Prenatal exposure to stressful life events is associated with masculinized anogenital distance (AGD) in female infants

In animal models, prenatal stress programs reproductive development in the resulting offspring, however little is known about effects in humans. Anogenital distance (AGD) is a commonly used, sexually dimorphic biomarker of prenatal androgen exposure in many species. In rodents, prenatally stressed males have shorter AGD than controls (suggesting lower prenatal androgen exposure), whereas prenatally stressed females have longer AGD than controls (suggesting greater prenatal androgen exposure). Our objective was to investigate the relationship between stressful life events in pregnancy and infant AGD. In a prospective cohort study, pregnant women and their partners reported exposure to stressful life events during pregnancy. Pregnancies in which the couple reported 4+ life events were considered highly stressed. After birth (average 16.5 months), trained examiners measured AGD in the infants (137 males, 136 females). After adjusting for age, body size and other covariates, females born to couples reporting high stress had significantly longer (i.e. more masculine) AGD than females born to couples reporting low stress (p=0.015). Among males, high stress was weakly, but not significantly, associated with shorter AGD. Our results suggest prenatal stress may masculinize some aspects of female reproductive development in humans. More sensitive measures of prenatal stress and additional measures of reproductive development are needed to better understand these relationships and clarify mechanisms.

Sex specific impact of perinatal bisphenol A (BPA) exposure over a range of orally administered doses on rat hypothalamic sexual differentiation

Bisphenol A (BPA) is a high volume production chemical used in polycarbonate plastics, epoxy resins, thermal paper receipts, and other household products. The neural effects of early life BPA exposure, particularly to low doses administered orally, remain unclear. Thus, to better characterize the dose range over which BPA alters sex specific neuroanatomy, we examined the impact of perinatal BPA exposure on two sexually dimorphic regions in the anterior hypothalamus, the sexually dimorphic nucleus of the preoptic area (SDN-POA) and the anterioventral periventricular (AVPV) nucleus. Both are sexually differentiated by estradiol and play a role in sex specific reproductive physiology and behavior. Long Evans rats were prenatally exposed to 10, 100, 1000, 10,000μg/kg bw/day BPA through daily, non-invasive oral administration of dosed-cookies to the dams. Offspring were reared to adulthood. Their brains were collected and immunolabeled for tyrosine hydroxylase (TH) in the AVPV and calbindin (CALB) in the SDN-POA. We observed decreased TH-ir cell numbers in the female AVPV across all exposure groups, an effect indicative of masculinization. In males, AVPV TH-ir cell numbers were significantly reduced in only the BPA 10 and BPA 10,000 groups. SDN-POA endpoints were unaltered in females but in males SDN-POA volume was significantly lower in all BPA exposure groups. CALB-ir was significantly lower in all but the BPA 1000 group. These effects are consistent with demasculinization. Collectively these data demonstrate that early life oral exposure to BPA at levels well below the current No Observed Adverse Effect Level (NOAEL) of 50mg/kg/day can alter sex specific hypothalamic morphology in the rat.

Women's exposure to phthalates in relation to use of personal care products

Several phthalates, particularly diethyl phthalate (DEP) and di-n-butyl phthalate, can be used in personal care products (PCPs) to fix fragrance and hold color. We investigated associations between women's reported use of PCPs within the 24 h before urine collection and concentrations of several urinary phthalate metabolites. Between 2002 and 2005, 337 women provided spot urine samples and answered questions regarding their use of 13 PCPs at a follow-up visit 3-36 months after pregnancy. We examined associations between urinary concentrations of several phthalate metabolites and use of PCPs using linear regression. Use of individual PCPs ranged from 7% (nail polish) to 91% (deodorant). After adjusting for age, education, and urinary creatinine, women reporting use of perfume had 2.92 times higher (95% CI: 2.20-3.89) concentration of monoethyl phthalate (MEP; the primary metabolite of DEP) than other women. Other PCPs that were significantly associated with MEP concentrations included: hair spray, nail polish, and deodorant. MEP concentrations increased with the number of PCPs used. PCP use was widespread in this group of recently pregnant women. Women's use of PCPs, particularly of perfumes and fragranced products, was positively associated with urinary concentration of multiple phthalate metabolites.

Physical activity and television watching in relation to semen quality in young men

BACKGROUND

Semen quality appears to have declined over the past decades but reasons for this decline are unresolved. The concurrent increase in sedentary behaviour may be a contributing factor. The objective of this study was to evaluate the relationship of physical activity and television (TV) watching with sperm parameters in a population of young, healthy men.

METHODS

Men aged 18-22 years (n=189) from the Rochester Young Men's Study (2009-2010) participated in this analysis. Physical activity (h/week of moderate and vigorous exercise) and TV watching (h/week of TV, video or DVD watching) over the past 3 months were assessed via questionnaire. Semen quality was assessed by sperm concentration, motility, morphology and total sperm count.

RESULTS

Sperm concentration and total sperm count were directly related to physical activity after multivariable adjustment (p-trend=0.01 and 0.04); men in the highest quartile of moderate-to-vigorous activity (≥15 h/week) had 73% (95% CI 15% to 160%) higher sperm concentration than men in the lowest quartile (<5 h/week). TV watching was inversely associated with sperm concentration and total sperm count in multivariable analyses (p-trend=0.05 and 0.06); men in the highest quartile of TV watching (>20 h/week) had 44% (95% CI 15 to 63%) lower sperm concentration than men in the lowest quartile (0 h/week). These measures of physical and leisure time activities were not significantly associated with sperm motility or morphology.

CONCLUSIONS

In this population of healthy men, higher moderate-to-vigorous activity and less TV watching were significantly associated with higher total sperm count and sperm concentration.

Sperm counts may have declined in young university students in Southern Spain

Several studies have investigated temporal trends in semen quality in Northern Europe, but none has examined this question in Southern Europe. A prior study conducted in Almeria Province (Southern Spain) reported higher sperm count and concentration among Spanish young men recruited from 2001 to 2002 compared with young men from Northern Europe. The aim of this new study was to examine whether semen quality has changed among Spanish young men in the last decade. In this cross-sectional study, questionnaires and semen samples were collected from 215 healthy young university students from Murcia Region between 2010 and 2011. The 273 men from the Almeria study previously studied were included in a trend analysis of the two populations from Southern Spain. Descriptive statistics were calculated for the Murcia study population and these and semen variables for the Murcia and Almeria study populations were compared. Study methods and population characteristics were similar across the two studies. Therefore, we used multiple linear regression analyses on the combined population (controlling for study centre, age, ejaculation abstinence time, season, smoking, medication during the last 3 months, Body mass index (BMI), presence of varicocoele and prenatal exposure to tobacco) to look for a birth-cohort effect over the combined study period (2001-2011). Sperm concentration and total sperm count declined significantly with year of birth in the pooled analysis (β = -0.04 and β = -0.06, respectively, both p < 0.01). Sperm counts were significantly lower in Murcia study subjects than in the Almeria participants; sperm concentration median (5th-95th) = 44.0 (8.9-129) million/mL vs. 51.0 (5.0-206) million/mL; p < 0.01 and total sperm count = 121 (17.8-400) million vs. 149 (8.0-599) million; p < 0.01. Other semen variables did not differ significantly between the two studies. Our study suggests that total sperm count and sperm concentration may have declined in young Spanish men over the last decade.

Quality Control of Laboratory Methods for Semen Evaluation in a Multicenter Research Study

Rigorously standardized laboratory protocols and strict quality control (QC) are essential for meaningful comparisons between semen quality data from multiple sites. We describe our experience with the Study for Future Families (SFF), a multicenter study of semen quality in the United States. Detailed protocols were developed, and technicians from each study site attended a training session at the central laboratory. Technicians received blinded replicates from diluted semen specimens for counting by MicroCell and hemacytometer. Sperm motility was assessed using videotaped recordings for simple percent motility and categorical assessment of individual sperm progression as recommended by the World Health Organization (WHO). The mean intertechnician coefficient of variation for individual specimens was 12.6% for MicroCell counts, 15.2% for hemacytometer counts, and 10.5% for percent motility. Intratechnician coefficients of variation averaged 10.3% for MicroCell counts, 12.5% for hemacytometer counts, and 5.2% for percent motility. The average percent differences between the technicians' values and the central standard for individual specimens were 13.5%, 16.6%, and 11.9% for MicroCell counts, hemacytometer counts, and simple percent motility, respectively. We achieved our goal of maintaining mean intratechnician coefficients of variation and mean percent differences from the standard values of 15% or less for measurements of simple percent motility and sperm concentration by MicroCell. Standardization using the Improved Neubauer hemacytometer chamber proved more difficult. We were not successful in standardizing a method for categorical assessment of individual sperm progression.

Anogenital distance is related to ovarian follicular number in young Spanish women: a cross-sectional study

BACKGROUND

In animals, anogenital distance (AGD) at birth reflects androgen levels during pregnancy and predicts adult AGD. Little is known about AGD in relation to female reproductive characteristics in humans, a question this study was designed to explore.

METHODS

We used multiple linear and logistic regression analyses to model the relationships between adult female reproductive system characteristics (e.g. ovarian morphology, menstrual cycle) and two measures of AGD [anus-fourchette (AGD(AF)) and anus-clitoris (AGD(AC))] in 100 college-age volunteers in Spain. Ovarian morphology was classified as having < 6 or ≥ 6 follicles per ovary.

RESULTS

Both AGD measures were positively associated with ovarian follicle number, with AGD(AF) being more strongly associated. Women in the upper tertile of the AGD(AF) and AGD(AC) distributions were more likely to have ≥ 6 ovarian follicles [OR: 6.0 (95% CI 2.0, 17.6) and 3.0 (95% CI 1.1, 8.6), respectively] compared to women in the lowest tertile.

CONCLUSIONS

Increased follicular recruitment has been related to excess androgen exposure in utero in toxicological studies. Our results suggest that the androgenic environment during early fetal life may influence reproductive system development, including AGD, in human females.

Dietary patterns and semen quality in young men

STUDY QUESTION

Are different dietary patterns associated with semen parameters in young men?

STUDY ANSWER

The consumption of a Prudent dietary pattern was significantly associated with higher progressive sperm motility and unrelated to sperm concentration and morphology. The consumption of a Western dietary pattern was unrelated to conventional semen quality parameters.

WHAT IS KNOWN ALREADY

Over the past decades there has been evidence of a concomitant decline in sperm and diet quality. Yet whether diet composition influences semen quality remains largely unexplored.

STUDY DESIGN, SIZE, DURATION

The Rochester Young Men's Study (n= 188) was a cross-sectional study conducted between 2009 and 2010 at the University of Rochester.

PARTICIPANTS, SETTING, METHODS

Men aged 18-22 years were included in this analysis. Diet was assessed via food frequency questionnaire and dietary patterns were identified by factor analysis. Linear regression was used to analyze the relation between diet patterns and conventional semen quality parameters (sperm concentration, progressive motility and morphology) adjusting for abstinence time, multivitamin use, race, smoking status, BMI, recruitment period, moderate-to-intense exercise and total calorie intake.

RESULTS

Two dietary patterns were identified by factor analysis. The 'Western' pattern was characterized by high intake of red and processed meat, refined grains, pizza, snacks, high-energy drinks and sweets. The 'Prudent' pattern was characterized by high intake of fish, chicken, fruit, vegetables, legumes and whole grains. The Prudent pattern was positively associated with percent progressively motile sperm in multivariate models (P-trend = 0.04). Men in the highest quartile of the Prudent diet had 11.3% (95% CI 1.3, 21.3) higher % progressively motile sperm compared with men in the lowest quartile. The Prudent pattern was unrelated to sperm concentration and morphology. The Western pattern was not associated with any semen parameter.

LIMITATIONS

This was a cross-sectional and observational study, which limited our ability to determine causality of diet on semen quality parameters.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings support the suggestion that a diet rich in fruits, vegetables, chicken, fish and whole grains may be an inexpensive and safe way to improve at least one measure of semen quality.

STUDY FUNDING/COMPETING INTERESTS

The authors are supported by NIH grant T32DK007703-16 and P30DK46200 and European Union DEER Grant 212844. The authors have no competing interests to declare.

Lifestyle behaviors associated with exposures to endocrine disruptors

Identifying and characterizing sources of exposure to phthalates and bisphenol A (BPA) have proved challenging due to the presence of multiple co-exposures resulting from a wide variety of home environments and lifestyles. We hypothesized that the consistent lifestyle of an Old Order Mennonite (OOM) community would provide an ideal setting in which to characterize sources of exposure to BPA and phthalates. We obtained urine samples from ten mid-term pregnant OOM women (ages-21-39) to determine concentrations of 9 phthalate metabolites and BPA and collected a self-reported survey of participants' household environment, product use, and lifestyle within a 48-h period prior to urine collection. We compared their metabolite concentrations to pregnant women included in the National Health and Nutrition Examination Survey (NHANES 2007-2008). Although OOM participants reported some use of plastic and fragranced household products, concentrations of metabolites were lower and significantly less for BPA (p=0.002) and phthalate metabolites MEHP (p=0.0215), MiBP (p=0.0020) and MEP (p=0.021), when compared to NHANES pregnant women. Levels of other phthalate metabolites were also lower in this population. Our data suggest three practices that may contribute to these lower levels: (1) consuming mostly homegrown produce (ingestion), (2) no cosmetics and limited use of personal care products, and (3) transportation primarily by sources other than automobiles.

Urinary concentrations of di(2-ethylhexyl) phthalate metabolites and serum reproductive hormones: pooled analysis of fertile and infertile men

Urinary concentrations of metabolites of the anti-androgenic xenobiotic di-(2-ethylhexyl) phthalate (DEHP) were previously shown to be weakly associated with serum levels of several hormones in 2 disparate US populations: partners of pregnant women participating in the Study for Future Families and partners in infertile couples from Massachusetts General Hospital infertility clinic. The observed associations between phthalate metabolites and reproductive hormones were robust and insensitive to the characteristics of the subpopulation or the laboratory in which the hormones were measured, despite the fact that these 2 populations span a range of fertility, urinary phthalate metabolites, and reproductive hormone levels. We therefore examined associations between urinary metabolites of DEHP and reproductive hormones-follicle-stimulating hormone, luteinizing hormone, testosterone (T), inhibin B, and estradiol (E(2))-and sex hormone-binding globulin (SHBG) in the pooled population. The magnitude of the associations seen were similar to those reported for each population separately, but effect estimates were more precise because of the increased sample size and the greater range of phthalate metabolite concentrations and hormone levels. Urinary concentrations of 3 metabolites of DEHP [mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP)] were inversely associated with the free androgen index (FAI = T/SHBG) and calculated free testosterone. Urinary concentrations of MEHHP and MEOHP were positively associated with SHBG, and MEHP was inversely associated with E(2). No other phthalate metabolites were associated with serum hormones, consistent with results in each population. Our results in this diverse population suggest that DEHP exposure is robustly associated with some male sex steroid hormones.

Socioeconomic factors and phthalate metabolite concentrations among United States women of reproductive age

INTRODUCTION

Relatively little is known about the socioeconomic correlates of phthalate metabolite urine concentrations among the general population, exposures of increasing public health concern, particularly for women of reproductive age.

METHODS

We pooled data from the 2001-2008 cycles of the National Health and Nutrition Examination Survey to examine the associations between phthalate metabolite concentrations (including the molar sum of four di-2-ethylhexyl phthalate (DEHP) metabolites, the molar sum of two dibutyl phthalate (DBP) metabolites, and metabolites of benzylbutyl phthalate (BzBP) and diethyl phthalate (DEP)) with socioeconomic indicators (including ethnicity, education, income, and food security status) among women 20 to 39 years age. We also derived a socioeconomic status summary measure using factor analysis and investigated its associations with metabolite concentrations.

RESULTS

In fully adjusted models, the lowest quartile of overall socioeconomic status was associated with 1.83 (95% CI=1.54-2.17) times the concentrations of mono-benzyl phthalate (MBzP), and 0.72 (95% CI=0.54-0.98) times the concentrations of (molar sum) DEHP metabolites compared with the highest quartile of overall socioeconomic status. This latter association was driven primarily by educational attainment. All Non-White ethnicities combined had 1.24 (95% CI=1.09-1.40) times the concentrations of (molar sum) DBP metabolites, 1.32 (95% CI=1.12-1.56) times the mono-ethyl phthalate (MEP) concentrations, and 0.82 (95% CI=0.71-0.96) the concentrations of MBzP of Non-Hispanic Whites.

CONCLUSIONS

Biomarkers of phthalate exposure vary with socioeconomic factors in women of reproductive age in the United States. Given the public health concern surrounding phthalate exposure, more research is needed to elucidate the reasons for these differences.

Associations between urinary metabolites of di(2-ethylhexyl) phthalate and reproductive hormones in fertile men

Widely used man-made chemicals, including phthalates, can induce hormonal alterations through a variety of cellular and molecular mechanisms. A number of rodent and observational studies have consistently demonstrated the anti-androgenic effect of several phthalates. However, there are only limited data on the relationship between exposure to these chemicals and reproductive hormone levels in men. All men (n=425) were partners of pregnant women who participated in the Study for Future Families in five US cities and provided urine and serum samples on the same day. Eleven phthalate metabolites were measured in urine and serum samples were analysed for reproductive hormones, including follicle-stimulating hormone, luteinizing hormone, testosterone, inhibin B and oestradiol and sex hormone-binding globulin (SHBG). Pearson correlations and parametric tests were used for unadjusted analyses, and multiple linear regression analysis was performed controlling for appropriate covariates. We observed weak or no associations with urinary phthalates other than di(2-ethylhexyl) phthalate (DEHP). All measures of testosterone [total, calculated free testosterone and the free androgen index (FAI)] were inversely correlated with the urinary concentrations of four DEHP metabolites. After adjustment by appropriate covariates, there was no longer an association between urinary DEHP metabolite concentrations and total testosterone levels; however, FAI was significantly associated with the urinary concentrations of several DEHP metabolites. SHBG was positively related to the urinary concentrations of mono(2-ethylhexyl) phthalate, but not with other DEHP metabolites, an association that was attenuated after adjustment. Our results suggest that DEHP exposure of fertile men is associated with minor alterations of markers of free testosterone.

Shorter anogenital distance predicts poorer semen quality in young men in Rochester, New York

BACKGROUND

In male rodents, anogenital distance (AGD) provides a sensitive and continuous correlate of androgen exposure in the intrauterine environment and predicts later reproductive success. Some endocrine-disrupting chemicals can alter male reproductive tract development, including shortening AGD, in both rodents and humans. Whether AGD is related to semen quality in human is unknown.

OBJECTIVE

We examined associations between AGD and semen parameters in adult males.

METHODS

We used multiple regression analyses to model the relationships between sperm parameters and two alternative measures of AGD [from the anus to the posterior base of the scrotum (AGD(AS)) and to the cephalad insertion of the penis (AGD(AP))] in 126 volunteers in Rochester, New York.

RESULTS

AGD(AS), but not AGD(AP), was associated with sperm concentration, motility, morphology, total sperm count, and total motile count (p-values, 0.002-0.048). Men with AGD(AS) below (vs. above) the median were 7.3 times more likely (95% confidence interval, 2.5-21.6) to have a low sperm concentration (< 20 × 10⁶/mL). For a typical study participant, sperm concentrations were 34.7 × 10⁶/mL and 51.6 × 10⁶/mL at the 25th and 75th percentiles of (adjusted) AGD(AS).

CONCLUSIONS

In our population, AGD(AS) was a strong correlate of all semen parameters and a predictor of low sperm concentration. In animals, male AGD at birth reflects androgen levels during the masculinization programming window and predicts adult AGD and reproductive function. Our results suggest, therefore, that the androgenic environment during early fetal life exerts a fundamental influence on both AGD and adult sperm counts in humans, as demonstrated in rodents.

Are environmental levels of bisphenol a associated with reproductive function in fertile men?

BACKGROUND

Rodent and in vitro studies have demonstrated the estrogenicity of bisphenol A (BPA). However, few studies have examined the relationship between human exposure to BPA and male reproductive function.

OBJECTIVES

We investigated the relationships between environmental BPA exposure and reproductive parameters, including semen quality and male reproductive hormones, in prospectively recruited fertile men.

METHODS

Participants (n = 375) were partners of pregnant women who participated in the Study for Future Families in four U.S. cities, and all of the men provided blood, semen, and urine samples. BPA was measured in urine. Serum samples were analyzed for reproductive hormones, including follicle-stimulating hormone, luteinizing hormone (LH), testosterone, inhibin B, estradiol, and sex hormone-binding globulin (SHBG), as well as the free androgen index (FAI). Semen analyses were performed according to World Health Organization criteria. Pearson correlations were used for unadjusted analyses, and multiple linear regression analyses were used to examine associations controlling for age, body mass index, smoking, ethnicity, urinary creatinine concentration, time of sample collection, and duration of abstinence.

RESULTS

After multivariate adjustment, we observed no significant associations between any semen parameter and urinary BPA concentration. However, a significant inverse association was found between urinary BPA concentration and FAI levels and the FAI/LH ratio, as well as a significant positive association between BPA and SHBG.

CONCLUSIONS

Our results suggest that, in fertile men, exposure to low environmental levels of BPA may be associated with a modest reduction in markers of free testosterone, but any effects on reproductive function are likely to be small, and of uncertain clinical significance.

Caffeine intake and semen quality in a population of 2,554 young Danish men

The authors examined the association between semen quality and caffeine intake among 2,554 young Danish men recruited when they were examined to determine their fitness for military service in 2001-2005. The men delivered a semen sample and answered a questionnaire including information about caffeine intake from various sources, from which total caffeine intake was calculated. Moderate caffeine and cola intakes (101-800 mg/day and < or =14 0.5-L bottles of cola/week) compared with low intake (< or =100 mg/day, no cola intake) were not associated with semen quality. High cola (>14 0.5-L bottles/week) and/or caffeine (>800 mg/day) intake was associated with reduced sperm concentration and total sperm count, although only significant for cola. High-intake cola drinkers had an adjusted sperm concentration and total sperm count of 40 mill/mL (95% confidence interval (CI): 32, 51) and 121 mill (95% CI: 92, 160), respectively, compared with 56 mill/mL (95% CI: 50, 64) and 181 mill (95% CI: 156, 210) in non-cola-drinkers, which could not be attributed to the caffeine they consumed because it was <140 mg/day. Therefore, the authors cannot exclude the possibility of a threshold above which cola, and possibly caffeine, negatively affects semen quality. Alternatively, the less healthy lifestyle of these men may explain these findings.

Serum inhibin-b in fertile men is strongly correlated with low but not high sperm counts: a coordinated study of 1,797 European and US men

OBJECTIVE

To describe associations between serum inhibin-b and sperm counts, adjusted for effect of time of blood sampling, in larger cohorts than have been previously reported.

DESIGN

Cross-sectional studies of spermatogenesis markers.

SETTING

Four European and four US centers.

PATIENT(S)

Fertile men (1,797) were included and examined from October 1996-February 2005.

INTERVENTION(S)

The study was observational and therefore without any intervention.

MAIN OUTCOME MEASURE(S)

Associations between inhibin-b and semen variables controlled for time of blood sampling and other covariates.

RESULT(S)

Inhibin-b decreased about 2.00% per hour from 8 am-12 pm and then about 3.25% per hour from 12 pm-4 pm. There was a strong positive association between inhibin-b levels less than 150 pg/mL and both sperm concentration and total sperm count (slopes of the regression lines were β=0.011 and β=0.013 for natural logarithm-transformed sperm concentration and total sperm count, respectively). For inhibin-b levels of 150-300 pg/mL the associations were not as steep (β=0.002), but still significant. For inhibin-b levels more than 300 pg/mL there was little association to the sperm counts. Neither sperm motility nor morphology was significantly related to inhibin-b level in any group.

CONCLUSION(S)

Serum inhibin-b levels decrease nonlinearly during the daytime, and are positively correlated with sperm counts, but the predictive power is best when inhibin-b is low.

Prenatal phthalate exposure and reduced masculine play in boys

Foetal exposure to antiandrogens alters androgen-sensitive development in male rodents, resulting in less male-typical behaviour. Foetal phthalate exposure is also associated with male reproductive development in humans, but neurodevelopmental outcomes have seldom been examined in relation to phthalate exposure. To assess play behaviour in relation to phthalate metabolite concentration in prenatal urine samples, we recontacted participants in the Study for Future Families whose phthalate metabolites had been measured in mid-pregnancy urine samples. Mothers completed a questionnaire including the Pre-School Activities Inventory, a validated instrument used to assess sexually dimorphic play behaviour. We examined play behaviour scores (masculine, feminine and composite) in relationship to (log(10)) phthalate metabolite concentrations in mother's urine separately for boys (N = 74) and girls (N = 71). Covariates (child's age, mother's age and education and parental attitude towards atypical play choices) were controlled using multivariate regression models. Concentrations of dibutyl phthalate metabolites, mono-n-butyl phthalate (MnBP) and mono-isobutyl phthalate (MiBP) and their sum, were associated with a decreased (less masculine) composite score in boys (regression coefficients -4.53,-3.61 and -4.20, p = 0.01, 0.07 and 0.04 for MnBP, MiBP and their sum respectively). Concentrations of two urinary metabolites of di(2-ethylhexyl) phthalate (DEHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) and mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and the sum of these DEHP metabolites plus mono(2-ethylhexyl) phthalate were associated with a decreased masculine score (regression coefficients -3.29,-2.94 and -3.18, p = 0.02, 0.04 and 0.04) for MEHHP, MEOHP and the sum respectively. No strong associations were seen between behaviour and urinary concentrations of any other phthalate metabolites in boys, or between girls' scores and any metabolites. These data, although based on a small sample, suggest that prenatal exposure to antiandrogenic phthalates may be associated with less male-typical play behaviour in boys. Our findings suggest that these ubiquitous environmental chemicals have the potential to alter androgen-responsive brain development in humans.

Phthalates and other additives in plastics: human exposure and associated health outcomes

Concern exists over whether additives in plastics to which most people are exposed, such as phthalates, bisphenol A or polybrominated diphenyl ethers, may cause harm to human health by altering endocrine function or through other biological mechanisms. Human data are limited compared with the large body of experimental evidence documenting reproductive or developmental toxicity in relation to these compounds. Here, we discuss the current state of human evidence, as well as future research trends and needs. Because exposure assessment is often a major weakness in epidemiological studies, and in utero exposures to reproductive or developmental toxicants are important, we also provide original data on maternal exposure to phthalates during and after pregnancy (n = 242). Phthalate metabolite concentrations in urine showed weak correlations between pre- and post-natal samples, though the strength of the relationship increased when duration between the two samples decreased. Phthalate metabolite levels also tended to be higher in post-natal samples. In conclusion, there is a great need for more human studies of adverse health effects associated with plastic additives. Recent advances in the measurement of exposure biomarkers hold much promise in improving the epidemiological data, but their utility must be understood to facilitate appropriate study design.

Plastics, the environment and human health: current consensus and future trends

Plastics have transformed everyday life; usage is increasing and annual production is likely to exceed 300 million tonnes by 2010. In this concluding paper to the Theme Issue on Plastics, the Environment and Human Health, we synthesize current understanding of the benefits and concerns surrounding the use of plastics and look to future priorities, challenges and opportunities. It is evident that plastics bring many societal benefits and offer future technological and medical advances. However, concerns about usage and disposal are diverse and include accumulation of waste in landfills and in natural habitats, physical problems for wildlife resulting from ingestion or entanglement in plastic, the leaching of chemicals from plastic products and the potential for plastics to transfer chemicals to wildlife and humans. However, perhaps the most important overriding concern, which is implicit throughout this volume, is that our current usage is not sustainable. Around 4 per cent of world oil production is used as a feedstock to make plastics and a similar amount is used as energy in the process. Yet over a third of current production is used to make items of packaging, which are then rapidly discarded. Given our declining reserves of fossil fuels, and finite capacity for disposal of waste to landfill, this linear use of hydrocarbons, via packaging and other short-lived applications of plastic, is simply not sustainable. There are solutions, including material reduction, design for end-of-life recyclability, increased recycling capacity, development of bio-based feedstocks, strategies to reduce littering, the application of green chemistry life-cycle analyses and revised risk assessment approaches. Such measures will be most effective through the combined actions of the public, industry, scientists and policymakers. There is some urgency, as the quantity of plastics produced in the first 10 years of the current century is likely to approach the quantity produced in the entire century that preceded.

Our plastic age

Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation.

Bisphenol A data in NHANES suggest longer than expected half-life, substantial nonfood exposure, or both

BACKGROUND

It is commonly stated in the literature on human exposure to bisphenol A (BPA) that food is the predominant BPA exposure source, and that BPA is rapidly and completely cleared from the body. If this is correct, BPA levels in fasting individuals should decrease with increased fasting time.

OBJECTIVES

We set out to investigate the relationship between urine BPA concentration and fasting time in a population-based sample.

METHODS

We modeled log BPA urine concentration as a function of fasting time, adjusted for urine creatinine and other confounders, in 1,469 adult participants in the 2003-2004 National Health and Nutrition Examination Survey. We estimated the BPA "population-based half-life" (pop(1/2)) for a fasting time of 0-24 hr, < 4.5 hr, 4.5-8.5 hr, and > 8.5 hr.

RESULTS

The overall pop(1/2) for the 0- to 24-hr interval was 43 hr [95% confidence interval (CI), 26-119 hr]. Among those reporting fasting times of 4.5-8.5 hr (n = 441), BPA declined significantly with fasting time, with a pop(1/2) of 4.1 hr (95% CI, 2.6-10.6 hr). However, within the fasting time intervals of 0-4.5 hr (n = 129) and 8.5-24 hr (n = 899), we saw no appreciable decline. Fasting time did not significantly predict highest (> 12 ng/mL) or lowest (below limit of detection) BPA levels.

CONCLUSIONS

Overall, BPA levels did not decline rapidly with fasting time in this sample. This suggests substantial nonfood exposure, accumulation in body tissues such as fat, or both. Explaining these findings may require experimental pharmacokinetic studies of chronic BPA exposure, further examination of BPA levels and effects in fat, and a search for important nonfood sources.

Maternal urinary metabolites of Di-(2-Ethylhexyl) phthalate in relation to the timing of labor in a US multicenter pregnancy cohort study

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer used in consumer and medical products that can cross the placenta, disrupt steroid hormone synthesis, and activate peroxisome proliferator-activated receptor gamma. The authors examined DEHP exposure in relation to the timing of labor in a pregnancy cohort study of 283 women recruited in 4 US states (California, Iowa, Minnesota, and Missouri) between 2000 and 2004. The authors estimated associations between concentrations of DEHP metabolites and gestational age at delivery using linear regression models and associations between DEHP metabolites and clinical outcomes using logistic regression models. After covariate adjustment, women at the 75th percentile of DEHP metabolite concentrations had a 2-day-longer mean length of gestation than women at the 25th percentile (95% confidence interval: 1.4, 3.3). Log-unit increases in mono-2-ethylhexyl phthalate and mono-2-ethyl-5-oxohexyl phthalate concentrations were associated with increased odds of cesarean section delivery (30% and 50% increased odds, respectively), increased odds of delivering at 41 weeks or later (100% and 120% increased odds), and reduced odds of preterm delivery (50% and 60% decreased odds). These data suggest that DEHP may interfere with signaling related to the timing of parturition.

Maternal and infant urinary phthalate metabolite concentrations: are they related?

BACKGROUND

Phthalates are synthetic chemicals that are ubiquitous in our society and may have adverse health effects in humans. Detectable concentrations of phthalate metabolites have been found in adults and children, but no studies have examined the relationship between maternal and infant phthalate metabolite concentrations.

OBJECTIVE

We investigated the relationship between maternal and infant urinary phthalate metabolite concentrations.

METHODS

We measured nine phthalate metabolites in urine samples from 210 mother/infant pairs collected on the same study visit day (1999-2005) and obtained demographic history from questionnaires. Using multivariate linear regression analyses, we examined the degree to which maternal urine phthalate metabolite concentration predicted infant phthalate metabolite concentration. All analyses were adjusted for infant age, creatinine concentration, and race.

RESULTS

Correlation coefficients between phthalate metabolite concentrations in the urine of mothers and their infants were generally low but increased with decreasing age of infant. In multivariate analyses, mother's phthalate metabolite concentrations were significantly associated with infants' concentrations for six phthalate metabolites: monobenzyl phthalate, monoethyl phthalate, monoisobutyl phthalate, and three metabolites of di(2-ethylhexyl) phthalate: mono(2-ethylhexyl) phthalate, mono(2-ethyl-5-hydroxy-hexyl) phthalate, and mono(2-ethyl-5-oxo-hexyl) phthalate (p-values for all coefficients <0.05).

DISCUSSION

Mother's urine phthalate metabolite concentration is significantly associated with infant urine phthalate metabolite concentration for six phthalate metabolites. It is plausible that shared exposures to phthalates in the immediate surrounding environment accounted for these relationships, but other unidentified sources may also contribute to infants' phthalate exposures. This study indicates the importance of further identifying infant phthalate exposures that may be distinct from maternal exposures in order to decrease overall infant phthalate exposures.