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.

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.

Airline pilot cosmic radiation and circadian disruption exposure assessment from logbooks and company records.

OBJECTIVES: US commercial airline pilots, like all flight crew, are at increased risk for specific cancers, but the relation of these outcomes to specific air cabin exposures is unclear. Flight time or block (airborne plus taxi) time often substitutes for assessment of exposure to cosmic radiation. Our objectives were to develop methods to estimate exposures to cosmic radiation and circadian disruption for a study of chromosome aberrations in pilots and to describe workplace exposures for these pilots. METHODS: Exposures were estimated for cosmic ionizing radiation and circadian disruption between August 1963 and March 2003 for 83 male pilots from a major US airline. Estimates were based on 523 387 individual flight segments in company records and pilot logbooks as well as summary records of hours flown from other sources. Exposure was estimated by calculation or imputation for all but 0.02% of the individual flight segments' block time. Exposures were estimated from questionnaire data for a comparison group of 51 male university faculty. RESULTS: Pilots flew a median of 7126 flight segments and 14 959 block hours for 27.8 years. In the final study year, a hypothetical pilot incurred an estimated median effective dose of 1.92 mSv (absorbed dose, 0.85 mGy) from cosmic radiation and crossed 362 time zones. This study pilot was possibly exposed to a moderate or large solar particle event a median of 6 times or once every 3.7 years of work. Work at the study airline and military flying were the two highest sources of pilot exposure for all metrics. An index of work during the standard sleep interval (SSI travel) also suggested potential chronic sleep disturbance in some pilots. For study airline flights, median segment radiation doses, time zones crossed, and SSI travel increased markedly from the 1990s to 2003 (P(trend) < 0.0001). Dose metrics were moderately correlated with records-based duration metrics (Spearman's r = 0.61-0.69). CONCLUSIONS: The methods developed provided an exposure profile of this group of US airline pilots, many of whom have been exposed to increasing cosmic radiation and circadian disruption from the 1990s through 2003. This assessment is likely to decrease exposure misclassification in health studies.

Tenth revision U.S. mortality rates for use with the NIOSH Life Table Analysis System.

OBJECTIVE: The objective of this study was to update rate files for the NIOSH Life Table Analysis System for Personal Computers (PC LTAS) reflecting the newly adopted tenth revision changes to the International Classification of Diseases. METHODS: PC LTAS allows researchers to conduct comparative mortality and morbidity analyses for the purpose of identifying disease-exposure associations using person-time-at-risk for age, race, sex, and calendar time-specific reference rates from 1940. Previously available through 1998, files for the United States and individual states were updated through 2004 using uncensored population data. Tenth revision causes were added if compatible with earlier NIOSH death categories, based on revisions 5 through 9. A few new cause categories were added. RESULTS: The resulting NIOSH categories are described for two new U.S. rate files: 1960 through 2004 and 1940 through 2004. CONCLUSION: The new U.S. rate files are available online or on request.

Polychlorinated biphenyls and neurodegenerative disease mortality in an occupational cohort.

BACKGROUND: Production of polychlorinated biphenyls (PCBs) ended in the United States in the 1970s, but PCBs persist in the environment and are detectable in the blood of approximately 80% of Americans over age 50. PCBs decrease dopamine levels in rats and monkeys. Loss of dopamine is the hallmark of Parkinson disease, a neurodegenerative disease. There are no epidemiologic studies of PCBs and neurodegenerative disease. METHODS: We conducted a retrospective mortality study of 17,321 PCB-exposed workers to determine whether mortality from Parkinson disease, dementia, and amyotrophic lateral sclerosis was elevated compared with the U.S. population. All workers had a least 90 days employment in 1 of 3 electrical capacitor plants using PCBs from the 1940s to the 1970s. PCB serum levels from a sample of these workers in the 1970s were approximately 10 times the level of community controls. RESULTS: We found no overall excess of Parkinson disease, amyotrophic lateral sclerosis, or dementia in the PCB-exposed cohort (standardized mortality ratios [SMRs]-1.40, 1.11, and 1.26, respectively, and number of deaths-14, 10, and 28 respectively). However, sex-specific analyses revealed that women had an excess of amyotrophic lateral sclerosis (SMR-2.26; 95% confidence interval [CI] = 1.08-4.15; 10 deaths). Furthermore, among highly exposed women (defined by a job-exposure matrix), we found an excess of Parkinson disease (SMR-2.95; 95% CI = 1.08-6.42; 6 deaths) and dementia (SMR-2.04; 95% CI = 1.12-3.43; 14 deaths). CONCLUSIONS: Our data are limited due to small numbers and reliance on mortality rather than incidence data, but are suggestive of an effect of PCBs on neurodegenerative disease for women. The literature does not offer an explanation for why women would be more affected than men by PCB exposure for these outcomes.