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

A Revised System of Radiological Protection Is Needed

ABSTRACT

The system of radiological protection has been based on linear no-threshold theory and related dose-response models for health detriment (in part related to cancer induction) by ionizing radiation exposure for almost 70 y. The indicated system unintentionally promotes radiation phobia, which has harmed many in relationship to the Fukushima nuclear accident evacuations and led to some abortions following the Chernobyl nuclear accident. Linear no-threshold model users (mainly epidemiologists) imply that they can reliably assess the cancer excess relative risk (likely none) associated with tens or hundreds of nanogray (nGy) radiation doses to an organ (e.g., bone marrow); for 1,000 nGy, the excess relative risk is 1,000 times larger than that for 1 nGy. They are currently permitted this unscientific view (ignoring evolution-related natural defenses) because of the misinforming procedures used in data analyses of which many radiation experts are not aware. One such procedure is the intentional and unscientific vanishing of the excess relative risk uncertainty as radiation dose decreases toward assigned dose zero (for natural background radiation exposure). The main focus of this forum article is on correcting the serious error of discarding risk uncertainty and the impact of the correction. The result is that the last defense of the current system of radiological protection relying on linear no-threshold theory (i.e., epidemiologic studies implied findings of harm from very low doses) goes away. A revised system is therefore needed.

Methods and Findings on Diet and Lifestyle Used to Support Estimation of Radiation Doses from Radioactive Fallout from the Trinity Nuclear Test

The Trinity nuclear test was detonated in south-central New Mexico on 16 July 1945; in the early 2000s, the National Cancer Institute undertook a dose and cancer risk projection study of the possible health impacts of the test. In order to conduct a comprehensive dose assessment for the Trinity test, we collected diet and lifestyle data relevant to the populations living in New Mexico around the time of the test. This report describes the methodology developed to capture the data used to calculate radiation exposures and presents dietary and lifestyle data results for the main exposure pathways considered in the dose reconstruction. Individual interviews and focus groups were conducted in 2017 among older adults who had lived in the same New Mexico community during the 1940s or 1950s. Interview questions and guided group discussions focused on specific aspects of diet, water, type of housing, and time spent outdoors for different age groups. Thirteen focus groups and 11 individual interviews were conducted among Hispanic, White, and Native American participants. Extensive written notes and audio recordings aided in the coding of all responses used to derive ranges, prevalence, means, and standard deviations for each exposure variable for various age categories by region and ethnicity. Children aged 11-15 y in 1940s or 1950s from the rural plains had the highest milk intakes (993 mL d), and lowest intakes were among 11- to 15-y-olds in mountainous regions (191 mL d). Lactose intolerance rates were 7-71%, and prevalence was highest among Native Americans. Meat was not commonly consumed in the summer in most communities, and if consumed, it was among those aged 11-15 y of age or older who had relatively small amounts of 100-200 g d. Most drinking and cooking water came from covered wells, and most homes were made of adobe, which provided more protection from external radiation than wooden structures. The use of multiple approaches to trigger memory and collect participant reports on diet and other factors from the distant past seemed effective. These data were summarized, and together with other information, these data have been used to estimate radiation doses for representative persons of all ages in the main ethnic groups residing in New Mexico at the time of the Trinity nuclear test.

The Methodology Used to Assess Doses from the First Nuclear Weapons Test (Trinity) to the Populations of New Mexico

Trinity was the first test of a nuclear fission device. The test took place in south-central New Mexico at the Alamogordo Bombing and Gunnery Range at 05:29 AM on 16 July 1945. This article provides detailed information on the methods that were used in this work to estimate the radiation doses that were received by the population that resided in New Mexico in 1945. The 721 voting precincts of New Mexico were classified according to ecozone (plains, mountains, or mixture of plains and mountains), and size of resident population (urban or rural). Methods were developed to prepare estimates of absorbed doses from a range of 63 radionuclides to five organs or tissues (thyroid, active marrow, stomach, colon, and lung) for representative individuals of each voting precinct selected according to ethnicity (Hispanic, White, Native American, and African American) and age group in 1945 (in utero, newborn, 1-2 y, 3-7 y, 8-12 y, 13-17 y, and adult). Three pathways of human exposure were included: (1) external irradiation from the radionuclides deposited on the ground; (2) inhalation of radionuclide-contaminated air during the passage of the radioactive cloud and, thereafter, of radionuclides transferred (resuspended) from soil to air; and (3) ingestion of contaminated water and foodstuffs. Within the ingestion pathway, 13 types of foods and sources of water were considered. Well established models were used for estimation of doses resulting from the three pathways using parameter values developed from extensive literature review. Because previous experience and calculations have shown that the annual dose delivered during the year following a nuclear test is much greater than the doses received in the years after that first year, the time period that was considered is limited to the first year following the day of the test (16 July 1945). Numerical estimates of absorbed doses, based on the methods described in this article, are presented in a separate article in this issue.

Estimated Radiation Doses Received by New Mexico Residents from the 1945 Trinity Nuclear Test

The National Cancer Institute study of projected health risks to New Mexico residents from the 1945 Trinity nuclear test provides best estimates of organ radiation absorbed doses received by representative persons according to ethnicity, age, and county. Doses to five organs/tissues at significant risk from exposure to radioactive fallout (i.e., active bone marrow, thyroid gland, lungs, stomach, and colon) from the 63 most important radionuclides in fresh fallout from external and internal irradiation were estimated. The organ doses were estimated for four resident ethnic groups in New Mexico (Whites, Hispanics, Native Americans, and African Americans) in seven age groups using: (1) assessment models described in a companion paper, (2) data on the spatial distribution and magnitude of radioactive fallout derived from historical documents, and (3) data collected on diets and lifestyles in 1945 from interviews and focus groups conducted in 2015-2017 (described in a companion paper). The organ doses were found to vary widely across the state with the highest doses directly to the northeast of the detonation site and at locations close to the center of the Trinity fallout plume. Spatial heterogeneity of fallout deposition was the largest cause of variation of doses across the state with lesser differences due to age and ethnicity, the latter because of differences in diets and lifestyles. The exposure pathways considered included both external irradiation from deposited fallout and internal irradiation via inhalation of airborne radionuclides in the debris cloud as well as resuspended ground activity and ingestion of contaminated drinking water (derived both from rivers and rainwater cisterns) and foodstuffs including milk products, beef, mutton, and pork, human-consumed plant products including leafy vegetables, fruit vegetables, fruits, and berries. Tables of best estimates of county population-weighted average organ doses by ethnicity and age are presented. A discussion of our estimates of uncertainty is also provided to illustrate a lower and upper credible range on our best estimates of doses. Our findings indicate that only small geographic areas immediately downwind to the northeast received exposures of any significance as judged by their magnitude relative to natural radiation. The findings presented are the most comprehensive and well-described estimates of doses received by populations of New Mexico from the Trinity nuclear test.