanding the Data Radiation and Health in Durham Region 2007

22 Respondents for whom municipality was unavailable were included in the total Durham Region estimates; as a result, municipality sample sizes total to slightly less than the Durham Region sample size. Confidence intervals (CIs) were calculated for proportions assuming SEp = square root (pq/n) and CI (95%) = p +/- 1.96*SEp, where SE = standard error, p is the calculated proportion, q = 1-p, and n is the sample size in the stratum. 37 The confidence interval indicated the precision of the estimate and gave the range around the sample estimate that contained the true population estimate 19 times out of 20. Percentages were determined to be different if 95% CIs did not overlap. Census Data The Census in Canada is conducted every 5 years in years that end in 1 or 6. The most recent census data available is from The census attempts to count everyone in the country and collects more extensive information on 20% of the population. The census provided information about population structure, mobility, immigrant status, first language, visible minority, lone-parent families, highest level of schooling, median household income, and average value of dwelling. Some of this information was derived from the report Durham Region Profile, produced by the Durham Region Planning Department 38 and others directly from Census 2001 data. Population Estimates Population estimates by age and sex from 1981 to 2004 for each geographical area were used in calculating cancer rates and ratios. The population estimates were extracted from the Provincial Health Planning Database (PHPDB) of the Ministry of Health and Long-Term Care in February Estimates from 1986 to 2001 were final estimates adjusted for census undercounts; 2002 were final postcensal estimates; 2003 were updated postcensal estimates; and 2004 were preliminary postcensal estimates. Since population estimates were unavailable for years before 1986, straight-line interpolation was used between 1981 and 1986 census counts to estimate populations for 1983, 1984 and Radiation and Health in Durham Region 2007 Understanding the Data 19

23 Results Population Growth The Regional Municipality of Durham Region is located east of the City of Toronto. Durham Region had an estimated 2003 population of close to 551,000 within its eight municipalities. Based on 2003 estimates, 285,000 people lived within the 10 km primary zones of Pickering NGS (174,500) and Darlington NGS (110,500). Durham Region s population doubled, growing 99%, between 1981 and 2004, the years for which cancer incidence data were presented in this report (see Table 4). In comparison, Ontario grew by 44%, Halton Region by 69% and Simcoe County by 86%. Growth within Durham Region was particularly high in Ajax-Pickering (185%) and Clarington (146%) the communities surrounding the two NGSs. Growth in these areas was highest between 1981 and 1992 (see Figure 5). This growth would be particularly relevant if the characteristics of the migrants were different and the characteristics of the population were changing over time. Table 4: Population counts and increases in the areas of interest, 1981 to 2004 Area 1981 Population 2004 Population Percent Increase 1981 to 1992 Percent Increase 1993 to 2004 Total Percent Increase 1981 to 2004 Ontario 8,625,105 12,407,347 21% 16% 44% Durham Region 283, ,153 49% 27% 99% Ajax-Pickering 63, , % 31% 185% Oshawa-Whitby 154, ,395 28% 22% 62% Clarington 32,225 79,430 59% 42% 146% North Durham 33,945 54,175 31% 18% 60% Halton Region 253, ,578 27% 28% 69% Simcoe County 225, ,449 33% 32% 86% Socio-Demographic Characteristics In terms of 2001 socio-demographic characteristics, there was large variation, not only between Durham Region, Halton Region and Simcoe County, but within Durham Region as well. Results are presented in Table 5 and are summarized: Durham Region had a younger population 77% of the population was aged 15 and over compared with 80% in Ontario. Ajax-Pickering and Clarington in particular had fewer adults at 76% and 75% respectively. Halton Region and Simcoe County were similar to Ontario at 79%. 20 Results Radiation and Health in Durham Region 2007

24 In 2001, Durham Region residents were slightly more likely to have lived at the same address in the past year (88% versus 86%) or past five years (58% versus 57%) compared to Ontario but there was generally little difference. There was much more of a difference in mobility in 1996 and 1991, particularly when moving within the municipality was combined with staying at the same address. Durham Region residents were less likely to have lived in the same municipality 5 years ago (see above under Limitations - Mobility), which was consistent with the large population growth at the time as people moved into Durham Region from elsewhere. Durham Region residents were more likely to be Canadian-born (81%) than in Ontario as a whole (72%), which was also the case in Halton Region (77%) and Simcoe County (88%). Ajax-Pickering had fewer Canadian-born residents (72%) than other areas of Durham Region, including Oshawa- Whitby (83%), Clarington (88%) and North Durham (89%). The higher percentage of foreign-born residents in Ajax-Pickering as compared to Durham Region was also reflected in a lower percentage of first language learned and still understood being English only (84% Ajax-Pickering, 87% Durham Region, 71% Ontario), and a higher visible minority population (25% Ajax-Pickering, 12% Durham Region, 19% Ontario). Clarington had a higher percentage of residents with first language English only (91%) and smaller visible minority population (4%). In terms of highest level of education, Halton Region had the highest percentage of 20-34, 35-44, year olds with a trades, college or university certificate, diploma or degree. Durham Region was similar to Ontario; Simcoe County had slightly lower education levels than Ontario. Within Durham Region, Whitby, Pickering and Ajax had the highest level of schooling. Within Durham Region, median household income varied from over $80,000 in Pickering to about $50,000 in Brock. Whitby, Ajax, Uxbridge and Clarington had median incomes that were higher than Durham Region as a whole. Halton Region s median income of about $75,000 was higher than Durham Region s ($68,800), and considerably higher than Simcoe County and Ontario s which were $53,800 and $53,600 respectively. Socio-demographic data showed that Halton Region had higher socio-economic status than Ontario, Durham Region and Simcoe County. Within Durham Region, the south-west municipalities of Pickering, Ajax and Whitby had higher socio-economic status than the other municipalities. Pickering and Ajax were also ethnically more diverse than other areas of Durham Region. These differences likely affected the health status of the residents in these areas in complex ways. Health Status Characteristics As with socio-demographic characteristics, health status was different across the seven areas. There is a wealth of evidence that shows that health can be greatly influenced by socio-economic status, specifically income, occupation and education, as well as many other related factors such as housing, family characteristics, labour force participation, immigration, language and ethnicity. 39 While in general, life expectancy is higher and health status is better for those with higher income and education levels, the relationship is not always clear and can be complex for some health indicators. The risk of developing breast cancer, for example, may be higher among those with higher socio-economic status. 40 Immigrants, depending upon when they came to Canada, may have higher educational levels than those who are Canadian-born but lower incomes due to fewer occupational opportunities. Certain ethnic groups may be at higher or lower risk for certain diseases because of genetic makeup and/or lifestyle factors such as diet and smoking. Radiation and Health in Durham Region 2007 Results 21

25 Because lifestyle factors such as tobacco use and diet can influence the risk of cancer and congenital anomalies, data from the Rapid Risk Factor Surveillance System (RRFSS) were used to describe smoking status, body mass index, consumption of fruits and vegetables, and screening mammography. RRFSS is an ongoing telephone survey that provides important health data to public health units. 41 While not all health units participate, Durham Region Health Department, Halton Region Health Department and Simcoe County District Health Unit (now Simcoe-Muskoka District Health Unit) have been a part of RRFSS since Questions on smoking status and height and weight (used to calculate the percentage overweight and obese) were asked throughout Questions on fruit and vegetable consumption and mammography were asked in different years in the three health units since they were optional modules. Smoking, consumption of less than five servings of fruits and vegetables per day, and obesity are all key risk factors for cancer. 42 Regular mammograms for women aged years can reduce breast cancer mortality by detecting cancer earlier and increasing the likelihood that treatment will be successful. 42 Percentages were presented with 95% confidence intervals. One-quarter (25%) of Durham Region adults aged 18+ reported smoking in , as compared with 20% in Halton Region and 26% in Simcoe County. Halton Region s smoking rate was significantly lower than Durham Region and Simcoe County s rates. Within Durham Region, although Oshawa- Whitby had the highest rate at 26%, the differences were not significantly different across Durham Region (see Figure 6). Previous analysis by municipality showed Oshawa to have the highest smoking rates and Whitby the lowest 43 ; combining these two areas averaged out the differences. In terms of body mass index, Halton Region again had the better outcome with a significantly lower percentage of overweight or obese adults in the population as compared to Durham Region and Simcoe County. Within Durham Region, there was little difference across the municipality groupings (see Figure 7). In general, almost two-thirds of adults consumed fruits and vegetables less than five times per day. While Halton Region adults were more likely to consume more fruits and vegetables, the difference was not significantly different from the other areas (see Figure 8). This may be the result of insufficient sample size since the questions were asked in Halton Region in 2005 only. Durham Region asked the questions in 2002 and 2004, while Simcoe County had the highest sample size by including the questions in 2001, 2002 and Results Radiation and Health in Durham Region 2007

26 There were also no differences in frequency of screening mammography across the areas, which might again be due to the smaller sample since the questions were not asked every year. In Durham Region, 42% of women aged had a screening mammogram in the last two years, which was identical to Simcoe County s rate and similar to Halton Region s at 39% (see Figure 9). While Clarington and North Durham had the highest screening rates, these were based on small sample sizes. In summary, Halton Region s adults were less likely to smoke and to be overweight or obese than adults living in Durham Region and Simcoe County. There were no differences in fruit and vegetable consumption or in screening mammography but this may reflect smaller sample sizes. Mother s Age at Time of Birth Advanced maternal age can increase the risk of adverse reproductive effects, including stillbirth and congenital anomalies such as Down syndrome. 44 Women in Durham Region, Ontario, and industrialized countries in general, are having babies at older ages. 44, 45 The average age of mother at time of birth for all live births increased in Ontario from 27.3 years in 1986 to 29.8 years in Although only 8% of Ontario live births in 1986 were to mothers aged 35 years and older, this increased to 20% in Ajax- Pickering and Halton Region had the highest percentage of births to mothers aged 35 and over in 2003, and this rate was significantly higher than Ontario (see Figure 10). Simcoe County had a significantly lower percentage of older mothers than Ontario. Other areas were similar to Ontario; however, while Oshawa-Whitby s percentage of older mothers was not significantly different from Ontario s, it was significantly lower than neighbouring Ajax-Pickering. Radiation and Health in Durham Region 2007 Results 23

27 CATEGORY 1 INDICATOR: Leukemia (excluding chronic lymphocytic leukemia) Overview Leukemia is cancer of the blood-forming organs. Leukemia incidence has been declining slightly in Canada with an average annual percent decrease of 0.2 in men and 0.5 in women from Mortality rates have also decreased from Incidence is higher in males than females. The main types of leukemia are: lymphocytic leukemia, which is further sub-divided into acute lymphatic leukemia (ALL) and chronic lymphocytic leukemia (CLL); and myeloid and monocytic leukemia, which can also be further divided into acute and chronic forms, including chronic myeloid leukemia (CML). Each of the sub-types of leukemia has different characteristics, including risk factors and demographic distributions. Most childhood leukemia cases are ALL, whereas CLL and CML tend to occur at older ages. Potential causes of leukemia include certain chemicals such as benzene and chemotherapeutic alkylating agents, viruses, and genetic factors. Smoking may also increase the risk of myeloid leukemia. 22 Leukemia and Radiation 22, 47 Ionizing radiation is a well-established risk factor 22, 48 for leukemia, especially myeloid leukemia. Most studies have failed to show an association between radiation and CLL specifically. 22 Studies of nuclear power workers in Canada and 14 other countries have shown a small excess risk of leukemia excluding CLL, even at the low doses 20, 49 that are typically received by nuclear workers. Studies of those exposed from Chernobyl have generally been inconclusive. 50 Incidence Results All leukemia data in this report excluded CLL. Leukemia decreased in Ontario from 1981 to 2004, with incidence in Durham Region, Halton Region and Simcoe County also on the decline but in a less consistent pattern (Figure 11). Incidence rates in Durham Region and Simcoe County were similar to Ontario; Halton Region rates were also similar but slightly higher during the 1990s. 24 CATEGORY 1 INDICATOR: Leukemia Radiation and Health in Durham Region 2007

28 Incidence in males was generally similar to Ontario for all areas, with some notable exceptions (Figure 12). Clarington males had a significantly higher incidence of leukemia in the second time period, but not the first. In , 21 cases of leukemia in males were expected in Clarington and 19 were observed; in , 33 cases were expected and 49 occurred. Rates among Ajax-Pickering males were lower than expected in , although not significantly so, with 66 expected and 52 observed. Simcoe County s rates were also lower than expected for both time periods, but the SIRs were not significantly low. Leukemia incidence in females was different from males is some areas (Figure 13). While Clarington males had high incidence after Darlington NGS began operating, Clarington females had lower incidence than Ontario in both time periods, although the SIR was significantly low only in Incidence in Ajax- Pickering females was the same as for Ontario in both time periods. There were no other significant differences. Mortality Results As with incidence, mortality rates for leukemia declined in Ontario over the 1981 to 2001 time frame (Figure 14). Mortality in males was similar to Ontario in all areas, although the rate in Halton Region in was slightly elevated and close to significant (Figure 15). Female mortality for leukemia was similar to Ontario s in all areas, except that mortality was significantly low in Ajax-Pickering in (Figure 16). Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; elevated rates in Clarington in Summary: Rates in Ajax-Pickering were similar to Ontario except that mortality in females was significantly low in Incidence was significantly high in Clarington males in and significantly low in females in Results for leukemia excluding CLL were not consistent with radiological effects in Ajax- Pickering or in Clarington females, but were in Clarington males for incidence only. Radiation and Health in Durham Region 2007 CATEGORY 1 INDICATOR: Leukemia 25

29 CATEGORY 1 INDICATOR: Thyroid Cancer Overview Thyroid cancer incidence has been increasing at an average rate of about 5% per year in Canada for both men and women, although incidence is two to three times higher in females than males. 46 Increases have also been reported in Europe and the United States, and is probably due to improved detection through ultrasound and needle biopsy. 46, 51, 52 These diagnostic techniques may be finding small thyroid cancers that would not have otherwise been detected since thyroid cancer can remain in a subclinical form for many years. 51 Analysis of thyroid cancer in Ontario has found that practice patterns in Toronto hospitals can greatly affect provincial incidence. 53 Since thyroid cancer is generally treatable, mortality rates are low. Mortality rates have not been increasing. 51 Risk factors other than radiation are not clear, although high levels of thyroid-stimulating hormone, multiparity, miscarriage, artificial menopause, iodine intake and diet may increase risk of thyroid cancer. 22 Thyroid Cancer and Radiation Thyroid cancer is considered a radiogenic cancer. The main health effect of radiation exposure from Chernobyl was a dramatic increase in thyroid cancer incidence in young people. 50 Radiation effects may be higher in children than adults because the thyroid gland undergoes tremendous growth during childhood. 54 Studies have also found that radiation-related thyroid cancer is 13, 20 more likely where there is iodine deficiency. Iodine deficiency causes thyroid glands to be even more active, thus accentuating the cellular damage of radiation. 54 Radiation treatment, particularly when it was common for benign conditions between the 1920s and 1950s, may explain increased thyroid cancer in certain cohorts CATEGORY 1 INDICATOR: Thyroid Cancer Radiation and Health in Durham Region 2007

30 Incidence Results Thyroid cancer rates in Ontario increased dramatically from 1981 to 2004, as did those in Durham Region, Halton Region and Simcoe County (Figure 17). When compared with Ontario, incidence was higher in Durham Region males for both time periods, but not significantly so. Halton Region males were the same as the province, and Simcoe County was slightly lower, but not significantly so (Figure 18). Female rates for the three areas were similar to Ontario except for a significantly low rate for Simcoe County females in (Figure 19). Within Durham Region, incidence was significantly high for Ajax-Pickering males in when 33 cases were expected and 52 were observed. The female SIRs were 1.32 and 1.14 for the two time periods but these were not significantly elevated. North Durham females had significantly low incidence in Incidence in Clarington and Oshawa-Whitby was similar to Ontario in both males and females. The number of thyroid cancers in children aged 0-19 years was small; results were not shown because there were often less than 5 cases for both sexes combined. Thyroid cancer in children was not significantly different from Ontario in all of the areas studied. Mortality Results Because mortality from thyroid cancer is rare, mortality rates showing the trend from 1981 to 2001 could only be shown for Ontario males and females (Figure 20). In contrast to incidence, mortality for thyroid cancer declined. The number of deaths from thyroid cancer was too small to present by Durham Region municipality and could only be presented for both sexes combined for Durham Region, Halton Region and Simcoe County (Figure 21). Mortality was lower in Durham Region than Ontario with SMRs of 0.78 and 0.53 in and respectively, but this was significantly low in the second time period only. Likewise, Simcoe County experienced significantly low mortality in Halton Region mortality was similar to Ontario. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Incidence was significantly high in in Ajax-Pickering males; rates in Clarington were similar to Ontario s. Mortality rates were too low to present for Ajax-Pickering and Clarington, although mortality in Durham Region was significantly low in in both sexes combined. Results for thyroid cancer incidence were consistent with radiological effects in Ajax-Pickering males in one time period. Radiation and Health in Durham Region 2007 CATEGORY 1 INDICATOR: Thyroid Cancer 27

31 CATEGORY 2 INDICATOR: All Cancers Combined Overview Although cancer is often thought of as one disease, it is really over 100 different diseases. All cancers are characterized by the uncontrolled growth and spread of abnormal cells. They are typically named after the part of the body where the cancer starts. Even within one organ or tissue (e.g. lung, leukemia), there are several different types of cancer with different causes, risk factors and characteristics. Since cancers often take many years to develop, there may be long latencies of 15 years or more between the beginning of a cancer (when there might be exposure to a carcinogen) and when it is diagnosed. Cancers are caused by a complex mix of heredity, lifestyle, infectious agents and other cancer-causing agents in the environment, which often act in combination. Many cancers are preventable. It is estimated that nearly twothirds of cancer deaths are linked to tobacco use, diet, obesity and lack of exercise. 17 Smoking is an important cause of many different types of cancer. About 38% of Canadian women and 44% of men will be diagnosed with cancer during their lifetimes; 24% and 29% respectively will die of the disease. Cancer is more common in men than women, except during the reproductive years. 46 Cancer and Radiation There is no doubt that ionizing radiation can cause cancer. What is less clear is what specific cancers may be related to radiation, the dose at which there is an effect, how dose rate and type of radiation affect carcinogenesis, and how factors such as age and sex affect risk. 48 It is difficult to interpret data for all cancers combined because the cancer types are so different and not all are affected by radiation. The most common cancers in males are prostate, lung and colorectal, and in females, breast, lung and colorectal. These cancers greatly influence 22, 48 patterns for all cancers combined. There is little evidence that prostate cancer is caused by radiation. 28 CATEGORY 2 INDICATOR: All Cancers Combined Radiation and Health in Durham Region 2007

32 Incidence Results Cancer incidence increased in Ontario since 1981, although it may be stabilizing in more recent time periods (Figure 22). A similar pattern was seen in Durham Region, Halton Region and Simcoe County. It appears that incidence in Canada may be beginning to decline in males and stabilize in females. 46 Because the number of cases was quite large when all cancers are combined, many more ratios were significantly different from Ontario than for site-specific cancers. Cancer incidence was significantly high in Durham Region and Simcoe County males in but significantly low in Halton Region males in (Figure 23). Incidence in females showed a similar pattern as the males in Durham Region and Simcoe County with significantly high rates in the second time period; however, incidence in Halton Region females was similar to Ontario (Figure 24). Within Durham Region, the SIRs for males were generally higher in the second time period than the first. The exception to this was Ajax-Pickering; the SIRs were 1.04 and 0.98 in and respectively, with incidence similar to Ontario. Oshawa-Whitby s incidence was significantly high in both time periods. Clarington had a significantly low SIR in and a significantly high one in North Durham showed a similar pattern as Clarington but the ratio was not significantly different from Ontario in the second time period. For Durham Region females, incidence was significantly high in Ajax-Pickering in the first time period only, and in Oshawa-Whitby in the second time period only. Incidence was significantly low in Clarington in All other ratios showed incidence to be similar to Ontario. Mortality Results In Canada, cancer mortality rates in males and females are declining. 46 Cancer mortality appears to also be decreasing in Ontario, with similar trends in Durham Region, Halton Region and Simcoe County (Figure 25). Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: All Cancers Combined 29

33 Cancer mortality showed a different pattern from incidence. While incidence tended to be high in Durham Region, mortality tended to be low or at provincial levels. SMRs for Durham Region were not different from Ontario for both males and females (Figures 26, 27). Halton Region s rates were significantly low for males and at provincial levels for females. Simcoe County had significantly high mortality in for both males and females with the earlier time period being similar to Ontario. Within Durham Region, Ajax-Pickering males had significantly low mortality in the second time period, Clarington males in both time periods, and North Durham males in the first period. Cancer mortality for females in all of these areas was similar to Ontario. Oshawa-Whitby was the only area in Durham Region that had a significantly high rate, which was high for both males and females in High mortality for all cancers combined in Oshawa-Whitby likely reflect high lung cancer rates, which was the leading cause of cancer death. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Incidence was significantly high in Ajax-Pickering females in and mortality was significantly low for males in Incidence in Clarington males went from significantly low to significantly high and in females from significantly low to Ontario levels. Mortality in Clarington males was significantly low. There was no consistent pattern for all cancers combined that was consistent with radiological effects in Ajax-Pickering and Clarington; however, the abrupt increase in Clarington from one time period to the next may need more examination. 30 CATEGORY 2 INDICATOR: All Cancers Combined Radiation and Health in Durham Region 2007

34 Radiation and Health in Durham Region

35 CATEGORY 2 INDICATOR: Childhood Cancer and Childhood Leukemia Overview Cancer is predominantly a disease of old age and is rare among children aged 0-19 years. Because of improved treatment, especially since 1970, most children who develop cancer will survive their illness. 46 The most common childhood cancers are the leukemias (26% of new cases), cancers of the brain and spinal cord (17%) and lymphomas (17%). 55 In Ontario, approximately 500 cases of childhood cancer are diagnosed per year. Incidence is higher in males than females. Very little is known about what causes cancer in children. Research suggests that many childhood cancers are related to genetic mutations or genetic predisposition. 56 A genetic predisposition might work together with other risk factors to cause cancer. Possible risk factors include exposure to certain chemicals (e.g., benzene, pesticides), drugs, viruses (Epstein-Barr virus, HIV), or bacteria (Helicobacter pylori). 57 Folate intake during pregnancy may help prevent leukemia in the developing fetus. 58 A particularly prominent theory is that leukemia results as an abnormal response to a common infectious disease through population mixing. 59 Clusters of leukemia tend to occur in remote and isolated populations that have had a large influx of new people, exposing the residents to infectious diseases for which they have not developed immunity at the usual ages. Although a specific infectious agent has not been identified, an association between leukemia and population mixing has been demonstrated in many different situations and is strongest for acute lymphocytic leukemia (ALL). 60, 61 High socio-economic status (SES) has been found to be associated with childhood leukemia in Canada; this association is consistent with the theory that those with lower SES may be exposed to a variety of viruses at an early age and have a lower risk of leukemia as a result. 62 However, the association between high SES and childhood leukemia is inconsistent CATEGORY 2 INDICATOR: Childhood Cancer and Childhood Leukemia Radiation and Health in Durham Region 2007

36 Childhood Cancer and Radiation Various studies in the 1950s found that women who had X-rays during pregnancy were more likely to have a child that later developed leukemia. The relationship is complex and difficult 64, 65 to characterize at low levels of radiation. Postnatal exposure to therapeutic doses has also been associated with leukemia and with brain tumours. Because of the risk, children and pregnant women are now rarely exposed to radiation. Therapeutic doses of ionizing radiation, together with a variety of inherited genetic disorders, are thought to account for only 5 10% of childhood cancers, leaving over 90% of childhood cancers of unknown cause. 57 Incidence Results for Childhood Cancer Childhood cancer rates remained fairly steady from 1981 to 2004 but appeared to increase slightly in Ontario. Incidence rates in Durham Region, Halton Region and Simcoe County were similar to Ontario but showed more variation because of the smaller numbers (Figure 28). SIRs for males and females showed that incidence was similar to Ontario for all areas, except that incidence for males was significantly low in Oshawa-Whitby in (Figures 29, 30). Mortality Results for Childhood Cancer Age-standardized mortality rates in Ontario for 1981 to 2001 showed the dramatic decrease in deaths from childhood cancer over time (Figure 31). The number of deaths was too low to show agestandardized rates for Durham Region, Halton Region and Simcoe County. SMRs for childhood cancers were presented for both sexes combined because the number of deaths was less than 5 in some of the areas when examined for males and females (Figure 32). Mortality was generally low in Durham Region, with a significantly low SMR in Durham Region in Mortality in Halton Region and Simcoe County was similar to Ontario. Within Durham Region, the mortality was low in Ajax-Pickering, although not significantly so; mortality was significantly low in both time periods in Oshawa-Whitby; mortality was no different from Ontario in Clarington and North Durham although the SMR could not be calculated for Clarington in because the number of deaths was less than 5. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; elevated rates in Clarington in Summary: Rates in Ajax-Pickering and Clarington were similar to Ontario for both incidence and mortality except that the SMR was not presented for Clarington in because the number of deaths was too small. Results for childhood cancer were not consistent with radiological effects in Ajax-Pickering or Clarington. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Childhood Cancer and Childhood Leukemia 33

37 Incidence Results for Childhood Leukemia Childhood leukemia rates remained fairly steady in Ontario from 1981 to 1998 but appeared to decrease in more recent time periods (Figure 33). Numbers were too small to show Durham Region, Halton Region and Simcoe County. Incidence of childhood leukemia for both sexes combined showed that incidence was similar to Ontario for all areas, including those within Durham Region (Figure 34). Males and females were not shown separately because of the small number of cases. Mortality Results for Childhood Leukemia As with childhood cancer, age-standardized mortality rates for childhood leukemia have decreased dramatically in Ontario (Figure 35). The number of deaths was too low (less than 25) to show age-standardized rates for Durham Region, Halton Region and Simcoe County. SMRs for childhood leukemia were presented for both sexes combined (Figure 36). Mortality was significantly low in Durham Region in Mortality in Halton Region and Simcoe County was similar to Ontario. The number of deaths in Ajax-Pickering, Clarington and North Durham was too small to present, as was mortality for Oshawa-Whitby in The SMR of 0.54 for Oshawa-Whitby in the earlier time period indicated that mortality was lower than Ontario but not significantly. 34 CATEGORY 2 INDICATOR: Childhood Cancer and Childhood Leukemia Radiation and Health in Durham Region 2007

38 Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; elevated rates in Clarington in Summary: Incidence of childhood leukemia in both Ajax-Pickering and Clarington were similar to Ontario. The number of deaths was too small to present. Results for childhood leukemia were not consistent with radiological effects in Ajax-Pickering or Clarington. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Childhood Cancer and Childhood Leukemia 35

39 CATEGORY 2 INDICATOR: Bladder Cancer Overview Cancer of the bladder is the fourth most common cancer among men in Canada, and the twelfth most common cancer among women. 46 Incidence is about three times higher in males than females. 66 Internationally, bladder cancer is most common in Europe and North America. Cigarette smoking is a leading cause with 50% of male bladder cancer and 30% of female bladder cancer attributable to smoking. Occupational exposures, such as aromatic amines, can also be important causes of the disease. Urinary tract infections, especially in women, increase risk. 22 Starting in 1989, the Ontario Cancer Registry excluded non-invasive bladder tumours from its incidence counts. This was possible with improved terminology in pathology reports. Some registries in Canada and elsewhere still include both preinvasive lesions and invasive bladder cancer together, making comparisons difficult. 66 Because of this change, SIRs and SMRs for bladder cancer were presented in this report for the time period only. The age-adjusted rates show data since 1981, demonstrating the impact of the coding change. Bladder Cancer and Radiation Epidemiologic studies of different populations have found bladder cancer to be associated with radiation. 22 Bladder cancer has a relatively high ranking in terms of carcinogenic influence of radiation as it is occasionally associated with radiation with valid risk estimates. 48 Incidence Results Bladder cancer incidence decreased slightly in Ontario since 1989 (Figure 37). This was consistent with Canadian data which showed a 0.7% per year decrease in males since 1993 and a 0.4% decrease in females. 46 A decreasing trend was not apparent in Durham Region, Halton Region and Simcoe County. 36 CATEGORY 2 INDICATOR: Bladder Cancer Radiation and Health in Durham Region 2007

40 When compared with Ontario, the SIRs for for both Durham Region and Halton Region males was high at 1.08 but were not quite significant (Figure 38). While Durham Region females did have significantly high rates of bladder cancer, Halton Region females were not significantly different from Ontario. Simcoe County had a significantly high incidence of bladder cancer for both males and females. Within Durham Region, the incidence of bladder cancer was quite similar to Ontario in Ajax-Pickering, Clarington and North Durham, but was significantly high in both males and females in Oshawa-Whitby. Mortality Results Bladder cancer mortality declined in Ontario from 1981 to 1998, but showed an increase in the most recent time period of (Figure 39). Patterns were more difficult to determine in Durham Region, Halton Region and Simcoe County. The SMRs showed that mortality for bladder cancer was generally at Ontario levels in all three areas, except that mortality was significantly high in Simcoe County females in (Figures 40, 41). Within Durham Region, bladder cancer mortality was significantly low in Oshawa- Whitby and Clarington males in All other SMRs showed that mortality was similar to Ontario levels. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Bladder cancer incidence was at Ontario levels in Ajax-Pickering and Clarington, except mortality was significantly low in Clarington males in Results for bladder cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Bladder Cancer 37

41 CATEGORY 2 INDICATOR: Breast Cancer in Females Overview Breast cancer is the most common cancer in females, although lung cancer causes a higher number of deaths. Breast cancer incidence in Canada rose steadily between 1977 and 1992, but has stabilized since The increase has been mainly attributed to the ability of mammography to detect more cases, and factors such as changing reproductive patterns. Mortality rates were steady from 1977 to 1992; they have declined at a rate of 2.7% annually since Age is the most important risk factor for breast cancer risk increases rapidly with age. Being born in North America or northern Europe also puts women at increased risk of developing the disease. Ontario s incidence is among the highest in the world. A number of reproductive factors increases risk, including early age at menarche, late age at menopause, late age at first full-term pregnancy, and never having children. Higher socioeconomic status tends to be associated with a higher incidence of breast cancer. Family history is another risk factor, specifically mutations in the BRCA1 and BRCA2 genes, which may account for 3 8% of all breast cancers. 40 Cancer and Radiation The female breast is one of the most radiogenic tissues. Radiation is a well-established risk factor for breast cancer, particularly if exposure is during childhood or adolescence. 22, 48 There appears to be little risk when exposure occurs after the age of 40 years. 48 There may be a multiplicative relationship between radiation exposure at an early age and reproductive factors such as late age of first pregnancy, whereby risk is much higher when both are present CATEGORY 2 INDICATOR: Breast Cancer in Females Radiation and Health in Durham Region 2007

42 Incidence Results Similar to Canadian trends, breast cancer incidence in Ontario increased during the 1980s but appeared to stabilize during the 1990s (Figure 42). Patterns were generally similar in Durham Region, Halton Region and Simcoe County, although there was much more variability than for Ontario and Halton Region s rates were consistently higher. The SIRs showed that incidence in Durham Region was similar to Ontario (Figure 43). In Simcoe County, incidence was low in and high in , although neither significantly. Halton Region s incidence was significantly high in both time periods. Within Durham Region, incidence was significantly high in Ajax-Pickering in ; the rate was slightly elevated in but was not significantly different from Ontario. Oshawa-Whitby s incidence was low in both time periods but was significant only in Clarington and North Durham were similar to Ontario with Clarington s incidence tending to be low for both time periods. Mortality Results Breast cancer mortality rates in Durham Region, Halton Region and Simcoe County have decreased from the time period to (Figure 44). SMRs show that mortality was at provincial levels in all areas, including those in Durham Region, except in Halton Region where they were significantly high in both time periods (Figure 45). Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Incidence was significantly high in Ajax-Pickering in but not in the second time period and mortality was at Ontario levels. Incidence and mortality in Clarington were similar to Ontario. Although the elevated rate of breast cancer in Ajax-Pickering in was consistent with radiological effects, no other rates, including mortality, were significantly high. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Breast Cancer in Females 39

43 CATEGORY 2 INDICATOR: Colorectal Cancer Overview Colorectal cancer is the third most common cancer in Canadian males after prostate cancer and lung cancer, and the second most common in females after breast cancer. It is the second most deadliest cancer in males, after lung cancer, and the third most deadliest in females, after lung cancer and breast cancer. 46 Colorectal cancer incidence increased 1.7% per year in males from 1997 to 2001, and 1.2% in females from 1996 to However, more recent data show that this trend is reversing and that incidence is beginning to decline. Mortality decreased 1.1% per year in males and 1.6% per year in females from 1993 to Some of these patterns in incidence and mortality may be explained by increased screening for colorectal cancer. Colorectal cancer is commonly referred to as bowel cancer. The colon and the rectum comprise the last 6 or 7 feet of the intestinal tract where waste is stored before passing out of the body as fecal material. Most colorectal cancers arise from benign polyps on the inner wall of the colon or rectum. 68 Physical activity decreases the risk of colorectal cancer, whereas obesity, a high waist:hip ratio, and smoking all increase risk. A diet rich in vegetables and fruits, folate and vitamin D can prevent colorectal cancer but a diet high in red meat and alcohol 22, 47, 68 increases risk of developing the disease. Family history can also be a factor. 68 Colorectal cancer incidence varies widely by geography; Ontario has among the highest rates in the world. 68 Colorectal Cancer and Radiation While there is a clear link between colon cancer and radiation, cancer of the rectum has been rarely associated with radiation. 16, 22, 48 It can be difficult to anatomically differentiate the two cancers. This report intended to include only colon plus non-specified colorectal cancers as one category; however, concern over the quality of these data, especially during the 1980s and for small geographical areas, necessitated that colorectal cancer be included as one category. 40 CATEGORY 2 INDICATOR: Colorectal Cancer Radiation and Health in Durham Region 2007

44 Incidence Results Cancer incidence decreased in Ontario during the 1980s and early 1990s but increased in the late 1990s (Figure 46). This was consistent with Canadian trends. 46 Patterns in Durham Region, Halton Region and Simcoe County were less apparent because of greater variability in these smaller areas. When compared with Ontario, Durham Region males had significantly low rates of colorectal cancer in but were no different from the province in (Figure 47). Females were similar to Ontario (Figure 48). Halton Region males were likewise similar to Ontario; incidence in females was low in both periods but not significantly so. Simcoe County males and females had significantly high incidence in ; incidence remained elevated in the second time period but not significantly so. Within Durham Region, the incidence was similar to provincial levels except for a significantly low SIR in Clarington males in Mortality Results Colorectal cancer mortality declined in Ontario from 1981 to 2001, with similar trends in Durham Region, Halton Region and Simcoe County (Figure 49). Mortality was similar to Ontario in all areas, including those within Durham Region (Figures 50, 51); however, SMRs were non-significantly elevated for males and females in Halton Region. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Incidence was similar to Ontario in Ajax-Pickering. Incidence was significantly low in Clarington males in Mortality was similar to Ontario in both areas for both time periods. Results for colorectal cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Colorectal Cancer 41

45 CATEGORY 2 INDICATOR: Lung Cancer Overview Lung cancer rates in Canadian women have continued to climb, tripling from 1977 to Rates in men leveled off in the mid-1980s and have since been declining. Lung cancer incidence and mortality closely reflect smoking rates from twenty years earlier. While men are seeing the benefit of the drop in tobacco consumption that began in the mid-1960s, the effects of decreased smoking rates have yet to be seen in women since that did not begin until the mid-1980s. 46 The most important cause of lung cancer is tobacco smoking; approximately 90% of lung cancers are caused by smoking. 17 As well, environmental tobacco smoke (ETS) causes lung cancer, increasing the risk by 20-30% among those with long-time exposure. 69 Some lung cancer is attributable to occupational exposures of substances such as radon, radioactive particulates, asbestos, coal tars and soot, arsenic, and nickel and chromium compounds. 70 A diet rich in fruits and vegetables can help reduce the risk of lung cancer. 17 Radiation and Lung Cancer While radiation and lung cancer are associated in most studies, smoking is a significant confounder. Some studies have suggested a synergistic effect between radiation (specifically radon) and smoking, meaning that the two interact to cause more lung cancer than would be expected by simply adding the individual effects of each. More recent data from the Life Span Study showed an additive effect between smoking and radiation for lung cancer. 13, 71 Studies from miners show the relationship to be somewhere between additive and multiplicative. Thus, the best way to reduce the risk of lung cancer is to not smoke CATEGORY 2 INDICATOR: Lung Cancer Radiation and Health in Durham Region 2007

46 Incidence Results Since cancer incidence trends were markedly different for males and females, both were shown separately. Lung cancer in males decreased in Ontario starting in the mid-1980s (Figure 52). The pattern was the same in Durham Region, Halton Region and Simcoe County. The trend was opposite in females as incidence climbed (Figure 53). Lung cancer might be beginning to level off or decline as of 2002/04. All areas had the same rate in , but incidence diverged over time, with the same increasing pattern in Durham Region, Halton Region and Simcoe County. Durham Region males had the same incidence of lung cancer as Ontario in both time periods, while incidence was significantly low in Halton Region and significantly high in Simcoe County (Figure 54). In females, incidence was at provincial rates for the first time period in all three areas but was significantly different in the time frame the SIRs were significantly high in Durham Region and Simcoe County, and significantly low in Halton Region (Figure 55). Within Durham Region, incidence in males was significantly low in Ajax-Pickering in , and in Clarington and North Durham in Incidence in males was significantly high in Oshawa- Whitby in The picture for females in Durham Region was much more troubling. Incidence appeared elevated in all areas in , although only significantly high in Oshawa-Whitby. Clarington s incidence in females went from significantly low in to almost significantly high in The same pattern was in North Durham, although neither SIR was significantly different from Ontario. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Lung Cancer 43

47 Mortality Results Mortality for lung cancer tends to mirror incidence because survival rates are poor. As with incidence, age-adjusted mortality rates declined among males but increased in women in Ontario, Durham Region, Halton Region and Simcoe County over 1981 to 2001 (Figures 56, 57). In males, mortality was similar to Ontario in Durham Region, but was significantly low in Halton Region for both time periods and was significantly high in Simcoe County in (Figure 58). In females, SMRs were significantly elevated in both Durham Region and Simcoe County in and were similar to Ontario in Halton Region (Figure 59). Within Durham Region, the SMRs for males were significantly low in Ajax-Pickering in and in North Durham in , but significantly high in Oshawa-Whitby in Mortality for lung cancer in Clarington was lower than Ontario but not significantly so. For females, mortality was significantly high in Oshawa-Whitby and Clarington in the second time period, 44 CATEGORY 2 INDICATOR: Lung Cancer Radiation and Health in Durham Region 2007

48 Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Incidence in Ajax-Pickering was either similar to Ontario or was significantly low. Clarington tended to have significantly low incidence in and much higher SIRs or SMRs in the second time period, which was often similar to Oshawa-Whitby and North Durham. Results for lung cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Lung Cancer 45

49 CATEGORY 2 INDICATOR: Stomach Cancer Overview Two decades ago, stomach cancer was the most common cancer in the world. 47 It is more prevalent in Asian countries than in North America. Incidence and mortality have decreased throughout the world. 47 In Canada, stomach cancer incidence declined 2.3% annually in men and 2.7% in females from 1992 to 2001; mortality decreased by 3.3% per year in men and 3.2% in women from The decline of stomach cancer may reflect improved diets and improved treatment for infectious agents. 46 While a diet high in fresh fruits and vegetables has been shown to protect against stomach cancer, preserved, smoked, pickled or salted foods increase risk, particularly if they contain chemicals called nitrites. Workplace exposures such as asbestos, nickel, coal dust and rubber processing materials may also increase risk. People whose stomachs produce less acid than normal, or whose stomachs carry the bacteria Helicobacter pylori, or who have a condition called pernicious anemia, all seem to be more likely to develop stomach cancer. Smoking is also a risk factor. 22, 72 Stomach Cancer and Radiation A number of epidemiologic studies have found stomach cancer to be associated with radiation, particularly in Asian populations where the disease is more prevalent. 22 Stomach cancer has a relatively high ranking in terms of carcinogenic influence of radiation as it is occasionally associated with radiation with valid risk estimates. 48 Incidence Results Cancer incidence decreased in Ontario from 1981 to 2004 (Figure 60). A decrease was also evident in Durham Region, Halton Region and Simcoe County, although the trend was less consistent because of greater variability in these smaller areas. 46 CATEGORY 2 INDICATOR: Stomach Cancer Radiation and Health in Durham Region 2007

50 When compared with Ontario, Durham Region and Simcoe County males had significantly low rates of stomach cancer in but were no different from the province in (Figure 61). Incidence in Halton Region males was low in both time periods, but not significantly so; however, Halton Region females did have significantly low incidence in (Figure 62). Durham Region females had rates similar to Ontario. The SIRs in Simcoe County females were significantly low in both time periods. Within Durham Region, the incidence among males was significantly low in Ajax-Pickering, Clarington and North Durham in Otherwise, stomach cancer incidence was similar to Ontario. Mortality Results As with incidence, stomach cancer mortality declined in Ontario from 1981 to 2001, with similar trends in Durham Region, Halton Region and Simcoe County (Figure 63). Because the number of deaths was even smaller than the number of cases, the age-adjusted rates varied greatly in the smaller areas. Mortality in Durham Region was significantly low in for males (Figure 64) but was no different from Ontario for females (Figure 65). In Halton Region, mortality was significantly low for both males and females in the second time period. In Simcoe County, mortality was lower than Ontario in the second time period for males and in both time periods for females. Within Durham Region, the SMRs were elevated for males in Oshawa-Whitby in , but were significantly low in Clarington and North Durham in All other SMRs showed that mortality was similar to Ontario levels. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Incidence was significantly low in Ajax-Pickering males in ; otherwise, incidence and mortality were similar to Ontario. In Clarington, males had significantly low incidence and mortality from stomach cancer in Results for stomach cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 2 INDICATOR: Stomach Cancer 47

51 CATEGORY 2 INDICATOR: Microcephalus and Brain Reduction Congenital Anomalies Overview Microcephalus is a rare, neurological disorder in which the circumference of the head is smaller than average (more than 3 standard deviations below the mean) for the age and gender of the infant. 73 This disorder can be present at birth or may develop in the first few years of life. Microcephalus can cause abnormal growth of the brain, and is often associated with chromosomal abnormalities. Children with microcephaly may have mental retardation, delayed motor functions and speech, hyperactivity, seizures or other physical problems. 74 Possible risk factors for microcephaly include maternal alcohol or drug use, infectious diseases (e.g., meningitis, encephalitis, herpes, syphilis, HIV, rubella, chicken pox), inadequate 73, 74 weight gain during pregnancy, and inadequate prenatal care. Microcephaly and Radiation A link between radiation exposure during pregnancy and microcephaly has been suggested for close to a hundred years. 75 A 1929 study showed that microcephaly occurred in 16 of 28 infants who were born to women undergoing radium therapy for uterine cancer during pregnancy. 76 The most definitive results have come from studies of the atomic bomb survivors. Women who had high radiation exposure and were pregnant at the time of the bombings, particularly during the critical period of 8-15 weeks gestation, were more likely to have children with small head circumference and severe mental retardation. 75, 77 It is thought that vulnerability to radiation is highest during this 8-15 week period because this is when neurons are reproducing in the embryo and migrating to the cerebral cortex. 75 Birth Prevalence Results Microcephaly is a rare disorder with a birth prevalence rate in Ontario of less than 7 per 10,000 births. Rates in Durham Region and Simcoe County were similar to Ontario; Halton Region had a significantly low rate in (Figure 66). Within Durham Region, rates were also similar to Ontario s, but the number of cases was too low to report in Clarington in and in North Durham in both time periods. The rate appeared high in Clarington in but was not significantly elevated and was based on a small number of cases, hence the unstable rates. Pattern to look for: Elevated rates in Ajax-Pickering in and ; elevated rates in Clarington in Summary: Rates in Ajax-Pickering and Clarington were similar to Ontario, with counts too low to report for Clarington in Results for microcephalus and brain reduction congenital anomalies were not consistent with radiological effects. 48 CATEGORY 2 INDICATOR: Microcephaly and Brain Reduction Congenital Anomalies Radiation and Health in Durham Region 2007

52 Radiation and Health in Durham Region

53 CATEGORY 3 INDICATOR: All Cancer Sites Combined in Young Adults Overview Although young adults may be defined many ways, in Canada, cancer in young adults most often applies to those aged years. While cancer is generally a disease of old age, it can strike at any age. Examining patterns of cancer in young adults may make it easier to understand some causes of cancer because trends may reflect more recent changes in exposure to cancer-causing agents. Children and adolescents may be particularly vulnerable to these exposures as they grow and develop, especially when combined with genetic susceptibility. The result may be development of cancer as a young adult. 78 Canada is fortunate in having excellent cancer incidence information for its whole population, which is rare for most countries. The types of cancers common in young adults are different than those in older adults. The three most common cancers in young men are testicular cancer (14%), non-hodgkin lymphoma (11%) and melanoma (9%). In young women, the most common cancers are breast cancer (34%), cervical cancer (10%) and thyroid cancer (9%). 78 Overall, cancer incidence in young men increased from 1983 to 1992 but decreased from 1992 to 1999; incidence has remained fairly steady in young women. Trends vary greatly depending upon the type of cancer. Mortality has been generally decreasing. 78 Because many types of cancer are grouped together, a number of risk factors may be involved, including genetic predisposition, tobacco, diet, physical inactivity, occupation, alcohol, reproductive factors, sexual activity, sunlight, drugs, and infectious agents. Cancer in Young Adults and Radiation Although radiation has not been specifically linked with overall cancer in young adults, it is logical to examine this group because research shows that earlier radiation exposure is more likely to result in cancer and that this cancer may develop earlier in life. A good example is 50 CATEGORY 3 INDICATOR: All Cancer Sites Combined in Young Adults Radiation and Health in Durham Region 2007

54 the increased incidence of thyroid cancer in children and young adults that resulted from the radiation exposure of Chernobyl. 50, 79 Since cancer in young adults is not strongly associated with radiation, this indicator is placed within Category 3 of the Radiation and Health framework. Incidence Results Cancer incidence in young adults increased slightly in Ontario since 1981, with a similar pattern in Durham Region, Halton Region and Simcoe County (Figure 67). Incidence was similar to Ontario in all three of these areas, except that both Halton Region and Simcoe County had significantly low incidence in males in (Figures 68, 69). Within Durham Region, the incidence of cancer in young adults was similar to Ontario for both males and females in both time periods. Mortality Results Cancer mortality in young adults declined in Ontario from 1981 to 2001, as well as in Durham Region, Halton Region and Simcoe County (Figure 70). SMRs showed that mortality was at Ontario levels in Durham Region, Halton Region and Simcoe County, except that mortality was significantly low in Simcoe County males in (Figure 71, 72). Within Durham Region, mortality was similar to Ontario, except for a significantly low SMR in Clarington in All other SMRs showed that mortality was similar to Ontario levels. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Cancer incidence and mortality in young adults were similar to Ontario levels in Ajax-Pickering and Clarington, except that mortality was significantly low in Clarington males in Results for cancer in young adults were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: All Cancer Sites Combined in Young Adults 51

55 CATEGORY 3 INDICATOR: Bone Cancer Overview Bone cancer is very rare with few known risk factors. Genetic predisposition and possibly exposure to chromium may explain some cases. 22 Bone Cancer and Radiation Although radiation has been found to induce bone cancer, this association has been confined to high-dose radiation, such as that used for cancer treatment. In the 1930s, radium dial painters developed high rates of bone cancer as a result of ingesting high levels of 226Ra and 228Ra when they would lick paint brushes to make a fine tip for painting. 80 No excess of bone cancer was detected among the atomic bomb survivors or among tuberculosis patients given large numbers of chest fluoroscopies. There is little evidence of an increase in bone cancer at 22, 80 low radiation doses. Incidence Results The age-adjusted rates were too low in Durham Region, Halton Region and Simcoe County to present time trends. In Ontario, incidence was higher in males than females with a general decreasing trend (Figure 73). Because of the small number of cases, both sexes were combined in the SIRs. They showed that bone cancer incidence in Durham Region, Halton Region and Simcoe County was similar to Ontario except for a significantly low rate in Halton Region in (Figure 74). Within Durham Region, the incidence of bone cancer was similar to Ontario, except for a significantly low rate in Oshawa-Whitby in ; however, ratios were not presented for Clarington and North Durham in because there were less than 5 cases. 52 CATEGORY 3 INDICATOR: Bone Cancer Radiation and Health in Durham Region 2007

56 Mortality Results Cancer mortality showed a general decrease over time in Ontario from 1981 to 2001 (Figure 75). Because of small numbers, mortality rates could not be presented for Durham Region, Halton Region and Simcoe County. The SMRs for both sexes combined showed that mortality was at Ontario levels in Durham Region, Halton Region and Simcoe County; however, the SMR was not presented for Simcoe County in because there was less than 5 cases (Figure 76). Similarly, mortality within Durham Region was at Ontario levels with ratios suppressed for Clarington and North Durham because of small numbers. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Bone cancer incidence and mortality were similar to Ontario levels in Ajax-Pickering and Clarington, although ratios were suppressed in Clarington because of a small number of cases. Results for bone cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Bone Cancer 53

57 CATEGORY 3 INDICATOR: Brain Cancer Overview Brain cancer in this report refers to cancer of the brain and other central nervous system (CNS), including the brain, meninges and spinal cord. In Ontario, this cancer ranks as the 12th most common malignancy diagnosed in men and the 14th most common in women, with incidence about 29% higher in men than women. 81 Brain cancer is very rare with little understanding of what causes it. Social class, head trauma, diet and some chemicals have been identified as potential risk factors. 22 Brain Cancer and Radiation Similar to bone cancer, the association between brain cancer and radiation has generally been confined to high-doses, such as for radiotherapy, particularly during childhood. 48 Most of the tumours linked to radiation have been benign tumours rather than malignant cancers. 22 Incidence Results The incidence of brain cancer was steady in Ontario from 1981 to 2004 (Figure 77). Trends in Durham Region, Halton Region and Simcoe County were more difficult to determine because of the smaller number of cases. When compared with Ontario, incidence in Durham Region, Halton Region and Simcoe County was similar to Ontario except for a significantly high rate in Simcoe County males in (Figure 78, 79). Within Durham Region, the incidence of brain cancer among males was similar to Ontario. In females, most areas were similar to Ontario as well but Ajax-Pickering females had significantly high incidence in and Clarington had significantly low incidence in CATEGORY 3 INDICATOR: Brain Cancer Radiation and Health in Durham Region 2007

58 Mortality Results Cancer mortality decreased over time in Ontario from 1981 to 2001 (Figure 80). SMRs showed that mortality was at Ontario levels in Durham Region, Halton Region and Simcoe County for both males and females; mortality for Simcoe County males in was high but not significantly so (Figure 81, 82). Similarly within Durham Region, mortality was at Ontario levels except for significantly low mortality in Clarington males in Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Brain cancer incidence was significantly high in Ajax-Pickering females in although mortality was not elevated. Clarington had significantly low incidence in females in and significantly low mortality in males in Although brain cancer was elevated in Ajax-Pickering females in one time period, no other results were consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Brain Cancer 55

59 CATEGORY 3 INDICATOR: Esophageal Cancer Overview Esophageal cancer is rare in Ontario, ranking as the 14th most commonly diagnosed cancer in men and 19th in women. The risk is about twice as high in men as women. Incidence in Ontario is similar to other industrialized countries and is substantially lower than in less developed countries. 82 Smoking and alcohol are the leading causes of cancer of the esophagus, with the combination increasing the risk substantially. About 75% of esophageal cancer is attributable to smoking and alcohol. 47 Other risk factors include a diet low in fruits and vegetables, chronic indigestion caused by gastro-esophageal reflux (Barrett s esophagus), consuming food and drink at high temperatures, and certain occupational exposures. 82 Esophageal Cancer and Radiation Cancer of the esophagus has been inconsistently associated with radiation whereby some studies have found a link and others have not. 22 Incidence Results The incidence of esophageal cancer was constant in Ontario from 1981 to 2004 (Figure 83). When compared with Ontario, incidence in Durham Region, Halton Region and Simcoe County was similar to Ontario except for a significantly low rate in Durham Region males in (Figure 84, 85). Within Durham Region, the incidence of esophageal cancer among males was significantly low in Ajax-Pickering in and in Clarington in In all other areas in males and in all areas in females, incidence was similar to Ontario. The SIR for Clarington females was suppressed in because there was less than five cases. 56 CATEGORY 3 INDICATOR: Esophageal Cancer Radiation and Health in Durham Region 2007

60 Mortality Results Cancer mortality increased over time in Ontario from 1981 to 2001 (Figure 86), specifically in males rather than females (not shown). The SMRs showed that mortality was at Ontario levels in Durham Region (Figures 87, 88). In Halton Region, females had a significantly low death rate in but Halton Region was otherwise similar to Ontario. Simcoe County males had significantly high mortality in ; the ratio was high in earlier time period as well but not significantly so. The ratios for Simcoe County females were similar to Ontario. Within Durham Region, mortality for esophageal cancer was no different from Ontario. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Esophageal cancer incidence and mortality in Ajax-Pickering and Clarington were at Ontario levels or significantly low. Results for esophageal cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Esophageal Cancer 57

61 CATEGORY 3 INDICATOR: Kidney Cancer Overview Kidney cancer is the 6th most common site of cancer in men in Ontario and is 11th in women. Incidence is about twice as high in males as females. Kidney cancer is rare in Asian populations and is high in Europe and North America. 83 Smoking is the most important cause of the disease, accounting for 30-40% of kidney cancers. 47 Depending upon which part of the kidney and renal system is affected, other risk factors include obesity, use of diuretic medication, and certain occupational exposures such as asbestos and cadmium. 83 Kidney Cancer and Radiation Although the epidemiologic evidence shows that radiation can cause cancer of the bladder, the association with cancer of the kidneys and other urinary organs is much weaker. 19 Incidence Results The incidence of kidney cancer increased in Ontario from 1981 to 2004, with similar patterns in Durham Region, Halton Region and Simcoe County, although Halton Region had a noticeable dip in incidence in (Figure 89). When compared with Ontario, incidence in Durham Region, Halton Region and Simcoe County was similar to Ontario for both males and females (Figures 90, 91). Within Durham Region, kidney cancer incidence was similar to Ontario in most areas, with the exception of significantly low incidence among males in North Durham in both time periods and significantly high incidence for females in Clarington in CATEGORY 3 INDICATOR: Kidney Cancer Radiation and Health in Durham Region 2007

62 Mortality Results Cancer mortality was stable in Ontario from 1981 to 2001, with a slight decline occurring since 1984 (Figure 92). Mortality was similar to Ontario in Durham Region, Halton Region and Simcoe County (Figures 93, 94). Within Durham Region, mortality for kidney cancer was no different from Ontario. Mortality in North Durham males in was not shown because of low numbers. Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Kidney cancer incidence and mortality in Ajax-Pickering were similar to Ontario. Clarington did have high incidence rates in males in but all other rates were not different in Ontario. Results for kidney cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Kidney Cancer 59

63 CATEGORY 3 INDICATOR: Multiple Myeloma Overview Multiple myeloma is a rare cancer that affects plasma cells. Incidence is higher in men than women and tends to occur in older ages, rarely in those less than 50. Although incidence increased in many parts of the world over the 1960s and 1970s, it has since stabilized. 84 There is little understanding of what causes multiple myeloma. Workers in agricultural occupations or with exposures from chemicals such as benzene may be at increased risk of developing multiple myeloma. 84 Multiple Myeloma and Radiation Multiple myeloma has been occasionally associated with radiation in various studies. 48 Since there are few established risk factors for this cancer, radiation is commonly listed as a risk factor. However, mortality studies, which have more often found an association, are inconsistent with incidence studies, even within the same population (e.g. the atomic bomb survivors). Since diagnostic information is better for cancer incidence data than on death certificates, there may be less of association between radiation and myeloma than is generally thought. 22 Incidence Results Analysis of multiple myeloma data found some unusual results which are being investigated by Cancer Care Ontario. It appears that some reported cases of multiple myeloma are not actual cancers but benign conditions that are very similar to multiple myeloma. In Ontario, 84% of all cancers from had microscopic confirmation. This was similar in Durham Region, Halton Region and Simcoe- Muskoka (note this is the health unit area and not the county of Simcoe) where the percentages were 85%, 83% and 84% respectively. Microscopic confirmation is much lower for multiple myeloma; only 62% of the Ontario cases were confirmed with laboratory data. Halton 60 CATEGORY 3 INDICATOR: Multiple Myeloma Radiation and Health in Durham Region 2007

64 Region and Simcoe-Muskoka had similar percentages to the province at 63% and 62% respectively. However, only 44% of Durham Region s multiple myeloma cases from were microscopically confirmed. 26 As a result, the last three years of data, which seemed particularly suspect, were removed from analysis in this report. Nevertheless, the multiple myeloma data should be interpreted with caution given that some cases may not be cancers and overrepresentation may be occurring in some areas more than others. The incidence of multiple myeloma was fairly stable in Ontario from 1981 to 2004 (Figure 95). Incidence increased in Durham Region and Halton Region. When compared with Ontario, incidence in Durham Region was significantly high in both males and females for both time periods (Figures 96, 97). Halton Region had significantly high incidence among males in both time periods but incidence in females was similar to Ontario. Incidence in Simcoe County was similar to Ontario for both males and females. Within Durham Region, myeloma incidence was significantly high in Oshawa-Whitby for both males and females. Mortality Results Mortality from multiple myeloma was stable in Ontario from 1981 to 2001 (Figure 98). Unlike incidence, mortality for the disease was similar to Ontario in Durham Region, Halton Region and Simcoe County (Figures 99, 100). Mortality within Durham Region was no different from Ontario except for a significantly low rate in Clarington males in The SMR for Clarington females was not presented for because of the small number of deaths. Pattern to look for: Elevated incidence and mortality rates in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Multiple myeloma incidence was not significantly different from Ontario in Ajax- Pickering and Clarington. Results for multiple myeloma were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Multiple Myeloma 61

65 CATEGORY 3 INDICATOR: Non-Hodgkin Lymphoma Overview Non-Hodgkin lymphoma (NHL) is a type of cancer that originates in the lympocytes, the white blood cells that fight infection and disease. Incidence and mortality has increased in many parts of the world, particularly industrialized countries. In Canada, rates are among the highest in the world; incidence rates doubled between 1972 and Incidence is higher in men than women. For the most part, it is not known what causes NHL. Risk factors for the disease include those that trigger immunosuppression autoimmune disease, organ transplants, ultraviolet radiation, and pathogens such as HIV, Epstein-Barr virus, Helicobacter pylori, hepatitis C and simian virus There is also increased risk with occupational and industrial exposure to herbicides. 47 Improved diagnosis, changes in classification and increases in AIDS-associated NHL may explain some of the increased incidence of the disease, but only a small fraction. 85 Non-Hodgkin Lymphoma and Radiation Studies of the link between NHL and radiation are mixed. The Japanese atomic bomb survivors as a whole did not show an association, although there was some evidence of an increasing trend in incidence with dose among males, but not females. Findings from other studies show no clear consistency. 6 Incidence Results Incidence of NHL increased in Ontario from to , then appeared to stabilize in and may now be starting to decrease (Figure 101). In general, similar patterns occurred in Durham Region, Halton Region and Simcoe County. When compared with Ontario, incidence in Durham Region was significantly low in males in while Halton Region and Simcoe County were similar to Ontario (Figure 102). Females in Durham Region, Halton Region and Simcoe County were no different than Ontario (Figure 103). 62 CATEGORY 3 INDICATOR: Non-Hodgkin Lymphoma Radiation and Health in Durham Region 2007

66 Within Durham Region, NHL incidence tended to be low as compared to Ontario, but was significantly low only in Ajax-Pickering females in Mortality Results Mortality from NHL increased in Ontario from 1981 to 2001; a similar pattern was apparent in Durham Region, Halton Region and Simcoe County, although there was much more variation in these smaller areas (Figure 104). The SMRs showed mortality to be similar to Ontario in these areas for both males and females (Figure 105, 106). Mortality patterns within Durham Region also tended to be similar to Ontario except for a significantly low rate in Clarington males in and in North Durham females in Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Non-Hodgkin lymphoma incidence and mortality in Ajax-Pickering and Clarington was either similar to Ontario or significantly low. Results for Non-Hodgkin lymphoma were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Non-Hodgkin Lymphoma 63

67 CATEGORY 3 INDICATOR: Ovarian Cancer Overview Ovarian cancer is the 7th most common site of cancer in women in Ontario. Internationally, rates are highest in North America and northern Europe and lowest in Asia, southern Europe and Australia. 87 Ovarian cancer is often difficult to diagnose because symptoms are non-specific and are similar to other common conditions. Various reproductive factors influence the risk of developing the disease. Ovarian cancer is more likely to occur in women who have not had any children and less likely in those who have taken oral contraceptives and those who have had hysterectomies. Family history and possessing the BRCA1 and BRCA2 genes is an established risk factor for a small percentage of cases. 88 The incidence of ovarian cancer increased in the late 1980s, mostly because borderline ovarian tumours became categorized as malignant as of 1988, increasing incidence by 10-15%. Mortality has been decreasing. 87 Ovarian Cancer and Radiation Ovarian cancer was found to be associated with radiation in the atomic bomb survivors, 77 but other findings are inconsistent. A review of the epidemiology of epithelial ovarian cancer (which makes up 80-90% of ovarian cancer) stated that ionizing radiation is unlikely to play a substantial role in ovarian cancer. 88 In general, ovarian cancer is occasionally associated with radiation with valid risk estimates. 48 Incidence Results The incidence of ovarian cancer increased slightly in Ontario in the later 1980s, was steady during the 1990s and recently decreased (Figure 107). Incidence patterns in Durham Region, Halton Region and Simcoe County were much more variable. When compared with Ontario, incidence in Durham Region and Halton Region was similar to Ontario (Figure 108). Simcoe County had a significantly high rate in Within Durham Region, ovarian cancer incidence was similar to Ontario in all areas for both time periods. 64 CATEGORY 3 INDICATOR: Ovarian Cancer Radiation and Health in Durham Region 2007

68 Mortality Results Cancer mortality decreased in Ontario from to (Figure 109). Because of the smaller number of deaths, mortality rates in Durham Region, Halton Region and Simcoe County did not indicate a clear trend. The SMRs showed mortality to be similar to Ontario in these areas; Halton Region did have lower mortality but not significantly low (Figure 110). Within Durham Region, mortality for ovarian cancer was no different from Ontario, except for a significantly low ratio in Oshawa-Whitby in Pattern to look for: Elevated incidence and mortality in Ajax-Pickering in and ; no excess expected in Clarington. Summary: Ovarian cancer incidence and mortality in Ajax-Pickering and Clarington were similar to Ontario. Results for ovarian cancer were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Ovarian Cancer 65

69 CATEGORY 3 INDICATOR: Stillbirths Overview Stillbirth or fetal mortality is defined as a product of conception of 20 or more weeks gestation or fetal weight of 500 grams or more, which did not breathe or show other signs of life at delivery. Death may occur before or during delivery. Fetal death that occurs before 20 weeks gestation or where weight is less than 500 grams is considered to be spontaneous abortion and should not be registered. Spontaneous abortions may be captured through some medical records (e.g. emergency room data) but many would not. Information on stillbirths is quite complete although it can sometimes be difficult to differentiate between spontaneous abortion, stillbirth, and cases of live birth where the baby dies soon after birth. Important causes of stillbirth include congenital anomalies, prenatal infections, fetal growth restriction, and maternal conditions such as gestational diabetes and preeclampsia. Advanced maternal age, obesity, and smoking during pregnancy can all increase the risk of stillbirth. 44 Since maternal age and obesity are generally increasing, stillbirth rates may begin to rise after years of decline. Declining rates are partly because of increased obstetric intervention. 44 Stillbirths and Radiation A review of pregnancy outcomes and parental exposure to radiation concluded that although there is no convincing evidence for an association between periconceptional radiation exposure and stillbirth, two studies of nuclear workers did find a relationship at higher doses. Other similar studies did not find an increased risk. Animal studies have found that radiation can cause stillbirth. 89 Stillbirth Results The stillbirth rate decreased significantly in Ontario between and (Figure 111). Rates declined in all areas between these two time periods, but not significantly. The rates were significantly lower than Ontario in Durham Region, Oshawa-Whitby, North Durham, and Halton Region in the time period. 66 CATEGORY 3 INDICATOR: Stillbirths Radiation and Health in Durham Region 2007

70 Because higher maternal age can increase the risk of stillbirth, and Ajax-Pickering and Halton Region had significantly higher percentages of older mothers than the province (see Mother s Age at Time of Birth above), stillbirth rates were adjusted for mother s age (Figure 112). When maternal age was taken into account, Durham Region and Oshawa-Whitby had significantly lower stillbirth rates in both time periods and Ajax-Pickering, Clarington, North Durham and Halton Region in Pattern to look for: Elevated rates in Ajax-Pickering in and ; elevated rates in Clarington in Summary: Stillbirth rates were similar to Ontario; however, when adjusted for maternal age, Ajax- Pickering and Clarington both had significantly lower stillbirth rates than expected in Results for stillbirths were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Stillbirths 67

71 CATEGORY 3 INDICATOR: All Congenital Anomalies Combined Overview A congenital anomaly is an abnormality of structure, function or body metabolism that is present at birth (even if not diagnosed until later in life) and results in physical or mental disability, or is fatal. 56 Congenital anomalies are the leading cause of perinatal infant death in Canada. 90 About 3% of all newborns in Canada are born with some type of congenital anomaly or birth defect. 91 This birth prevalence increases to 7% within the first two years of life as many congenital anomalies are not detected at birth. 90 Congenital anomalies are caused by a combination of genetic and environmental influences with most babies being born to women with no family history and no known risk factors for congenital anomalies. The majority of congenital anomalies have unexplained causes. 90 Nevertheless, maternal health status and health behaviors can affect the development of congenital anomalies. Maternal alcohol use, diabetes, obesity, and use of anticonvulsant medication can increase risk, whereas the intake of the folic acid before and during early pregnancy can actually prevent some congenital anomalies, particularly neural tube defects. 92 Some environmental influences can impact in the early stages of pregnancy, acting as teratogens to produce abnormalities in the fetus. Examples of teratogens include infectious agents (e.g. rubella, cytomegalovirus, varicella), illicit drugs, medications, chemicals, and physical exposures such as heat and radiation. The most commonly used teratogen is alcohol. 90 While there is growing concern about whether exposures from the physical environment such as air pollution, hazardous waste sites, industrial areas polluted with lead, and pesticides contribute to increased risk of congenital anomalies, the evidence is not clear. It is important, however, that potentially harmful exposures be reduced in order to reduce the overall risk. 90 Congenital Anomalies and Radiation Although animals studies have found that high doses of radiation can damage germ cells (which divide to become the egg or sperm) and cause congenital anomalies, the evidence of a link between radiation and total congenital anomalies in humans is not strong at the doses studied. 89 Studies of nuclear workers, the atomic bomb survivors, and of workers and populations exposed from the Chernobyl accident have not shown increases in congenital anomalies that could be linked to radiation. 22, 89, 93 A study specifically of Ontario nuclear workers likewise found no increased risk in those exposed to low levels of radiation before conception. 94 Indeed, Motherisk at the Hospital for Sick Children in Toronto advises that pregnant women inadvertently exposed to as much as 5000 mrad (50 Sv) of radiation through radiodiagnostic procedures are not at significant increased risk for major malformations. 15 These women have similar pregnancy outcomes to controls who received only background radiation. 68 CATEGORY 3 INDICATOR: All Congenital Anomalies Combined Radiation and Health in Durham Region 2007

72 Birth Prevalence Results While the congenital anomaly rate decreased significantly in Durham Region and Oshawa-Whitby from to , the rate significantly increased in Ontario (Figure 113). Within Durham Region, rates in Ajax-Pickering, Clarington and North Durham remained consistent over the two time periods. There were also no significant changes over time in Halton Region or Simcoe County. Some congenital anomaly rates were significantly lower than Ontario s, including those in Durham Region, Ajax-Pickering, and Oshawa-Whitby in , and North Durham in Halton Region had significantly low rates in both time periods and Simcoe County in the most recent period. The only significantly high rate was in Oshawa-Whitby in It is noteworthy that Ajax-Pickering and Halton Region had low congenital anomaly rates despite having a significantly higher percentage of older mothers than Ontario (see Mother s Age at Time of Birth above). Pattern to look for: Elevated rates in Ajax-Pickering in and ; elevated rates in Clarington in Summary: There were significantly low rates of all congenital anomalies combined in Ajax-Pickering in ; rates in Clarington were similar to Ontario. Results for total congenital anomalies were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: All Congenital Anomalies Combined 69

73 CATEGORY 3 INDICATOR: Down Syndrome Overview Down syndrome, also known as Trisomy 21, occurs in about 1 in 800 births in Canada. It primarily occurs as a result of non-disjunction during cell division resulting in three copies of chromosome 21 in the fetus instead of two for a total of 47 human chromosomes rather than 46 chromosomes. 90 The main risk factor for Down syndrome is increasing maternal age. In addition, women with a history of Down syndrome in previous pregnancies are at increased risk in subsequent pregnancies. 90 Down syndrome results in developmental delay, intellectual impairment and increased risk for other congenital anomalies and health problems, including congenital heart defects, gastrointestinal tract obstruction, hypothyroidism, cataracts, and hearing defects. 95 Individuals with Down syndrome are also at increased 56, 96 risk of developing leukemia. Down Syndrome and Radiation Speculation that radiation could cause Down syndrome arises because most cases are caused by nondisjunction during oocytic meiosis whereby paired chromosomes fail to separate and an extra chromosome 21 ends up in the oocyte (egg cell). Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced and the number of chromosomes is reduced to 23 so that a merging of egg and sperm will produce the full complement of 46 chromosomes in the embryo. Radiation can damage DNA, and experimental studies of fruit flies and other animals have shown that radiation may cause nondisjunction during egg and sperm production, although results vary by type of animal, dose, dose rate, and timing of exposure. 97 Human studies are inconsistent. 97 Excess numbers of Down syndrome cases were detected in Berlin nine months after Chernobyl; 98 however, radiation is thought to be an unlikely cause, particularly since no increase was found in other European countries where radiation levels were much higher. 99 Studies of populations living in areas of high natural radiation or of medically irradiated groups have provided inconclusive results and often have problematic study designs. 97 While theoretically possible, radiation is generally not thought to cause Down syndrome since there is no consistent evidence to show an association. 14 Down syndrome was elevated in Ajax-Pickering during the 1980s and was found to be significantly higher than Ontario for the time period in the 1996 Radiation and Health in Durham Region report. 1 The results were consistent with a study done by Health and Welfare Canada for the Atomic Energy Control Board which found significantly high rates in Pickering in the time period. 100 The study found no consistent pattern between tritium releases and Down syndrome birth prevalence. Analysis of stillbirths, neonatal mortality, infant mortality and 21 other birth defects did not find any other excess rates in Ajax or Pickering. 100 Birth Prevalence Results There were 71 infants born with Down syndrome in Durham Region within and 85 within , corresponding to a birth prevalence of 12 per 10,000 total births in both time periods. Rates in Durham Region were comparable to Ontario, Halton Region, and Simcoe County (Figure 114). Within Durham Region, rates were likewise not significantly different from Ontario. Ajax-Pickering (and Halton Region) did not have elevated rates of Down syndrome despite their significantly higher percentage of live births born to mothers aged 35 years and older (see Mother s Age at Time of Birth above). 70 CATEGORY 3 INDICATOR: Down Syndrome Radiation and Health in Durham Region 2007

74 Pattern to look for: Elevated rates in Ajax- Pickering in and ; elevated rates in Clarington in Summary: Down syndrome rates in Ajax- Pickering and Clarington were similar to Ontario, although the Clarington rate was suppressed due to low numbers. Birth prevalence results for Down syndrome were not consistent with radiological effects. Maternal Serum Screening Prenatal screening can indicate if a pregnancy is at increased risk of developing a congenital anomaly. 90 Maternal serum screening (MSS) consists of a blood test from a woman at weeks of pregnancy. By measuring specific proteins and hormones that have different values within an affected fetus, increased risk of spina bifida, anencephaly, Down Syndrome and trisomy 18 can be determined. Trisomy 13 and Turner syndrome may also be detected. High risk pregnancies are followedup with prenatal diagnosis such as amniocentesis or chorionic villus sampling. 90 Prenatal diagnostic tests are particularly important because many women will be rated as high risk for maternal serum screening even though there is no congenital anomaly. Information about MSS is collected provincially in the Ontario Maternal Multiple Marker Screening Database (OMMMSD). MSS Results for Down Syndrome From October 1993 to September 2000, over 400,000 women in Ontario were screened and tracked through the OMMMSD. In Durham Region, where 26,799 women were screened over that time, 36 cases of Down syndrome were identified resulting in a rate of 13.4 cases per 10,000 women screened. This was lower than Ontario s rate of 16.7, but was not statistically different (Figure 115). Likewise, rates in Ajax-Pickering, Oshawa-Whitby, and Clarington were lower than Ontario rates but the differences were not statistically significant. The rate in North Durham was not presented due to the small number of cases. The rate in Halton Region was similar to Ontario. The rate of Down syndrome detected through MSS was higher in Simcoe County than Ontario but was not significantly elevated. Pattern to look for: Elevated rates in Ajax-Pickering and Clarington. Summary: Rates of Down syndrome in Ajax-Pickering and Clarington, as detected through maternal serum screening, were similar to Ontario. MSS results for Down syndrome were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Down Syndrome 71

75 CATEGORY 3 INDICATOR: Other Chromosomal Congenital Anomalies Chromosomal Anomalies and Radiation In general, chromosomal anomalies involve either the inheritance of extra genetic material or the deletion of genetic material. Most chromosomal anomalies are lethal and often result in spontaneous abortion, particularly when there is an extra chromosome. In addition to Down syndrome, other chromosomal anomalies include Turner s syndrome (TS), Trisomy 18 and Trisomy 13. TS involves the loss of an X chromosome, resulting in a missing sex chromosome. Trisomy 18 occurs when there is an extra copy of chromosome 18; likewise, Trisomy 13 is characterized by three copies of chromosome 13 rather than two. Those with chromosomal anomalies often have other congenital anomalies such as cleft lip and/or cleft palate, and congenital heart defects. As with Down syndrome, speculation about radiation causing chromosomal congenital anomalies arises because ionizing radiation is known to induce genetic effects in plants and animals. These effects have not been demonstrated in human populations at the doses studied. 14 Birth Prevalence Results The category of other chromosomal anomalies in CCASS data included a number of conditions including Trisomy 18, Trisomy 13, autosomal syndromes, and sex chromosome conditions. Down syndrome was considered separately. Since the number of infants with other chromosomal anomalies was very small, variation in rates was large and confidence intervals were wide. There were 77 cases of chromosomal congenital anomalies in Durham Region over the 22 year period from 1979 to 2000, including 29 in Ajax- Pickering and 35 in Oshawa-Whitby. Rates could not be reported in Clarington and North Durham for because counts were less than 5. Rates across Durham Region were not statistically different than Ontario s (Figure 116). There was a significant increase in the birth prevalence of other chromosomal anomalies in Ontario from one time period to the next. Halton Region s rates were similar to Ontario. Simcoe County s rate for was significantly lower than Ontario's. Pattern to look for: Elevated rates in Ajax-Pickering in and ; elevated rates in Clarington in Summary: Rates in Ajax-Pickering and Clarington were similar to Ontario, although the rate in Clarington not presented due to low numbers. Birth prevalence results for other chromosomal congenital anomalies were not consistent with radiological effects. 72 CATEGORY 3 INDICATOR: Other Chromosomal Congenital Anomalies Radiation and Health in Durham Region 2007

76 MSS Results for Other Chromosomal Anomalies The OMMMSD considers a smaller number of disorders in its category of other chromosomal anomalies than CCASS birth prevalence because not all anomalies are detected prenatally. Only Trisomy 18, Trisomy 13 and Turner s syndrome were included in MSS results. The number of cases identified was very low and could not be presented below the Durham Region level. In Ontario, 202 cases were identified during the 7-year period from October 1993 to September 2000, resulting in a rate of 4.7 cases per 10,000 women screened. In Durham Region, 11 cases were identified. The rate of 4.1 was not significantly different from Ontario s (Figure 117). Similarly, Halton Region s rate of 4.5 per 10,000 women screened was similar to Ontario. Because the number of cases was less than 5, Simcoe County s rate could not be presented. Pattern to look for: Elevated rates in Ajax-Pickering and Clarington. Summary: Rates in Ajax-Pickering and Clarington could not be presented due to small numbers. Durham Region was similar to Ontario. MSS results for other chromosomal disorders were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Other Chromosomal Congenital Anomalies 73

77 CATEGORY 3 INDICATOR: Neural Tube Defects Overview Neural tube defects (NTDs) are congenital anomalies that result from the failure of the neural tube to close during the third and fourth week of pregnancy. The three types of NTDs in decreasing birth prevalence are spina bifida, anencephalus and encephalocele. The birth prevalence for NTDs has been 35, 101 decreasing in Durham Region and Ontario, Canada 102, and many parts of the world. The decrease has been attributed to prenatal screening and folic acid. Supplementation of a woman s diet with the B vitamin folic acid at the time of conception can prevent NTDs. As a result, women who are planning a pregnancy are encouraged to eat food rich in folate and to take a vitamin supplement with folic acid. As well, all enriched white flour and pasta products in Canada have been fortified with folic acid since November These initiatives have decreased the number of babies born with NTDs. 102 In general, NTDs occur from a combination of genetic and environmental factors. Genetic factors are suggested because NTDs can run in families and are more likely to occur in some ethnic groups and geographical locations. Environmental factors are important as shown by the fact that low socioeconomic status, maternal obesity, low intake of folic acid and other factors can increase the risk of NTDs. The causes of NTDs are multifactorial and complex. 90 Neural Tube Defects and Radiation The Committee on Medical Aspects of Radiation in the Environment (COMARE) conducted a review of the scientific evidence of adverse reproductive outcomes in the offspring of people exposed to radiation. 89 The report found that there was little evidence of adverse pregnancy outcomes at the low parental doses studied. One possible association was a weak link between paternal exposure and increased NTDs (spina bifida and anencephaly) in their offspring. This conclusion was drawn from animal research and studies of nuclear workers at Sellafield UK and Hanford USA. The higher rates in these nuclear workers were not found in other studies, including a study of Ontario Hydro workers. 94 Birth Prevalence Results Rates of NTDs dropped between the two time periods of and in all areas except Clarington where there was no change (Figure 118). The decreases were significant in Durham Region, Oshawa-Whitby and Ontario. Rates were significantly low in Ajax-Pickering and Halton Region in and significantly high in Oshawa-Whitby in All other areas were similar to Ontario. The number of cases in North Durham was too low to present in CATEGORY 3 INDICATOR: Neural Tube Defects Radiation and Health in Durham Region 2007

78 Pattern to look for: Elevated rates in Ajax- Pickering in and ; elevated rates in Clarington in Summary: Rates in Ajax-Pickering were significantly lower than Ontario in the second time period. Clarington rates were similar to Ontario s. Birth prevalence results for neural tube defects were not consistent with radiological effects. MSS Results Over 26,000 pregnant women from Durham Region were screened and followed up in the OMMMSD from October 1993 to September 2000; 26 cases of neural tube defects were detected. The number of cases in Ajax- Pickering, Clarington and North Durham were below 5 and could not be reported. There were 19 cases in Oshawa-Whitby, resulting in a rate of 15.1 NTD cases per 10,000 women screened. The rates in Oshawa-Whitby, Durham Region, Halton Region and Simcoe County were all higher than the Ontario rate of 8.7 but not significantly higher (Figure 119). Since the neural tube defects were rare, the number of cases was small and unstable. Pattern to look for: Elevated rates in Ajax-Pickering and Clarington. Summary: The number of cases in both Ajax-Pickering and Clarington was less than 5. Rates in Durham Region were not elevated. MSS results for neural tube defects were not consistent with radiological effects. Radiation and Health in Durham Region 2007 CATEGORY 3 INDICATOR: Neural Tube Defects 75

79 Summary of Findings This study compared Durham Region, Ajax-Pickering, Oshawa-Whitby, Clarington, North Durham, Halton Region and Simcoe County with Ontario for 18 cancer groupings (incidence and mortality) and 9 perinatal outcome indicators, resulting in approximately 966 comparisons. Forty-eight (5%) of these would theoretically be high or low just by chance. Within Ajax-Pickering, 138 comparisons were made with Ontario; 5 were significantly high, 9 were significantly low and 6 could not be reported because the number of cases or deaths was less than 5. For Clarington, 6 of the rates/ratios were significantly high, 17 were significantly low and 16 were non-reportable. Rather than focus on instances where there was one isolated high or low rate, the summary below describes some of the patterns apparent in the data. A table of the significantly high and low results is presented in Appendix 2. Radiation and Health in Durham Region 2007 was built on assumptions that health effects from the NGSs, if they existed and could be measured, would be seen primarily in Ajax-Pickering and Clarington, but not in the nearby communities of Oshawa-Whitby and North Durham, or the comparison areas of Halton Region and Simcoe County. Patterns of health effects would need to be consistent with latent periods recorded in the scientific literature, particularly with cancer which often takes fifteen or more years to develop after exposure. Emphasis was on Category 1 and 2 indicators, which were more likely to be associated with radiation. Category 1 Indicators The two Category 1 indicators of leukemia (excluding chronic lymphocytic leukemia) and thyroid cancer did show some high rates that could be consistent with a radiological effect. Leukemia incidence in males was significantly high in Clarington in , the period after the Darlington NGS began operating. The pattern was far from clear since incidence was lower than expected in Clarington females in this time period, although not significantly so. As well, leukemia was not elevated in Ajax-Pickering, and in fact mortality was significantly low in High incidence in Clarington males might reflect other exposures or could be a random occurrence since there were no other elevated rates. Thyroid cancer incidence in Ajax-Pickering males was significantly high in Incidence in males in and in females in both time periods was elevated but not significantly so. While this is consistent with a radiological effect, it may reflect more active case finding that is occurring in some areas, particularly the Greater Toronto Area. Thyroid cancer incidence has greatly increased because of improved detection techniques in recent years. Category 2 Indicators Durham Region, particularly Oshawa-Whitby, and Simcoe County had higher rates of all cancers combined. Lung cancer, which was the most common and deadly cancer in Ontario in both sexes combined, accounted for over 14% of all cancer cases and 25% of all cancer deaths in the province from Thus, it was no surprise that lung cancer was also high in Durham Region and Simcoe County. High lung cancer was consistent with smoking data from the Rapid Risk Factor Surveillance System (RRFSS) which found that Durham Region and Simcoe County had significantly higher smoking rates than Halton Region. Halton Region tended to have significantly low rates of all cancers combined and lung cancer. 76 Summary of Findings Radiation and Health in Durham Region 2007

80 Although incidence of all cancers combined was significantly high in many Durham Region areas, this was not reflected in mortality. This may mean that active case finding and diagnosis of cancer was more likely in Durham Region. Clarington tended to have low cancer incidence in the first period and high in the second. While this may seem to coincide with the start-up of the Darlington NGS, the latency period would be too early to see effects for most cancers. Large population growth in the area during that time contributed to the difficulty in interpreting these findings since the population characteristics of this area might have changed. Most Category 2 indicators were significantly low or at provincial levels in Ajax-Pickering and Clarington, including childhood cancer, childhood leukemia, bladder cancer, colorectal cancer, stomach cancer and the congenital anomaly microcephaly. Breast cancer incidence was significantly elevated in Ajax-Pickering females in , which was also reflected in high rates of all cancers combined for women in this time period. Since breast cancer mortality was at Ontario levels, screening may be more prevalent in Ajax-Pickering, leading to greater detection of the disease; however, data from the RRFSS did not suggest that mammography rates were higher in the area. Breast cancer incidence and mortality were consistently high in Halton Region. This may be a reflection of Halton Region s higher socio-economic status, which has been found to be associated with breast cancer. In general, Simcoe County was a good comparison for Durham Region because it showed how health indicators varied within an area. Simcoe County experienced higher rates of all cancers combined and lung cancer, as discussed above, but also tended to have higher bladder cancer and colorectal cancer. On the other hand, Simcoe County had lower rates of stomach cancer and thyroid cancer. Category 3 Indicators Almost all category 3 indicators were significantly low or at provincial levels in Ajax-Pickering and Clarington, including cancer in young adults, bone cancer, esophageal cancer, kidney cancer, multiple myeloma, non-hodgkin lymphoma, ovarian cancer, congenital anomalies, Down syndrome, other chromosomal anomalies, neural tube defects and stillbirths. Brain cancer incidence was elevated in Ajax- Pickering females for one time period only, and likewise for kidney cancer in Clarington females. Category 3 indicators have the lowest association with radiation and likely reflect other influences in the population. Nevertheless, they do not suggest a pattern consistent with a radiological effect. Radiation and Health in Durham Region 2007 Summary of Findings 77

81 Conclusion Radiation and Health in Durham Region 2007 brought three components together in order to assess possible health effects from the Pickering and Darlington NGSs: 1) A review of the scientific literature on the health effects of radiation, specifically with respect to cancer, congenital anomalies and stillbirths, 2) Information on public radiation dose as determined through OPG s Radiological Environmental Monitoring Program, 3) Local health data organized within a framework of health indicators according to their association with radiation. While each component has its limitations, the combination provides an overall picture of radiation and health in Durham Region. It is a common perception that areas with high cancer rates must have a physical entity that is causing the cancer. Yet, most often high cancer rates result when people of similar characteristics, be it socioeconomic status, occupations, lifestyle habits, age, etc., tend to live in a particular area. A physical entity such as a nuclear station makes an easy target for assumptions to take hold because it is a large imposing structure that releases radiation, a hazard that cannot be seen or felt. While we do not fully understand the patterns of disease occurring in our population, it is important to keep in mind what we do know. Cancer is not one disease but many, with each cancer, indeed even sub-types, having very different characteristics and risk factors. No area will have high rates of every cancer but all areas will have high rates of at least one cancer. Some of this may be due to chance, some due to the characteristics of the people living in a particular area, some due to better case finding, and some due to other factors that we do not have good information about. Similarly, congenital anomalies and stillbirths are complex health outcomes for which causes are often not known. An extensive environmental monitoring program done by Ontario Power Generation measures radiation from the stations and allows the public dose to be calculated. Annual assessments show that populations living within 2 km of the Pickering NGS and Darlington NGS are exposed to very low levels of radiation from the plants, less than 0.5% of background. Evaluating whether radiation released from the stations is causing adverse health effects is akin to trying to determine whether a two-hour plane ride once a year leads to a higher risk of cancer. On the other hand, radiation is a known hazard and the perception that the stations could be causing adverse health effects is an important consideration that cannot be ignored. The Health Department has met the challenge to explore the issue by reviewing the scientific literature and using local data on cancer incidence, cancer mortality, congenital anomalies and stillbirths to describe patterns of these health outcomes in the population. The limitations of the ecological study design used in this study are extensive. The argument can be made that more needs to be done to control for confounders such as socio-economic status; while this may be true, the descriptive analysis completed in this report is a necessary first step if more extensive analyses were thought to be necessary. Compiling this report increases our understanding of the issues. In conclusion, disease rates in Ajax-Pickering and Clarington did not indicate a pattern to suggest that the Pickering NGS and the Darlington NGS were causing health effects in the population. Many of the same patterns were shown in Simcoe County in particular, and some in Halton Region. Given the extremely low levels of radiation exposure from the stations, it would be unlikely that any effects would occur. 78 Conclusion Radiation and Health in Durham Region 2007

82 Moving Forward Results from Radiation and Health in Durham Region 2007 provide opportunities for the Durham Region Health Department and others to further advance the understanding of health status patterns and possible health effects from the nuclear generating stations: The Durham Region Health Department will continue to lead and participate in the Durham Nuclear Health Committee (DNHC). The DNHC, which provides a forum for discussing health concerns about the nuclear generating stations in Durham Region, is an excellent vehicle for engaging the community in studies such as Radiation and Health in Durham Region 2007 and keeping abreast of developments within the nuclear stations. The Durham Region Health Department will continue to monitor the health status of Durham Region residents. Given the limitations of an ecological study such as Radiation and Health in Durham Region 2007, efforts need to focus on better understanding patterns of health in Durham Region with respect to socio-economic status, environmental pollution and other factors, with less emphasis specifically on radiation. Development of a spatial analysis tool will greatly contribute to this better understanding. Cancer Care Ontario should develop ways to better support local public health agencies in their efforts to analyze cancer rates for their populations. This could involve: clarifying privacy concerns and streamlining the process by which local public health agencies access data for areas within their health unit; providing training for public health epidemiologists on more sophisticated data analysis techniques; and documenting and sharing data quality issues so that local public health agencies are better able to interpret their findings. A congenital anomaly surveillance system should be established in Ontario to combine high quality live birth, stillbirth and prenatal screening data within a single database that is accessible to public health units. Radiation and Health in Durham Region 2007 Moving Forward 79