Exposure to ionizing radiations arising from the operation of nuclear installations and its possible relationship with cancer mortality in Spain.

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1 Exposure to ionizing radiations arising from the operation of nuclear installations and its possible relationship with cancer mortality in Spain. Gonzalo López-Abente Carlos III Institute of Health National Center for Epidemiology Madrid. Spain Analysis of Cancer Risks in Populations near Nuclear Facilities: Phase 1 Third Committee Meeting: May 23-24, 2011 Atlanta, Georgia

2 Background Controversy has surrounded the question of whether exposure to ionising radiations stemming from effluent discharges during the operation of nuclear power plants (NPPs) could increase the ocurrence of cancer in the exposed population Spanish Parlament decission commissioned research Collaboration agreement Nuclear Safety Council-ISCIII Two previous papers

3 Environmental Health Perspectives 2001, 109(7): Cancer Epidemiology Biomarkers & Prevention :

4 Outline Objectives Methods Results for Nuclear Power Plants Results for Nuclear Fuel Facilities Conclusions

5 Agreement of collaboration NSC-ISCIII in 2006 Objectives To analyse cancer mortality in towns close to Spanish NPPs and NFFs by reference to their history of exposure to artificial radiation generated by such emissions Include the possible effect of the natural radiation in the analysis as confounding factor on cancer mortality Relative risks estimations ajusted for socio-demographic covariates

6 Methods Cancer mortality in the period in towns situated near 7 NPPs and 5 NFFs. With the exception of El Cabril and Juzbado, the NFFs are uraniumconcentrate processing facilities located in mining areas where the ore is extracted. Ecological study of retrospective cohorts. The study base are the populations of the towns included Exposed zone: The area falling within a 30-km radius of any such installation Reference zone: Towns at 50- to 100-km radius, matched with the exposed by income level, number of inhabitants, percentage of illiteracy, farmers and unemployed, and province. The reference towns were selected at random from among all those that met the matching criteria. The area falling within a 30-km radius of these installations is subjected to radiosurveillance by the Nuclear Safety Council. Exposure to artificial radiation in the reference zone was assumed to be nil.

7 Methods NPPs: 328 towns in 30 km and 303 in km NFFs: 177 and 174 towns in exposed and reference areas respectively Population included in exposed area people (1991 census) Induction period of 10 years except for leukemias (1 year) Importance of local towns matching: Improve the comparability of the groups and To reduce the problem of the spatial heterogeneity of the mortality due to many cancer sites in Spain

8 Municipal Cancer Mortality Atlas in Spain Lung cancer ( ) B a y e s e s tim a te d R R to to 1.5 to 1.3 to 1.1 to to to to a 0.6 7

9 Methods

10 Methods Main exposure covariate: Estimated effective dose arising from the operation of the facilities. Provided by tne National Safety Council Ecological covariate for each town by year Available data allow the allocation to each population group to one exposure leveal in each municipality

11 Exposure data to IR of the population arising from the operation of the facilities (CSN) Models applied in international collective-dose calculation practices, as compiled by the International Atomic Energy Agency (IAEA) (2001) The magnitude of discharges was taken into account, using original data obtained through a historical review of the records kept by the respective installations from the time they entered into service. Efluents, dietary habits, meteorological data, water consumption, etc. The estimated effective doses (microsv/year. Annual data) for town populations are the mean annual doses received by the average adult person, for each town studied. Cumulative dose We took into account the cumulative population dose according to age group and study period, i.e., the average cumulative dose received by each birth cohort in each exposure period.

12 Methods Analysis based on mortality rate ratios among populations exposed to different levels of artificial radiation and non exposed Log-linear models (GLM) were fitted on the assumption that the number of deaths per stratum followed a Poisson distribution. The study's main exposure variable was the effective exposure dose for each year and town. The measure of exposure used was the cumulative effective dose: this involved taking individual age strata and birth cohorts for each town and considering the estimated doses in each year of exposure relevant for the stratum in question. Effect measure was relative risk of mortality, estimated using the mortality rates ratios (RRs) for the exposure variables in each malignant tumour, with person-years included as offset in the models. In addition to age group and period, the adjustment variables included in the models were naturally occurring radiation and socio-demographic matching variables (percentage of unemployment, illiteracy and farmers; income level). In the joint analysis of the installations, the variable 'installation' was included as a random effects term (GLMM)

13 Methods Radiation dose effect estimators Dose as continuous Dose categorized Dose-response tests Point rate-ratio estimators and confidence intervals by robust methods

14 Facility location

15 NPPs and NFFs in Spain. Study areas within 30 km radius and reference areas km.

16 Exposure covariate catagorization Mixed criteria: Data sorted by cumulative exposure dose, quartiles of person-years and largers dosimetric jump, set the cutt-off points Maximize heterogeneity among categories

17 Range of annual cumulative artificial and natural radiation doses in towns lying in the vicinity of installations No. of towns 0-30 km Cumulative artificial radiation Dose range microsv 0-30km Annual natural radiation Dose range microsv 0-30km José Cabrera Santa Mª de Garona Vandellós (I y II) Almaraz Ascó (I y II) Cofrentes Trillo * Andujar El Cabril La Haba Saelices El Chico Nuclear power plants TOTAL Nuclear fuel facilities Juzbado TOTAL

18 Effective doses by year and town GAROÑA Effective dose log(microsv) Effective dose log(microsv) Year Year

19 Distribution of cumulative effective doses arising from effluents discharged by nuclear power plants, depicted on a single scale. Isodose lines estimated using kriging.

20 Results Cumulative effective maximun dose of artificial radiation estimated for population around facilities was 350 microsievert This dose (350 micro Sv) is that each of us got from natural origin in 40 days

21 Joint analysis of all nuclear power plants. Both sexes Deathsa Dose category microsv d0 ref. d1 d2 d3 d4 RRb d1 RR d2 RR d3 RR d4 ( ) Trend pvalue. RRc dose 95% CI Homog p-value Lung cancer d 0.811d Bone cancer Cancer of the CNS 306 Thyroid cancer 36 NH L 217 Hodgkin None of the cancer sites shown statisticaly association with exposure levels (trend tests) d Myeloma d Bladder cancer Connective tissue Kidney cancer Stomach cancer d Colorectal cancer Breast cancer (women) Ovarian cancer ( ) Testicular cancer Heterogeneity RR among NPP for some cancer sites The exploration of the results has not identified consistent patterns of risk and clear dose-response effects Dose category microsv e Leukaemias

22 Joint analysis of all nuclear fuel cycle facilities. Both sexes. Deathsa Dose category microsv d0 ref Lung cancer Bone cancer 81 d1 23 RRb d1 RR d2 RR d3 RR d4 ( ) d 1.209d d d d2 d3 18 d4 26 Trend p-value RR c dose 1.303d < d % CI Homog p-value Hodgkin 61 Myeloma 181 Dose response statistically (for associations categorized or0.762continuous covariate) for1.002lung, bone, colorectal cancer, breast cancer0.966in women, and leukemias Bladder cancer Cancer of the CNS Thyroid cancer LNH Connective tissue Kidney cancer 263 Stomach cancer findings almost to 0.267one These ara limited NFF d 0.728d 0.774d Colorectal cancer d d Breast cancer (women) d Ovarian cancer d ( ) Testicular cancer Dose category microsv Leukaemiase

23 Nuclear Fuel Facilities Results of the analysis in the area adjacent to the Andújar Uranium Plant Lung cancer Rate Ratio excess only in men Bone, colorectal Rate Ratio excess only in women Breast cancer (women) Rate Ratio excess

24 Discussion Magnitude of exposure. Artificial radiation much lower than natural radiation Ecologic study. Limited control of counfounding Mortality study. Our study adds no new information about possible excess childhood leukaemias in the vicinity of installations, due to the non-existence of cancer-incidence registries in most of the areas studied and to the fact that mortality data are insufficient to study tumours with good survival Quality of the dose estimation We do not have systems/techniques for validating dose estimations

25 Discussion Strengths Previous papers recommends It is important to use dosimetric information in all future studies Design of the study and possibility of including all the facilities Systematic approach with a mortality study and recorded data These results may serve, besides to know the levels of exposure, to reassure the resident population near the NPP with the normal working of the facilities

26 CONCLUSSIONS This study shows that the cumulative doses of artificial radiation which the population would have received as a consequence of the operation of the installations across the study period, are very small. Current knowledge in the fields of radiobiology and epidemiology does not suggest that this exposure might be related to higher cancer mortality in neighbouring populations. In general terms, this study has detected no results that would consistently indicate an effect of a systematic increase in mortality due to different types of cancer associated with the dose of artificial radiation incurred.