Mortality in a combined cohort of uranium enrichment workers.

OBJECTIVE: To examine the patterns of cause-specific mortality and relationship between internal exposure to uranium and specific causes in a pooled cohort of 29,303 workers employed at three former uranium enrichment facilities in the United States with follow-up through 2011. METHODS: Cause-specific standardized mortality ratios (SMRs) for the full cohort were calculated with the U.S. population as referent. Internal comparison of the dose-response relation between selected outcomes and estimated organ doses was evaluated using regression models. RESULTS: External comparison with the U.S. population showed significantly lower SMRs in most diseases in the pooled cohort. Internal comparison showed positive associations of absorbed organ doses with multiple myeloma, and to a lesser degree with kidney cancer. CONCLUSION: In general, these gaseous diffusion plant workers had significantly lower SMRs than the U.S. POPULATION: The internal comparison however, showed associations between internal organ doses and diseases associated with uranium exposure in previous studies. Am. J. Ind. Med. 60:96-108, 2017. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Retrospective cohort study of a microelectronics and business machine facility.

OBJECTIVES: We examined health outcomes among 34,494 workers employed at a microelectronics and business machine facility 1969-2001. METHODS: Standardized mortality ratio (SMR) and standardized incidence ratios were used to evaluate health outcomes in the cohort and Cox regression modeling to evaluate relations between scores for occupational exposures and outcomes of a priori interest. RESULTS: Just over 17% of the cohort (5,966 people) had died through 2009. All cause, all cancer, and many cause-specific SMRs showed statistically significant deficits. In hourly males, SMRs were significantly elevated for non-Hodgkin's lymphoma and rectal cancer. Salaried males had excess testicular cancer incidence. Pleural cancer and mesothelioma excesses were observed in workers hired before 1969, but no available records substantiate use of asbestos in manufacturing processes. A positive, statistically significant relation was observed between exposure scores for tetrachloroethylene and nervous system diseases. CONCLUSIONS: Few significant exposure-outcome relations were observed, but risks from occupational exposures cannot be ruled out due to data limitations and the relative youth of the cohort.

Retrospective assessment of exposure to chemicals for a microelectronics and business machine manufacturing facility.

A retrospective exposure assessment was performed for use in a health outcomes study of a facility manufacturing circuit boards, business machines, and other equipment during the years 1969-2002. A matrix was developed identifying chemical use by department-year based on company-provided information. Use of six chemical agents (fiberglass, lead, methylene chloride, methyl chloroform, perchloroethylene, and trichloroethylene) and six chemical classes (acid-base, aromatic hydrocarbons, chlorinated hydrocarbons, other hydrocarbons, chlorofluorocarbons, and metals), and general (including unspecified) chemicals was identified. The matrix also contained an assignment for each department-year categorizing the potential for use of chemicals as negligible, intermittent/incidental, or routine. These department-based exposure matrix data were combined with work history data to provide duration of potential chemical use for workers. Negligible, intermittent/incidental or routine extent-of-chemical-use categories comprised 42.6%, 39.4%, and 17.9%, respectively, of total person-years of employment. Cumulative exposure scores were also developed, representing a relative measure of the cumulative extent of potential exposure to the six chemical agents, six chemical classes, and general (including unspecified) chemicals. Additionally, the study period was divided into manufacturing eras showing trends in chemical use, and showing that process use of trichloroethylene and methylene chloride ended in the mid-1980s and the mid-1990s, respectively. This approach may be useful in other assessments addressing a variety of chemicals, and with data constraints common to retrospective chemical exposure studies.

Mortality and ionising radiation exposures among workers employed at the Fernald Feed Materials Production Center (1951-1985).

OBJECTIVES: To examine mortality patterns and dose-response relations between ionising radiation and mortality outcomes of a priori interest in 6409 uranium workers employed for at least 30 days (1951-1985), and followed through 2004. METHODS: Cohort mortality was evaluated through standardised mortality ratios (SMR). Linear excess relative risk (ERR) regression models examined associations between cause-specific mortality and exposures to internal ionising radiation from uranium deposition, external gamma and x-ray radiation, and radon decay products, while adjusting for non-radiologic covariates. RESULTS: Person-years at risk totalled 236 568 (mean follow-up 37 years), and 43% of the cohort had died. All-cause mortality was below expectation only in salaried workers. Cancer mortality was significantly elevated in hourly males, primarily from excess lung cancer (SMR=1.25, 95% CI 1.09 to 1.42). Cancer mortality in salaried males was near expectation, but lymphohaematopoietic malignancies were significantly elevated (SMR=1.52, 95% CI 1.06 to 2.12). A positive dose-response relation was observed for intestinal cancer, with a significant elevation in the highest internal organ dose category and a significant dose-response with organ dose from internal uranium deposition (ERR=1.5 per 100 µGy, 95% CI 0.12 to 4.1). CONCLUSIONS: A healthy worker effect was observed only in salaried workers. Hourly workers had excess cancer mortality compared with the US population, although there was little evidence of a dose-response trend for any cancer evaluated except intestinal cancer. The association between non-malignant respiratory disease and radiation dose observed in previous studies was not apparent, possibly due to improved exposure assessment, different outcome groupings, and extended follow-up.

A nested case-control study of multiple myeloma risk and uranium exposure among workers at the Oak Ridge Gaseous Diffusion Plant.

The primary risk factors of multiple myeloma are age, race and sex, but several studies have found an association between radiological hazards and multiple myeloma. The purpose of this nested case-control study was to investigate whether workers with chronic low-level exposure to internally deposited uranium at the Oak Ridge Gaseous Diffusion Plant in eastern Tennessee were at higher risk of dying of multiple myeloma than those without occupational exposure to uranium, with the consideration of potential confounders of external ionizing radiation and occupational chemical hazards such as mercury, nickel and trichloroethylene. The main analyses were carried out using conditional logistic regression on 98 cases and 490 controls (five controls matched to each case on gender, race and age at risk). Our study showed a weak association between internal uranium dose estimated from urinalysis results and multiple myeloma risk: OR = 1.04 (95% CI 1.00-1.09) at 10 microGy with the inclusion of other risk factors. The parameter estimates and the corresponding odds ratios were very similar when internal doses were imputed for subjects without urine samples. Further studies that include updating this cohort and combining with workers from other gaseous diffusion plants are needed to investigate the relationship between multiple myeloma risk and radiation or other chemical exposures.

Chronic lymphocytic leukaemia and radiation: findings among workers at five US nuclear facilities and a review of the recent literature.

The aetiology of chronic lymphocytic leukaemia (CLL) is largely unknown. Despite compelling evidence for ionising radiation as a cause of most forms of leukaemia, CLL was not found to be radiogenic in early studies. Herein we describe the recent evidence for causation of CLL by ionising and non-ionising radiation, including a nested case-control study conducted within a cohort of 94 517 US workers at four nuclear weapons facilities and a nuclear naval shipyard. Forty-three cases of CLL deaths and 172 age-matched controls were identified with follow-up up to between 1990 and 1996. Radiation exposure from external sources and plutonium (lagged 10 years) was assessed for each worker, based on monitoring records. The excess relative rate (ERR) was estimated for workers receiving elevated doses compared to unexposed workers, controlling for possible risk factors. The ERR per 10 mSv was -0.020 (95% confidence interval: <0, 0.14) based on all exposed workers. However, for workers receiving <100 mSv, the ERR per 10 mSv was 0.20 (-0.035, 0.96). Recent studies of uranium miners and other populations have shown elevations of CLL possibly associated with ionising and non-ionising radiation. New studies should use incident cases and sufficient latency to account for the expected lengthy induction period for CLL.

Risk of chronic myeloid and acute leukemia mortality after exposure to ionizing radiation among workers at four U.S. nuclear weapons facilities and a nuclear naval shipyard.

A nested case-control study was conducted among workers at five U.S. nuclear facilities to evaluate leukemia mortality risk (excluding chronic lymphocytic) from ionizing radiation using worksite doses and adjusting for potential confounding. Conditional logistic regression was used to estimate the relative risk (RR) of exposed workers and the excess relative risk (ERR) per unit of radiation among 206 cases and 823 age-matched controls. Adjusting for sex and benzene, the RR of leukemia for workers receiving more than 10 mSv was higher compared to those receiving lower or no dose; however, the risk increase was attenuated in the highest dose group. The ERR per 10 mSv was 1.44% (95% CI: < -1.03%, 7.59%) but was higher for workers born after 1921 compared to workers born earlier or when excluding leukemias of uncertain type. Excluding the 7% who were high-dose workers (> 100 mSv), the sex- and benzene-adjusted ERR per 10 mSv was 6.82% (95% CI: -2.87%, 24.1%). The results suggest that risks among these nuclear workers are comparable to those observed in high-dose populations, although no evidence was observed of a positive quadratic dose-response term in this study. This large study is among the first to jointly evaluate benzene and ionizing radiation risk.

Internal exposure to uranium in a pooled cohort of gaseous diffusion plant workers.

Intakes and absorbed organ doses were estimated for 29 303 workers employed at three former US gaseous diffusion plants as part of a study of cause-specific mortality and cancer incidence in uranium enrichment workers. Uranium urinalysis data (>600 000 urine samples) were available for 58 % of the pooled cohort. Facility records provided uranium gravimetric and radioactivity concentration data and allowed estimation of enrichment levels of uranium to which workers may have been exposed. Urine data were generally recorded with facility department numbers, which were also available in study subjects' work histories. Bioassay data were imputed for study subjects with no recorded sample results (33 % of pooled cohort) by assigning department average urine uranium concentration. Gravimetric data were converted to 24-h uranium activity excretion using department average specific activities. Intakes and organ doses were calculated assuming chronic exposure by inhalation to a 5-µm activity median aerodynamic diameter aerosol of soluble uranium. Median intakes varied between 0.31 and 0.74 Bq d(-1) for the three facilities. Median organ doses for the three facilities varied between 0.019 and 0.051, 0.68 and 1.8, 0.078 and 0.22, 0.28 and 0.74, and 0.094 and 0.25 mGy for lung, bone surface, red bone marrow, kidneys, and liver, respectively. Estimated intakes and organ doses for study subjects with imputed bioassay data were similar in magnitude.

Exposure assessment for a cohort of workers at a former uranium processing facility.

Exposure was assessed for a cohort of 6409 workers at a former uranium processing facility as part of a mortality study. Workers at the facility had potential for exposure to a wide variety of radiological and chemical agents including uranium, thorium, radon, external ionizing radiation, acid mists, asbestos, and various solvents. Organ dose from internal exposure to uranium was assessed, along with dose from external ionizing radiation and exposure to radon. Qualitative assessment of exposure to thorium, acid mists, asbestos, coal dust, welding fumes, and other chemicals was also performed. Mean cumulative organ dose from internal uranium exposure ranged from 1.1 mGy (lung) to 6.7 µGy (pancreas). Mean cumulative external ionizing radiation dose was 13.4 mGy. Mean cumulative radon exposure was 26 working level months (WLMs). The chemical agents to which the largest numbers of study subjects were exposed were acid mists, machining fluids, and a tributyl phosphate/kerosene mixture used in the refining process.