Assessment of the Scientific Information for the Radiation Exposure Screening and Education Program (2005) / Chapter Skim
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6 Expanding RECA Eligibility: Implementation
6 Expanding RECA Eligibility: Implementation
Pages 148-171
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From page 148... ...
PROBABILITY OF CAUSATION/ASSIGNED SHARE Background An important health detriment after exposure to ionizing radiation is the increased risk of several types of cancers, referred to as radiogenic, that can be caused by radiation. Such radiogenic cancers can also be caused by other agents 148
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From page 149... ...
. Two positive factors affecting the committee's decision to adopt PC/AS are its widespread use in current compensation programs and the availability of user-friendly tools designed to implement the PC/ AS approach.
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From page 150... ...
The risks to two individuals of different ages living in the same county would differ not only because their estimated doses may be different but also because their risk coefficients may be different. Similarly, the 2001 draft feasibility study by the CDC-NCI shows the importance of factors other than location in the estimate of doses that individuals may have received from other radionuclides in fallout.
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From page 151... ...
EXPOSURE TO FALLOUT RADIATION Exposure of the Thyroid to NTS Fallout Radiation Chapter 5 showed the distribution of the estimated thyroid dose from 131I in fallout across all counties in Utah and showed which counties are compensated under RECA 2000 from NTS operations. As an example, the committee considered a male in each Utah County, born on January 1, 1948, residing in the same county during the nuclear-test period, and consuming an average amount of milk daily.
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From page 152... ...
The estimated dose is also sharply lower for people born after 1952 because the major fallout events for this particular county occurred before their births. That illustrates further a problem in defining a geographic area for future RECA compensation: any such area would include people who received estimated doses that varied over a wide range, some of which would not be significant.
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From page 153... ...
The highest thyroid dose in this set of people was estimated by the NCI thyroid dose calculator to be 0.61 Gy, for a person born on January 1, 1952. The uncertainties in the dose estimates are large; the 90% uncertainty limits are 0.11 to 8.4 Gy.
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From page 154... ...
Assumptions include average milk consumption, diagnosis of thyroid cancer in 2000, and exposures from NTS operations. The "step-like" structure of graph is due to age-interval-based assumptions about variables, such as food consumption, and doseconversion factors in dose calculator.
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From page 155... ...
PC/AS and estimated thyroid dose are highest for a newborn and decrease with age at exposure. If, for example, the compensation criterion is that the diagnosed thyroid cancer has to be "as likely as not" due to fallout radiation exposure, PC/AS would have to be at least 0.5.
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From page 156... ...
As an example of a possible PC/AS-based approach, to determine PC/AS for a particular person born in Custer County, Idaho, on January 1, 1950, the NCI dose calculator would be used to estimate the thyroid dose received from 131 I each year. This illustrative use of the calculator yielded the doses shown in Table 6.1.
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From page 157... ...
. The committee agrees with the authors of the draft feasibility study that the dose estimates would have to be defined TABLE 6.2 PC/AS for Person Who Received Thyroid Doses Shown in Table 6.1 and Had a Thyroid Cancer Diagnosed in 2000a Percentile PC/AS 1st 15.00% 5th 26.83% 50th 66.55% 95th 92.10% 99th 95.67% aFor example, the 50th percentile shows the PC/AS value (66.55%)
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From page 158... ...
Because of the importance of external radiation from fallout deposited on the ground, the time a person spent outdoors would also affect the estimated dose. In the draft feasibility study, the uncertainties in estimated dose were not thoroughly studied, but we considered a higherupper bound dose to investigate the possible range of PC/AS for leukemia.
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From page 159... ...
for estimated bone marrow doses of 10 and 40 mGy in 1952. sessment; such variations may increase the estimate of the dose and were discussed but not specifically included in the dose estimates in the draft feasibility study.
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From page 160... ...
. The CDC-NCI draft feasibility study reviewed the health consequences for the US population of global fallout as well as NTS fallout (CDC-NCI, 2001)
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From page 161... ...
. The CDC-NCI draft feasibility study also indicated that the relative contribution of a country's tests to global fallout could be roughly determined from the relative fission yield of its tests compared with that from tests conducted by other countries.
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From page 162... ...
The acceptability of the PC/AS approach and the proposed equivalency of RECA compensation criteria and population-based preassessment criteria rests on the assumption that the preassessments will be done using values for variables in the calculations that will in fact mimic "worst-case" scenarios and produce the highest possible dose estimates for the population groups in question. In this way, possible bias against individuals with specific characteristics different from the majority of the population group under consideration can be minimized.
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From page 163... ...
This should include all the major sources of dose related to US nuclear-weapons tests considered to have potential health consequences that the CDC-NCI 2001 draft feasibility study described. · An updated dose calculator, similar to the existing NCI dose calculator for 131I, should be developed for determining dose to the thyroid and other important 3The dose estimates depend on the measured deposition of radionuclides taken at the time of the nuclear weapons tests.
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From page 164... ...
That conclusion is especially true for diseases other than thyroid cancer. As discussed earlier, the CDC-NCI draft feasibility study found that estimated radiation doses to organs and tissues other than the thyroid were less than 10 mGy in a typical exposure scenario.
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From page 165... ...
Another possibility would be a series of maps that show areas of eligibility, similar to those presented in the NCI report on 131I. It might also be useful to develop a web-based program, similar to the NCI dose calculator or IREP that would allow a potential claimant or agency staff member to enter variables from the claimant's
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From page 166... ...
. If Congress were to adopt compensation criteria for RECA that include some high percentile of the uncertainty, as in the other compensation programs, the PC/AS value at this high percentile value could exceed the criteria even for some very small estimated doses.
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From page 167... ...
The 75th percentile for PC/AS increases with GSD, but remains below 0.2. The 95th percentile for PC/AS increases as the uncertainty of the estimated dose increases and eventually exceeds 0.5 when the 1 Median 0.8 75% 95% 99% 0.6 PC/AS 0.4 0.2 0 1 2 3 4 Geometric Standard Deviation FIGURE 6.5 Values of PC/AS based on the median, 75th percentile, 95th percentile, and 99th percentile of the distribution for PC/AS as a function of the uncertainty based on the geometric standard deviation for a distribution of dose having a geometric mean of 80 mGy (8 rads)
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From page 168... ...
The committee recommends that the provision which allows individual states not currently covered under Section 5 of the Radiation Exposure Compensation Act to apply for inclusion under RECA if uranium mining occurred in the state during the January 1, 1942 to December 31, 1971 period be expanded to include not only uranium mining but also uranium milling and ore transportation occurring during that period in support of the US nuclearweapons program. Probability of Causation/Assigned Share for White and Navajo Uranium Miners The 2002 amendment to RECA added the duration-of-exposure option to the criteria for compensation.
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From page 169... ...
Relative risk appears to increase for a fixed level of WLM as duration of exposure increases. The model is similar to that developed specifically for the Colorado Plateau uranium miners (Hornung et al., 1998)
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From page 170... ...
Estimated radiation doses to organs other than thyroid and the corresponding PC/AS values for the tissues at risk are substantially lower than those for the thyroid. Because of the low radiation doses estimated for organs other than the thyroid, the committee suggests that the preassessment would enable the implementing agency to focus on selected diseases, areas and population groups.
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From page 171... ...
The committee also reviewed the geographic areas and population groups that RECA now covers for uranium mining, milling, and ore transporting. The committee recommended that the RECA provision allowing states not currently covered for uranium mining to apply for coverage be expanded to include uranium milling and ore transporting as well.
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