Projected Cancer Risks to Residents of New Mexico from Exposure to Trinity Radioactive Fallout

The Trinity nuclear test, conducted in 1945, exposed residents of New Mexico to varying degrees of radioactive fallout. Companion papers in this issue have detailed the results of a dose reconstruction that has estimated tissue-specific radiation absorbed doses to residents of New Mexico from internal and external exposure to radioactive fallout in the first year following the Trinity test when more than 90% of the lifetime dose was received. Estimated radiation doses depended on geographic location, race/ethnicity, and age at the time of the test. Here, these doses were applied to sex- and organ-specific risk coefficients (without applying a dose and dose rate effectiveness factor to extrapolate from a population with high-dose/high-dose rates to those with low-dose/low-dose rates) and combined with baseline cancer rates and published life tables to estimate and project the range of radiation-related excess cancers among 581,489 potentially exposed residents of New Mexico. The total lifetime baseline number of all solid cancers [excluding thyroid and non-melanoma skin cancer (NMSC)] was estimated to be 183,000 from 1945 to 2034. Estimates of ranges of numbers of radiation-related excess cancers and corresponding attributable fractions from 1945 to 2034 incorporate various sources of uncertainty. We estimated 90% uncertainty intervals (UIs) of excess cancer cases to be 210 to 460 for all solid cancers (except thyroid cancer and NMSC), 80 to 530 for thyroid cancer, and up to 10 for leukemia (except chronic lymphocytic leukemia), with corresponding attributable fractions ranging from 0.12% to 0.25%, 3.6% to 20%, and 0.02% to 0.31%, respectively. In the counties of Guadalupe, Lincoln, San Miguel, Socorro, and Torrance, which received the greatest fallout deposition, the 90% UI for the projected fraction of thyroid cancers attributable to radioactive fallout from the Trinity test was estimated to be from 17% to 58%. Attributable fractions for cancer types varied by race/ethnicity, but 90% UIs overlapped for all race/ethnicity groups for each cancer grouping. Thus, most cancers that have occurred or will occur among persons exposed to Trinity fallout are likely to be cancers unrelated to exposures from the Trinity nuclear test. While these ranges are based on the most detailed dose reconstruction to date and rely largely on methods previously established through scientific committee agreement, challenges inherent in the dose estimation, and assumptions relied upon both in the risk projection and incorporation of uncertainty are important limitations in quantifying the range of radiation-related excess cancer risk.