Barbara Grajewski

Video Display Terminals and the Risk of Spontaneous Abortion

BACKGROUND The relation between spontaneous abortion and the use of video display terminals (VDTs) is of great public health concern. Previous investigators of this issue have reported inconsistent findings. METHODS To determine whether electromagnetic fields emitted by VDTs are associated with an increased risk of spontaneous abortion, a cohort of female telephone operators who used VDTs at work was compared with a cohort of operators who did not use VDTs. To obtain reliable estimates of exposure, we determined the number of hours of VDT use per week from company records and measured electromagnetic fields at VDT workstations and, for purposes of comparison, at workstations without VDTs. Operators who used VDTs had higher abdominal exposure to very-low-frequency (15 kHz) electromagnetic fields (workstations without VDTs did not emit very-low-frequency energy). Abdominal exposure to extremely-low-frequency fields (45 to 60 Hz) was similar for both operators who used VDTs and those who did not. Among 2430 women interviewed, there were 882 pregnancies that met our criteria for inclusion in the study. RESULTS We found no excess risk of spontaneous abortion among women who used VDTs during the first trimester of pregnancy (odds ratio = 0.93; 95 percent confidence interval, 0.63 to 1.38), and no dose-response relation was apparent when we examined the womens hours of VDT use per week (odds ratio for 1 to 25 hours per week = 1.04; 95 percent confidence interval, 0.61 to 1.79; odds ratio for greater than 25 hours per week = 1.00; 95 percent confidence interval, 0.61 to 1.64). There continued to be no risk associated with the use of VDTs when we accounted for multiple pregnancies, conducted separate analyses of early abortion, late abortion, and all fetal losses, or limited our analyses to spontaneous abortions for which a physician was consulted. CONCLUSIONS The use of VDTs and exposure to the accompanying electromagnetic fields were not associated with an increased risk of spontaneous abortion in this study.

Work schedule during pregnancy and spontaneous abortion.

Background: There is inconsistent evidence as to whether work schedule (including rotating shifts and night work) can affect reproductive outcomes. Methods: We investigated the association between work schedule and risk of spontaneous abortion in U.S. nurses. The Nurses’ Health Study II is a prospective cohort study established in 1989. In 2001, information about occupational activities and exposures during pregnancy was collected from female nurses for the most recent pregnancy since 1993. Of 11,178 eligible respondents, 9547 (85%) indicated willingness to participate in the occupational study, and 8461 of those (89%) returned the questionnaire, for an overall participation rate of 76%. Of these, 7688 women had pregnancies that were eligible for analysis. Results: Participants reported 6902 live births and 786 (10%) spontaneous abortions. Compared with women who reported usually working “days only” during their first trimester, women who reported usually working “nights only” had a 60% increased risk of spontaneous abortion (RR = 1.6; 95% confidence interval [CI] = 1.3–1.9). A rotating schedule, with or without night shifts, was not associated with an increase in risk (RR = 1.2 [CI = 0.9–1.5] and 1.0 [CI = 0.8–1.2], respectively). Women who reported working more than 40 hours per week during the first trimester were also at increased risk of spontaneous abortion (1.5; 1.3–1.7) compared with women working 21–40 hours, even after adjustment for work schedule. Conclusions: Nightwork and long work hours may be associated with an increased risk of spontaneous abortion. Further studies are needed to determine whether hormonal disturbances attributed to night work affect pregnancy outcome.

Prevalence of respiratory symptoms among female flight attendants and teachers

Background: Potential health effects of the indoor environment in office buildings and aircraft have generated considerable concern in recent years. Aims: To analyse the prevalence of self reported respiratory symptoms and illnesses in flight attendants (FAs) and schoolteachers. Methods: Data were collected as part of a study of reproductive health among female FAs. The prevalences of work related eye, nose, and throat symptoms, wheezing, physician diagnosed asthma, chest illness, and cold or flu were calculated and stratified by smoking status in 1824 FAs and 331 schoolteachers. Results: FAs and teachers were significantly more likely to report work related eye (12.4% and 7.4 %, respectively), nose (15.7% and 8.1%), and throat symptoms (7.5% and 5.7%) than were other working women (2.9% eye, 2.7% nose, and 1.3% throat symptoms). FAs were significantly more likely than teachers and referent working women to report chest illness during the prior three years (32.9%, 19.3%, 7.2%, respectively). Both study groups were more likely to report five or more episodes of cold or flu in the past year than were other working women (10.2% of FAs, 8.2% of teachers, 2.3% of referents), and both groups were more likely to report wheezing than other working women (22.8% of FAs, 28.4% of teachers, 16.4% of referents). FAs were significantly less likely than teachers and other working women to report ever having been diagnosed with asthma (8.2%, 13.3%, 11.8%, respectively). Conclusions: Overall, FAs and schoolteachers report a higher prevalence of work related upper respiratory symptoms, chest illness, and cold or flu than the general working population.

Semen Quality and Hormone Levels Among Radiofrequency Heater Operators

Approximately 9,000,000 US workers are occupationally exposed to radiofrequency (RF) radiation; over 250,000 operate RF dielectric heaters. Our purpose was to determine whether male RF heater operators experience increased adverse reproductive effects reflected in reduced semen quality or altered hormone levels. We measured incident RF heater radiation exposures and RF-induced foot currents at four companies. For 12 male heater operators and a comparison group of 34 RF-unexposed men, we measured 33 parameters of semen quality and four serum hormones. Despite wide variation in individual exposure levels, near field strengths and induced foot currents did not exceed current standard levels and guidelines. We observed minor semen quality and hormonal differences between the groups, including a slightly higher mean follicle-stimulating hormone level for exposed operators (7.6 vs 5.8 mIU/mL). Further occupational studies of RF-exposed men may be warranted.

Mortality from cancer and other causes in commercial airline crews: a joint analysis of cohorts from 10 countries

Background Commercial airline crew is one of the occupational groups with the highest exposures to ionising radiation. Crew members are also exposed to other physical risk factors and subject to potential disruption of circadian rhythms. Methods This study analyses mortality in a pooled cohort of 93 771 crew members from 10 countries. The cohort was followed for a mean of 21.7 years (2.0 million person-years), during which 5508 deaths occurred. Results The overall mortality was strongly reduced in male cockpit (SMR 0.56) and female cabin crews (SMR 0.73). The mortality from radiation-related cancers was also reduced in male cockpit crew (SMR 0.73), but not in female or male cabin crews (SMR 1.01 and 1.00, respectively). The mortality from female breast cancer (SMR 1.06), leukaemia and brain cancer was similar to that of the general population. The mortality from malignant melanoma was elevated, and significantly so in male cockpit crew (SMR 1.57). The mortality from cardiovascular diseases was strongly reduced (SMR 0.46). On the other hand, the mortality from aircraft accidents was exceedingly high (SMR 33.9), as was that from AIDS in male cabin crew (SMR 14.0). Conclusions This large study with highly complete follow-up shows a reduced overall mortality in male cockpit and female cabin crews, an increased mortality of aircraft accidents and an increased mortality in malignant skin melanoma in cockpit crew. Further analysis after longer follow-up is recommended.

The NIOSH/FAA working women's health study : Evaluation of the cosmic-radiation exposures of flight attendants

Air crew are exposed to elevated levels of cosmic ionizing radiation of galactic and solar origin and are among the more highly exposed occupational groups to ionizing radiation in the United States. Depending on flight route patterns, the annual dose may range from 0.2 to 5 mSv. By comparison, the average annual radiation dose equivalent of occupationally exposed adults in the United States is estimated to be 1.1 mSv. Cosmic-radiation dose depends primarily on altitude and geomagnetic latitude and to a lesser degree on solar activity. Although the International Commission on Radiological Protection has recommended that air crew exposures to natural radiation in-flight be treated as occupational exposures, United States flight crew exposures to natural cosmic radiation are not regulated or typically monitored. There are approximately 148,000 air crew (flight deck crew and flight attendants) in the United States.

Job Stress Among Female Flight Attendants

We evaluated the presence of chronic job stressors among flight attendants (FAs) to examine the relationships between these job stressors and psychological distress and job dissatisfaction. Seventy-three female FAs (90% participation) employed at two commercial airlines completed a detailed questionnaire. Standard questions and scale measures were used to assess job stressors, psychological distress, and job dissatisfaction. The association between job stressors and these outcomes was evaluated using multiple regression analysis. Except for fatigue, distress and job dissatisfaction were moderate to low. Job stressors were found to have a substantive effect on these outcomes, following adjustment for individual factors. Despite moderate-to-low levels of distress and dissatisfaction, targeted efforts to reduce selected job stressors and to enhance social support may be important steps toward improving the well-being and satisfaction of FAs.

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.

Cause‐specific mortality among a cohort of U.S. flight attendants

BACKGROUND We evaluated mortality among 11,311 former U.S. flight attendants. The primary a priori outcomes of interest were breast cancer and melanoma. METHODS Vital status was ascertained through 2007, and life table analyses was conducted. Cumulative exposure to cosmic radiation and circadian rhythm disruption were estimated from work history data and historical published flight schedules. RESULTS All-cause mortality was less than expected among women but was elevated among men, primarily due to elevated HIV-related disease mortality. Mortality from breast cancer among women and melanoma was neither significantly elevated nor related to metrics of exposure. Mortality was elevated for non-Hodgkins lymphoma among men; for alcoholism, drowning, and intentional self-harm among women; and for railway, water, and air transportation accidents. CONCLUSIONS We found no evidence of increased breast cancer or melanoma mortality. Limitations include reliance on mortality data and limited power resulting from few melanoma deaths and relatively short employment durations.

Work with video display terminals and the risk of reduced birthweight and preterm birth

To determine whether the use of video display terminals (VDTs) is associated with an increased risk of reduced birthweight (RBW) and preterm birth, a cohort of telephone operators who used VDTs at work was compared to a cohort of non-VDT-users. Among 2,430 women interviewed, 713 eligible singleton live births were reported. Exposure was estimated from company records and a representative sample of electromagnetic fields was measured at the VDT workstations. For RBW (< or = 2,800 g), we found no excess risk associated with any VDT use during pregnancy (odds ratio [OR] = 0.9; 95% confidence interval [CI] = 0.5-1.7). For preterm birth (< or = 37 weeks), we similarly found no excess risk (OR = 0.7; 95% CI = 0.4-1.1). The risks estimated did not change substantially when hours working with VDTs were used as exposure variables. By contrast, increased risks were found for several known risk factors for LBW and preterm birth. We conclude that occupational VDT use does not increase the risk of RBW and preterm birth.