Increased frequency of chromosome translocations in airline pilots with long-term flying experience.

BACKGROUND: Chromosome translocations are an established biomarker of cumulative exposure to external ionising radiation. Airline pilots are exposed to cosmic ionising radiation, but few flight crew studies have examined translocations in relation to flight experience. METHODS: We determined the frequency of translocations in the peripheral blood lymphocytes of 83 airline pilots and 50 comparison subjects (mean age 47 and 46 years, respectively). Translocations were scored in an average of 1039 cell equivalents (CE) per subject using fluorescence in situ hybridisation (FISH) whole chromosome painting and expressed per 100 CE. Negative binomial regression models were used to assess the relationship between translocation frequency and exposure status and flight years, adjusting for age, diagnostic x ray procedures, and military flying. RESULTS: There was no significant difference in the adjusted mean translocation frequency of pilots and comparison subjects (0.37 (SE 0.04) vs 0.38 (SE 0.06) translocations/100 CE, respectively). However, among pilots, the adjusted translocation frequency was significantly associated with flight years (p = 0.01) with rate ratios of 1.06 (95% CI 1.01 to 1.11) and 1.81 (95% CI 1.16 to 2.82) for a 1- and 10-year incremental increase in flight years, respectively. The adjusted rate ratio for pilots in the highest compared to the lowest quartile of flight years was 2.59 (95% CI 1.26 to 5.33). CONCLUSIONS: Our data suggests that pilots with long-term flying experience may be exposed to biologically significant doses of ionising radiation. Epidemiological studies with longer follow-up of larger cohorts of pilots with a wide range of radiation exposure levels are needed to clarify the relationship between cosmic radiation exposure and cancer risk.

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.

Spontaneous abortion, sex ratio, and paternal occupational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

There is conflicting research regarding an association between fetal death and paternal exposure to Agent Orange, a phenoxy herbicide widely used in Vietnam that was contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Men who worked in the U.S. factories that produced Agent Orange were exposed to TCDD at levels hundreds of times higher than TCDD levels in the general population. Wives of TCDD-exposed chemical workers and wives of nonexposed neighborhood referents were interviewed to determine reproductive history. Paternal serum TCDD level at time of conception was estimated for each pregnancy using serum samples taken in 1987. Estimated TCDD levels of workers during or after exposure were high (median, 254 ppt; range, 3-16,340 ppt) compared to referent levels (median, 6 ppt; range, 2-19 ppt). No association between paternal TCDD level at the time of conception and spontaneous abortion was observed among pregnancies fathered by workers with TCDD levels of < 20 ppt [odds ratio (OR) = 0.77; 95% confidence interval (CI), 0.48-1.22], 20 to < 255 ppt (OR = 0.81; 95% CI, 0.40-1.63), 255 to < 1,120, (OR = 0.69; 95% CI, 0.30-1.58), and >or= 1,120 ppt (OR = 0.95; 95% CI, 0.42-2.17) compared to pregnancies fathered by referents. The sex ratio [males/(males + females)] of offspring also did not differ by TCDD exposure (0.53 and 0.54 among workers and referents, respectively). We did not find an association between paternal serum TCDD level and spontaneous abortion or sex ratio of offspring in this population. The estimated TCDD levels in this exposed worker population were much higher than in other studies, providing additional evidence that paternal TCDD exposure does not increase the risk of spontaneous abortion at levels above those observed in the general population. The study could not evaluate the effect of father's childhood or prenatal TCDD exposure on subsequent sex ratio.

Hemoglobin adducts and sister chromatid exchanges in hospital workers exposed to ethylene oxide: effects of glutathione S-transferase T1 and M1 genotypes.

Ethylene oxide (EtO) is a genotoxic carcinogen with widespread uses as an industrial chemical intermediate and sterilant. We examined the effects of glutathione S-transferase T1 (GSTT1) and M1 (GSTM1) genotypes on the levels of N-(2-hydroxyethyl)valine (HEV) adducts in the erythrocytes and sister chromatid exchange (SCE) in lymphocytes from a group of 58 operators of sterilizers that used EtO and nonexposed workers from nine hospitals in the United States and one hospital in Mexico City. Cumulative exposure to EtO was estimated during the 4-month period before the collection of blood samples. Results showed that EtO exposure was significantly associated with the levels of HEV adducts and SCE after adjusting for cigarette smoking and other potential confounders. A significantly higher HEV adduct level (0.17 +/- 0.03 versus 0.08 +/- 0.01, mean +/- SE; P = 0.02) but lower SCE frequency (5.31 +/- 0.39 versus 6.21 +/- 0.17; P = 0.04) was observed in subjects with homozygous deletion of the GSTT1 gene (null genotype) as compared with those with at least one copy of the gene (positive genotype). In multiple regression analysis, the GSTT1-null genotype was associated with an increase in HEV adduct level (beta = 1.62; P = 0.02) and a decrease in SCE frequency (beta = -1.25; P = 0.003) after adjusting for age, gender, race, education, cigarette smoking, and EtO exposure status. The inverse SCE-GSTT1 relationship remained unchanged when SCE was further examined in relation to HEV adducts as an indicator of the internal EtO dose. The GSTM1 genotype was not associated with the level of either HEV adduct or SCE. These data indicate that the GSTT1-null genotype is associated with increased formation of EtO-hemoglobin adducts in relation to occupational EtO exposure, suggesting that individuals with homozygous deletion of the GSTT1 gene may be more susceptible to the genotoxic effects of ETO: The unexpected finding of decreased SCEs, which is less clear, may be attributed to the nonchemical specificity of this end point and the lack of expression of the GSTT1 enzyme in lymphocytes.

Menstrual and reproductive risk factors for ischemic heart disease.

The role of hormones in ischemic heart disease is of considerable interest, but limited data are available pertaining to risk factors associated with endogenous hormones. We examined the association between menstrual and reproductive factors and ischemic heart disease in a cohort of 867 white, college-educated women who prospectively recorded menstrual cycle data for at least 5 years from their early 20s through their menopause. Ischemic heart disease history was obtained from a self-administered (N = 714) or proxy-administered (N = 153) questionnaire completed at a mean age of 73 years. The analysis included 44,899 person-years of follow-up and 45 cases of myocardial infarction, angioplasty, heart bypass surgery, or ischemic heart disease-related mortality. Ischemic heart disease risk decreased with increasing age at menarche (age-adjusted RR 0.76 per year, 95% CI = 0.60-0.95). Considering menstrual cycle characteristics ages 28-32, there was little overall association with length, variability, or bleeding duration. Ischemic heart disease risk increased with later age at first birth (age-adjusted RR 2.90 for ages 33-43 compared with 25-29) and later age at last birth (age-adjusted RR 3.79 for ages > or =40 compared with 35-39), but there was little association with high parity.

Elevated blood lead levels in children of construction workers.

OBJECTIVES: This study examined whether children of lead-exposed construction workers had higher blood lead levels than neighborhood control children. METHODS: Twenty-nine construction workers were identified from the New Jersey Adult Blood Lead Epidemiology and Surveillance (ABLES) registry. Eighteen control families were referred by workers. Venous blood samples were collected from 50 children (31 exposed, 19 control subjects) under age 6. RESULTS: Twenty-six percent of workers children had blood lead levels at or over the Centers for Disease Control and Prevention action level of 0.48 mumol/L (10 micrograms/dL), compared with 5% of control children (unadjusted odds ratio = 6.1; 95% confidence interval = 0.9, 147.2). CONCLUSIONS: Children of construction workers may be at risk for excessive lead exposure. Health care providers should assess parental occupation as a possible pathway for lead exposure of young children.

Elevated lead contamination in homes of construction workers.

National Institute for Occupational Safety and Health investigators studied lead exposures among 37 families of construction workers; 22 neighborhood families with no known lead exposures were included for comparison. Workers were identified as having blood lead levels at or above 25 micrograms/dL. This article reports the levels of lead contamination on hands and interior surfaces of homes and automobiles of study participants. Results indicate that the hands of lead-exposed workers were seven times more contaminated with lead compared with control workers; no difference was found between exposed and control family members' hands. Surface lead contamination was significantly higher in automobiles driven by the lead-exposed workers; some locations, such as armrests, were 10 times more contaminated for the exposed group. High lead loadings in lead workers' automobiles were found on the driver's floor (geometric mean [GM] = 1100 micrograms/m2), driver's armrest (2000 micrograms/m2), and passenger's armrest (1200 micrograms/m2). Surface lead concentrations were significantly higher for exposed homes compared with control homes in rooms where work clothing was changed (GM = 370 versus 120 ppm; p = 0.005). While environmental sources of lead were also evaluated, study results strongly suggest that construction workers' occupational exposures together with poor hygiene practices were the primary causes of lead contamination. Requirements intended to prevent "take-home" lead exposures were reported by workers in this study to be infrequently followed by employers. These findings may be limited in representativeness since only highly exposed workers were selected from a specific geographic area. Regardless, targeted education and enforcement efforts are necessary to help ensure that preventive measures are adequately practiced throughout the construction industry.

Association of physical and behavioral characteristics with menstrual cycle patterns in women age 29-31 years.

We examined the association between menstrual cycle characteristics (cycle length, variability, and bleeding length) and physical and behavioral attributes in 766 women age 29-31 years. Menstrual cycle data were prospectively recorded as part of the Menstruation and Reproductive History Study of college women in Minnesota, begun by Alan Treloar in 1934. Data on lifetime height, weight, physical activity, alcohol and caffeine consumption, and smoking history were collected in 1990 using a self-administered questionnaire. Cycle variability, as measured by the standard deviation of the cycle length, was increased, and menstrual cycles > or = 42 days in length were more common among women in the lowest quartile of Quetelet index [odds ratio (OR) for long cycle = 1.6;95% confidence interval (CI) = 0.82-3.0] and among the most physically active (OR = 1.7;95% CI = 0.93-3.1). Long menstrual cycles were less common (OR = 0.40;95% CI = 0.22-0.73) among women who drank alcohol than among nondrinkers. Variable or long menstrual cycles may reflect anovulation and relatively low levels of estrogen exposure. We would expect, based on our data, reduced estrogen exposure among lean women, physically active women, and those who do not consume alcohol. These findings suggest an explanation for the reported associations between these factors and breast cancer risk.

Evaluation of reproductive function among men occupationally exposed to a stilbene derivative: I. Hormonal and physical status.

This is the first of two reports describing a National Institute for Occupational Safety and Health (NIOSH) Health Hazard Evaluation conducted in response to complaints of impotence and decreased libido among male employees who manufactured 4,4'-diaminostilbene-2,2' disulfonic acid (DAS; CAS 81-11-8), an intermediate in the manufacture of fluorescent whitening agents. DAS is structurally similar to the synthetic estrogen diethylstilbestrol (DES). Levels of six reproductive hormones in 30 male workers who manufactured DAS (current DAS workers) and 20 former DAS workers were compared to levels of 35 workers who manufactured plastics additives. Current and former DAS workers had lower mean total testosterone (TT) levels compared to additives workers (458 and 442, respectively, vs. 556 ng/dL; p = 0.05 and 0.04). Current and former DAS workers were 3.6 (95% CI, 0.5-24.4) and 2.2 (95% CI, 0.3-18.0) times more likely than additives workers to have lowest quartile TT levels (< 386 ng/dL) after adjustment for age and body mass index. Duration of employment in DAS production was negatively related to the workers' testosterone levels. These data suggest that occupational DAS exposure may be associated with alterations in male reproductive hormone levels.

Evaluation of reproductive function among men occupationally exposed to a stilbene derivative: II. Perceived libido and potency.

This is the second of two reports of a National Institute for Occupational Safety and Health (NIOSH) Health Hazard Evaluation conducted in response to complaints of sexual dysfunction among men who manufacture the stilbene derivative 4,4'-diaminostilbene-2,2'-disulfonic acid (DAS; CAS 81-11-8), an intermediate in the manufacture of fluorescent whitening agents. The first report [Grajewski et al. (1995): Am J Ind Med 29:53-61] describes results of the analysis of reproductive hormone levels. This second report provides results from the analysis of perceived libido and potency. In a cross-sectional design, self-reported sexual function of 30 male workers who manufacture DAS and 20 former DAS workers was compared to that of 35 workers who manufactured plastics additives in a different manufacturing area. Questionnaire items were examined by factor analysis, reducing the data to these components of sexual function: sexual activity/performance (two factors), interest, satisfaction, and physiologic competence. Adjusting for age, currently exposed workers were more likely than unexposed workers to have a value in the lowest quartile for interest (adjusted odds ratio [OR] = 1.9, 95% confidence interval [CI] 0.5-7.2), physiologic competence (adjusted OR = 1.9, 95% CI 0.6-6.4), and activity/performance factor II (adjusted OR = 5.8, 95% CI 1.3-27.3). Former DAS workers reported problems associated with activity/performance factors I and II compared to unexposed workers (adjusted OR = 2.2, 95% CI 0.5-10.1 and adjusted OR = 6.7, 95% CI 1.2-35.9, respectively). Although the small study size limits the precision of the effect estimates, the pattern of results suggests a possible effect on sexual function of working in the DAS manufacturing area.

Menstrual cycle patterns and risk of breast cancer.

Menstrual cycle characteristics may reflect underlying endocrine patterns that influence the risk of breast cancer. Most previous studies of menstrual function and breast cancer risk have used retrospective reports of menstrual bleeding, which may be unreliable. To examine this association, the authors conducted a mail survey among 997 women who had recorded menstrual events prospectively over as many as 50 years, beginning in 1934. Compared with women with a median menstrual cycle length of 26-29 days, women who had cycles of extreme length at ages 25-29 years had a nearly twofold increased incidence of breast cancer (for a median cycle length of less than 26 days, adjusted relative risk (RR) = 1.9, 95% CI 0.9-4.1; for > or = 34 days, RR = 1.9, 95% CI 0.9-3.9). Statistical adjustment was made for age, family history of breast cancer, parity, age at menopause, age at first pregnancy, and Quetelet index (weight (kg)/height (m)2). Adjusting for age and other potential confounders and restricting the analysis to women who did not use hormones, women who experienced either a lesser (< 150) or a greater (> 350) cumulative number of cycles had an increased incidence of breast cancer (adjusted RR = 1.9, 95% CI 0.3-10.6, and RR = 1.8, 95% CI 0.5-6.0, respectively) compared with women who experienced 150-350 cycles. The findings are discussed in the context of current hormonal theories of breast cancer etiology.

Maternal employment and reproductive risk factors.

Studies of reproductive hazards in the workplace must address potential biases related to selection for employment. The National Natality Survey, a probability sample of live births to married women in 1980, was used to examine the relation between female employment during pregnancy and factors that might affect reproductive outcome by analyzing the 5,927 women with complete occupational data. Demographic and behavioral attributes as well as reproductive history were compared for the 3,712 women employed and the 2,215 women not employed during pregnancy. Employed mothers were of more optimal reproductive age, were more highly educated, had higher incomes, began prenatal care earlier, had greater weight gain during pregnancy, and were slightly less likely to be heavy smokers. Employed women had markedly fewer previous births and less favorable reproductive histories (more stillbirths, miscarriages, and induced abortions) than unemployed women, controlling for gravidity. Full- and part-time workers were similar with regard to demographic and behavioral characteristics, but part-time workers had higher parity. Differences were noted by employment sector: professional women had especially favorable demographic and behavioral traits, and women employed as operatives and service workers were less advantaged. These results indicate that substantial differences in pregnancy-related risk factors exist in relation to employment, with working women generally having more favorable demographic and behavioral characteristics and less favorable reproductive histories. This pattern could produce selection bias in studies of work and reproductive health, and it encourages the restriction of comparison groups to other employed women, with a need to consider heterogeneity among working women as well.

Menstrual and reproductive characteristics and age at natural menopause.

Data from women who enrolled between 1935 and 1939 in a long-term prospective study of menstrual and reproductive health, in which menstrual cycles and other events were recorded as they occurred, were analyzed to examine factors associated with age at natural menopause. Analysis was restricted to 561 women who enrolled before age 25 years and recorded data through at least age 44 years. Women with a median cycle length that was less than 26 days at ages 20-35 years reached menopause 1.4 years earlier than those with cycles between 26 and 32 days. The difference in mean menopausal age between women with short cycle length (less than 26 days) and women with long cycle length (33 days or longer) was 2.2 years. Women who had ever been pregnant reached menopause slightly, but statistically significantly, later than women who had never been pregnant. Similarly, women who had ever had a live birth had a slightly later age at menopause compared with nulliparous women. A trend of later age at menopause with increasing parity was also observed. There was no association with age at menarche. Certain of these observations are consistent with proposed mechanisms of cessation of menstrual function.

Self-reported exposure to pesticides and radiation related to pregnancy outcome--results from National Natality and Fetal Mortality Surveys.

Although fetal development is known to be sensitive to environmental agents, relatively little epidemiologic research has addressed this concern. Effects on pregnancy outcome of self-reported parental exposure to pesticides and to radiation were examined using data from the National Natality and Fetal Mortality Surveys, large national probability samples of live births and stillbirths occurring in 1980. In case-control analyses, maternal exposure to pesticides at home or work was associated with increased risk of stillbirth (odds ratios (ORs) = 1.5-1.6). Paternal pesticide exposure was associated with stillbirth (ORs = 1.2-1.4) and delivery of small-for-gestational-age infants (ORs = 1.4-2.0). A small increased risk of stillbirth (OR = 1.3) was found in relation to either parent's reported exposure to radiation. In spite of limitations in the quality of exposure data and the possibility of biased recall related to pregnancy outcome, associations of reported pesticide exposure to either parent with risk of stillbirth and small-for-gestational-age infants warrant further evaluation.

Effect of parents' occupational exposures on risk of stillbirth, preterm delivery, and small-for-gestational-age infants.

Epidemiologic research on the effects of parental occupational exposures on fetal development has been limited. The National Natality and Fetal Mortality surveys obtained applicable data on probability samples of live births and fetal deaths which occurred in the US in 1980 among married women. Analyses were conducted for case groups of stillbirths (2,096 mothers, 3,170 fathers), preterm deliveries (less than 37 weeks completed gestation) (363 mothers, 552 fathers), and small-for-gestational-age infants (218 mothers, 371 fathers) compared with controls. Occupational exposures were defined by industry of employment and by imputed exposures based on a job-exposure linkage system. For stillbirth, maternal work in the rubber, plastics, and synthetics industry (odds ratio (OR) = 1.8, 95% confidence interval (Cl) 0.8-4.0) and lead exposure (OR = 1.6, 95% Cl 0.8-3.1), and paternal employment in the textile industry (OR = 1.9, 95% Cl 1.2-2.9), had the largest odds ratios. Preterm birth was most strongly associated with maternal lead exposure (OR = 2.3, 95% Cl 0.7-7.0), corroborating previous findings. Twofold increased risk of preterm delivery was found with paternal employment in the glass, clay, and stone; textile; and mining industries. Paternal exposures to x-rays and polyvinyl alcohol were associated with 1.5-fold increase in risk. The occupation of the mother was not associated with delivery of a small-for-gestational-age infant, in contrast to paternal employment in the art (OR = 2.6, 95% Cl 1.2-5.6) and textile industries (OR = 2.5, 95% Cl 1.3-4.7). Several toxic agents were associated with risk elevation of 1.3 or greater for fathers, most notably benzene (OR = 1.5, 95% Cl 1.1-2.3). In spite of limitations in the exposure data, the size of the exposed populations, and possible confounding, the results in this study encourage further evaluation of the effects of maternal exposure to lead and possibly solvents, as well as paternal exposure in the textile industry and to x-rays and benzene.