1. Effects of Low Doses Probability of Causation and implications for Public Policy Lecture at UC Berkeley March 2nd 2001 by Richard Wilson Mallinckrodt Research Professor of Physics Harvard University

2. The Future of Nuclear Power may depend upon a Rational Approach to Risks of Radiation Exposure and their regulation. What are they? Do we compensate those exposed? If not what?

3. LINEARITY AT LOW DOSES IS USUAL!! Walking blindfold across University Avenue is safe: (Risk (R) = 0) IF THERE ARE NO CARS! The risk (R) increases roughly in proportion to the number of cars.

4. Alternate Dose- Response Models

5. Acute Effects Characteristics One dose or dose accumulated in a short time KILLS 1/10 the dose repeated 10 times DOES NOT KILL

6. CHRONIC EFFECTS including CANCER Characteristics A dose just sub-acute can give effects if repeated. Usually not all people affected - dose response is flatter

7. Typically an accumulated Chronic Dose = Acute LD 50 gives CANCER to 10% of the population. E.g. LD 50 for radiation is about 350 Rems. At 350 Rems about 10% of exposed get cancer. (more or less depending on rate of exposure)

8. Early Optimism Based on Poisons There is a threshold below which nothing happens __________ J.G. Crowther 1924 Probability of Ionizing a Cell Linear with Dose

9. Repair Mechanisms BUT Does the Mechanism Reject/Repair: ALL DAMAGED CELLS UP TO XXXX? (implying a threshold) OR 99.999% of CELLS INDEPENDENT OF DOSE WE DON’T KNOW

10. CRITICAL ISSUES FOR LINEARITY The POLLUTANT ACTS in the same way as WHATEVER ELSE INFLUENCES THE CANCER RATE CANCERS CAUSED BY THE POLLUTANT ARE INDISTINGUISHABLE FROM OTHER CANCERS

13. DATA HIROSHIMA - NAGASAKI (RERF) RADON COHEN OTHERS NUCLEAR INDUSTRY IARC MEDICAL

32. Probability of Causation Come let us Cast Lots to find out who is to blame for this ordeal. Jonah 1:7

33. Probability of Causation equals Risk from Substance divided by Risk from all Causes

34. Risk from all causes can be approximated as the Prevalence in a similar Population. If the cancer is rare, POC can be high even if the risk is low. E.g POC for berylliosis is unity for beryllium as a cause POC for asbestos exposure as a cause of mesothelioma among males is 80% and 20% among females

35. Administrative Uses of the POC concept. Aluminum workers in Quebec (compensate if POC > 50%) Radiation Workers in UK (compensate if POC >20%)

36. Compensation for Radiation Exposures 1985 veteran “Downwinders” (if upper 99th percentile of POC > 50%; effectively POC >5%) 1996 UK Workers (if POC >20%) 2000 Old AEC employees (if upper 99th percentile of POC > 50%; effectively POC >5%)

37. Medical Causation General Causation: the Postulated Cause is Known to Cause the Disease under some conditions (POC>0) Specific Causation, exposure and other circumstances make POC large enough (>50%)

38. What do the Courts say? US Supreme Court Daubert Joiner Kumho Tire

39. General Causation needs a Risk Ratio that is significant, statistically and otherwise Usually RR>2 (POC >50%)

40. Rule to avoid frivolous lawsuits: The postulated cause must be “more likely than not” POC>50% But Rutherford instruction If total asbestos exposure is a proven cause, it can be assigned to individual suppliers even if POC < 50%.

41. RISK of respiratory ailments due to LIFETIME exposure to AIR POLLUTION is 3 to 5% average in the USA! POC varies from 30% to 80%

42. If I develop leukemia: The POC from my Medical Exposures would be over 50% Can I sue using the Rutherford case? Minister of Health, UK US State Department Harvard University Commonwealth of Massachussets ONR DOE (AEC)

43. Assignment of a Cause does not mean that Compensation is payable. E.g. Chemotherapy agents are often carcinogenic and increase risk of future cancers even as they cure.

44. Go back to the beginning: Does it make sense? Can we study those cohorts where NIH calculate POC near 50%? Risk Ratio of 2? Those x-rayed just post world war II?