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1.  Occupational risk factors for endometriosis in a cohort of flight attendants 
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.
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 (ORadj) and 95% confidence intervals (95% CI) for associations between exposures and endometriosis, adjusting for potential confounders.
Flight attendants and teachers were equally likely to report endometriosis (ORadj 1.0, 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 (ORadj 2.2, 1.1–4.2 for highest versus lowest quartile, P trend= 0.02) but block hours (taxi plus flight time) per year was not (ORadj 1.2, 95% CI 0.6–2.2 for highest versus lowest quartile, P trend=0.38).
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.
PMCID: PMC5193113  PMID: 26645630
circadian disruption; cohort; cohort study; endometriosis; flight attendant; occupational risk; radiation; risk factor; work schedule
2.  Miscarriage Among Flight Attendants 
Epidemiology (Cambridge, Mass.)  2015;26(2):192-203.
Cosmic radiation and circadian disruption are potential reproductive hazards for flight attendants.
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.
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 firsttrimester 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.
Miscarriage was associated with flight attendant work during sleep hours and high physical job demands and may be associated with cosmic radiation exposure.
PMCID: PMC4510952  PMID: 25563432
3.  Occupational exposures among nurses and risk of spontaneous abortion 
We investigated self-reported occupational exposure to antineoplastic drugs, anesthetic gases, antiviral drugs, sterilizing agents (disinfectants), and X-rays and the risk of spontaneous abortion in U.S. nurses.
Study Design
Pregnancy outcome and occupational exposures were collected retrospectively from 8,461 participants of the Nurses’ Health Study II. Of these, 7,482 were eligible for analysis using logistic regression.
Participants reported 6,707 live births, and 775 (10%) spontaneous abortions (<20 weeks). After adjusting for age, parity, shift work, and hours worked, antineoplastic drug exposure was associated with a 2-fold increased risk of spontaneous abortion, particularly with early spontaneous abortion before the 12th week, and 3.5-fold increased risk among nulliparous women. Exposure to sterilizing agents was associated with a 2-fold increased risk of late spontaneous abortion (12–20 weeks), but not with early spontaneous abortion.
This study suggests that certain occupational exposures common to nurses are related to risks of spontaneous abortion.
PMCID: PMC4572732  PMID: 22304790
antineoplastic agents; health personnel; occupational exposure; pregnancy
4.  Exposure Assessment at 30 000 Feet: Challenges and Future Directions 
Few studies of cancer mortality and incidence among flight crew have included a detailed assessment of both occupational exposures and lifestyle factors that may influence the risk of cancer. In this issue, Kojo et al. (Risk factors for skin cancer among Finnish airline cabin crew. Ann. Occup. Hyg 2013; 57: 695–704) evaluated the relative contributions of ultraviolet and cosmic radiation to the incidence of skin cancer in Finnish flight attendants. This is a useful contribution, yet the reason flight crew members have an increased risk of skin cancer compared with the general population remains unclear. Good policy decisions for flight crew will depend on continued and emerging effective collaborations to increase study power and improve exposure assessment in future flight crew health studies. Improving the assessment of occupational exposures and non-occupational factors will cost additional time and effort, which are well spent if the role of exposures can be clarified in larger studies.
PMCID: PMC4509733  PMID: 23818455
cosmic radiation; exposure assessment; flight crew; skin cancer; ultraviolet radiation
5.  Occupational factors and risk of preterm birth in nurses 
We evaluated the risk of first-trimester exposures among nurses and the risk of preterm birth among participants of the Nurses’ Health Study II.
Study Design
Log binomial regression was used to estimate the relative risk (RR) for preterm birth in relation to occupational risk factors, adjusting for age, parity, work schedule, physical factors, and exposures to chemicals and x-rays.
Part-time work (<= 20 hours a week) was associated with a lower risk for preterm birth [RR=0.7, 95% confidence interval (CI) = 0.6–0.9]. Self-reported exposure to sterilizing agents was associated with an increased risk (RR=1.9, 95% CI = 1.1–3.4). Other exposures, including shift work, physical factors, anesthetic gases, antineoplastic drugs, antiviral drugs, and x-ray radiation were not associated with risk of preterm birth.
These data suggest that sterilizing agents may be related to preterm birth, while physically demanding work and work schedule are not strong predictors.
PMCID: PMC4249587  PMID: 18976732
Nurses; Occupational Exposure; Pregnancy; Preterm Birth; Work Schedule Tolerance
6.  Airline Pilot Cosmic Radiation and Circadian Disruption Exposure Assessment from Logbooks and Company Records 
Annals of Occupational Hygiene  2011;55(5):465-475.
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 (Ptrend < 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.
PMCID: PMC3113148  PMID: 21610083
circadian disruption; cosmic radiation; exposure assessment; flight crew; pilots
7.  Workgroup Report: Implementing a National Occupational Reproductive Research Agenda—Decade One and Beyond 
Environmental Health Perspectives  2005;114(3):435-441.
The initial goal of occupational reproductive health research is to effectively study the many toxicants, physical agents, and biomechanical and psychosocial stressors that may constitute reproductive hazards in the workplace. Although the main objective of occupational reproductive researchers and clinicians is to prevent recognized adverse reproductive outcomes, research has expanded to include a broader spectrum of chronic health outcomes potentially affected by reproductive toxicants. To aid in achieving these goals, the National Institute for Occupational Safety and Health, along with its university, federal, industry, and labor colleagues, formed the National Occupational Research Agenda (NORA) in 1996. NORA resulted in 21 research teams, including the Reproductive Health Research Team (RHRT). In this report, we describe progress made in the last decade by the RHRT and by others in this field, including prioritizing reproductive toxicants for further study; facilitating collaboration among epidemiologists, biologists, and toxicologists; promoting quality exposure assessment in field studies and surveillance; and encouraging the design and conduct of priority occupational reproductive studies. We also describe new tools for screening reproductive toxicants and for analyzing mode of action. We recommend considering outcomes such as menopause and latent adverse effects for further study, as well as including exposures such as shift work and nanomaterials. We describe a broad domain of scholarship activities where a cohesive system of organized and aligned work activities integrates 10 years of team efforts and provides guidance for future research.
PMCID: PMC1392239  PMID: 16507468
communication; environmental exposure; occupational exposure; reproduction; research design; risk factors
8.  An occupational reproductive research agenda for the third millennium. 
Environmental Health Perspectives  2003;111(4):584-592.
There is a significant public health concern about the potential effects of occupational exposure to toxic substances on reproductive outcomes. Several toxicants with reported reproductive and developmental effects are still in regular commercial or therapeutic use and thus present potential exposure to workers. Examples of these include heavy metals, organic solvents, pesticides and herbicides, and sterilants, anesthetic gases, and anticancer drugs used in health care. Many other substances are suspected of producing reproductive or developmental toxicity but lack sufficient data. Progress has been limited in identifying hazards and quantifying their potencies and in separating the contribution of these hazards from other etiologic factors. Identifying the causative agents, mechanisms by which they act, and any potential target populations, present the opportunity to intervene and protect the reproductive health of workers. The pace of laboratory studies to identify hazards and to underpin the biologic plausibility of effects in humans has not matched the pace at which new chemicals are introduced into commerce. Though many research challenges exist today, recent technologic and methodologic advances have been made that allow researchers to overcome some of these obstacles. The objective of this article is to recommend future directions in occupational reproductive health research. By bridging interdisciplinary gaps, the scientific community can work together to improve health and reduce adverse outcomes.
PMCID: PMC1241449  PMID: 12676620

Results 1-8 (8)