Cancer mortality risk among military participants of a 1958 atmospheric nuclear weapons test

Mortality among U.S. military participants at eight aboveground nuclear weapons test series

BACKGROUND

Approximately 235,000 military personnel participated at one of 230 U.S. atmospheric nuclear weapons tests from 1945 through 1962. At the Nevada Test Site (NTS), the atomic veterans participated in military maneuvers, observed nuclear weapons tests, or provided technical support. At the Pacific Proving Ground (PPG), they served aboard ships or were stationed on islands during or after nuclear weapons tests.

MATERIAL AND METHODS

Participants at seven test series, previously studied with high-quality dosimetry and personnel records, and the first test at TRINITY formed the cohort of 114,270 male military participants traced for vital status from 1945 through 2010. Dose reconstructions were based on Nuclear Test Personnel Review records, Department of Defense. Standardized mortality ratios (SMR) and Cox and Poisson regression models were used in the analysis.

RESULTS

Most atomic veterans were enlisted men, served in the Navy at the PPG, and were born before 1930. Vital status was determined for 96.8% of the veterans; 60% had died. Enlisted men had significantly high all-causes mortality SMR (1.06); officers had significantly low all-causes mortality SMR (0.71). The pattern of risk over time showed a diminution of the 'healthy soldier effect': the all-causes mortality SMR after 50 years of follow-up was 1.00. The healthy soldier effect for all cancers also diminished over time. The all-cancer SMR was significantly high after 50 years (SMR 1.10) primarily from smoking-related cancers, attributed in part to the availability of cigarettes in military rations. The highest SMR was for mesothelioma (SMR 1.56) which was correlated with asbestos exposure in naval ships. Prostate cancer was significantly high (SMR 1.13). Ischemic heart disease was significantly low (SMR 0.84). Estimated mean doses varied by organ were low; e.g., the mean red bone marrow dose was 6 mGy (maximum 108 mGy). Internal cohort dose-response analyses provided no evidence for increasing trends with radiation dose for leukemia (excluding chronic lymphocytic leukemia (CLL)) [ERR (95% CI) per 100 mGy -0.37 (-1.08, 0.33); n = 710], CLL, myelodysplastic syndrome, multiple myeloma, ischemic heart disease, or cancers of the lung, prostate, breast, and brain.

CONCLUSION

No statistically significant radiation associations were observed among 114,270 nuclear weapons test participants followed for up to 65 years. The 95% confidence limits were narrow and excluded mortality risks per unit dose that are two to four times higher than those reported in other investigations. Significantly elevated SMRs were seen for mesothelioma and asbestosis, attributed to asbestos exposure aboard ships.

The Million Person Study, whence it came and why

PURPOSE

The study of low dose and low-dose rate exposure is of immeasurable value in understanding the possible range of health effects from prolonged exposures to radiation. The Million Person Study (MPS) of low-dose health effects was designed to evaluate radiation risks among healthy American workers and veterans who are more representative of today's populations than are the Japanese atomic bomb survivors exposed briefly to high-dose radiation in 1945. A million persons were needed for statistical reasons to evaluate low-dose and dose-rate effects, rare cancers, intakes of radioactive elements, and differences in risks between women and men.

METHODS AND MATERIALS

The MPS consists of five categories of workers and veterans exposed to radiation from 1939 to the present. The U.S. Department of Energy (DOE) Health and Mortality study began over 40 years ago and is the source of ∼360,000 workers. Over 25 years ago, the National Cancer Institute (NCI) collaborated with the U.S. Nuclear Regulatory Commission (NRC) to effectively create a cohort of nuclear power plant workers (∼150,000) and industrial radiographers (∼130,000). For over 30 years, the Department of Defense (DoD) collected data on aboveground nuclear weapons test participants (∼115,000). At the request of NCI in 1978, Landauer, Inc., (Glenwood, IL) saved their dosimetry databases which became the source of a cohort of ∼250,000 medical and other workers.

RESULTS

Overall, 29 individual cohorts comprise the MPS of which 21 have been or are under active study (∼810,000 persons). The remaining eight cohorts (∼190,000 persons) will be studied as resources become available. The MPS is a national effort with critical support from the NRC, DOE, National Aeronautics and Space Administration (NASA), DoD, NCI, the Centers for Disease Control and Prevention (CDC), the Environmental Protection Agency (EPA), Landauer, Inc., and national laboratories.

CONCLUSIONS

The MPS is designed to address the major unanswered question in radiation risk understanding: What is the level of health effects when exposure is gradual over time and not delivered briefly. The MPS will provide scientific understandings of prolonged exposure which will improve guidelines to protect workers and the public; improve compensation schemes for workers, veterans and the public; provide guidance for policy and decision makers; and provide evidence for or against the continued use of the linear nonthreshold dose-response model in radiation protection.

Asbestos Exposure and Mesothelioma Mortality among Atomic Veterans

BACKGROUND

During the Cold War the United States (U.S.) conducted 230 above-ground atmospheric nuclear weapons tests between 1945 and 1962 at the Nevada Test Site and the Pacific Proving Grounds. These tests involved over 250,000 military personnel. Asbestos was used on the naval vessels for insulation in the boiler room, engine room, and other areas. This is the first quantitative assessment of asbestos-related mesothelioma, including cancers of the pleura and peritoneum, among military personnel who participated in above-ground nuclear weapons testing.

METHODS

Approximately 114,000 atomic veterans were selected for an epidemiological study because they were in one of eight series of weapons tests that were associated with somewhat higher personnel exposures than the other tests and because they have been previously studied. We were able to categorize specific jobs into potential for asbestos exposure based on a detailed database of the military activities of the atomic veterans, developed using historical records provided by the Defense Threat Reduction Agency. Standardized mortality ratios (SMR) were calculated by service, rank(officer/enlisted) and ratings (occupation code and work location aboard ship) after 65 years of follow-up… Results: Mesothelioma deaths were significantly increased overall (SMR 1.56; 95% CI 1.32-1.82; n= 153). This increase was seen only among those serving in the Pacific Proving Ground (SMR 1.97; 95% CI 1.65-2.34; n= 134), enlisted men (SMR 1.81; 95% CI 1.53-2.13; n= 145) and the 70,309 navy personnel (SMR 2.15; 95% CI 1.80-2.56; n= 130). No increased mortality rates were seen among the other services: army (SMR 0.45), air force (SMR 0.85) or marines (SMR 0.75). Job categories with the highest potential for asbestos exposure (machinist's mates, boiler technicians, water tender, pipe fitters, and fireman) had an of SMR 6.47. Job categories with lower potential (SMR =1.35) or no potential (SMR =1.28) for asbestos exposure had non-significantly elevated mesothelioma mortality.

CONCLUSIONS

Although jobs with high potential for exposure to asbestos products were held by only 20% of the enlisted naval population, sailors with these jobs (machinist's mate, pipe fitter, boiler technician, water tender and fireman) experienced 55% of mesothelioma deaths. The significantly higher mortality rate overall was explained by asbestos exposure among enlisted naval personnel in this low-dose radiation exposed cohort.

Mortality among military participants at the 1957 PLUMBBOB nuclear weapons test series and from leukemia among participants at the SMOKY test

Health effects following low doses of ionizing radiation are uncertain. Military veterans at the Nevada test site (NTS) during the SMOKY atmospheric nuclear weapons test in 1957 were reported to be at increased risk for leukemia in 1979, but this increase was not evaluated with respect to radiation dose. The SMOKY test was one of 30 tests in 1957 within the PLUMBBOB test series. These early studies led to public laws where atomic veterans could qualify for compensation for presumptive radiogenic diseases. A retrospective cohort study was conducted of 12219 veterans at the PLUMBBOB test series, including 3020 at the SMOKY nuclear test. Mortality follow-up was through 2010 and observed causes of death were compared with expected causes based on general population rates. Radiation dose to red bone marrow was based on individual dose reconstructions, and Cox proportional hazards models were used to evaluate dose response for all leukemias other than chronic lymphocytic leukemia (non-CLL leukemia). Vital status was determined for 95.3% of the 12 219 veterans. The dose to red bone marrow was low (mean 3.2 mGy, maximum 500 mGy). Military participants at the PLUMBBOB nuclear test series remained relatively healthy after 53 years and died at a lower rate than the general population. In contrast, and in comparison with national rates, the SMOKY participants showed significant increases in all causes of death, respiratory cancer, leukemia, nephritis and nephrosis, and accidents, possibly related in part to lifestyle factors common to enlisted men who made up 81% of the SMOKY cohort. Compared with national rates, a statistically significant excess of non-CLL leukemia was observed among SMOKY participants (Standardized Mortality Ratio  =  1.89, 95% 1.24-2.75, n  =  27) but not among PLUMBBOB participants after excluding SMOKY (SMR  =  0.87, 95% 0.64-1.51, n  =  47). Leukemia risk, initially reported to be significantly increased among SMOKY participants, remained elevated, but this risk diminished over time. Despite an intense dose reconstruction, the risk for leukemia was not found to increase with increasing levels of radiation dose to the red bone marrow. Based on a linear model, the estimated excess relative risk per mGy is  -0.05 (95% CI -0.14, 0.04). An explanation for the observed excess of leukemia remains unresolved but conceivably could be related to chance due to small numbers, subtle biases in the study design and/or high tobacco use among enlisted men. Larger studies should elucidate further the possible relationship between fallout radiation, leukemia and cancer among atomic veterans.

Dose reconstruction for the million worker study: status and guidelines

The primary aim of the epidemiologic study of one million U.S. radiation workers and veterans [the Million Worker Study (MWS)] is to provide scientifically valid information on the level of radiation risk when exposures are received gradually over time and not within seconds, as was the case for Japanese atomic bomb survivors. The primary outcome of the epidemiologic study is cancer mortality, but other causes of death such as cardiovascular disease and cerebrovascular disease will be evaluated. The success of the study is tied to the validity of the dose reconstruction approaches to provide realistic estimates of organ-specific radiation absorbed doses that are as accurate and precise as possible and to properly evaluate their accompanying uncertainties. The dosimetry aspects for the MWS are challenging in that they address diverse exposure scenarios for diverse occupational groups being studied over a period of up to 70 y. The dosimetric issues differ among the varied exposed populations that are considered: atomic veterans, U.S. Department of Energy workers exposed to both penetrating radiation and intakes of radionuclides, nuclear power plant workers, medical radiation workers, and industrial radiographers. While a major source of radiation exposure to the study population comes from external gamma- or x-ray sources, for some of the study groups, there is a meaningful component of radionuclide intakes that requires internal radiation dosimetry assessments. Scientific Committee 6-9 has been established by the National Council on Radiation Protection and Measurements (NCRP) to produce a report on the comprehensive organ dose assessment (including uncertainty analysis) for the MWS. The NCRP dosimetry report will cover the specifics of practical dose reconstruction for the ongoing epidemiologic studies with uncertainty analysis discussions and will be a specific application of the guidance provided in NCRP Report Nos. 158, 163, 164, and 171. The main role of the Committee is to provide guidelines to the various groups of dosimetrists involved in the MWS to ensure that certain dosimetry criteria are considered: calculation of annual absorbed doses in the organs of interest, separation of low and high linear-energy transfer components, evaluation of uncertainties, and quality assurance and quality control. It is recognized that the MWS and its approaches to dosimetry are a work in progress and that there will be flexibility and changes in direction as new information is obtained with regard to both dosimetry and the epidemiologic features of the study components. This paper focuses on the description of the various components of the MWS, the available dosimetry results, and the challenges that have been encountered. It is expected that the Committee will complete its report in 2016.

Military participants at U.S. Atmospheric nuclear weapons testing--methodology for estimating dose and uncertainty

Methods were developed to calculate individual estimates of exposure and dose with associated uncertainties for a sub-cohort (1,857) of 115,329 military veterans who participated in at least one of seven series of atmospheric nuclear weapons tests or the TRINITY shot carried out by the United States. The tests were conducted at the Pacific Proving Grounds and the Nevada Test Site. Dose estimates to specific organs will be used in an epidemiological study to investigate leukemia and male breast cancer. Previous doses had been estimated for the purpose of compensation and were generally high-sided to favor the veteran's claim for compensation in accordance with public law. Recent efforts by the U.S. Department of Defense (DOD) to digitize the historical records supporting the veterans' compensation assessments make it possible to calculate doses and associated uncertainties. Our approach builds upon available film badge dosimetry and other measurement data recorded at the time of the tests and incorporates detailed scenarios of exposure for each veteran based on personal, unit, and other available historical records. Film badge results were available for approximately 25% of the individuals, and these results assisted greatly in reconstructing doses to unbadged persons and in developing distributions of dose among military units. This article presents the methodology developed to estimate doses for selected cancer cases and a 1% random sample of the total cohort of veterans under study.

[Mortality study among veterans with dosimeter monitoring during the French nuclear tests in the Pacific]

BACKGROUND

A mortality study was carried out in a cohort of veterans present on the sites of the French nuclear experiments center in the Pacific (CEP) from 1966 to 1996, and for whom external dosimeter monitoring recordings were available.

METHODS

The cohort included 32,550 veterans having had at least one dosimetry recording. Current vital status was collected from the National Register of Identification of Physical People and causes of death data from the national causes of death database. Total mortality and mortality by cause were compared with mortality of the French population using standardized mortality ratios (SMR). To test the effect of a dosimeter recording higher than the threshold (0.2 mSv), i.e., no null dosimetry, the mortality of veterans was compared inside the cohort, using standardized ratios and Poisson regression models.

RESULTS

The mortality analysis was performed among 26,524 men, of whom 8% had had at least one non-null dosimeter. Five thousand four hundred and ninety-two (21%) veterans died before December 31, 2008 and causes were available for nearly 97% of these deaths. Comparing the mortality between the cohort and the French population highlighted a deficit of mortality, for all causes, by cancer and for radiation-induced pathologies; these results were related to the "healthy worker effect". The data showed that all causes mortality and cancer mortality of the cohort of veterans with no null dosimeter were not different from those of other veterans, but also showed an excess of hematological malignancies in this sub-population: this excess was significant in the regression model (RR=1.82; CI 95% [1.6-2.0]).

CONCLUSION

Among veterans with an external dosimeter monitoring recording, presence on the sites of CEP from 1966 to 1996 does not constitute a factor of increased mortality compared with the national population. However, an increased risk was observed for mortality by hematological malignancies among veterans with no null dosimetry. This result is in line with studies on veterans present during nuclear experiments abroad.

Relationship between monoclonal gammopathy of undetermined significance and radiation exposure in Nagasaki atomic bomb survivors

Radiation exposure is a possible predisposing factor for monoclonal gammopathy of undetermined significance (MGUS), but the association has been uncertain. We investigated the relationship between radiation exposure and MGUS prevalence by using data from the M-protein screening for Nagasaki atomic bomb survivors between 1988 and 2004. Radiation exposure was assessed by exposure distance from the hypocenter and exposure radiation dose. We computed prevalence ratios (PRs) and the 95% confidence intervals (CIs) adjusting for exposure age and sex. A total of 1082 cases of MGUS were identified from 52 525 participants. MGUS prevalence was significantly higher in people exposed at distance within 1.5 km than beyond 3.0 km (PR, 1.4; 95% CI, 1.1-1.9) among those exposed at age 20 years or younger, but it was not found among those exposed at age 20 years or older. MGUS prevalence was also significantly higher in people exposed to more than 0.1 Gy than those exposed to less than 0.01 Gy (PR, 1.7; 95% CI, 1.0-2.8) among those exposed at age 20 years or younger. Thus, people exposed at younger age exhibited a significantly high risk of MGUS when exposed to a high radiation dose. There was no clear association between radiation exposure and the malignant progression of MGUS. Further detailed analysis is needed.

Radiation exposure due to local fallout from Soviet atmospheric nuclear weapons testing in Kazakhstan: solid cancer mortality in the Semipalatinsk historical cohort, 1960-1999

Little information is available on the health effects of exposures to fallout from Soviet nuclear weapons testing and on the combined external and internal environmental exposures that have resulted from these tests. This paper reports the first analysis of the Semipalatinsk historical cohort exposed in the vicinity of the Semipalatinsk nuclear test site, Kazakhstan. The cohort study, which includes 19,545 inhabitants of exposed and comparison villages of the Semipalatinsk region, was set up in the 1960s and comprises 582,750 person-years of follow-up between 1960 and 1999. Cumulative effective radiation dose estimates in this cohort range from 20 mSv to approximately 4 Sv. Rates of mortality and cancer mortality in the exposed group substantially exceeded those of the comparison group. Dose-response analyses within the exposed group confirmed a significant trend with dose for all solid cancers (P < 0.0001) and for digestive and respiratory cancers (P = 0.0255 and P < 0.0001), whereas no consistent dose-response trend was found for all causes of death (P = 0.4296). Regarding specific cancer sites, a significant trend with dose was observed for lung cancer (P = 0.0001), stomach cancer (P = 0.0050), and female breast cancer (P = 0.0040) as well as for esophagus cancer in women (P = 0.0030). The excess relative risk per sievert for all solid cancers combined was 1.77 (1.35; 2.27) based on the total cohort data, yet a selection bias regarding the comparison group could not be entirely ruled out. The excess relative risk per sievert based on the cohort's exposed group was 0.81 (0.46; 1.33) for all solid cancers combined and thus still exceeds current risk estimates from the Life Span Study. Future epidemiological assessments based on this cohort will benefit from extension of follow-up and ongoing validation of dosimetric data.

Epidemiological studies of UK test veterans: II. Mortality and cancer incidence

An epidemiological study was set up in the 1980s of UK participants in the UK atmospheric nuclear weapons testing programme. A large cohort of test participants was established along with a closely matched comparison or control group. Three analyses of mortality and cancer incidence have been carried out. This review describes the development of the evidence on possible effects on test participants with especial emphasis on the most recent analysis. Other sources of evidence, particularly from studies of other groups of test participants, are also considered. It was concluded that overall levels of mortality and cancer incidence in UK nuclear weapons test participants were similar to those in a matched control group, and overall mortality was lower than expected from national rates. There was no evidence of an increased raised risk of multiple myeloma among test participants in recent years, and the suggestion in the first analysis of this cohort of a raised myeloma risk relative to controls is likely to have been a chance finding. There was some evidence of a raised risk of leukaemia other than chronic lymphatic leukaemia among test participants relative to controls, particularly in the early years after the tests. Whilst this could be a chance finding, the possibility that test participation caused a small absolute risk of leukaemia other than chronic lymphatic leukaemia cannot be ruled out.

Under-ascertainment of multiple myeloma among participants in UK atmospheric atomic and nuclear weapons tests

An inter-comparison of cases of multiple myeloma among UK participants in the UK's atmospheric atomic and nuclear weapons tests ascertained by direct follow up methods detected at least a third more cases than a strategy relying solely on data linkage between the Office of National Statistics and the Service Records Offices. These finding have implications for the conduct and robustness of follow up studies of long term health effects among participants in nuclear weapons tests.

[Cancer mortality among Brazilian Navy personnel]

OBJECTIVE

To identify differences in cancer proportionate mortality among male servicemen of the Brazilian Navy when compared to a referent population and to detect potential occupational risk factors.

METHODS

Cancer proportionate mortality was estimated using death certificates and occupational histories of Brazilian navy servicemen aged 19 or more in the period of 1991 to 1995. The population of Rio de Janeiro (Brazil) was chosen as referent group because this city concentrates 70% of all Navy servicemen.

RESULTS

Servicemen are more likely to die from brain neoplasm (age-adjusted cancer proportionate mortality ratio - ACPMR=339.27), prostate cancer (ACPMR=135.04), and non-Hodgkin lymphoma (ACPMR=152.28) than the referent population. Health-related occupations show an excess of brain neoplasm (ACPMR=2.7, 95% confidence interval, CI: 1.1-6.5) and liver cancer (ACPMR=2.9; 95% CI: 1.1-7.8); colon-rectal cancer was higher among officials of the Army Corp and other administrative occupations (ACPMR=2.4, 95% CI: 1.3-4.5); larynx cancer (ACPMR=2.3, 95% CI; 1.1-5.0) is more common among men working in maintenance and repair occupations.

CONCLUSIONS

In this study, servicemen of the Brazilian Navy Force have a distinct cancer mortality profile from the general reference population. Risk factors for cancer need to be further evaluated, by using more specific diagnosis and occupational-related exposure data.

Cancer mortality among the highest exposed US atmospheric nuclear test participants

Of the estimated 205,000 military personnel who participated in the US atmospheric nuclear weapons testing program from 1945 to 1962, less than 1% had ionizing radiation doses that met or exceeded the current federal occupational guideline for dose of 5 rem (roentgen equivalents in humans) in a 12-month period. The objective of this study was to determine whether veterans who received the highest gamma radiation doses (n = 1010) have experienced increased cancer mortality compared with a group of Navy veterans who received a minimal radiation dose as participants of HARDTACK I (n = 2870). Mortality from all causes of death (relative risk, 1.22; 95% confidence interval, 1.04 to 1.44) and from all lymphopoietic cancers (relative risk, 3.72; 95% confidence interval, 1.28 to 10.83) was significantly elevated among the 5-rem cohort compared with the Navy controls. The lack of statistically significant excesses in deaths from many of the known radiogenic cancers suggests that the observed excess mortality may be the result of many factors, of which radiation exposure was only one.