Chih-Yu Tseng

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

Abstract Schubauer-Berigan, M. K., Daniels, R. D., Fleming, D. A., Markey, A. M., Couch, J. R., Ahrenholz, S. H., Burphy, J. S., Anderson, J. L. and Tseng, C-Y. 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. Radiat. Res. 167, 222–232 (2007). 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.

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.

Miscarriage among flight attendants.

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.

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.

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.

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.

Flight Attendant Radiation Dose from Solar Particle Events

INTRODUCTION Research has suggested that work as a flight attendant may be related to increased risk for reproductive health effects. Air cabin exposures that may influence reproductive health include radiation dose from galactic cosmic radiation and solar particle events. This paper describes the assessment of radiation dose accrued during solar particle events as part of a reproductive health study of flight attendants. METHODS Solar storm data were obtained from the National Oceanic and Atmospheric Administration Space Weather Prediction Center list of solar proton events affecting the Earth environment to ascertain storms relevant to the two study periods (1992-1996 and 1999-2001). Radiation dose from exposure to solar energetic particles was estimated using the NAIRAS model in conjunction with galactic cosmic radiation dose calculated using the CARI-6P computer program. RESULTS Seven solar particle events were determined to have potential for significant radiation exposure, two in the first study period and five in the second study period, and over-lapped with 24,807 flight segments. Absorbed (and effective) flight segment doses averaged 6.5 μGy (18 μSv) and 3.1 μGy (8.3 μSv) for the first and second study periods, respectively. Maximum doses were as high as 440 μGy (1.2 mSv) and 20 flight segments had doses greater than 190 μGy (0.5 mSv). DISCUSSION During solar particle events, a pregnant flight attendant could potentially exceed the equivalent dose limit to the conceptus of 0.5 mSv in a month recommended by the National Council on Radiation Protection and Measurements.

Exposure to Recycled Uranium Contaminants in Gaseous Diffusion Plants

As part of an ongoing study of health effects in a pooled cohort of gaseous diffusion plant workers, organ dose from internal exposure to uranium was evaluated. Due to the introduction of recycled uranium into the plants, there was also potential for exposure to radiologically significant levels of 99Tc, 237Np and 238,239Pu. In the evaluation of dose response, these radionuclide exposures could confound the effect of internal uranium. Using urine bioassay data for study subjects reported in facility records, intakes and absorbed dose to bone surface, red bone marrow and kidneys were estimated as these organs were associated with a priori outcomes of interest. Additionally, 99Tc intakes and doses were calculated using a new systemic model for technetium and compared to intakes and doses calculated using the current model recommended by the International Commission on Radiological Protection. Organ absorbed doses for the transuranics were significant compared to uranium doses; however, 99Tc doses calculated using the new systemic model were significant as well. Use of the new model resulted in an increase in 99Tc-related absorbed organ dose of a factor of 8 (red bone marrow) to 30 (bone surface).

Occupational Risk Factors for Endometriosis in a Cohort of Flight Attendants

OBJECTIVES This study aimed to (i) compare odds of endometriosis in a cohort of flight attendants against a comparison group of teachers and (ii) investigate occupational risk factors for endometriosis among flight attendants. METHODS We included 1945 flight attendants and 236 teachers aged 18-45 years. Laparoscopically confirmed endometriosis was self-reported via telephone interview, and flight records were retrieved from airlines to obtain work schedules and assess exposures for flight attendants. We used proportional odds regression to estimate adjusted odds ratios (OR adj) and 95% confidence intervals (95% CI) for associations between exposures and endometriosis, adjusting for potential confounders. RESULTS Flight attendants and teachers were equally likely to report endometriosis (OR adj1.0, 95% CI 0.5-2.2). Among flight attendants, there were no clear trends between estimated cosmic radiation, circadian disruption, or ergonomic exposures and endometriosis. Greater number of flight segments (non-stop flights between two cities) per year was associated with endometriosis (OR adj2.2, 1.1-4.2 for highest versus lowest quartile, P trend= 0.02) but block hours (taxi plus flight time) per year was not (OR adj1.2, 95% CI 0.6-2.2 for highest versus lowest quartile, P trend=0.38). CONCLUSION Flight attendants were no more likely than teachers to report endometriosis. Odds of endometriosis increased with number of flight segments flown per year. This suggests that some aspect of work scheduling is associated with increased risk of endometriosis, or endometriosis symptoms might affect how flight attendants schedule their flights.

0113 Occupational risk factors for endometriosis among flight attendants

Objectives Previous studies suggest that flight attendants could have a higher risk for endometriosis than women in other occupations. Our objectives were to compare the rate of endometriosis among flight attendants to the rate in a comparison group of teachers, and to investigate occupational risk factors for endometriosis among flight attendants. Method We included 1780 flight attendants and 240 teachers aged 18–45 at enrollment. Endometriosis diagnosis was self-reported via telephone interview, and records of individual flights were retrieved from airlines to obtain work schedules and assess exposures for flight attendants. Cox regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for associations between exposures and endometriosis, adjusting for body mass index at interview and using age as time scale. Results Flight attendants were no more likely to report endometriosis than teachers (adjusted OR 1.3, 95% CI 0.7–2.3). Among flight attendants, there were no clear trends between yearly cosmic radiation exposure, hours worked during normal sleeping hours, or ergonomic factors and endometriosis. A greater number of flights per day (adjusted OR 2.0, 95% CI 1.2–3.3 for 3+ versus 1 flights/day, p trend = 0.007) and fewer time zones crossed per flight (adjusted OR 2.0, 95% CI 1.0–3.7 for 0 vs. 2+ time zones/flight, p trend = 0.04) were associated with a higher rate of endometriosis. Conclusions The rate of endometriosis increased with number of flights and decreased with time zones crossed, which might be surrogates for exposures specific to flying a series of short flights during the workday.