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5 Expanding RECA Eligibility: Scientific Issues
Pages 122-147

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From page 122...
... . The committee reviewed the criteria and compared them with those of other compensation programs related to radiation exposure (Chapter 2, Table 2.4)
From page 123...
... The counties on the X axis are arranged from the highest thyroid dose to the lowest. The variation in dose is large, ranging from 30 mGy for the lowest value in Iron County to 210 mGy in Washington County.
From page 124...
... This is not a comprehensive survey of all counties in the continental United States. It does however demonstrate that thyroid doses in other regions of the country can be greater that for counties currently eligible for compensation.
From page 125...
... The mandate before the committee involved scientific justification. One approach that is being used in other compensation programs, both in the United States and in the UK, is referred to as probability of causation (PC)
From page 126...
... The committee has adopted the nomenclature PC/AS for the purposes of this report. PC/AS is now widely used for claims against the government or its contractors in compensation programs such as Radiation-Exposed Veterans Compensation Act (REVCA)
From page 127...
... Rrad = ERR · Rbaseline, (4) where RR is relative risk factor and ERR is excess relative risk factor (see Chapter 3)
From page 128...
... Presume that the risk of developing thyroid cancer from that absorbed dose and the person's age at exposure is found to be twice the baseline risk of thyroid cancer.
From page 129...
... Figures 5.5 shows that for any given case, the range of possible values can be very large. The arrow represents the median, or central, value of PC/AS (half the Distribution of Excess Relative Risk Probability 0 1 2 3 4 5 6 7 8 9 10 ERR FIGURE 5.4 A probability distribution of excess relative risk, ERR resulting from uncertainties in estimates of the absorbed dose and associated cancer risks.
From page 130...
... 130 1 1 B D risk. 0.9 0.9 and 0.8 0.8 dose of 0.7 0.7 0.6 0.6 estimates 0.5 PC/AS 0.5 PC/AS 0.4 0.4 different 0.3 0.3 from 0.2 0.2 0.1 0.1 obtained 0 0 D and C, B, A, 1 1 A C 0.9 0.9 individuals 0.8 0.8 for 0.7 0.7 PC/AS 0.6 0.6 of 0.5 0.5 PC/AS PC/AS 0.4 0.4 Distribution 0.3 0.3 0.2 0.2 5.5 0.1 0.1 0 0 FIGURE
From page 131...
... as a part of Senate bill S 1483, which became the Radiation Exposure Compensation Act. The tables were intended to provide a means for estimating the likelihood that a person who has or had any of several radiogenic cancers developed it as a result of exposure to ionizing radiation from the nuclear-weapons tests in Nevada.
From page 132...
... Its report (NIH, 1985) identified 13 different cancer sites that had statistical evidence of an association between absorbed dose and cancer in human populations.4 The final NIH report was issued in 1985 and has been used by VA as a guide to adjudicating compensation claims, through the Veterans Dioxin and Radiation Exposure Compensation Act, for cancers diagnosed in persons who were exposed during military service.
From page 133...
... The 2003 report is based on linear dose-response models for all solid cancers, which included dose and dose-rate reduction effectiveness factors (DDREFs) to allow for the possibility that risk per unit dose decreases with decreasing dose and dose rate.
From page 134...
... Leukemia, all types (except chronic lymphocytic leukemia)
From page 135...
... The PC/AS calculations are based on cancer-incidence data from the study of the Japanese atomic-bomb survivors and radon-induced lung cancer. The computer code allows consideration of uncertainty in an estimated dose and uncertainties in all the other items that enter into a calculation of PC/AS.
From page 136...
... Under that law, it is presumed that a veteran's disease was caused by radiation if the veteran was present during a nuclear detonation regardless of the dose received. Thirteen radiogenic cancers were included in the list of presumptive diseases.
From page 137...
... The PC/AS process is one of several tools in the medical decision process. It is not the only factor used in deciding whether a veteran with a nonpresumptive radiogenic disease receives compensation for service-connected exposures to radiation.
From page 138...
... While in the high-fallout area, he consumed 1-3 glasses of milk a day.5 Thyroid cancer was diagnosed in 2004. NCI Dose Calculator The NCI calculator was used to estimate the absorbed dose to the thyroid from 131I (http://ntsi131.nci.nih.gov/, accessed February 22, 2005)
From page 139...
... Figure 5.5-D illustrates a situation where the estimated PC/AS has a wide credibility interval because of large uncertainties in estimated dose and the corresponding risk for a particular organ. For these situations, the true PC/AS might be very low, but the upper tail of the distribution could exceed established eligibility criteria.
From page 140...
... . They found shortcomings in both methods, but the YLL procedure had the advantages of being "robust" to model misspecification and "economically rational." Payment schemes can be "potentially optimal," and a scheme based on actual but unknown, biologic mechanisms and population heterogeneity is "truly optimal." They define a payment scheme as robust if the average payment to a worker harmed by a radiation exposure equals the average payment under a truly optimal scheme.
From page 141...
... The concept is used in many compensation programs that involve radiation exposure. There is a welldocumented infrastructure of tools and methods that has taken many years to develop.
From page 142...
... 100% 100% 25% 0 PC/ASmed with linear scale (Figure 5.6) 100% 100% 20% 0 Fraction of PCdist 0.5 100% 50% 0 2% Integrate PC/ASdist with linear scale 100% 81% 23% 8% aPC/Asmed refers to the median value for each distribution, shown in parentheses at the head of each column.
From page 143...
... used the following expression to determine the ERR of solid tumors caused by low-dose low-dose-rate radiation exposure: ERR= REFL × R,H × D (11) DDREF where REFL is the radiation effectiveness factor for the radiation type and cancer type, R,H is the ERR per Gy at high doses and high dose rates of the reference high energy gamma radiation, L and H refer to low and high doses and dose rates, DDREF is the dose and dose-rate effectiveness factor, and D is the estimated absorbed dose (Gy)
From page 144...
... . The 6 mGy/hr dose rate is higher than what would occur for the 131I thyroid doses considered here as long as the total dose from one exposure is less than about 150 rad.
From page 145...
... Results of the Monte Carlo calculation are shown in Figures 5.8a, 5.8b, and 5.8c. The computations were repeated for the case in which the person was born in 1931 and was thus 20 years old at the time of exposure.
From page 146...
... Median value of distribution is 32 rad, as indicated by arrow. ERR for Thyroid Exposure to 131I at Age = 1 Probability 0 100 200 300 400 ERR FIGURE 5.8b Distribution of excess relative risk of thyroid cancer from exposure to 131I in fallout at age of 1.
From page 147...
... EXPANDING RECA ELIGIBILITY: SCIENTIFIC ISSUES 147 1 0.9 0.8 0.7 y A at exposure = 1 0.6 Probability 0.5 e 0.4 Age at exposure = 20 Complimentar ulativ 0.3 Cum 0.2 0.1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 PC/AS FIGURE 5.8c Complementary cumulative distribution of PC/AS for exposure of thyroid to 131I at age of 1 and age of 20. Curves show probability that PC/AC is greater than given value on X axis.


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