Exposures to environmental phenols in Southern California firefighters and findings of elevated urinary benzophenone-3 levels

Firefighters are at increased risk for exposure to toxic chemicals compared to the general population, but few studies of this occupational group have included biomonitoring. We measured selected phenolic chemicals in urine collected from 101 Southern California firefighters. The analytes included bisphenol A (BPA), triclosan, benzophenone-3 (BP-3), and parabens, which are common ingredients in a range of consumer products. BP-3, BPA, triclosan, and methyl paraben were detected in almost all study subjects (94-100%). The BP-3 geometric mean for firefighters was approximately five times higher than for a comparable National Health and Nutrition Examination Survey (NHANES) subgroup. Demographic and exposure data were collected from medical records and via a questionnaire, and covariates were examined to assess associations with BP-3 levels. BP-3 levels were elevated across all firefighter age groups, with the highest levels observed in the 35 to 39year old group. Body fat percentage had a significant inverse association with BP-3 concentrations. Our results indicate pervasive exposure to BP-3, BPA, triclosan, and methyl paraben in this population of firefighters, consistent with studies of other populations. Further research is needed to investigate possible explanations for the higher observed BP-3 levels, such as occupational or California-specific exposures.

Factors associated with serum polybrominated diphenyl ether (PBDE) levels among school-age children in the CHAMACOS cohort

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants historically used in textiles, furniture, and electronic products. Recent studies have documented widespread PBDE exposure to humans, with higher levels measured in children than adults. We analyzed 10 tri- to hepta-BDE congener levels in blood collected from 7-year old Mexican-American children living in an agriculture community in California (n = 272). The most frequently detected PBDE congeners in child serum were BDE-47, -99, -100, and -153, all of which were measured in >99% of the children. We used multiple linear regression models to examine associations between child total PBDE levels (ng/g lipid) and determinants of exposure. Factors positively associated with higher PBDE levels in the children were total PBDE levels in maternal serum during pregnancy, duration of exclusive breastfeeding, and having no safe places to play in their neighborhood. Child BMI was inversely associated with serum PBDE levels (regression p-values <0.05). Our findings confirm that exposure to the penta-BDE mixture is ongoing, and that Mexican-American children living in California may be experiencing higher PBDE exposure from their environment compared to children sampled from the general U.S. population. Additional research is needed to assess the health impacts of these exposures.

A comparison of PBDE serum concentrations in Mexican and Mexican-American children living in California

BACKGROUND

Polybrominated diphenyl ethers (PBDE), which are used as flame retardants, have been found to be higher in residents of California than of other parts of the United States.

OBJECTIVES

We aimed to investigate the role of immigration to California on PBDE levels in Latino children.

METHODS

We compared serum PBDE concentrations in a population of first-generation Mexican-American 7-year-old children (n = 264), who were born and raised in California [Center for Health Analysis of Mothers and Children of Salinas (CHAMACOS) study], with 5-year-old Mexican children (n = 283), who were raised in the states in Mexico where most CHAMACOS mothers had originated (Proyecto Mariposa).

RESULTS

On average, PBDE serum concentrations in the California Mexican-American children were three times higher than their mothers' levels during pregnancy and seven times higher than concentrations in the children living in Mexico. The PBDE serum concentrations were higher in the Mexican-American children regardless of length of time their mother had resided in California or the duration of the child's breast-feeding. These data suggest that PBDE serum concentrations in these children resulted primarily from postnatal exposure.

CONCLUSIONS

Latino children living in California have much higher PBDE serum levels than their Mexican counterparts. Given the growing evidence documenting potential health effects of PBDE exposure, the levels in young children noted in this study potentially present a major public health challenge, especially in California. In addition, as PBDEs are being phased out and replaced by other flame retardants, the health consequences of these chemical replacements should be investigated and weighed against their purported fire safety benefits.

Determinants of serum polybrominated diphenyl ether (PBDE) levels among pregnant women in the CHAMACOS cohort

We measured levels of 10 polybrominated diphenyl ether (PBDE) congeners in serum collected during pregnancy and at delivery from 416 pregnant, predominantly immigrant, women living in Monterey County, CA. The most frequently detected congeners were BDE-47, -99, -100, and -153, all components of the penta mixture, detected in >97% of samples. We used multivariable regression models to examine factors associated with exposure to individual PBDE congeners as well as their total summed concentration (ng/g lipid). Prenatal and delivery total PBDE levels were correlated between sampling times (n = 21; Pearson r = 0.99, p < 0.001). In multivariable models, total PBDE levels increased significantly with time residing in the U.S. (p < 0.001) and among women with ≥3 pieces of stuffed furniture in their homes (p < 0.05). Women's total PBDE levels increased 4.0% (95% CI = 2.8, 5.3) for each additional year residing in the U.S., after adjustment for prepregnancy BMI, weight gain during pregnancy, and SES. Having ≥3 pieces of stuffed furniture in the home was associated with a 26.8% (95% CI = 2.0, 57.5) increase in women's serum PBDE levels. Findings suggest PBDE indoor contamination in California homes is contributing to human exposures in a population of recent immigrants.

Serum persistent organic pollutants and duration of lactation among Mexican-American women

BACKGROUND

Research suggests that estrogenic endocrine-disrupting chemicals interfere with lactation.

OBJECTIVES

(1) to determine if estrogenic persistent organic pollutants (POPs) are associated with shortened lactation duration; (2) to determine whether previous breastfeeding history biases associations.

METHODS AND RESULTS

We measured selected organochlorines and polychlorinated biphenyls (p, p'-DDE, p, p'-DDT, o, p'-DDT, beta-hexachlorocyclohexane, hexachlorobenzene, and PCBs 44, 49, 52, 118, 138, 153, and 180) in serum from 366 low-income, Mexican-American pregnant women living in an agricultural region of California and assessed breastfeeding duration by questionnaires. We found no association between DDE, DDT, or estrogenic POPs with shortened lactation duration, but rather associations for two potentially estrogenic POPs with lengthened lactation duration arose (HR [95% CI]: 0.6 [0.4, 0.8] for p, p'-DDE & 0.8 [0.6, 1.0] for PCB 52). Associations between antiestrogenic POPs (PCBs 138 and 180) and shortened lactation duration were attributed to a lactation history bias.

CONCLUSION

Estrogenic POPs were not associated with shortened lactation duration, but may be associated with longer lactation duration.

Comparison of current-use pesticide and other toxicant urinary metabolite levels among pregnant women in the CHAMACOS cohort and NHANES

BACKGROUND

We measured 34 metabolites of current-use pesticides and other precursor compounds in urine samples collected twice during pregnancy from 538 women living in the Salinas Valley of California, a highly agricultural area (1999-2001). Precursors of these metabolites included fungicides, carbamate, organochlorine, organophosphorus (OP), and pyrethroid insecticides, and triazine and chloroacetanilide herbicides. We also measured ethylenethiourea, a metabolite of the ethylene-bisdithiocarbamate fungicides. Repeat measurements of the compounds presented here have not been reported in pregnant women previously. To understand the impact of the women's regional environment on these findings, we compared metabolite concentrations from the CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas) cohort with U.S. national reference data for 342 pregnant women sampled by the National Health and Nutrition Examination Survey (1999-2002).

RESULTS

The eight metabolites detected in > 50% of samples [2,4-dichlorophenol (2,4-DCP); 2,5-dichlorophenol (2,5-DCP); 1- and 2-naphthol; ortho-phenylphenol (ORTH); para-nitrophenol (PNP); 2,4,6-trichlorophenol (2,4,6-TCP); and 3,4,6-trichloro-2-pyridinol (TCPy)] may be related to home or agricultural pesticide use in the Salinas Valley, household products, and other sources of chlorinated phenols. More than 78% of women in this study had detectable levels of at least one of the OP pesticide-specific metabolites that we measured, and > 30% had two or more. The 95th percentile values of six of the most commonly detected (> 50%) compounds were significantly higher among the CHAMACOS women after controlling for age, race, socioeconomic status, and smoking [(2,4-DCP; 2,5-DCP; ORTH; PNP; 2,4,6-TCP; and TCPy); quantile regression p < 0.05].

CONCLUSIONS

Findings suggest that the CHAMACOS cohort has an additional burden of precursor pesticide exposure compared with the national sample, possibly from living and/or working in an agricultural area.

Residential exposure to traffic and spontaneous abortion

BACKGROUND

Studies have shown associations between air pollution or traffic exposure and adverse birth outcomes, such as low birth weight. However, very few studies have examined the effect of traffic emissions on spontaneous abortion (SAB).

OBJECTIVE

The goal of this study was to determine whether residential exposure to vehicular traffic was associated with SAB.

METHODS

Pregnant women from a prepaid health plan in California were recruited into a prospective cohort study in 1990-1991. Three measures of traffic exposure were constructed for the 4,979 participants using annual average daily traffic (AADT) counts near each residence and distance from residence to major roads. SAB was examined in relation to the traffic exposure measures using logistic regression adjusting for a number of demographic and lifestyle variables.

RESULTS

Of the traffic measures, maximum annual average traffic within 50 m showed the strongest association with SAB, although it was not statistically significant. The adjusted odds ratio (AOR) for the top 90th percentile (AADT greater than 15,199) versus the bottom 75th percentile (AADT = 0-1,089) was 1.18 [95% confidence interval (CI), 0.87-1.60]. However, subgroup analyses showed statistically significant associations for traffic with SAB among African Americans (AOR = 3.11; 95% CI, 1.26-7.66) and nonsmokers (AOR = 1.47; 95% CI, 1.07-2.04).

CONCLUSION

In this cohort, living within 50 m of a road with AADT of 15,200 or more was significantly associated with SAB among African Americans and nonsmokers. Further research is needed to confirm these results and possibly elucidate the mechanisms responsible for the findings.

Environmental contaminants and pregnancy outcomes

OBJECTIVE

To review selected environmental, occupational, and other important risk factors for the following adverse pregnancy outcomes: low birth weight (LBW), intrauterine growth retardation (IUGR), and preterm delivery (PTD).

DESIGN

The evidence is explored in greater detail for environmental tobacco smoke, drinking water disinfection byproducts, and organochlorine (DDT) and organophosphate pesticides, partly using a weight of evidence approach.

MAIN OUTCOME MEASURE(S)

Low birth weight and IUGR are surrogate measures of fetal growth that are determined at delivery. Low birth weight is defined as <2,500 grams, and occurs in about 7% of US births. Intrauterine growth retardation is commonly defined as birth weight less than the tenth percentile for gestational week, using a standard population. Preterm delivery is birth at <37 weeks gestational age, and occurs in approximately 12% of US births.

RESULT(S)

Numerous factors are associated with these endpoints that may be important to consider in studies of environmental exposures, such as young or old maternal age, race/ethnicity, multiple births, low socioeconomic status, inadequate prenatal care, low maternal weight gain, and infections and premature rupture of the membranes. Environmental contaminants found associated with increased risk of one or more of the endpoints include: tobacco smoke, carbon monoxide, air pollutants, heavy metals, pesticides, chlorination byproducts, and solvents.

CONCLUSION(S)

Future research directions include measurement of exposure biomarkers during critical windows and consideration of genetic polymorphisms.

Pesticide toxicity and the developing brain

Organochlorine pesticides are used in some countries for malaria control and organophosphate pesticides are widely used in agriculture and in homes. Previous literature documents children's exposure to these chemicals both in utero and during development. Animal studies suggest that many of these chemicals are neurodevelopmental toxicants even in moderate doses, but there are few studies in human beings. Associations of children's pesticide exposure with neurodevelopment from studies being conducted worldwide are summarized. In addition, we present the work of the CHAMACOS study, a longitudinal birth cohort study of Mexican-American children living in the Salinas Valley of California. In this study, we investigated the relationship of children's neurodevelopment with maternal dichlorodiphenyltrichloroethane and dichlorodiphenyldichloroethylene serum levels, as well as prenatal and child organophosphate urinary metabolite levels. We have examined the association with children's performance on the Brazelton Neonatal Assessment Scales and at 6, 12 and 24 months on the Bayley Scales of Infant Development (mental development and psychomotor development) and mothers report on the Child Behaviour Checklist. We observed a negative association of prenatal dichlorodiphenyltrichloroethane exposure and child mental development. We also observed adverse associations of prenatal but not postnatal organophosphate pesticide exposure with mental development and pervasive developmental disorder at 24 months.

Associations between prenatal exposure to polychlorinated biphenyls and neonatal thyroid-stimulating hormone levels in a Mexican-American population, Salinas Valley, California

BACKGROUND

Studies have reported that prenatal exposure to polychlorinated biphenyls (PCBs) may alter neurodevelopment in both humans and animals. Furthermore, prenatal exposure to some PCB congeners and commercial mixtures has been shown to decrease free and total thyroxine (T(4)) blood levels in animals. Because thyroid hormones (TH) are essential for normal neurologic development, it has been suggested that the deleterious neurodevelopmental effect of PCBs may occur through TH disruption. PCBs may in turn affect TH levels by inducing the microsomal enzyme uridinediphosphate glucuronosyltransferase (UDP-GT), which is involved in TH elimination.

OBJECTIVES

Our goals were to group PCB congeners based on their potential to induce microsomal enzymes in animals, and to examine the relationship between neonatal TSH levels and prenatal exposure to PCB congeners grouped according to their structure and potential mechanisms of action.

METHODS

We measured the concentration of 34 PCB congeners in serum samples collected from 285 pregnant women and the thyroid-stimulating hormone (TSH) levels in their children's blood collected shortly after birth.

RESULTS

We found no association between the sum of PCB congeners, the toxic equivalents, or structure-based groupings (mono- or di-ortho substituted congeners), and TSH blood concentration. However, we found a positive association between the sum of congeners suspected to be UDP-GT inducers (more specifically cytochrome P450 2B inducers) in animals and neonatal TSH levels. In individual congener analyses, PCBs 99, 138, 153, 180, 183, 187, 194, and 199 were positively associated with neonatal TSH levels after adjustment for covariates. PCBs 194 and 199 remained significant after adjustment for multiple hypothesis testing.

CONCLUSIONS

Our results support grouping PCB congeners based on their potential mechanism of action of enzyme induction when investigating associations with TH. Findings also suggest that PCBs affect TH homeostasis even at the low background level of exposure found in the CHAMA-COS (Center for the Health Assessment of Mothers and Children of Salinas) population.

Factors predicting organochlorine pesticide levels in pregnant Latina women living in a United States agricultural area

Organochlorine (OC) pesticide use was restricted starting in the 1970s in developed countries and the 1980s and 1990s in developing countries. Current exposure to OC pesticides - dichlorodiphenyltrichloroethane (DDT), lindane (99% pure gamma-hexachlorocyclohexane (gamma-HCH)), hexachlorobenzene (HCB) - occurs on a limited basis. We measured para, para' (p,p')-DDE, p,p'-DDT, ortho, para' (o,p')-DDT, HCB, beta (beta)-HCH (the most persistent isomer of technical-grade HCH) and gamma-HCH in serum from 426 low-income pregnant Latina women living in an agricultural community in California. Detection frequencies were 94% to 100%. Median levels (ng/g lipid) of p,p'-DDE (1,052), p,p'-DDT (13), beta-HCH (37) and HCB (65) were significantly higher than United States population levels. Multivariate analyses of p,p'-DDE, p,p'-DDT, o,p'-DDT, beta-HCH and HCB indicate that time spent living outside the United States and birthplace in an area of Mexico with recent use of OC pesticides were significant predictors of exposure. Time spent living in the United States was associated with increased serum levels of p,p'-DDE and beta-HCH, but the increase for each year lived in the United States was lower than for each year lived outside the United States. There was no difference between the increase of HCB levels over time spent in or outside the United States, suggesting current and thus preventable exposure routes. However, we observed no associations between serum levels of any OC compound and current intake of saturated fat or agricultural take-home exposure risk factors. Lactation history and recent weight gain were negatively associated with serum levels of some, but not all OC compounds studied. Smoking history was borderline associated with elevated HCB levels. We observed no significant associations with body mass index. Although the weight of evidence from this study indicates that most exposure occurred before moving to the United States, the results for HCB indicate the possibility of ongoing exposure in this country.

Factors predicting organochlorine pesticide levels in pregnant Latina women living in a United States agricultural area

Organochlorine (OC) pesticide use was restricted starting in the 1970s in developed countries and the 1980s and 1990s in developing countries. Current exposure to OC pesticides - dichlorodiphenyltrichloroethane (DDT), lindane (99% pure gamma-hexachlorocyclohexane (gamma-HCH)), hexachlorobenzene (HCB) - occurs on a limited basis. We measured para, para' (p,p')-DDE, p,p'-DDT, ortho, para' (o,p')-DDT, HCB, beta (beta)-HCH (the most persistent isomer of technical-grade HCH) and gamma-HCH in serum from 426 low-income pregnant Latina women living in an agricultural community in California. Detection frequencies were 94% to 100%. Median levels (ng/g lipid) of p,p'-DDE (1,052), p,p'-DDT (13), beta-HCH (37) and HCB (65) were significantly higher than United States population levels. Multivariate analyses of p,p'-DDE, p,p'-DDT, o,p'-DDT, beta-HCH and HCB indicate that time spent living outside the United States and birthplace in an area of Mexico with recent use of OC pesticides were significant predictors of exposure. Time spent living in the United States was associated with increased serum levels of p,p'-DDE and beta-HCH, but the increase for each year lived in the United States was lower than for each year lived outside the United States. There was no difference between the increase of HCB levels over time spent in or outside the United States, suggesting current and thus preventable exposure routes. However, we observed no associations between serum levels of any OC compound and current intake of saturated fat or agricultural take-home exposure risk factors. Lactation history and recent weight gain were negatively associated with serum levels of some, but not all OC compounds studied. Smoking history was borderline associated with elevated HCB levels. We observed no significant associations with body mass index. Although the weight of evidence from this study indicates that most exposure occurred before moving to the United States, the results for HCB indicate the possibility of ongoing exposure in this country.

In utero exposure to DDT and performance on the Brazelton neonatal behavioral assessment scale

We investigated whether decrements in neonatal neurodevelopment, as determined by the Brazelton neonatal behavioral assessment scale (BNBAS), were associated with in utero exposure to dichlorodiphenyltrichloroethane (DDT): p,p'-dichlorodiphenyl trichloroethane (p,p'-DDT), o,p'-dichlorodiphenyl trichloroethane (o,p'-DDT) and p,p'-DDT's primary breakdown product p,p'-dichlorodiphenyl dichloroethylene (p,p'-DDE) (heretofore collectively referred to as DDT/DDE). Our subjects were a birth cohort of 303 infants whose mothers were low-income Latinas living in the Salinas Valley, an agricultural community in California. We assessed neonates < or =2 months old using the seven BNBAS clusters (habituation, orientation, motor performance, range of state, regulation of state, autonomic stability, and reflex) and examined performance in relationship to DDT/DDE measures in maternal serum samples collected during pregnancy. We did not find any detrimental associations between in utero DDT/DDE levels and neonatal performance on the BNBAS. In this same cohort, we previously demonstrated that exposures to DDT/DDE were related to decrements in neurodevelopment at 6-24 months of age. The failure to observe effects on the BNBAS in these same children may be due to limited sensitivity of a single BNBAS assessment or a delay in the manifestations of neurodevelopmental effects of DDT/DDE until after the neonatal period.

Polybrominated diphenyl ether levels in the blood of pregnant women living in an agricultural community in California

BACKGROUND

Recent studies have raised concerns about polybrominated diphenyl ether (PBDE) flame retardant exposures to pregnant women and women of child-bearing age in the United States. Few studies have measured PBDEs in immigrant populations.

OBJECTIVES

Our goal was to characterize levels of seven PBDE congeners, polychlorinated biphenyl (PCB)-153, and polybrominated biphenyl (PBB)-153 in plasma from 24 pregnant women of Mexican descent living in an agricultural community in California.

RESULTS

The median concentration of the sum of the PBDE congeners was 21 ng/g lipid and ranged from 5.3 to 320 ng/g lipid. Consistent with other studies, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was found at the highest concentration (median = 11 ng/g lipid; range, 2.5-205) followed by 2,2',4,4',5-pentabromobiphenyl (BDE-99) (median = 2.9 ng/g lipid; range, 0.5-54), 2,2',4,4',5-pentaBDE (BDE-100) (median = 1.8 ng/g lipid; range, 0.6-44), and 2,2',4,4',5,5'-hexaBDE (BDE-153) (median = 1.5 ng/g lipid; range, 0.4-35). Levels of PCB-153 (median= 4.4 ng/g lipid; range, < 2-75) were lower than U.S. averages and uncorrelated with PBDE levels, suggesting different exposure routes.

CONCLUSIONS

The overall levels of PBDEs found were lower than levels observed in other U.S. populations, although still higher than those observed previously in Europe or Japan. The upper range of exposure is similar to what has been reported in other U.S. populations. PBDEs have been associated with adverse developmental effects in animals. Future studies are needed to determine the sources and pathways of PBDE exposures and whether these exposures have adverse effects on human health.

In utero exposure to dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) and neurodevelopment among young Mexican American children

OBJECTIVE

We investigated the relationship between prenatal exposure to dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) and neurodevelopment of Mexican farm-workers' children in California.

METHODS

Participants from the Center for the Health Assessment of Mothers and Children of Salinas study, a birth cohort study, included 360 singletons with maternal serum measures of p,p'-DDT, o,p'-DDT, and p,p'-DDE. Psychomotor development and mental development were assessed with the Bayley Scales of Infant Development at 6, 12, and 24 months.

RESULTS

We found a approximately 2-point decrease in Psychomotor Developmental Index scores with each 10-fold increase in p,p'-DDT levels at 6 and 12 months (but not 24 months) and p,p'-DDE levels at 6 months only. We found no association with mental development at 6 months but a 2- to 3-point decrease in Mental Developmental Index scores for p,p'-DDT and o,p'-DDT at 12 and 24 months, corresponding to 7- to 10-point decreases across the exposure range. Even when mothers had substantial exposure, breastfeeding was usually associated positively with Bayley scale scores.

CONCLUSIONS

Prenatal exposure to DDT, and to a lesser extent DDE, was associated with neurodevelopmental delays during early childhood, although breastfeeding was found to be beneficial even among women with high levels of exposure. Countries considering the use of DDT should weigh its benefit in eradicating malaria against the negative associations found in this first report on DDT and human neurodevelopment.

Association of in utero organochlorine pesticide exposure and fetal growth and length of gestation in an agricultural population

From 1940 through the 1970s, organochlorine compounds were widely used as insecticides in the United States. Thereafter, their use was severely restricted after recognition of their persistence in the environment, their toxicity in animals, and their potential for endocrine disruption. Although substantial evidence exists for the fetal toxicity of organochlorines in animals, information on human reproductive effects is conflicting. We investigated whether infants' length of gestation, birth weight, and crown-heel length were associated with maternal serum levels of 11 different organochlorine pesticides: p,p -dichlorodiphenyltrichloroethane (p,p -DDT), p,p -dichlorodiphenyldichloroethylene (p,p -DDE), o,p -dichlorodiphenyltrichloroethane (o,p -DDT), hexachlorobenzene (HCB), gamma-hexachlorocyclohexane (gamma-HCCH), gamma-hexachlorocyclohexane (gamma-HCCH), dieldrin, heptachlor epoxide, oxychlordane, trans-nonachlor, and mirex. Our subjects were a birth cohort of 385 low-income Latinas living in the Salinas Valley, an agricultural community in California. We observed no adverse associations between maternal serum organochlorine levels and birth weight or crown-heel length. We found decreased length of gestation with increasing levels of lipid-adjusted HCB (adjusted gamma = -0.47 weeks; p = 0.05). We did not find reductions in gestational duration associated with any of the other organochlorine pesticides. Our finding of decreased length of gestation related to HCB does not seem to have had clinical implications for this population, given its relatively low rate of preterm delivery (6.5%).

Influence of paternal age on the risk of spontaneous abortion

The frequency of chromosomal anomalies in spermatozoa appears to increase with male age. Because these anomalies play a role in the etiology of spontaneous abortion, an influence of paternal age on risk of spontaneous abortion is plausible but not established. The aim was to characterize this influence in a prospective study among 5,121 California women, who as members of a prepaid health plan were interviewed in 1990 or 1991 when they were less than 13 weeks' pregnant and who were followed until the end of pregnancy. The risk of spontaneous abortion between weeks 6 and 20 of pregnancy was studied using a Cox model adjusted for maternal age. The adjusted hazard ratio of spontaneous abortion associated with paternal age of 35 years or more, compared with less than 35 years, was 1.27 (95% confidence interval: 1.00, 1.61), with no modification by maternal age. Among women aged less than 30 years, the hazard ratio of spontaneous abortion associated with paternal age of 35 years or more was 1.56 for first trimester spontaneous abortion and 0.87 for early second trimester spontaneous abortion (test of interaction, p = 0.25). In conclusion, the risk of spontaneous abortion increased with increasing paternal age, with a suggestion that the association is stronger for first trimester losses.

Age at menarche in relation to maternal use of tobacco, alcohol, coffee, and tea during pregnancy

To investigate the potential effects of common early life exposures on age at menarche, the authors examined data collected in a follow-up study of pregnancies that occurred during the 1960s in California. Among 994 female offspring interviewed as adolescents, 98% had started their menstrual periods at a mean age of 12.96 years. After adjustment, the mean age at menarche was a few months earlier among girls whose mothers smoked a pack or more of cigarettes daily during pregnancy compared with unexposed girls (difference = -0.22 years, 95% confidence interval (CI): -0.49, 0.05) and more so among girls who were not White (difference = -0.52 years, 95% CI: -1.1, 0.08). Girls with both high prenatal and childhood passive smoke exposure had an adjusted mean age at menarche about 4 months earlier than those unexposed. The daughter's mean age at menarche varied little by maternal prenatal alcohol consumption. Daughters of tea consumers had a later mean age (difference = 0.41 years at >/= 3 cups (0.7 liter)/day, 95% CI: 0.03, 0.80) and were more likely to start menarche later (>13 years) (odds ratio = 1.7, 95% CI: 0.91, 3.2), but daughters of coffee consumers did not. These suggestive findings, which merit further investigation, may be related to hormonal effects.

Trihalomethane Levels in Home Tap Water and Semen Quality

BACKGROUND

Trihalomethanes (THMs) are byproducts of drinking water chlorination whose effects on semen quality have not been previously studied in humans.

METHODS

We examined the relationship of THMs to semen quality in 157 healthy men from couples without known risk factors for infertility. Total THM (TTHM) levels were assigned based on water utility measurements taken during the 90 days preceding semen collection. We analyzed continuous semen parameters in relation to total and individual THMs, adjusting for potential confounders by using repeated measures analyses.

RESULTS

TTHM level was not associated with decrements in semen quality. Percent normal morphology decreased and percent head defects increased at higher levels of an ingestion metric (TTHM multiplied by cold home tap water consumption). At the highest level of the ingestion metric (>160 mug/L x glasses/day, which is equivalent to >2 glasses/day of water containing 80 mug/L) we observed a difference of -7.1 (95% confidence interval = -12.7 to -1.6) for percent morphologically normal sperm compared with the lowest level (</= 40 mug/L x glasses/day). Of the individual THMs, bromodichloromethane exposure was inversely related to linearity (a motility parameter); we observed a small decrease (beta = -0.09, SE 0.04) for every unit increase in bromodichloromethane.

CONCLUSION

Although our study had a limited exposure assessment and a selective sample, our results suggest the need for further study of the effects of THMs on semen quality.

Chlorination by-products in drinking water and menstrual cycle function

We analyzed data from a prospective study of menstrual cycle function and early pregnancy loss to explore further the effects of trihalomethanes (THM) on reproductive end points. Premenopausal women ((italic)n(/italic) = 403) collected urine samples daily during an average of 5.6 cycles for measurement of steroid metabolites that were used to define menstrual parameters such as cycle and phase length. Women were asked about consumption of various types of water as well as other habits and demographics. A THM level was estimated for each cycle based on residence and quarterly measurements made by water utilities during a 90-day period beginning 60 days before the cycle start date. We found a monotonic decrease in mean cycle length with increasing total THM (TTHM) level; at > 60 microg/L, the adjusted decrement was 1.1 days [95% confidence interval (CI), -1.8 to -0.40], compared with less than or equal to 40 microg/L. This finding was also reflected as a reduced follicular phase length (difference -0.94 day; 95% CI, -1.6 to -0.24). A decrement in cycle and follicular phase length of 0.18 days (95% CI, -0.29 to -0.07) per 10 microg/L unit increase in TTHM concentration was found. There was little association with luteal phase length, menses length, or cycle variability. Examining the individual THMs by quartile, we found the greatest association with chlorodibromomethane or the sum of the brominated compounds. Incorporating tap water consumption showed a similar pattern of reduced cycle length with increasing TTHM exposure. These findings suggest that THM exposure may affect ovarian function and should be confirmed in other studies.

Ovarian hormones in premenopausal women: variation by demographic, reproductive and menstrual cycle characteristics

BACKGROUND

Ovarian function influences many areas of concern in women's health, including breast cancer and other chronic diseases. However, ovarian function has been little studied in healthy, premenopausal women, partly because of cyclical variation.

METHODS

We measured biomarkers of ovarian function (daily urinary metabolites of estrogen and progesterone) among 411 women age 18-39 years, who were Kaiser Permanente members in Northern California in 1990-1991. We have summarized the hormone metabolite levels of about 1,500 cycles and examined their associations with demographic and menstrual cycle characteristics.

RESULTS

Cycles with a short follicular phase showed elevations of 10-13% in both baseline (days 1-5) and average follicular-phase estrogen metabolite levels, as well as some elevations in progesterone metabolites. Progesterone metabolite levels were directly related to the length of the luteal phase. Compared with whites, Hispanics had estrogen metabolite levels that were 7-13% higher in the follicular and luteal phases, whereas nonwhite, non-Hispanic women (primarily Asians) had slightly lower levels. Generally, women with a prior pregnancy or those with a later age at menarche had lower estrogen metabolite levels, whereas women with prior induced abortions had higher levels. Luteal-phase progesterone metabolite levels tended to be lower among women who were overweight, were less educated, were older at their first livebirth, or had an induced abortion.

CONCLUSIONS

Some menstrual cycle characteristics provide a crude surrogate of the hormonal milieu, particularly luteal-phase length and progesterone levels. Hormone levels varied by reproductive characteristics, potentially explaining their relevance to breast cancer risk.

Influence of exposure assessment methods on risk estimates in an epidemiologic study of total trihalomethane exposure and spontaneous abortion

Trihalomethanes are common contaminants of chlorinated drinking water. Studies of their health effects have been hampered by exposure misclassification, due in part to limitations inherent in using utility sampling records. We used two exposure assessment methods, one based on utility-wide sampling averages, and one based on measurements from the utility sampling site closest to the subject's residence, to reestimate total trihalomethane (TTHM) exposure for 4212 participants in a preexisting study of risk factors for spontaneous abortion (SAB). For both approaches we performed unweighted, weighted, and subset analyses. The weighted and subset analyses were intended to reduce exposure misclassification, and were based on within-utility variance in TTHM measurements for the utility-wide average approach, and the distance between the subject's residence and sampling site for the closest-site approach. In general, the utility-wide average methods produced odds ratios equivalent to or slightly higher than the closest-site methods. Odds ratios obtained using the utility-wide average, but not the closest-site, approach also became progressively stronger in the weighted and subset analyses. A dose-response was seen between SAB and an exposure metric incorporating both TTHM concentration (utility-wide average approach) and personal ingestion, with SAB rates ranging from 8.3% to 13.7% (unweighted), 7.9% to 16.6% (variance weighted), and 6.6% to 23.1% (low-variance subset). Utility-wide average TTHM exposure assessment methods together with variance-based weights and subsets are relatively simple exposure assessment techniques, which may increase the epidemiologic usefulness of utility sampling records.

The question of declining sperm density revisited: an analysis of 101 studies published 1934-1996

In 1992 Carlsen et al. reported a significant global decline in sperm density between 1938 and 1990 [Evidence for Decreasing Quality of Semen during Last 50 Years. Br Med J 305:609-613 (1992)]. We subsequently published a reanalysis of the studies included by Carlsen et al. [Swan et al. Have Sperm Densities Declined? A Reanalysis of Global Trend Data. Environ Health Perspect 105:1228-1232 (1997)]. In that analysis we found significant declines in sperm density in the United States and Europe/Australia after controlling for abstinence time, age, percent of men with proven fertility, and specimen collection method. The declines in sperm density in the United States (approximately 1.5%/year) and Europe/Australia (approximately 3%/year) were somewhat greater than the average decline reported by Carlsen et al. (approximately 1%/year). However, we found no decline in sperm density in non-Western countries, for which data were very limited. In the current study, we used similar methods to analyze an expanded set of studies. We added 47 English language studies published in 1934-1996 to those we had analyzed previously. The average decline in sperm count was virtually unchanged from that reported previously by Carlsen et al. (slope = -0.94 vs. -0.93). The slopes in the three geographic groupings were also similar to those we reported earlier. In North America, the slope was somewhat less than the slope we had found for the United States (slope = -0.80; 95% confidence interval (CI), -1.37--0.24). Similarly, the decline in Europe (slope = -2.35; CI, -3.66--1.05) was somewhat less than reported previously. As before, studies from other countries showed no trend (slope = -0.21; CI, -2.30-1.88). These results are consistent with those of Carlsen et al. and our previous results, suggesting that the reported trends are not dependent on the particular studies included by Carlsen et al. and that the observed trends previously reported for 1938-1990 are also seen in data from 1934-1996.

Prenatal active or passive tobacco smoke exposure and the risk of preterm delivery or low birth weight

We examined the association of exposure to environmental tobacco smoke with birth weight and gestational age in a large, prospective study. We also compared these endpoints between infants of active maternal smokers and those of non-smoking, non-ETS exposed women. Pregnant women were interviewed by telephone during the first trimester, and pregnancy outcome was determined for 99%. Among the 4,454 singleton live births that could be linked to their birth certificate, we confirmed increased risks of low birth weight and small for gestational age with heavier maternal smoking (> 10 cigarettes/day), as well as noting an increased risk for "very preterm" birth (< 35 weeks). These associations were generally stronger among infants of older (> or = 30 years) than those of younger mothers, as well as among non-whites. High environmental tobacco smoke exposure (> or = 7 hours/day in non-smokers) was moderately associated with low birth weight (adjusted odds ratio (AOR) 1.8, 95% confidence limits (95% CL) = 0.82, 4.1), preterm birth (AOR 1.6, 95% CL = 0.87, 2.9), and most strongly with very preterm birth (AOR 2.4, 95% CL = 1.0, 5.3). These associations were generally greater among non-whites than whites. The data support earlier studies suggesting that prenatal environmental tobacco smoke exposure, in addition to maternal smoking, affects infant health.

Caffeine consumption and menstrual function

The relation between caffeine intake and menstrual function was examined in 403 healthy premenopausal women who belonged to Kaiser Permanente Medical Care Program in 1990-1991. A telephone interview collected information about caffeinated beverage intake as well as other lifestyle, demographic, occupational, and environmental factors. Subjects collected daily urine samples and completed a daily diary for an average of five menstrual cycles. Metabolites of estrogen and progesterone were measured in the urine, each cycle was characterized as anovulatory or ovulatory, and a probable day of ovulation was selected when appropriate. Logistic regression and repeated measures analyses were performed on menstrual parameters. Women whose caffeine consumption was heavy (>300 mg of caffeine per day) had less than a third of the risk for long menses (> or =8 days) compared with women who did not consume caffeine (adjusted odds ratio = 0.30, 95% confidence interval 0.14-0.66). Those whose caffeine consumption was heavy also had a doubled risk for short cycle length (< or =24 days) (adjusted odds ratio = 2.00, 95% confidence interval 0.98-4.06); this association was also evident in those whose caffeine consumption was heavy who did not smoke (adjusted odds ratio = 2.11, 95% confidence interval 1.03-4.33). Caffeine intake was not strongly related to an increased risk for anovulation, short luteal phase (< or =10 days), long follicular phase (> or =24 days), long cycle (> or =36 days), or measures of within-woman cycle variability.

Exposure to environmental and mainstream tobacco smoke and risk of spontaneous abortion

The authors examined the risk of spontaneous abortion from environmental tobacco smoke (ETS) exposure in a prospective study of over 5,000 women conducted in California during 1990-1991. Among nonsmokers, there was little association by hours of ETS exposure at home or work (adjusted odds ratio (OR) for any exposure = 1.01, 95% confidence interval (CI) 0.80-1.27), or by paternal smoking. However, the risks associated with ETS exposure were increased among nonsmokers who had moderate alcohol or heavy caffeine consumption. A moderate association with maternal smoking was observed (adjusted OR for > or = 5 cigarettes per day = 1.3, 95% CI 0.91-1.9).

Psychological stress in the workplace and menstrual function

The relation between psychological stress at work and menstrual function was examined for 276 healthy, working, premenopausal women who participated in the California Women's Reproductive Health Study in 1990-1991. Subjects collected daily urine samples and completed a daily diary for an average of five menstrual cycles. Metabolites of estrogen and progesterone were measured in the urine, and computer algorithms were developed to characterize each cycle as ovulatory or anovulatory and to select a probable day of ovulation. A telephone interview collected information about psychological stress at work as well as other occupational, demographic, lifestyle, and environmental factors. Logistic regression was used to model stressful work and risk of anovulation (> or = 36 days without ovulating) and measures of within-woman cycle variability. Repeated measures analyses were performed on other menstrual cycle parameters. Stressful work (high demand in combination with low control) was not strongly related to an increased risk for anovulation or cycle variability or to any of the following cycle endpoints: short luteal phase (< or = 10 days), long follicular phase (> or = 24 days), long menses (> or = 8 days), or long cycle (> or = 36 days). However, women in stressful jobs had a more than doubled risk for short cycle length (< or = 24 days) compared with women not working in stressful jobs (adjusted odds ratio = 2.24, 95% confidence interval 1.09-4.59).

Cigarette smoking and effects on menstrual function

OBJECTIVE

To examine the relationship between smoking and menstrual function, using biologic measures rather than self-report of menstrual cycle characteristics.

METHODS

In a prospective study, 408 women collected urine daily for one to seven menstrual segments (cycles), maintained daily diaries, and completed detailed interviews. Smoking data from the diaries were averaged over each segment and verified by cotinine assay. Urine samples were analyzed for metabolites of steroid hormones to define the day of ovulation and various menstrual characteristics, including: 1) segment, follicular, luteal phase, and menses length, 2) variability, and 3) anovulation.

RESULTS

Heavy smoking (at least 20 cigarettes per day) was associated with nearly four times the risk of short segment (less than 25 days) as was nonsmoking (adjusted odds ratio 3.8, 95% confidence limits 1.1, 12.7). Mean segment length was on average 2.6 days shorter with heavy versus no smoking (95% confidence limits 0.14, 5.0), due almost entirely to shortening of the follicular phase. Women who smoked an average of ten or more cigarettes per day had significantly more variable segment and menses lengths than nonsmokers. Based on small numbers, the data suggested that with greater smoking, there was a possible increased risk of anovulation and short luteal phase. Segments of exsmokers with ten or more pack-years of exposure were more likely to be short and have shorter luteal phases than those of never smokers.

CONCLUSION

The effects found in this study of smoking on the menstrual cycle might explain in part associations of smoking with other reproductive endpoints, such as subfecundity and early menopause.

Use of urine biomarkers to evaluate menstrual function in healthy premenopausal women

A total of 403 healthy, premenopausal women, residing near Santa Clara, California, were recruited from a large health care plan in California for a study of menstrual function. After a telephone interview, participants collected daily urine samples and recorded bleeding and other information in diaries. Data were collected during 1990-1991. Urine samples were analyzed for creatinine and for estradiol and progesterone metabolites by enzyme-linked immunoassay. Computer algorithms were developed to derive menstrual segment length, ovulatory status, day of ovulation, and other parameters from the urine and diary data. (We use "segment" rather than "cycle" to avoid implying that normal cycling occurred.) The average length of participation was 141 (standard deviation, 45) days. The mean segment length was 28.8 (standard deviation, 4.4) days; follicular phase length, 16.0 (standard deviation, 4.4) days; and luteal phase length, 12.9 (standard deviation, 1.7) days; 19 (4.7%) women experienced anovulatory episodes. In exploratory multivariate analyses, important associations included the following: age of > or = 35 years with decreased segment and follicular phase lengths; heavier weight (upper quartile) with anovulation and increased follicular phase and decreased luteal phase lengths; Hispanic ethnicity with anovulation and increased segment length; and past difficulty in achieving pregnancy with anovulation and increased length and variability of segments and follicular phases. Urine biomarkers can be used successfully to evaluate menstrual function in epidemiologic studies.

Rate of caffeine metabolism and risk of spontaneous abortion

In a case-control study of 73 women with and 141 women without spontaneous abortion, the authors determined the activity of the three principal caffeine-metabolizing enzymes--cytochrome P-4501A2 (CYP1A2), xanthine oxidase, and N-acetyltransferase 2--by measuring levels of caffeine metabolites in urine. After examining the effect of enzyme activity and different levels of caffeine intake, they concluded that there was no evidence that an interaction between enzyme activity and caffeine intake during pregnancy resulted in risk of spontaneous abortion. In a subsample comparing 24 cases with recurrent (two or more) spontaneous abortions and 21 controls with two or more livebirths and no previous spontaneous abortions, the unadjusted odds ratio for low CYP1A2 enzyme activity (below the median) was 0.92 (95% confidence interval (CI) 0.28-3.04) compared with higher CYP1A2 activity. The odds ratio for risk of recurrent spontaneous abortion and low xanthine oxidase activity (below the median) versus higher activity was 0.37 (95% CI 0.10-1.29). Phenotypically slow acetylators (N-acetyltransferase 2 index <0.37) had an odds ratio of 1.58 (95% CI 0.48-5.13) for recurrent loss compared with rapid acetylators. Thus, some association of the latter two caffeine-metabolizing enzymes with recurrent spontaneous abortion is suggested but may also be due to chance.

A prospective study of spontaneous abortion: relation to amount and source of drinking water consumed in early pregnancy

In 1992, we published four retrospective studies, conducted primarily within a single California county, which found higher spontaneous abortion rates among women who drank more tapwater than bottled water in early pregnancy. The current prospective study extends that investigation to other water systems. Pregnant women from three regions in California were interviewed during their first trimester. Multivariate analyses modeled the amount and type of water consumed at 8 weeks' gestation in each region in relation to spontaneous abortion rate. In Region I, which was within the previous study area, the adjusted odds ratio (OR) comparing high (> or = 6 glasses per day) consumption of cold tapwater with none was 2.17 [95% confidence interval (CI) = 1.22-3.87]. Furthermore, when women with high cold tapwater and no bottled water consumption were compared with those with high bottled water and no cold tapwater consumption, the adjusted odds ratio was 4.58 (95% CI = 1.97-10.64). Conversely, women with high bottled water consumption and no tapwater had a reduced rate of spontaneous abortion compared with those drinking tapwater and no bottled water (adjusted OR = 0.22; 95% CI = 0.09-0.51). Neither tap nor bottled water consumption altered the risk of spontaneous abortion in Regions II and III. Although controlling for age, prior spontaneous abortion, race, gestational age at interview, and weight somewhat strengthened the association in Region I, the distribution of these confounders did not vary appreciably across regions. This study confirms the association between cold tapwater and spontaneous abortion first seen in this county in 1980. If causal, the agent(s) is not ubiquitous but is likely to have been present in Region I for some time.

Have sperm densities declined? A reanalysis of global trend data

In 1992 a worldwide decline in sperm density was reported; this was quickly followed by numerous critiques and editorials. Because of the public health importance of this finding, a detailed reanalysis of data from 61 studies was warranted to resolve these issues. Multiple linear regression models (controlling for abstinence time, age, percent proven fertility, specimen collection method, study goal and location) were used to examine regional differences and the interaction between region (United States, Europe, and non-Western countries) and year. Nonlinear models and residual confounding were also examined in these data. Using a linear model (adjusted R2 = 0. 80), means and slopes differed significantly across regions (p = 0. 02). Mean sperm densities were highest in Europe and lowest in non-Western countries. A decline in sperm density was seen in the United States (studies from 1938-1988; slope = -1.50; 95% confidence interval (CI), -1.90--1.10) and Europe (1971-1990; slope = -3.13; CI, -4.96- -1.30), but not in non-Western countries (1978-1989; slope = 1.56; CI, -1.00-4.12). Results from nonlinear models (quadratic and spline) were similar. Thus, further analysis of these studies supports a significant decline in sperm density in the United States and Europe. Confounding and selection bias are unlikely to account for these results. However, some intraregional differences were as large as mean decline in sperm density between 1938 and 1990, and recent reports from Europe and the United States further support large interarea differences in sperm density. Identifying the cause(s) of these regional and temporal differences, whether environmental or other, is clearly warranted.

Caffeinated beverages, decaffeinated coffee, and spontaneous abortion

We examined the relations between spontaneous abortion and the consumption of caffeine, individual caffeine-containing beverages (coffee, tea, and soda), and decaffeinated coffee in a prospective study of 5,144 pregnant women. We collected information about potential risk factors for spontaneous abortion, including consumption of caffeinated beverages and decaffeinated coffee before and during pregnancy, by interview in the first trimester. Neither total estimated caffeine nor individual caffeinated beverage consumption during the first trimester was associated with an appreciable increase in risk for spontaneous abortion. The adjusted odds ratio for consumption of greater than 300 mg per day of caffeine was 1.3 [95% confidence interval (CI) = 0.8-2.1] after adjustment for maternal age, pregnancy history, cigarette and alcohol consumption, employment, race, gestational age at interview, and marital and socioeconomic status. The adjusted odds ratio for spontaneous abortion related to consumption of three or more cups of decaffeinated coffee during the first trimester was 2.4 (95% CI = 1.3-4.7) in the same model. Although we could not demonstrate this with available data, we suspect that this association was due to bias resulting from the relations among fetal viability, symptoms of pregnancy such as nausea, and consumption patterns during pregnancy.

Moderate maternal alcohol consumption and risk of spontaneous abortion

Maternal alcoholism is known to have adverse effects on reproduction and fetal development, but the effects of moderate consumption remain controversial. In a previous case-control study, we found a doubled risk of spontaneous abortion with an average consumption of seven or more drinks per week during the first trimester. To confirm this finding while avoiding potential biases from the case-control design, we examined moderate alcohol consumption in a prospective cohort study of over 5,000 pregnant women. An interview in the first trimester asked about alcohol consumption during the week before interview ("during the first trimester") and before pregnancy. We found an increased risk of spontaneous abortion in women who drank more than three drinks per week during the first trimester, with an adjusted odds ratio (OR) of 2.3 [95% confidence interval (CI) = 1.1-4.5]. The increased risk associated with this moderate alcohol consumption may be higher in first than in second trimester abortions, and it is even higher in the first 10 weeks (OR = 3.8; 95% CI = 1.7-8.7), based on small numbers. Consumption of alcohol before pregnancy was not strongly associated with spontaneous abortion.

Effects of psychological stress on human semen quality

We investigated the relationship between psychological stress and sperm concentration, motility, and morphometry in a prospective study of 157 volunteers who were enrolled in a prepaid health plan. We measured psychological job stress and life-event stress by telephone interview. Sperm-kinematic and nuclear-morphometric variables were measured using computer-assisted image analyses. Sperm concentration, percent motility, and semen volume were determined by objective visual methods. We performed multiple linear regression for each semen variable to examine its relationship to stress, controlling for potential confounders. Stress at work and total number of life events were not related to differences in semen quality. However, the recent death of a close family member was associated with a reduction in straight-line velocity (P = 0.002) and percent of progressively motile sperm (P = 0.02); it was also marginally associated with an increase in the fraction of sperm with larger and more tapered nuclei. These findings suggest that the fecundity of men experiencing the stress of a family member's death might be temporarily diminished.

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. III. Guidelines for field studies of male reproductive disorders

Exposures to environmental toxicants can have detrimental effects on several aspects of human male reproduction: fertility, sexual function, hormone status, and pregnancy/birth outcomes. However, no simple prescreening methods are available for reliably identifying potential hazards; questionnaires alone are relatively imprecise and inefficient in the absence of field data. Multidisciplinary field studies are required that include detailed exposure information, health and reproductive histories, physical examinations, semen analyses, and possibly, hormone analyses. Semen analysis is a critical component of field studies for evaluating two aspects of male reproduction: 1) changes in sperm or seminal content, which may be indicative of adverse effects on the male reproductive system with possible implications for fertility potential; and 2) defects in sperm DNA or chromosomes, which may be associated with subsequent changes in viability during embryonic development and health risks to the offspring. Semen analyses may be tiered: 1) initially, each semen study may include conventional semen assays (concentration, motility, and morphology) as well as specific biomarkers indicated by the health effect of concern in the study cohort: and 2) archived samples (i.e., frozen, videotaped, or smeared) may be utilized in later second-tier analyses to further characterize specific findings. Before initiating any field study, it is cost effective to critically evaluate the suitability of the cohort by confirming exposure and determining that there are adequate numbers of male participants in each exposure category. Such evaluations must be based on the statistical sensitivities of the specific tissue biomarkers and health endpoints for detecting changes. This article summarizes the components of the ideal field study and identifies research needs for improving field studies of male effects and for understanding the mechanisms of male reproductive toxicity. Several promising semen methods currently under development are also discussed.

A prospective study of work-related physical exertion and spontaneous abortion

We examined the relation of physical exertion to spontaneous abortion in a prospective study of 5,144 pregnant women. In a first trimester interview, we obtained data on employment and physical activity at work and at home, as well as other potential risk factors for spontaneous abortion. We measured exertion as follows: time spent working, standing and bending at work, hours between breaks, and hours spent doing housework or yardwork; shift worked; number of times lifted weights and more than 15 pounds at work or at home; number of children under age 5 years cared for at home. None of the exertion measures was appreciably associated with an increased risk of spontaneous abortion overall. In addition, physical activity at work and at home combined was not related to increased risk. For women with a history of two or more spontaneous abortions, standing at work more than 7 hours per day was associated with an adjusted odds ratio (OR) of 4.3 [95% confidence limits (CL) = 1.6, 11.7], whereas standing at work for 7 hours or less was associated with an adjusted OR of 1.7 (95% CL = 1.1, 2.6). Women without such a history who stood more than 7 hours at work had an adjusted OR near unity.

Bone mass and subtle abnormalities in ovulatory function in healthy women

Women with occasional anovulatory or short luteal phase menstrual cycles have been reported to lose bone mineral density (BMD) at a greatly accelerated rate compared to women without such abnormalities. To investigate this association, we performed a longitudinal study of BMD in a group of healthy premenopausal women enrolled in a comprehensive study of ovulatory function. Subjects had collected daily urine samples that were analyzed for estrone and progesterone metabolites by enzyme-linked immunoassay. The 53 participants collected urine for an average of 4.1 cycles. Computer algorithms identified 7 (13.2%) women with luteal phase abnormalities (> 1 anovulatory cycle or cycle with luteal phase length < or = 10 days) and 17 (32.1%) women with other menstrual abnormalities. Areal BMD (grams per cm2) was measured at the lumbar spine, hip, and whole body using dual energy x-ray absorptiometry; BMD was measured 2-3 times over an average observation period of 17.5 months. At baseline, women with luteal abnormalities had mean BMD similar to those of the 29 women with no abnormal cycles: lumbar spine, 1.06 vs. 1.09 g/cm2; total hip, 0.95 vs. 0.94 g/cm2; whole body, 1.15 vs. 1.11 g/cm2 (P > 0.10; adjusted for age and weight at baseline, parity, physical activity level, and calcium intake). When compared at follow-up to women with no abnormal cycles, women with luteal abnormalities tended to gain BMD at the spine and hip (P > 0.10). On whole body measurement, women with luteal abnormalities tended to lose BMD compared to women with no abnormal cycles (-1.1%/yr vs. 0%/yr; P = 0.08); however, the magnitude of loss was not unusual for women in this age range and was within the coefficient of variation for replicate measurements. Neither mean luteal phase length, percent time in luteal phase, nor average daily excretion of progesterone metabolites was associated with baseline BMD or percent annual change in BMD at any measurement site. Thus, we did not confirm a relationship between luteal abnormalities and accelerated bone loss in this population of healthy premenopausal women.

Psychologic stress in the workplace and spontaneous abortion

The relation of work-related psychologic stress to spontaneous abortion was examined in a prospective study of 3,953 pregnant, employed members of a prepaid health plan in California, recruited between 1990 and 1991. Information on occupation, psychologic stress-related factors at work, social support at work, physical exertion at work, life events, pregnancy worries, and potential confounders was obtained by a telephone interview. Psychologic job stress and social support at work were assessed using an abbreviated version of the instrument developed by Karasek and colleagues (Los Angeles: University of Southern California, 1986). Results from the multivariate model indicated that, overall, stressful work was not associated with an increased risk of spontaneous abortion. However, interactions were observed between stressful work and maternal age over 32 years (p = 0.04), cigarette smoking (p = 0.02), and primigravidity (p = 0.06). Relative to the odds ratio for stressful work in young, nonsmoking, multigravid women without a history of two or more spontaneous abortions, the odds ratios for spontaneous abortion given stressful work were higher by 2.45 (95% confidence interval (CI) 1.03-5.81) for older women, 2.96 (95% CI 1.16-7.52) for smokers, and 2.27 (95% CI 0.97-5.27) for primigravid women.

The association of moderate maternal and paternal alcohol consumption with birthweight and gestational age

Heavy maternal alcohol consumption during pregnancy has been associated with fetal growth retardation, but whether more moderate consumption also is associated remains a controversial issue. We examined moderate consumption in 1233 women with singleton livebirths, by calculating a weighted average of weekly consumption in the first 20 weeks from questions that asked about alcohol consumption before pregnancy, as well as any changes during the first half of pregnancy. The adjusted odds ratio for ("moderate") consumption of three or more drinks per week for low birthweight was 2.6 [95% confidence limits (CL) = 1.2, 5.7], and that for intrauterine growth retardation was 2.3 (95% CL = 1.2, 4.6). Examining the joint effect of smoking with alcohol consumption revealed associations that differed by outcome; we found a synergistic effect for low birthweight, but not for intrauterine growth retardation. Moderate alcohol consumers had an average birthweight decrement of 143 gm, which varied by smoking. There was little association of alcohol consumption with preterm delivery (< 37 weeks). Paternal alcohol consumption was not associated with any of the fetal growth measures after adjustment for other variables.

Physical exertion as a risk factor for spontaneous abortion

This study examined the association of physical exertion and spontaneous abortion in a case-control study of 607 women whose pregnancies ended in spontaneous abortion and 1,287 women who delivered livebirths in Santa Clara County, CA, in 1986 and 1987. We interviewed women about the number of hours they spent doing heavy housework and caring for young children. We also interviewed women employed during their pregnancies (71% in each group) about their work schedule; the number of hours they worked, stood, commuted, and stooped or bent; and the number of times per day they lifted weights of > 15 pounds. Standing > 8 hours per day at work was the only variable associated with increased risk [adjusted odds ratio (OR) = 1.6; 95% confidence limits (CL) = 1.1, 2.3]. This association was present only for women with a history of spontaneous abortion (adjusted OR = 2.8; 95% CL = 1.4, 5.9). Among women with this history, the OR for a second trimester abortion was 4.9 (95% CL = 1.9, 12.2). Cleaning house for > 7 hours per week or caring for young children for > 50 hours per week was associated with decreased risk (adjusted OR = 0.6, 95% CL = 0.5, 0.9; adjusted OR = 0.8, 95% CL = 0.6, 1.0, respectively). Again, these associations were specific to women with a history of spontaneous abortion (adjusted OR = 0.4, 95% CL = 0.2, 0.7; adjusted OR = 0.5, 95% CL = 0.3, 0.8). These results indicate that the specific type of physical exertion, the amount of exertion, and the context of the exertion may be important.

Fetal growth retardation in infants of multiparous and nulliparous women with preeclampsia

OBJECTIVE

Infants of women with preeclampsia are considered at high risk of fetal growth retardation. The purpose of our study was to determine whether the risk differed by parity.

STUDY DESIGN

We compared the outcomes of 133 case patients with preeclampsia (101 nulliparous women and 32 multiparous women) and 132 normotensive control patients (52 nulliparous women and 80 multiparous women) who delivered at Northern California Kaiser Permanente hospitals between 1984 and 1985.

RESULTS

Women with preeclampsia were more likely than control patients to deliver a small-for-gestational-age infant (adjusted odds ratio 7.0, 95% confidence interval 2.8 to 18.1). After we controlled for smoking status, age, Quetelet index, and race, multiparous women with preeclampsia were at greater risk of having a small-for-gestational-age infant (adjusted odds ratio 29.4, 95% confidence interval 5.2 to 167.5) than were nulliparous women (adjusted odds ratio 4.1, 95% confidence interval 1.2 to 14.1) when compared with normotensive control patients of similar parity. Although multiparous women with preeclampsia had higher mean arterial pressures and somewhat earlier onsets of elevated mean arterial pressure than nulliparous women with preeclampsia, neither of these variables predicted whether the infants would be small for gestational age.

CONCLUSION

Multiparous women with preeclampsia are at higher risk of having an infant with fetal growth retardation than are nulliparous women with preeclampsia.

Employment in electronics manufacturing and risk of spontaneous abortion

A large case-control study of environmental risk factors for spontaneous abortion was conducted among women living in Santa Clara County, California. Because of the prevalence of electronics production work within this population, a specialized questionnaire was administered to women who self-identified as electronics production workers. Spontaneous abortions were identified from pathology records, and controls were identified from birth certificates. The odds ratio for spontaneous abortion and any electronics production work was 0.94 (95% confidence interval = 0.58, 1.5). Odds ratios for the three main branches of electronics production (semiconductor fabrication, printed circuit board manufacturing, and assembly) were likewise near or below unity. Specific production activities with elevated odds ratios included semiconductor diffusion, parts encapsulation, soldering, and flux removal, although the numbers were small and none of the confidence intervals excluded unity. Limitations of this study included modest statistical power and a potential for nondifferential misclassification of exposures, both of which could bias findings toward the null.

Moderate maternal and paternal alcohol consumption and the risk of spontaneous abortion

Maternal alcoholism can lead to the fetal alcohol syndrome in offspring, but the effect of more moderate alcohol consumption during pregnancy remains an issue of concern. Therefore, we analyzed data from a large case-control study of spontaneous abortion (626 cases, 1,300 controls) that ascertained maternal alcohol consumption before and during pregnancy, as well as paternal consumption. Asking when in pregnancy alcohol consumption changed allowed us to calculate a weighted average of the amount consumed weekly during the first trimester. The odds ratio for consumption of seven or more drinks per week was 1.9 [95% confidence interval (CI) = 1.1-3.4] when adjusted for maternal smoking, passive smoking, and maternal age. Data were too sparse to examine higher consumption levels. There was some evidence that cases may have had less opportunity than controls to decrease consumption during their shorter pregnancies, potentially biasing the odds ratio upward. The adjusted odds ratio for any paternal alcohol consumption was 1.2 (CI = 0.93-1.5), with no dose-response effect seen. Among pregnancies in which the mother did not drink, there was no association with paternal drinking.

Parental cigarette smoking and the risk of spontaneous abortion

Although cigarette smoking is often considered a risk factor for spontaneous abortion, the epidemiologic literature is actually inconsistent. Therefore, the authors examined maternal and paternal smoking and maternal passive smoke exposure using data from a large case-control study of spontaneous abortion (626 cases and 1,300 controls) conducted in Santa Clara County, California, in 1986 and 1987. No excess risk of spontaneous abortion was seen in the 1% of women who smoked an average of more than 20 cigarettes per day in the first trimester. Moderate smokers (11-20 cigarettes per day) had a slightly elevated crude odds ratio of 1.3 (95% confidence interval 0.9-1.9), which was close to unity after adjustment for covariates. Paternal smoking showed a slight crude elevation for moderate and heavy smoking, but no association after adjustment. In contrast, maternal exposure to environmental tobacco smoke for 1 hour or more per day was associated with spontaneous abortion, even after adjustment (odds ratio = 1.5, 95% confidence interval 1.2-1.9). For both maternal direct and environmental exposure, the association appeared to be stronger in second-trimester abortions. Several studies have found stronger associations of smoking with late versus early abortions, perhaps reflecting smoking-associated placental insufficiency and fetal hypoxia.

Is drinking water related to spontaneous abortion? Reviewing the evidence from the California Department of Health Services Studies

Because preliminary data suggested a relation between risk of spontaneous abortion and tapwater consumption during pregnancy, the California Department of Health Services included questions on prenatal water consumption in all reproductive studies conducted between 1982 and 1988. Results from four of these five retrospective data bases suggest that women abstaining from tapwater or drinking bottled water during the first trimester of pregnancy may be at reduced risk of spontaneous abortion. Fetal resorption frequencies seen in an accompanying toxicology study were consistent with these epidemiologic findings, although not conclusive. Tap and bottled water samples from these study areas were analyzed for agents that might account for these findings. Differences in trace element composition and biological activity were observed, but the reproductive significance of these differences is unknown. This paper presents an overview of these studies, which are presented in detail separately. Three alternative explanations for these findings--bias, chance, and causality--are reviewed.

Tap or bottled water consumption and spontaneous abortion: a 1986 case-control study in California

To investigate whether drinking tap or bottled water during pregnancy affects the risk of spontaneous abortion, we asked questions about water consumption in a large case-control study (626 cases, 1,300 controls). The study ascertained cases from hospital pathology laboratory reports of pregnancies that began in 1986 and obtained controls from birth certificates. The crude odds ratio for consumption of any vs no cold tapwater at home during the first trimester was 1.2 (95% confidence interval = 1.0-1.5), with no dose-response effect. The crude odds ratio for any bottled water consumption was 0.79 (95% confidence interval = 0.65-0.96), with a downward trend by amount consumed. Adjusting for many potential confounders did not alter these associations appreciably, although some variables appeared to be effect modifiers. The point estimates were stronger among women who were more difficult to contact, suggesting the possibility of bias.