Technical Considerations for NAS Proposed Study of Cancer Risks in Populations Living Near Nuclear Facilities

Transcription

1 Technical Considerations for NAS Proposed Study of Cancer Risks in Populations Living Near Nuclear Facilities National Academy of Science July 21, 2011 Irvine, California

2 Electric Power Research Institute (EPRI) Founded in 1973 Independent, nonprofit center for public interest energy and environmental research Mission: To conduct research on key issues facing the electricity sector on behalf of its members, energy stakeholders, and society. Chauncey Starr EPRI Founder 2

3 Mission of EPRI Low Dose Committee Assess and synthesize state of knowledge of health effects from exposures to low dose ionizing radiation. Engage in stakeholder discussions to communicate radiation risks and inform scientific discussion. Collaborate with domestic and international research groups to enhance low dose research Provide study design considerations to the NAS committee responsible for scoping the update to the 1990 NCI report and help facilitate meaningful study results. 3

4 EPRI Low Dose Committee (expanded) Principal Investigators: Antone Brooks, PhD* Washington State University Tri-cities (retired professor), specialist in health effects of internal emitters Larry Dauer, PhD Memorial Sloan-Kettering Cancer Center, specialist in medical health physics and nuclear power effluents Helen Grogan, PhD* Cascade Scientific, Inc, specialist in environmental dosimetry and risk assessment Clark Heath, MD Formerly with CDC and ACS, specialist in chronic disease epidemiology David Hoel, PhD* - Medical University of South Carolina, specialist in epidemiology and risk assessments William Morgan, PhD Pacific Northwest Lab, specialist in radiation biology William Wendland, P.E.* CN Associates (formerly Director of Engineering at American Nuclear Insurers), specialist in nuclear power plant effluents EPRI Project Manager: Phung Tran, MHS* *Presenting at today s NAS public meeting 4

5 Summary of Key Considerations Epidemiological studies based on small dose relative to annual background and medical exposures will increase the difficulty of providing a definitive answer on cancer risks in population living near nuclear facilities. Close coordination of dosimetric efforts with epidemiologic efforts are needed: Estimate actual dose instead of using surrogates (e.g. distance) Public dose estimates reported for regulatory compliance often do not represent actual dose to any real population; developing a comprehensive and consistent exposure assessment methodology for dose evaluation is preferable Plan and conduct an analytic study (perhaps a case-control design) regarding childhood cancer with special attention given to leukemia and non-hodgkins lymphoma in children under age 5. Develop risk communication plan during Phase 1 to explain study challenges and expectations for how results will be used. 5

6 Epidemiological Considerations Dr. David Hoel

7 Major Previous Multisite Studies NCI (Jablon et al.) study of cancer mortality rates in counties with NPPs compared with control counties. Seascale in U.K. (4 vs 0.25 expected childhood leukemias) became COMARE multisite study of all NPPs. No cancer increases at the 13 NPPs with some increases at the nuclear sites such as at Seascale. German studies of 16 NPP sites with the most recent being a case-control of childhood leukemia. (37 cases < 5yrs within 5km) French studies at 23 sites recently used marrow doses instead of distances. There were 394 leukemia cases with 415 expected for ages <5 yrs within no dose response. U.K. follow-up using ages < 5 yrs within 5 km found 18 cases with 14.6 expected (non significant) Swiss (7/2011) reported on 5 sites with no increases observed. 7

8 Previous studies exposure estimates NCI monitored emissions for the maximally exposed was 30 µsv/yr French studies estimated exposure to marrow was 0.06 to 1.33 µsv/yr. Other studies estimated the exposures to be a factor of 1,000 to 10,000 less than natural background. German studies estimated exposures to be a factor of 1,000 to 100,000 less than natural background. Swiss estimated exposure at <1mSv /yr or <1/500 of background. 8

9 Childhood Leukemia in the German Studies For ages less than 5 within 5 km leukemia cases but not other cancers were increased. Other risk factors not able to be obtained in the case-control study. The increases were not present at distances greater than 5 km. The increases in leukemia are decreasing over time. The childhood leukemias were not increased for ages less than 15 within 5 km. Suggests a shift in age at onset. See Bernd Grosche as well as the reports in German. The new COMARE report 14 discusses the German studies as well as the others. 9

10 Recommendations Focus on childhood cancer incidences and populations living very near the nuclear sites. If case-control, assess confounders such as parental smoking, environmental and industrial pollution, infections, inoculations, day care etc. (Also the California Childhood Leukemia Project should provide new information on risk factors and genetics: see Pat Buffler at Berkeley) Major confounder is the Kinlen Hypothesis which suggests infectious agents brought into rural sites from population mixing. Evaluate and incorporate the estimated exposures from radioactive materials including meteorological considerations. 10

11 Dosimetry Assessments and Nuclear Power Plant Effluent & Dose Reporting Dr. Helen Grogan Bill Wendland, P.E.

12 Exposure & Dose to Members of the Public NRC 12

13 Sources of Dose from Nuclear Plants Direct N-16 Gamma Rays (BWR Turbine Buildings) Gamma Rays On-Site Dry Fuel Storage (ISFSI) Gamma Rays On-Site Storage of Highly Radioactive Materials (e.g. S/G s, Turbine Rotors, Heat Exchangers) Gamma Rays Low Level Waste Stored On-Site Indirect Effluent Releases Airborne Liquid Inadvertent Releases from Leaks & Spills to Groundwater On-Site Burial of Radioactive Material On-Site Contaminations [10CFR50.75(g)] (Note - Effluent Release Dose Consequence can be <10% of Total at Select Sites) 13

14 Facility Reporting of Exposures and Dose Facility Annual Reports 10CFR50.36(a)(2) Regulatory Guide 1.21 Guidance Annual Radioactive Effluent Release Reports Effluents and Dose Consequences from Effluents Facility Annual Reports Also Contain Dose Consequence Information from Direct Radiation Sources as well as Effluent Releases 40CFR190 EPA Radiation Standards for NPP Operations Aggregates Dose Consequences from All Sources Not all Facilities Report Details of Computations 14

15 Public Information Sources Exposure & Dose Site Annual Radioactive Effluent Release Reports (ARERR) RETS Program Site Annual Radiological Environmental Operating Reports (AREOR) REMP Program NRC Effluent Database & Source Documents (REIRS, ADAMS) NUREG/CR-2907 Radioactive Material Released from Nuclear Power Plants Compiled Effluents Information Only (Discontinued ~ 1985) NUREG/CR-2850 Population Dose Commitments Due to Radioactive Materials Releases from Nuclear Power Plant Sites (Discontinued ~1992) Compiled Total Body Population Approach to Dose Calculations for Effluent Releases Using Site Specific Data and the ARERRs 15

16 Acronym Definitions ARERR Annual Radioactive Effluent Release Report AREOR Annual Radiological Environmental Operating Report RETS Radiological Effluent Technical Specifications REMP Radiological Environmental Monitoring Program NRC REIRS - Radiation Exposure Information and Reporting System NRC ADAMS - Agencywide Documents Access and Management System 16

17 Example Range of Calculated Doses to Adult PWR BWR Airborne Releases mgy mrad mgy mrad Beta 5.24E E E E E E E E-1 Gamma 4.21E E E E E E E E-1 msv mrem msv mrem Organ 1.45E E E E E E E E0 Total body 2.75E E E E E E E E0 Liquid Releases msv mrem msv mrem Organ 2.28E E E E E E E E-2 Total body 5.85E E E E E E E E-2 17

18 Exposure & Dose to Members of the Public NRC 18

19 Dose Calculation Considerations Need a consistent methodological approach site-specific factors to the extent possible comprehensive exposure pathways model dose coefficients based on current understanding Distance from a NPP does NOT provide an accurate surrogate for dose 19

20 Estimating Actual Doses NPP characteristics reactor type (PWR, BWR), reactor age, electrical output, fuel condition, cycle length other sources of radiation Physical environment and meteorology terrain, wind speed and direction Land use and demographics urban, rural, changes over time Dose calculation methodology compliance vs. epidemiology 20

21 Dose-Response in the Low Dose Region: Confounders and Mechanisms of Action Dr. Antone L. Brooks

22 My Background Early interest in radiation (Watching atomic weapons in Southern Utah) MS in radiation ecology (Chasing fallout),phd in radiation biology and genetics Studied health effects induced by low doses from internally deposited radio-nuclides important in nuclear power plants Invested my life in research on genetic effects and cancer from low doses and dose-rate radiation (DOE Low Dose Radiation Research Program) 22

23 U.S Radiation Dose Rates from Natural Background 23

24 Nevada Test Fallout Simon et al

25 World wide fallout in the United States 25

26 26

27 What Causes Cancer? WHO 27

28 What Radiation Exposures Can we Modify? Man-made vs Natural Radiation Occupational 1% Fallout 1% Nuclear fuel cycle 0.5% Consumer products 6.5% Nuclear medicine/x-rays 91% Man-made radiation 52% Natural background radiation 48% Brenner and Hall 2008 Mettler

29 Medical Radiation Exposures 200 million medical x-rays/year X-ray 0.1 mgy 100 million dental x-rays/year Dental 0.06 mgy 16 million doses of radiopharmaceuticals/yr 80 million CT scans/year Head scan 4-6 mgy/scan Body scan mgy/scan Large doses from radiation therapy Brenner and Hall AAPM TG-204,

30 Doses to Public from Nuclear Power Plants External Exposure (Highest allowed at Boundary of the Plant (0.25 msv/year) Exposure to Internally Deposited Radioactive Material (much/much smaller) Natural Background doses (2-4 msv/yr USA, msv/year Brazil, 200 msv/yr Iran) 30

31 Mechanistic Studies of Low Dose Effects The risk for radiation induced cancer in human populations is low and undetectable at low doses and dose-rates thus mechanistic studies are required. DOE Low Dose Radiation Research Program Cells can detect and respond to very low doses of ionizing radiation Radiation responses at all levels of biological organization are different at high doses than at low doses. High dose-rate produces more biological damage than low dose-rate exposures Bystander effects, adaptive responses, ROS status of the cells, and genomic instability are interrelated and can be related to protective mechanisms. This resulted in major paradigm shifts in Radiation biology. Thus, mechanisms of radiation action change as a function of dose and dose-rate. Data suggest that radiation exposures are detrimental at high doses and protective at low doses. 31

32 Risk Communication Previous work with DOE found that communication is important and challenging. Well thought out communication plan is essential to avoid misinterpretation of the results Technical work will largely be consumed by nontechnical audience Must take care to distinguish correlation vs causation Regardless of the outcome of the NAS study, it is important to recognize and communicate the other possible confounding factors including other radiation sources, life style and other environmental factors. 32

33 Helpful Reviews of Health Effects from Low dose and dose-rate radiation Health Physics 97: November 2009, Special Issue: 44 th Annual Meeting of the National Council on Radiation Protection and Measurements: Low Dose and Low Dose-Rate Radiation Effects and Models. Dauer, LT, Brooks, AL, Hoel, D, Morgan W, Stram D, Tran P. (2010) Evaluation of updated research on the health effects associated with low-dose ionizing radiation, Radiation Protection Dosimetry 140 (2) Health Physics 100:, March 2011, Special Issue: Proceedings of the Conference on Biological Consequences and Health Risks of Low- Level Exposure to Ionizing Radiation: In honor of Victor P. Bond. 33

34 Next Steps Executive Summary of Key Considerations available for download: Full report will be published and available for download in 4 th Quarter Review and feedback provided by 7 external scientists/experts EPRI Low Dose Committee experts are available to answer questions- continued dialogue encouraged 34

35 Together Shaping the Future of Electricity 35