Linear and non-linear dose-response relationships between radiation absorbed dose to the lung from internally deposited uranium and external sources and circulatory system disease (CSD) mortality ...were examined in a cohort of 23 731 male and 5552 female US uranium enrichment workers.
Rate ratios (RRs) for categories of lung dose and linear excess relative rates (ERRs) per unit lung dose were estimated to evaluate the associations between lung absorbed dose and death from ischaemic heart disease (IHD) and cerebrovascular disease.
There was a suggestion of modestly increased IHD risk in workers with internal uranium lung dose above 1 milligray (mGy) (RR=1.4, 95% CI 0.76 to 2.3) and a statistically significantly increased IHD risk with external dose exceeding 150 mGy (RR=1.3, 95% CI 1.1 to 1.6) compared with the lowest exposed groups. ERRs per milligray were positive for IHD and uranium internal dose and for both outcomes per gray external dose, although the CIs generally included the null.
Non-linear dose-response models using restricted cubic splines revealed sublinear responses at lower internal doses, suggesting that linear models that are common in radioepidemiological cancer studies may poorly describe the association between uranium internal dose and CSD mortality.
The primary objective of this work was to characterize employee exposure to radon and progeny while performing guide/interpretation and concessions duties in a tourist cavern. Radon gas and progeny ...concentrations, fraction of unattached progeny, and other environmental parameters were evaluated in a popular tourist cavern in Southeastern New Mexico. Alpha-track detectors were used to measure radon gas in several cavern locations during a 9-mo period. Additionally, radon gas and attached and unattached fractions of radon progeny were measured at three primary cavern work locations during a 1-d period using a SARAD EQF 3220. Radon gas concentrations in the cavern were elevated due to extremely low air exchange rates with substantial seasonal variation. Mean measured radon concentrations ranged from 970 to 2,600 Bq m-3 in the main cavern and from 5,400 to 6,000 Bq m-3 in a smaller cave associated with the regional cave system. Measurements of unattached fractions (0.40-0.60) were higher than those commonly found in mines and other workplaces, leading to the potential for relatively high worker dose. Although radon gas concentrations were below the Occupational Safety and Health Administration Permissible Exposure Limit, employees working in the cavern have the potential to accrue ionizing radiation dose in excess of the annual effective dose limit recommended by the National Council on Radiation Protection and Measurements due to a high unattached fraction of radon progeny. There was a strong negative correlation between unattached fractions and equilibrium factors, but these parameters should be further evaluated for seasonal variation. Introduction of engineering controls such as ventilation could damage the cavern environment, so administrative controls, such as time management, are preferred to reduce employee dose.
Background
Flight attendants may have an increased risk of some cancers from occupational exposure to cosmic radiation and circadian disruption.
Methods
The incidence of thyroid, ovarian, and uterine ...cancer among ∼6000 female flight attendants compared to the US population was evaluated via life table analyses. Associations of these cancers, melanoma, and cervical cancer with cumulative cosmic radiation dose and metrics of circadian disruption were evaluated using Cox regression.
Results
Incidence of thyroid, ovarian, and uterine cancer was not elevated. No significant, positive exposure‐response relations were observed. Weak, non‐significant, positive relations were observed for thyroid cancer with cosmic radiation and time zones crossed and for melanoma with another metric of circadian disruption.
Conclusions
We found little evidence of increased risk of these cancers from occupational cosmic radiation or circadian disruption in female flight attendants. Limitations include few observed cases of some cancers, limited data on risk factors, and misclassification of exposures.
Objective
To examine dose‐response relationships between internal uranium exposures and select outcomes among a cohort of uranium enrichment workers.
Methods
Cox regression was conducted to examine ...associations between selected health outcomes and cumulative internal uranium with consideration for external ionizing radiation, work‐related medical X‐rays and contaminant radionuclides technetium (99Tc) and plutonium (239Pu) as potential confounders.
Results
Elevated and monotonically increasing mortality risks were observed for kidney cancer, chronic renal diseases, and multiple myeloma, and the association with internal uranium absorbed organ dose was statistically significant for multiple myeloma. Adjustment for potential confounders had minimal impact on the risk estimates.
Conclusion
Kidney cancer, chronic renal disease, and multiple myeloma mortality risks were elevated with increasing internal uranium absorbed organ dose. The findings add to evidence of an association between internal exposure to uranium and cancer. Future investigation includes a study of cancer incidence in this cohort.
Miscarriage Among Flight Attendants Grajewski, Barbara; Whelan, Elizabeth A.; Lawson, Christina C. ...
Epidemiology,
2015-March, Volume:
26, Issue:
2
Journal Article
Peer reviewed
Open access
BACKGROUND:Cosmic radiation and circadian disruption are potential reproductive hazards for flight attendants.
METHODS:Flight attendants from 3 US airlines in 3 cities were interviewed for pregnancy ...histories and lifestyle, medical, and occupational covariates. We assessed cosmic radiation and circadian disruption from company records of 2 million individual flights. Using Cox regression models, we compared respondents (1) by levels of flight exposures and (2) to teachers from the same cities, to evaluate whether these exposures were associated with miscarriage.
RESULTS:Of 2654 women interviewed (2273 flight attendants and 381 teachers), 958 pregnancies among 764 women met study criteria. A hypothetical pregnant flight attendant with median first-trimester exposures flew 130 hours in 53 flight segments, crossed 34 time zones, and flew 15 hours during her home-base sleep hours (10 pm–8 am), incurring 0.13 mGy absorbed dose (0.36 mSv effective dose) of cosmic radiation. About 2% of flight attendant pregnancies were likely exposed to a solar particle event, but doses varied widely. Analyses suggested that cosmic radiation exposure of 0.1 mGy or more may be associated with increased risk of miscarriage in weeks 9–13 (odds ratio = 1.7 95% confidence interval = 0.95–3.2). Risk of a first-trimester miscarriage with 15 hours or more of flying during home-base sleep hours was increased (1.5 1.1–2.2), as was risk with high physical job demands (2.5 1.5–4.2). Miscarriage risk was not increased among flight attendants compared with teachers.
CONCLUSIONS:Miscarriage was associated with flight attendant work during sleep hours and high physical job demands and may be associated with cosmic radiation exposure.
In retrospective epidemiological studies of large cohorts of workers exposed to radioactive materials, it is often necessary to analyze large numbers of bioassay data sets containing censored values, ...or values recorded as less than a detection limit. Censored bioassay data create problems for all bioassay analysis methods, including analytical techniques based on least-squares regression to estimate intakes. A method is presented here that uses a simple empirically-derived equation for imputing replacement values for urine uranium concentration results reported as zero or less than a detection limit, that produces minimal bias in intakes estimated using least-square regression methods with the assumption of lognormally distributed measurement errors.
Pooling of individual-level data for workers involved in uranium refining and processing (excluding enrichment) may provide valuable insights into risks from occupational uranium and external ...ionizing radiation exposures.
Data were pooled for workers from four uranium processing facilities (Fernald, Mallinckrodt and Middlesex from the U.S.; and Port Hope, Canada). Employment began as early as the 1930s and follow-up was as late as 2017. Workers were exposed to high concentrations of uranium, radium, and their decay products, as well as gamma radiation and ambient radon decay products. Exposure and outcome data were harmonized using similar definitions and dose reconstruction methods. Standardized mortality ratios (SMR) were estimated.
In total, 560 deaths from lung cancer, 503 non-malignant respiratory diseases, 67 renal diseases, 1,596 ischemic heart diseases, and 101 dementia and Alzheimer's disease (AD) were detected in the pooled cohort of over 12,400 workers (∼1,300 females). Mean cumulative doses were 45 millisievert for whole-body external ionizing radiation exposure and 172 milligray for lung dose from radon decay products. Only SMR for dementia and AD among males was statistically significant (SMR=1.29; 95% confidence interval: 1.04, 1.54).
This is the largest study to date to examine long-term health risks of uranium processing workers.
Objective The aim of this study was to examine the association of breast cancer incidence with cosmic radiation dose and circadian rhythm disruption in a cohort of 6093 US female flight attendants. ...Methods The association of breast cancer risk with cumulative cosmic radiation dose, time spent working during the standard sleep interval, and time zones crossed (all lagged by ten years), adjusted for non-occupational breast cancer risk factors, was evaluated using Cox regression. Individual exposure estimates were derived from work history data and domicile- and era-specific exposure estimates. Breast cancers were identified from telephone interviews and state cancer registries, and covariate data were obtained from telephone interviews. Results Breast cancer incidence in the overall cohort was not associated with exposure. Positive associations in breast cancer incidence were observed with all three exposures only among the 884 women with parity of ≥3. Adjusted excess relative risks for women with parity of ≥3 were 1.6 95% confidence interval (95% CI) 0.14–6.6, 0.99 (95% CI -0.04–4.3), and 1.5 (95% CI 0.14–6.2) per 10 mGy, per 2000 hours spent working in the standard sleep interval, and per 4600 time zones crossed (the approximate means of the fourth exposure quintiles among breast cancer cases), respectively. Conclusions Positive exposure–response relations, although observed only in a small subset of the cohort, were robust. Future studies of breast cancer incidence among other workers with circadian rhythm disruption should assess interaction with parity to see if our findings are confirmed.
After a nuclear detonation, workers and volunteers providing first aid, decontamination, and population monitoring in public shelters and community reception centers will potentially be exposed to ...radiation from people they are assisting who may be contaminated with radioactive fallout. A state-of-the-art computer-aided design program and radiation transport modeling software were used to estimate external radiation dose to workers in three different exposure scenarios: performing radiation surveys/decontamination, first aid, and triage duties. Calculated dose rates were highest for workers performing radiation surveys due to the relative proximity to the contaminated individual. Estimated cumulative doses were nontrivial but below the occupational dose limit established for normal operations by the Occupational Safety and Health Administration.
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.
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