Prenatal phenol and phthalate exposures and birth outcomes

Exposure to environmental endocrine disruptors and child development

Exposure to exogenous chemicals can impact endocrine function at multiple sites and through numerous specific modes of action, which may have far-reaching impacts on human health and development. Widespread human exposure to numerous known or suspected endocrine disrupting chemicals (EDCs) has been documented in the US and worldwide, as have trends for increased rates of endocrine-related diseases and disorders among children. While human epidemiology studies of exposure to EDCs and children’s health remain extremely limited, there is a growing body of evidence showing that exposure to a number of chemicals commonly found in consumer goods, personal care products, food, drinking water, and other sources may adversely impact child development through altered endocrine function. This narrative review provides a brief introduction to several common EDCs (with a specific focus on persistent organic pollutants, phthalates, bisphenol A, and contemporary use pesticides, which only represents a small number of all known or suspected EDCs), an overview of the state of the human evidence for adverse impacts of EDCs on child development (fetal growth, early reproductive tract development, pubertal development, neurodevelopment, and obesity), guidance for health care providers based on current knowledge, and recommendations for future research.

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.

Correcting for the influence of sampling conditions on biomarkers of exposure to phenols and phthalates: a 2-step standardization method based on regression residuals

BACKGROUND

Environmental epidemiology and biomonitoring studies typically rely on biological samples to assay the concentration of non-persistent exposure biomarkers. Between-participant variations in sampling conditions of these biological samples constitute a potential source of exposure misclassification. Few studies attempted to correct biomarker levels for this error. We aimed to assess the influence of sampling conditions on concentrations of urinary biomarkers of select phenols and phthalates, two widely-produced families of chemicals, and to standardize biomarker concentrations on sampling conditions.

METHODS

Urine samples were collected between 2002 and 2006 among 287 pregnant women from Eden and Pélagie cohorts, from which phthalates and phenols metabolites levels were assayed. We applied a 2-step standardization method based on regression residuals. First, the influence of sampling conditions (including sampling hour, duration of storage before freezing) and of creatinine levels on biomarker concentrations were characterized using adjusted linear regression models. In the second step, the model estimates were used to remove the variability in biomarker concentrations due to sampling conditions and to standardize concentrations as if all samples had been collected under the same conditions (e.g., same hour of urine collection).

RESULTS

Sampling hour was associated with concentrations of several exposure biomarkers. After standardization for sampling conditions, median concentrations differed by--38% for 2,5-dichlorophenol to +80 % for a metabolite of diisodecyl phthalate. However, at the individual level, standardized biomarker levels were strongly correlated (correlation coefficients above 0.80) with unstandardized measures.

CONCLUSIONS

Sampling conditions, such as sampling hour, should be systematically collected in biomarker-based studies, in particular when the biomarker half-life is short. The 2-step standardization method based on regression residuals that we proposed in order to limit the impact of heterogeneity in sampling conditions could be further tested in studies describing levels of biomarkers or their influence on health.

Exposure to phthalates and phenols during pregnancy and offspring size at birth

BACKGROUND

Data concerning the effects of prenatal exposures to phthalates and phenols on fetal growth are limited in humans. Previous findings suggest possible effects of some phenols on male birth weight.

OBJECTIVE

Our aim was to assess the relationships between prenatal exposures to phthalates and phenols and fetal growth among male newborns.

METHODS

We conducted a case-control study on male malformations of the genitalia nested in two French mother-child cohorts with recruitment between 2002 and 2006. We measured, in maternal urinary samples collected between 6 and 30 gestational weeks, the concentrations (micrograms per liter) of 9 phenol (n = 191 pregnant women) and 11 phthalate metabolites (n = 287). Weight, length, and head circumference at birth were collected from maternity records. Statistical analyses were corrected for the oversampling of malformation cases.

RESULTS

Adjusted birth weight decreased by 77 g [95% confidence interval (CI): -129, -25] and by 49 g (95% CI: -86, -13) in association with a 1-unit increase in ln-transformed 2,4-dichlorophenol (DCP) and 2,5-DCP urinary concentrations, respectively. Benzophenone-3 (BP3) ln-transformed concentrations were positively associated with weight (26 g; 95% CI: -2, 54) and head circumference at birth (0.1 cm; 95% CI: 0.0, 0.2). Head circumference increased by 0.3 cm (95% CI: 0.0, 0.7) in association with a 1-unit increase in ln-transformed BPA concentration. For phthalate metabolites there was no evidence of monotonic associations with birth weight.

CONCLUSIONS

Consistent with findings of a previous study, we observed evidence of an inverse association of 2,5-DCP and a positive association of BP3 with male birth weight.

Association between pregnancy loss and urinary phthalate levels around the time of conception

BACKGROUND

Animal studies indicate that some phthalate metabolites may harm female reproductive function.

OBJECTIVES

We assessed the associations between exposure to phthalate metabolites and pregnancy loss.

METHODS

Using a previously established cohort of couples planning their first pregnancy, we analyzed four primary and two oxidized secondary phthalate metabolites in urine samples collected on day 10 after the first day of the last menstrual period before conception occurred (n = 128) and during the previous cycle (if any, n = 111). Subclinical embryonal loss was identified by repeated measurement of urinary human chorionic gonadotropin, and information on clinical spontaneous abortions was obtained by telephone interview with the mother.

RESULTS

Pregnancy loss (n = 48) was increased among women with urinary concentration of monoethylhexyl phthalate (MEHP) in the upper tertile in the conception sample compared with women in the lowest tertile [adjusted odds ratio (OR) = 2.9; 95% confidence interval (CI): 1.1, 7.6]. The corresponding OR for subclinical embryonal loss (n = 32) was 40.7 (95% CI: 4.5, 369.5).

CONCLUSIONS

The phthalate metabolite MEHP was associated with higher occurrence of pregnancy loss. Because this is the first human study to show this association and the sample size is small, the findings need to be corroborated in independent studies.

Urinary, Circulating, and Tissue Biomonitoring Studies Indicate Widespread Exposure to Bisphenol A

Bisphenol A (BPA) is one of the highest-volume chemicals produced worldwide, and human exposure to BPA is thought to be ubiquitous. Thus, there are concerns that the amount of BPA to which humans are exposed may cause adverse health effects. We examined many possibilities for why biomonitoring and toxicokinetic studies could come to seemingly conflicting conclusions. More than 80 published human biomonitoring studies that measured BPA concentrations in human tissues, urine, blood, and other fluids, along with two toxicokinetic studies of human BPA metabolism were examined. Unconjugated BPA was routinely detected in blood (in the nanograms per milliliter range), and conjugated BPA was routinely detected in the vast majority of urine samples (also in the nanograms per milliliter range). In stark contrast, toxicokinetic studies proposed that humans are not internally exposed to BPA. Available data from biomonitoring studies clearly indicate that the general population is exposed to BPA and is at risk from internal exposure to unconjugated BPA. The two toxicokinetic studies that suggested human BPA exposure is negligible have significant deficiencies, are directly contradicted by hypothesis-driven studies, and are therefore not reliable for risk assessment purposes.

Relationships between urinary biomarkers of phytoestrogens, phthalates, phenols, and pubertal stages in girls

Phytoestrogens, phthalates, and phenols are estrogen-disrupting chemicals that have a pronounced effect at puberty. They are exogenous chemicals that are either plant-derived or man-made, and can alter the functions of the endocrine system and cause various health defects by interfering with the synthesis, metabolism, binding, or cellular responses of natural estrogens. Phytoestrogens, phthalates, and phenols are some of the potent estrogens detectable in urine. Phytoestrogens are plant-derived xenestrogens found in a wide variety of food products, like soy-based food, beverages, several fruits, and vegetables. Exposure to phytoestrogens can delay breast development and further lead to precocious puberty. The effect of phytoestrogens is mediated through estrogen receptors α and β or by binding with early immediate genes, such as jun and fos. Phthalates are multifunctional synthetic chemicals used in plastics, polyvinyl chloride products, cosmetics, hair spray, and children’s toys. Phthalates have been shown to cause defeminization, thelarche, precocious puberty, and an increase in breast and pubic hair in pubertal girls. However, reports are also available that show no association of phthalates with precocious puberty in girls. Phthalates can act through a receptor-mediated signaling pathway or affect the production of luteinizing hormone and follicle-stimulating hormone that has a direct effect on estrogen formation. Phenols like bisphenol A are industrial chemicals used mainly in the manufacture of polycarbonates and plastic materials. Bisphenol A has been shown to cause precocious puberty and earlier menarche in pubertal girls. Reports suggest that the neurotoxic effect of bisphenol A can be mediated either by competing with estradiol for binding with estrogen receptors or via the ERK/NK-kappa or ERRγ pathway. This review demonstrates the effects of phytoestrogens, phthalates, and phenols on the development of girls during puberty.

Associations between phthalate metabolite urinary concentrations and body size measures in New York City children

OBJECTIVE

To examine prospectively associations between urinary phthalate metabolite concentrations and body size measures in children.

METHODS

Urinary concentrations of nine phthalate metabolites: monoethyl (MEP); mono-n-butyl (MBP); mono-(3-carboxypropyl) (MCPP); monobenzyl (MBzP); mono-isobutyl (MiBP); mono-(2-ethylhexyl) (MEHP); mono-(2-ethyl-5-oxohexyl) (MEOHP); mono-(2-ethyl-5-carboxypentyl) (MECPP); and mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and the molar sum of the low molecular-weight phthalate metabolites (low MWP: MEP, MBP and MiBP) and high molecular-weight phthalate metabolites (high MWP: MECPP, MEHHP, MEOHP, MEHP and MBzP) and of four di-(2-ethylhexyl) phthalate (DEHP) metabolites (ΣDEHP: MEHP, MEHHP, MEOHP, MECPP) and anthropometry, including body mass index and waist circumference were measured among 387 Hispanic and Black, New York City children who were between six and eight years at cohort enrollment (2004-2007). Relationships between baseline metabolite concentrations and body size characteristics obtained one year later were examined using multivariate-adjusted geometric means for each body size characteristic by continuous and categories of phthalate metabolite concentrations. Stratified analyses by body size (age/sex specific) were conducted.

RESULTS

No significant associations are reported among all girls or boys. Dose response relationships were seen with monoethyl phthalate and the sum of low molecular-weight phthalates and body mass index and waist circumference among overweight children; for increasing monoethyl phthalate concentration quartiles among girls, adjusted mean body mass indexes were as follows: 21.3, 21.7, 23.8, 23.5 and adjusted mean waist circumference (cm) were as follows: 73.4, 73.5, 79.2, 78.8 (p-trend<0.001 for both).

CONCLUSION

In this prospective analysis we identified positive relationships between urinary concentrations of monoethyl phthalate and the sum of low molecular-weight phthalates and body size measures in overweight children. These are metabolites with concentrations above 1 μM.

Thyroid disrupting chemicals in plastic additives and thyroid health

The globally escalating thyroid nodule incidence rates may be only partially ascribed to better diagnostics, allowing for the assessment of environmental risk factors on thyroid disease. Endocrine disruptors or thyroid-disrupting chemicals (TDC) like bisphenol A, phthalates, and polybrominated diphenyl ethers are widely used as plastic additives in consumer products. This comprehensive review studied the magnitude and uncertainty of TDC exposures and their effects on thyroid hormones for sensitive subpopulation groups like pregnant women, infants, and children. Our findings qualitatively suggest the mixed, significant (α = 0.05) TDC associations with natural thyroid hormones (positive or negative sign). Future studies should undertake systematic meta-analyses to elucidate pooled TDC effect estimates on thyroid health indicators and outcomes.

Impact of early-life bisphenol A exposure on behavior and executive function in children

OBJECTIVES

To estimate the impact of gestational and childhood bisphenol A (BPA) exposures on behavior and executive function at 3 years of age and to determine whether child gender modified those associations.

METHODS

We used a prospective birth cohort of 244 mothers and their 3-year-old children from the greater Cincinnati, Ohio, area. We characterized gestational and childhood BPA exposures by using the mean BPA concentrations in maternal (16 and 26 weeks of gestation and birth) and child (1, 2, and 3 years of age) urine samples, respectively. Behavior and executive function were measured by using the Behavior Assessment System for Children 2 (BASC-2) and the Behavior Rating Inventory of Executive Function-Preschool (BRIEF-P).

RESULTS

BPA was detected in >97% of the gestational (median: 2.0 μg/L) and childhood (median: 4.1 μg/L) urine samples. With adjustment for confounders, each 10-fold increase in gestational BPA concentrations was associated with more anxious and depressed behavior on the BASC-2 and poorer emotional control and inhibition on the BRIEF-P. The magnitude of the gestational BPA associations differed according to child gender; BASC-2 and BRIEF-P scores increased 9 to 12 points among girls, but changes were null or negative among boys. Associations between childhood BPA exposure and neurobehavior were largely null and not modified by child gender.

CONCLUSIONS

In this study, gestational BPA exposure affected behavioral and emotional regulation domains at 3 years of age, especially among girls. Clinicians may advise concerned patients to reduce their exposure to certain consumer products, but the benefits of such reductions are unclear.

Endocrine disrupting chemicals and disease susceptibility

Environmental chemicals have significant impacts on biological systems. Chemical exposures during early stages of development can disrupt normal patterns of development and thus dramatically alter disease susceptibility later in life. Endocrine disrupting chemicals (EDCs) interfere with the body's endocrine system and produce adverse developmental, reproductive, neurological, cardiovascular, metabolic and immune effects in humans. A wide range of substances, both natural and man-made, are thought to cause endocrine disruption, including pharmaceuticals, dioxin and dioxin-like compounds, polychlorinated biphenyls, DDT and other pesticides, and components of plastics such as bisphenol A (BPA) and phthalates. EDCs are found in many everyday products--including plastic bottles, metal food cans, detergents, flame retardants, food additives, toys, cosmetics, and pesticides. EDCs interfere with the synthesis, secretion, transport, activity, or elimination of natural hormones. This interference can block or mimic hormone action, causing a wide range of effects. This review focuses on the mechanisms and modes of action by which EDCs alter hormone signaling. It also includes brief overviews of select disease endpoints associated with endocrine disruption.

Prenatal exposure to phthalates and infant development at 6 months: prospective Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

There are increasing concerns over adverse effects of prenatal phthalate exposure on the neurodevelopment of infants.

OBJECTIVES

Our goal was to explore the association between prenatal di(2-ethylhexyl) phthalate and dibutyl phthalate exposure and the Mental and Psychomotor Developmental Indices (MDI and PDI, respectively) of the Bayley Scales of Infant Development at 6 months, as part of the Mothers and Children's Environmental Health Study.

METHODS

Between 2006 and 2009, 460 mother-infant pairs from Seoul, Cheonan, and Ulsan, Korea, participated. Prenatal mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono-n-butyl phthalate (MBP) were measured in one urine sample acquired from each mother during the third trimester of pregnancy. Associations with log-transformed creatinine-corrected phthalate concentrations were estimated using linear regression models adjusted for potential confounders.

RESULTS

MDI was inversely associated with the natural log concentrations (micrograms per gram creatinine) of MEHHP [β = -0.97; confidence interval (CI), -1.85 to -0.08] and MEOHP (β = -0.95; CI, -1.87 to -0.03), and PDI was inversely associated with MEHHP (β = -1.20; CI, -2.33 to -0.08). In males, MDI was inversely associated with MEHHP (β = -1.46; CI, -2.70 to -0.22), MEOHP (β = -1.57; CI, -2.87 to -0.28), and MBP (β = -0.93; CI, -1.82 to -0.05); PDI was inversely associated with MEHHP (β = -2.36; CI, -3.94 to -0.79), MEOHP (β = -2.05; CI, -3.71 to -0.39), and MBP (β = -1.25; CI, -2.40 to -0.11). No significant linear associations were observed for females.

CONCLUSIONS

The results suggest that prenatal exposure to phthalates may be inversely associated with the MDI and PDI of infants, particularly males, at 6 months.

Prenatal exposure to bisphenol A and phthalates and infant neurobehavior

OBJECTIVE

To examine the association of prenatal exposure to bisphenol A and select common phthalates with infant neurobehavior measured at 5 weeks.

METHODS

We compared the concentration of maternal urinary metabolites of bisphenol A and phthalates at two distinct time points in pregnancy (16w, 26w) with scores on the NICU Network Neurobehavioral Scale (NNNS) at 5 weeks of age in a cohort of 350 mother/infant pairs.

RESULTS

Prenatal exposure to BPA was not significantly associated with neurobehavioral outcomes at 5 weeks. Significant associations between prenatal exposure to measured phthalates and infant neurobehavioral outcomes differed by type of phthalate and were only seen with exposure measured at 26 weeks. Higher total di-butyl phthalate (DBP) metabolites at 26w were associated with improved behavioral organization evidenced by decreased arousal (p=.04), increased self-regulation (p=.052), and decreased handling (p=.02). In males, higher total di-2-ethylhexyl phthalate (DEHP) metabolites at 26w were associated with more nonoptimal reflexes (p=.02).

CONCLUSION

The association between prenatal phthalate exposure and infant neurobehavior differed by type of phthalate and was evident only with exposure measured at 26w. Prenatal exposure to DBP was associated with improved behavioral organization in 5-week-old infants. Prenatal exposure to DEHP was associated with nonoptimal reflexes in male infants. There was no evidence of an association between prenatal BPA exposure and infant neurobehavior.

Bisphenol-A and phthalates contamination of urine samples by catheters in the Elfe pilot study: implications for large-scale biomonitoring studies

Exposure to phthalates and Bisphenol A could cause developmental and reproductive toxicity. This study provides a first assessment of these exposures for more than 250 French pregnant women. The median concentrations of total and free Bisphenol A in urine were similar to those in other studies except the highest concentrations (5% of women had total and free Bisphenol A >50μg/L). Our study highlights high levels of Di-(2-ethylhexyl)-phthalate metabolites in pregnant women, suggesting recent exposure, probably in hospital. Differences between types of delivery (caesarean vs. natural) support this hypothesis. This is a significant implication for large-scale biomonitoring studies among this population.

Urinary concentrations of phthalates and phenols in a population of Spanish pregnant women and children

BACKGROUND

Phthalate and phenol exposure is prevalent among the general population and of potential concern for pregnant women and children because of their suspected susceptibility to endocrine effects.

OBJECTIVES

To evaluate the extent of exposure to several phthalates and phenols in a sample of Spanish pregnant women - according to their individual characteristics (age, social class, education, and body mass index) - and children who participated in the INMA - Infancia y Medio Ambiente (Environment and Childhood) project.

METHODS

One spot urine sample was taken during the third trimester of pregnancy from 120 pregnant women and from 30 4-year old children belonging to 5 Spanish birth cohorts, and analyzed for 11 phthalate metabolites and 9 phenols.

RESULTS

Three metabolites of di(2-ethylhexyl) phthalate, mono-2-ethyl-5-carboxypentyl phthalate, mono-2-ethyl-5-hydroxyhexyl phthalate, and mono-2-ethyl-5-oxohexyl phthalate; two metabolites of dibutyl phthalates, mono-isobutyl phthalate and mono-n-butyl phthalate; monoethyl phthalate (MEP), the main metabolite of diethyl phthalate; and two phenols, methyl paraben (M-PB) and 2,5-dichlorophenol were detected in the urine samples of all women. The highest urinary concentrations were for MEP and M-PB. Urinary concentrations of all phthalate metabolites and of 2,4-dichlorophenol, 2,5-dichlorophenol, and bisphenol A were lower in the pregnant women than in the children. Among women, a positive relationship with social class and education was shown for most of the phthalate metabolites and phenols. Almost all phthalate metabolites varied by region even after adjusting for social class and education.

CONCLUSIONS

Phthalate and phenol exposures are prevalent in a group of pregnant women and young children, two susceptible populations, and these exposures might be positively related to social class.

Environmental toxicant exposure during pregnancy

This literature review is meant to serve as a brief reference for acute and chronic poisonings in pregnant women, specifically involving environmental toxicants commonly present in the home or workplace. These scenarios are familiar to primary care providers but cause great confusion for practitioners and anxiety in the pregnant patient. Herein, we review metals and metalloids, organic solvents, disinfectant byproducts, pesticides, plasticizers, and multiple air pollutants. Reviews of specific studies involving these toxicants are provided to assist practitioners in providing information to patients regarding potential sources, mechanism of action, current laboratory and epidemiological studies, and possible treatments. Literature-based associations with specific toxicants and various pregnancy outcomes are also outlined. Finally, a contact list of important federal and state toxicology support services is provided.

TARGET AUDIENCE

Obstetricians & Gynecologists.

LEARNING OBJECTIVES

After completing this CME activity, physicians should be better able to assess both acute and chronic consequences of various environmental toxic exposures in pregnancy; to evaluate possible pregnancy related specific events surrounding environmental pollutants; and to identify common exposure routes and implement therapeutic interventions where appropriate.

Exposure to phthalates: reproductive outcome and children health. A review of epidemiological studies

Phthalates are a family of industrial chemicals that have been used for a variety of purposes. As the potential consequences of human exposure to phthalates have raised concerns in the general population, they have been studied in susceptible subjects such as pregnant women, infants and children. This article aims at evaluating the impact of exposure to phthalates on reproductive outcomes and children health by reviewing most recent published literature. Epidemiological studies focusing on exposure to phthalates and pregnancy outcome, genital development, semen quality, precocious puberty, thyroid function, respiratory symptoms and neurodevelopment in children for the last ten years were identified by a search of the PubMed, Medline, Ebsco, Agricola and Toxnet literature bases. The results from the presented studies suggest that there are strong and rather consistent indications that phthalates increase the risk of allergy and asthma and have an adverse impact on children's neurodevelopment reflected by quality of alertness among girls, decreased (less masculine) composite score in boys and attention deficit hyperactivity disorder. Results of few studies demonstrate negative associations between phthalate levels commonly experienced by the public and impaired sperm quality (concentration, morphology, motility). Phthalates negatively impact also on gestational age and head circumference; however, the results of the studies were not consistent. In all the reviewed studies, exposure to phthalates adversely affected the level of reproductive hormones (luteinizing hormone, free testosterone, sex hormone-binding globulin), anogenital distance and thyroid function. The urinary levels of phthalates were significantly higher in the pubertal gynecomastia group, in serum in girls with premature thelarche and in girls with precocious puberty. Epidemiological studies, in spite of their limitations, suggest that phthalates may affect reproductive outcome and children health. Considering the suggested health effects, more epidemiologic data is urgently needed and, in the meantime, precautionary policies must be implemented.

Phthalates and their metabolites in breast milk--results from the Bavarian Monitoring of Breast Milk (BAMBI)

Phthalates have long been used as plasticizers to soften plastic products and, thus, are ubiquitous in modern life. As part of the Bavarian Monitoring of Breast Milk (BAMBI), we aimed to characterize the exposure of infants to phthalates in Germany. Overall, 15 phthalates, including di-2-ethylhexyl phthalate (DEHP), di-n-butyl phthalate (DnBP), di-isobutyl phthalate (DiBP), di-isononyl phthalate (DiNP), three primary metabolites of DEHP [mono-(2-ethylhexyl) phthalate (MEHP), mono-isobutyl phthalate (MiBP), and mono-n-butyl phthalate (MnBP)], and two secondary metabolites of DEHP were analyzed in 78 breast milk samples. We found median concentrations of 3.9 ng/g for DEHP, 0.8 ng/g for DnBP, and 1.2 ng/g for DiBP, while other parent phthalates were found in only some or none of the samples at levels above the limit of quantitation. In infant formula (n=4) we observed mean values of 19.7 ng/g (DEHP), 3.8 ng/g (DnBP), and 3.6 ng/g (DiBP). For MEHP, MiBP, and MnBP, the median values in breast milk were 2.3 μg/l, 11.8 μg/l, and 2.1 μg/l, respectively. The secondary metabolites were not detected in any samples. Using median and 95th percentile values, we estimated an "average" and "high" daily intake for an exclusively breast-fed infant of 0.6 μg/kg body weight (b.w.) and 2.1 μg/kg b.w., respectively, for DEHP, 0.1 μg/kg b.w. and 0.5 μg/kg b.w. for DnBP, and 0.2 μg/kg b.w. and 0.7 μg/kg b.w. for DiBP. For DiNP, intake values were 3.2 μg/kg b.w. and 6.4 μg/kg b.w., respectively, if all values in milk were set half of the detection limit or the detection limit. The above-mentioned "average" and "high" intake values corresponded to only about 2% to 7%, respectively, of the recommended tolerable daily intake. Thus, it is not likely that an infant's exposure to phthalates from breast milk poses any significant health risk. Nevertheless, other sources of phthalates in this vulnerable phase have to be considered. Moreover, it should be noted that for infants nourished with formula, phthalate intake is of the same magnitude or slightly higher (DEHP) than for exclusively breast-fed infants.

Developmental toxic potential of di-n-propyl phthalate administered orally to rats

The objective of this study was to evaluate the developmental toxic potential of di-n-propyl phthalate (DnPP) in rats. Pregnant Sprague-Dawley rats were given DnPP at doses of 0 (olive oil), 0.5, 1 and 1.5 g kg⁻¹ per day, by gavage, on gestation days 6-20. Benchmark doses were calculated for the effects of DnPP on fetal weight and anogenital distance of the male fetuses. Maternal body weight gain was significantly reduced at 1.5 g kg⁻¹ per day, over gestation days 6-9. DnPP-treated dams also showed a statistically significant increase in liver weight and a mild but statistically significant peroxisomal enzyme induction at 1 or 1.5 g kg⁻¹ per day. Male and female fetal body weights were significantly reduced at 1.5 g kg⁻¹ per day. There was a statistically significant decrease in the anogenital distance of the male fetuses at 1 and 1.5 g kg⁻¹ per day, and three males (of 75) showed malpositioned testis at the high dose. The mean percentage of fetuses per litter with cervical and thoracic rudimentary ribs was significantly increased at 1 and 1.5 g kg⁻¹ per day. Delayed ossification was seen at 1 g kg⁻¹ per day (phalanges) and 1.5 g kg⁻¹ per day (hyoid, sternebrae, and phalanges). No treatment-related effects on prenatal viability or on fetal external or visceral malformations or variations were observed at any dose. Thus, there was no evidence of teratogenicity up to the high dose of 1.5 g kg⁻¹ per day. The no-observed-adverse-effect level (NOAEL) for developmental toxicity was 0.5 g kg⁻¹ per day.

Bisphenol A and children's health

PURPOSE OF REVIEW

Bisphenol A (BPA) is a widely used chemical that has been shown to adversely affect health outcomes in experimental animal studies, particularly following fetal or early life exposure. Despite widespread human exposure in the United States and developed countries, there are limited epidemiological studies on the association of BPA with adverse health outcomes. This review briefly summarizes the epidemiological literature with special emphasis on childhood health outcomes.

RECENT FINDINGS

Several studies report correlations between urinary BPA and serum sex steroid hormone concentrations in adults. Two studies report weak associations between urinary BPA concentrations and delayed onset of breast development in girls. One study found a relationship between prenatal BPA exposure and increased hyperactivity and aggression in 2-year-old female children.

SUMMARY

Additional large prospective cohort studies are needed to confirm and validate findings from animal studies. Even in the absence of epidemiological studies, concern over adverse effects of BPA is warranted given the unique vulnerability of the developing fetus and child. Healthcare providers are encouraged to practice primary prevention and counsel patients to reduce BPA exposures.

In utero exposure to bisphenol-A and its effect on birth weight of offspring

To examine the effect of in utero BPA exposure on the birth weight of offspring, a total of 587 children from families in which parent(s) did or did not have occupational exposure to BPA were examined. Their birth weights were obtained by an in-person interview of the mother. Parental BPA exposure level during the index pregnancy was determined through personal air sampling measurements and exposure history. After controlling for potential confounders, parental exposure to BPA in the workplace during pregnancy was associated with decreased birth weight. The association was stronger for maternal exposure which is statistically significant (P=0.02). A dose-response relationship was observed with increased BPA exposure levels in pregnancy associated with greater magnitude of decrease of birth weight in offspring (P=0.003). Our findings provide the new epidemiologic evidence suggesting that in utero exposure to BPA during pregnancy may be associated with decreased birth weight in offspring.

Bisphenol A: developmental toxicity from early prenatal exposure

Bisphenol A (BPA) exposure has been documented in pregnant women, but consequences for development are not yet widely studied in human populations. This review presents research on the consequences for offspring of BPA exposure during pregnancy. Extensive work in laboratory rodents has evaluated survival and growth of the conceptus, interference with embryonic programs of development, morphological sex differentiation, sex differentiation of the brain and behavior, immune responsiveness, and mechanism of action. Sensitive measures include RAR, aryl hydrocarbon receptor, and Hox A10 gene expression, anogenital distance, sex differentiation of affective and exploratory behavior, and immune hyperresponsiveness. Many BPA effects are reported at low doses (10-50 µg/kg d range) by the oral route of administration. At high doses (>500,000 µg/kg d) fetal viability is compromised. Much of the work has centered around the implications of the estrogenic actions of this agent. Some work related to thyroid mechanism of action has also been explored. BPA research has actively integrated current knowledge of developmental biology, concepts of endocrine disruption, and toxicological research to provide a basis for human health risk assessment.

Ultraviolet radiation: a hazard to children and adolescents

Ultraviolet radiation (UVR) causes the 3 major forms of skin cancer: basal cell carcinoma; squamous cell carcinoma; and cutaneous malignant melanoma. Public awareness of the risk is not optimal, overall compliance with sun protection is inconsistent, and melanoma rates continue to rise. The risk of skin cancer increases when people overexpose themselves to sun and intentionally expose themselves to artificial sources of UVR. Yet, people continue to sunburn, and teenagers and adults alike remain frequent visitors to tanning parlors. Pediatricians should provide advice about UVR exposure during health-supervision visits and at other relevant times. Advice includes avoiding sunburning, wearing clothing and hats, timing activities (when possible) before or after periods of peak sun exposure, wearing protective sunglasses, and applying and reapplying sunscreen. Advice should be framed in the context of promoting outdoor physical activity. Adolescents should be strongly discouraged from visiting tanning parlors. Sun exposure and vitamin D status are intertwined. Cutaneous vitamin D production requires sunlight exposure, and many factors, such as skin pigmentation, season, and time of day, complicate efficiency of cutaneous vitamin D production that results from sun exposure. Adequate vitamin D is needed for bone health. Accumulating information suggests a beneficial influence of vitamin D on many health conditions. Although vitamin D is available through the diet, supplements, and incidental sun exposure, many children have low vitamin D concentrations. Ensuring vitamin D adequacy while promoting sun-protection strategies will require renewed attention to children's use of dietary and supplemental vitamin D.

Ultraviolet radiation: a hazard to children and adolescents

Sunlight sustains life on earth. Sunlight is essential for vitamin D synthesis in the skin. The sun's ultraviolet rays can be hazardous, however, because excessive exposure causes skin cancer and other adverse health effects. Skin cancer is a major public health problem; more than 2 million new cases are diagnosed in the United States each year. Ultraviolet radiation (UVR) causes the 3 major forms of skin cancer: basal cell carcinoma; squamous cell carcinoma; and cutaneous malignant melanoma. Exposure to UVR from sunlight and artificial sources early in life elevates the risk of developing skin cancer. Approximately 25% of sun exposure occurs before 18 years of age. The risk of skin cancer is increased when people overexpose themselves to sun and intentionally expose themselves to artificial sources of UVR. Public awareness of the risk is not optimal, compliance with sun protection is inconsistent, and skin-cancer rates continue to rise in all age groups including the younger population. People continue to sunburn, and teenagers and adults are frequent visitors to tanning parlors. Sun exposure and vitamin D status are intertwined. Adequate vitamin D is needed for bone health in children and adults. In addition, there is accumulating information suggesting a beneficial influence of vitamin D on various health conditions. Cutaneous vitamin D production requires sunlight, and many factors complicate the efficiency of vitamin D production that results from sunlight exposure. Ensuring vitamin D adequacy while promoting sun-protection strategies, therefore, requires renewed attention to evaluating the adequacy of dietary and supplemental vitamin D. Daily intake of 400 IU of vitamin D will prevent vitamin D deficiency rickets in infants. The vitamin D supplementation amounts necessary to support optimal health in older children and adolescents are less clear. This report updates information on the relationship of sun exposure to skin cancer and other adverse health effects, the relationship of exposure to artificial sources of UVR and skin cancer, sun-protection methods, vitamin D, community skin-cancer-prevention efforts, and the pediatrician's role in preventing skin cancer. In addition to pediatricians' efforts, a sustained public health effort is needed to change attitudes and behaviors regarding UVR exposure.

Developmental basis of disease: environmental impacts

Exposure to environmental chemicals and other environmental stressors have health impacts on the fetus that may not be apparent until later in life. The concept of developmental origins of disease should be expanded to include these early life exposures in addition to the effects of nutrition and maternal factors. This paper will describe the toxicological, biological and epidemiological issues that are pertinent to conducting research on environmental exposures early in life and their health consequences over the life span.

Leveraging Epidemiology to Improve Risk Assessment

The field of environmental public health is at an important crossroad. Our current biomonitoring efforts document widespread exposure to a host of chemicals for which toxicity information is lacking. At the same time, advances in the fields of genomics, proteomics, metabolomics, genetics and epigenetics are yielding volumes of data at a rapid pace. Our ability to detect chemicals in biological and environmental media has far outpaced our ability to interpret their health relevance, and as a result, the environmental risk paradigm, in its current state, is antiquated and ill-equipped to make the best use of these new data. In light of new scientific developments and the pressing need to characterize the public health burdens of chemicals, it is imperative to reinvigorate the use of environmental epidemiology in chemical risk assessment. Two case studies of chemical assessments from the Environmental Protection Agency Integrated Risk Information System database are presented to illustrate opportunities where epidemiologic data could have been used in place of experimental animal data in dose-response assessment, or where different approaches, techniques, or studies could have been employed to better utilize existing epidemiologic evidence. Based on the case studies and what can be learned from recent scientific advances and improved approaches to utilizing human data for dose-response estimation, recommendations are provided for the disciplines of epidemiology and risk assessment for enhancing the role of epidemiologic data in hazard identification and dose-response assessment.

Endocrine disruptors and childhood social impairment

Prenatal exposure to endocrine disruptors has the potential to impact early brain development. Neurodevelopmental toxicity in utero may manifest as psychosocial deficits later in childhood. This study investigates prenatal exposure to two ubiquitous endocrine disruptors, the phthalate esters and bisphenol A (BPA), and social behavior in a sample of adolescent inner-city children. Third trimester urines of women enrolled in the Mount Sinai Children's Environmental Health Study between 1998 and 2002 (n=404) were analyzed for phthalate metabolites and BPA. Mother-child pairs were asked to return for a follow-up assessment when the child was between the ages of 7 and 9 years. At this visit, mothers completed the Social Responsiveness Scale (SRS) (n=137), a quantitative scale for measuring the severity of social impairment related to Autistic Spectrum Disorders (ASD) in the general population. In adjusted general linear models increasing log-transformed low molecular weight (LMW) phthalate metabolite concentrations were associated with greater social deficits (β=1.53, 95% CI 0.25-2.8). Among the subscales, LMWP were also associated with poorer Social Cognition (β=1.40, 95% CI 0.1-2.7); Social Communication (β=1.86, 95% CI 0.5-3.2); and Social Awareness (β=1.25, 95% CI 0.1-2.4), but not for Autistic Mannerisms or Social Motivation. No significant association with BPA was found (β=1.18, 95% CI -0.75, 3.11). Prenatal phthalate exposure was associated with childhood social impairment in a multiethnic urban population. Even mild degrees of impaired social functioning in otherwise healthy individuals can have very important adverse effects over a child's lifetime. These results extend our previous finding of atypical neonatal and early childhood behaviors in relation to prenatal phthalate exposure.

Bisphenol a exposure in Mexico City and risk of prematurity: a pilot nested case control study

BACKGROUND

Presence of Bisphenol A (BPA) has been documented worldwide in a variety of human biological samples. There is growing evidence that low level BPA exposure may impact placental tissue development and thyroid function in humans. The aim of this present pilot study was to determine urinary concentrations of BPA during the last trimester of pregnancy among a small subset of women in Mexico City, Mexico and relate these concentrations to risk of delivering prematurely.

METHODS

A nested case-control subset of 60 participants in the Early Life Exposure in Mexico to ENvironmental Toxicants (ELEMENT) study in Mexico City, Mexico were selected based on delivering less than or equal to 37 weeks of gestation and greater than 37 weeks of gestation. Third trimester archived spot urine samples were analyzed by online solid phase extraction coupled with high performance liquid chromatography isotope dilution tandem mass spectrometry.

RESULTS

BPA was detected in 80.0% (N = 48) of the urine samples; total concentrations ranged from < 0.4 μg/L to 6.7 μg/L; uncorrected geometric mean was 1.52 μg/L. The adjusted odds ratio of delivering less than or equal to 37 weeks in relation to specific gravity adjusted third trimester BPA concentration was 1.91 (95%CI 0.93, 3.91, p-value = 0.08). When cases were further restricted to births occurring prior to the 37th week (n = 12), the odds ratio for specific-gravity adjusted BPA was larger and statistically significant (p < 0.05).

CONCLUSIONS

This is the first study to document measurable levels of BPA in the urine of a population of Mexican women. This study also provides preliminary evidence, based on a single spot urine sample collected during the third trimester, that pregnant women who delivered less than or equal to 37 weeks of gestation and prematurely (< 37 weeks) had higher urinary concentrations of BPA compared to women delivering after 37 weeks.

Prenatal exposure to phthalate esters and PAHs and birth outcomes

The purpose of this study was to investigate the relationship between the levels of prenatal exposure to phthalate ester and PAHs and birth outcomes among 149 Japanese pregnant women. Urinary concentrations of 9 phthalate ester metabolites, mono methyl phthalate (MMP), mono ethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), mono benzyl phthalate (MBzP), mono-2-ethylhexyl phthalate (MEHP), mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP), mono-2-ethyl-5-oxohexyl phthalate (MEOHP), mono-iso-nonyl phthalate (MINP) and mono-n-octyl phthalate (MnOP) and PAHs metabolite (1-hydroxypyrene, 1-OHP) were analyzed in spot urine samples collected from pregnant women. Correlation analysis and multiple regression analysis were conducted between the concentrations of maternal urinary metabolites and birth outcomes such as birth weight, birth length, head circumference and gestational age. Creatinine-corrected concentration (geometric mean; microg/g cre) was 9.14 (MMP), 9.76 (MEP), 51.6 (MnBP), 5.62 (MBzP), 5.45 (MEHP), 10.6 (MEHHP), 11.3 (MEOHP), 0.031 (MINP), 0.025 (MnOP) and 0.121 (1-OHP). These concentrations are comparable with literature value. The relationships between prenatal exposure to phthalate esters and birth outcomes were not significant. Statistically significant negative correlation was observed between 1-OHP and birth weight, birth length and head circumstances although the correlation was insignificant when only non-smokers were included in multiple regression analysis. In conclusion, we found that prenatal exposure to phthalate esters or PAHs did not affect birth outcomes at the exposure level of the present subjects.

Childhood exposure to phthalates: associations with thyroid function, insulin-like growth factor I, and growth

BACKGROUND

Phthalates are widely used chemicals, and human exposure is extensive. Recent studies have indicated that phthalates may have thyroid-disrupting properties.

OBJECTIVE

We aimed to assess concentrations of phthalate metabolites in urine samples from Danish children and to investigate the associations with thyroid function, insulin-like growth factor I (IGF-I), and growth.

METHODS

In 845 children 4-9 years of age, we determined urinary concentrations of 12 phthalate metabolites and serum levels of thyroid-stimulating hormone, thyroid hormones, and IGF-I.

RESULTS

Phthalate metabolites were detected in all urine samples, of which monobutyl phthalate was present in highest concentration. Phthalate metabolites were negatively associated with serum levels of free and total triiodothyronine, although statistically significant primarily in girls. Metabolites of di(2-ethylhexyl) phthalate and diisononyl phthalate were negatively associated with IGF-I in boys. Most phthalate metabolites were negatively associated with height, weight, body surface, and height gain in both sexes.

CONCLUSIONS

Our study showed negative associations between urinary phthalate concentrations and thyroid hormones, IGF-I, and growth in children. Although our study was not designed to reveal the mechanism of action, the overall coherent negative associations between urine phthalate and thyroid and growth parameters may suggest causative negative roles of phthalate exposures for child health.

Childhood exposure to phthalates: associations with thyroid function, insulin-like growth factor I, and growth

BACKGROUND

Phthalates are widely used chemicals, and human exposure is extensive. Recent studies have indicated that phthalates may have thyroid-disrupting properties.

OBJECTIVE

We aimed to assess concentrations of phthalate metabolites in urine samples from Danish children and to investigate the associations with thyroid function, insulin-like growth factor I (IGF-I), and growth.

METHODS

In 845 children 4-9 years of age, we determined urinary concentrations of 12 phthalate metabolites and serum levels of thyroid-stimulating hormone, thyroid hormones, and IGF-I.

RESULTS

Phthalate metabolites were detected in all urine samples, of which monobutyl phthalate was present in highest concentration. Phthalate metabolites were negatively associated with serum levels of free and total triiodothyronine, although statistically significant primarily in girls. Metabolites of di(2-ethylhexyl) phthalate and diisononyl phthalate were negatively associated with IGF-I in boys. Most phthalate metabolites were negatively associated with height, weight, body surface, and height gain in both sexes.

CONCLUSIONS

Our study showed negative associations between urinary phthalate concentrations and thyroid hormones, IGF-I, and growth in children. Although our study was not designed to reveal the mechanism of action, the overall coherent negative associations between urine phthalate and thyroid and growth parameters may suggest causative negative roles of phthalate exposures for child health.

Bisphenol A and related compounds in dental materials

CONTEXT

Dental sealants and composite filling materials containing bisphenol A (BPA) derivatives are increasingly used in childhood dentistry. Evidence is accumulating that BPA and some BPA derivatives can pose health risks attributable to their endocrine-disrupting, estrogenic properties.

OBJECTIVES

To systematically compile and critically evaluate the literature characterizing BPA content of dental materials; to assess BPA exposures from dental materials and potential health risks; and to develop evidence-based guidance for reducing BPA exposures while promoting oral health.

METHODS

The extant toxicological literature and material safety data sheets were used as data sources.

RESULTS

BPA is released from dental resins through salivary enzymatic hydrolysis of BPA derivatives, and BPA is detectable in saliva for up to 3 hours after resin placement. The quantity and duration of systemic BPA absorption is not clear from the available data. Dental products containing the bisphenol A derivative glycidyl dimethacrylate (bis-GMA) are less likely to be hydrolyzed to BPA and have less estrogenicity than those containing bisphenol A dimethacrylate (bis-DMA). Most other BPA derivatives used in dental materials have not been evaluated for estrogenicity. BPA exposure can be reduced by cleaning and rinsing surfaces of sealants and composites immediately after placement.

CONCLUSIONS

On the basis of the proven benefits of resin-based dental materials and the brevity of BPA exposure, we recommend continued use with strict adherence to precautionary application techniques. Use of these materials should be minimized during pregnancy whenever possible. Manufacturers should be required to report complete information on the chemical composition of dental products and encouraged to develop materials with less estrogenic potential.

Cumulative effects of in utero administration of mixtures of reproductive toxicants that disrupt common target tissues via diverse mechanisms of toxicity

Although risk assessments are typically conducted on a chemical-by-chemical basis, the 1996 Food Quality Protection Act required the US Environmental Protection Agency to consider cumulative risk of chemicals that act via a common mechanism of toxicity. To this end, we are conducting studies with mixtures of chemicals to elucidate mechanisms of joint action at the systemic level with the goal of providing a framework for assessing the cumulative effects of reproductive toxicants. Previous mixture studies conducted with antiandrogenic chemicals are reviewed briefly and two new studies are described. In all binary mixture studies, rats were dosed during pregnancy with chemicals, singly or in pairs, at dosage levels equivalent to approximately one-half of the ED50 for hypospadias or epididymal agenesis. The binary mixtures included androgen receptor (AR) antagonists (vinclozolin plus procymidone), phthalate esters [di(n-butyl) phthalate (DBP) plus benzyl n-butyl phthalate (BBP) and diethyl hexyl phthalate (DEHP) plus DBP], a phthalate ester plus an AR antagonist (DBP plus procymidone), a mixed mechanism androgen signalling disruptor (linuron) plus BBP, and two chemicals which disrupt epididymal differentiation through entirely different toxicity pathways: DBP (AR pathway) plus 2,3,7,8 TCDD (AhR pathway). We also conducted multi-component mixture studies combining several 'antiandrogens'. In the first study, seven chemicals (four pesticides and three phthalates) that elicit antiandrogenic effects at two different sites in the androgen signalling pathway (i.e. AR antagonist or inhibition of androgen synthesis) were combined. In the second study, three additional phthalates were added to make a 10 chemical mixture. In both the binary mixture studies and the multi-component mixture studies, chemicals that targeted male reproductive tract development displayed cumulative effects that exceeded predictions based on a response-addition model and most often were in accordance with predictions based on dose-addition models. In summary, our results indicate that compounds that act by disparate mechanisms of toxicity to disrupt the dynamic interactions among the interconnected signalling pathways in differentiating tissues produce cumulative dose-additive effects, regardless of the mechanism or mode of action of the individual mixture component.

Perinatal exposure to di-(2-ethylhexyl) phthalate leads to restricted growth and delayed lung maturation in newborn rats

BACKGROUND

Pregnant women and infants have significant exposures to the most commonly used plasticizer di-(2-ethylhexyl) phthalate (DEHP).

OBJECTIVES

This study was designed to evaluate the effects of DEHP exposure on growth and lung maturation in rats and determine if DEHP regulation of 11beta-hydroxysteroid dehydrogenase type 1 gene (Hsd11b1) expression in the lung tissue plays a role in its effects on lung maturation.

METHOD

Pregnant Sprague-Dawley rats were treated from gestational day 12 to postnatal day (PND) 21 with DEHP orally at dosages of 0, 10, 100 or 750 mg/kg/day, respectively (n=8 for each group). Two rat pups (one male and one female) from each litter were sacrificed at PND 1 and 21. Body weight was measured and the lung was processed for histology and calculation of lung interstitial tissue proportion as well as real-time PCR determination of the expressions of Hsd11b1, surfactant associated protein-A1 gene (Sftpa1) and B gene (Sftpb).

RESULTS

The perinatal DEHP exposure led to a dose dependent intrauterine and postnatal growth restriction (P<0.001). High dose DEHP (750 mg/kg/day) exposure led to decreased gas-exchange space as evidenced by increased lung interstitial tissue proportion (P<0.001), but did not cause significant changes in Hsd11b1, Sftpa1 or Sftpb gene expression in the rat lung at PND 1. The DEHP-induced change in lung histology remained significant at PND 21 with improvement despite continual exposure to DEHP.

CONCLUSION

Perinatal DEHP exposure leads to growth restriction and delayed lung maturation in newborn rats.

Exposure to selected endocrine disruptors and neonatal outcome of 86 healthy boys from Nice area (France)

In utero and lactational exposure to endocrine disruptors is thought to be potentially harmful on fetal and infant development. Data of exposure in France is scarce. This is a prospective study with (1) collection of 84 cord bloods (CB) and 69 milks from 86 mothers delivering healthy boys (gestational age >or= 34 weeks) at two maternity wards in Southern France, between 2002 and 2005 and (2) screening for 15 xenobiotics with anti-androgenic and/or estrogenic effects: DDE, 7 PCBs, dibutylphthalate and its metabolite mBP, HCB, lindane, linuron, procymidone and vinclozoline. Correlations were made with delivery and neonatal outcomes. All CB and milks were contaminated by one or more xenobiotics (mainly PCBs, DDE, HCB, and phthalates) with good correlation between CB and milk concentrations. Compared to other geographical areas, exposure was usually in the lower bracket. Milk [PCB180] was associated with lower birth weight. Infant head circumference correlated negatively with [HCB] and positively with [mBP] in CB. There was a similar but not significant trend for birth weight and length. [DDE] in milk was higher in older mothers and in women born in Africa. In utero and lactational exposure is ubiquitous in our area. Contamination of milk with HCB, mBP, and PCB 180 showed weak correlations with infant growth. This snapshot of exposure in an area with no major industry will serve for further monitoring.

Urinary, circulating, and tissue biomonitoring studies indicate widespread exposure to bisphenol A

BACKGROUND

Bisphenol A (BPA) is one of the highest-volume chemicals produced worldwide, and human exposure to BPA is thought to be ubiquitous. Thus, there are concerns that the amount of BPA to which humans are exposed may cause adverse health effects. Importantly, results from a large number of biomonitoring studies are at odds with the results from two toxicokinetic studies.

OBJECTIVE

We examined several possibilities for why biomonitoring and toxicokinetic studies could come to seemingly conflicting conclusions.

DATA SOURCES

We examined > 80 published human biomonitoring studies that measured BPA concentrations in human tissues, urine, blood, and other fluids, along with two toxicokinetic studies of human BPA metabolism.

DATA EXTRACTION AND SYNTHESIS

The > 80 biomonitoring studies examined included measurements in thousands of individuals from several different countries, and these studies overwhelmingly detected BPA in individual adults, adolescents, and children. Unconjugated BPA was routinely detected in blood (in the nanograms per milliliter range), and conjugated BPA was routinely detected in the vast majority of urine samples (also in the nanograms per milliliter range). In stark contrast, toxicokinetic studies proposed that humans are not internally exposed to BPA. Some regulatory agencies have relied solely on these toxicokinetic models in their risk assessments.

CONCLUSIONS

Available data from biomonitoring studies clearly indicate that the general population is exposed to BPA and is at risk from internal exposure to unconjugated BPA. The two toxicokinetic studies that suggested human BPA exposure is negligible have significant deficiencies, are directly contradicted by hypothesis-driven studies, and are therefore not reliable for risk assessment purposes.

Dietary intake is associated with phthalate body burden in a nationally representative sample

BACKGROUND

Phthalates are compounds that are used in a wide range of consumer products. However, the contribution of dietary intake to phthalate exposure has not been well defined.

OBJECTIVE

The objective of this study was to assess the contribution of different food types to phthalate exposure. Phthalates are chemicals of concern because of the high levels measured in people and the environment, as well as the demonstrated toxicity in animal studies and limited epidemiological studies. Previous research, although limited, has suggested that phthalates contaminate food in various countries.

METHODS

We conducted an exploratory analysis of data collected as part of the 2003-2004 National Health and Nutrition Examination Survey (NHANES). Associations between dietary intake (assessed by a 24-hr dietary recall) for a range of food types (meat, poultry, fish, fruit, vegetable, and dairy) and phthalate metabolites measured in urine were analyzed using multiple linear regression modeling.

RESULTS

We found that metabolites of di-(2-ethylhexyl) phthalate (DEHP) and high-molecular-weight phthalate metabolites were associated with the consumption of poultry. Monoethyl phthalate, the metabolite of diethyl phthalate (DEP), was associated with vegetable consumption, specifically tomato and potato consumption.

DISCUSSION

These results, combined with results from previous studies, suggest that diet is an important route of intake for phthalates. Further research is needed to determine the sources of food contamination with these toxic chemicals and to describe the levels of contamination of U.S. food in a large, representative U.S. sample.

Relationship between environmental phthalate exposure and the intelligence of school-age children

BACKGROUND

Concern over phthalates has emerged because of their potential toxicity to humans.

OBJECTIVE

We investigated the relationship between the urinary concentrations of phthalate metabolites and children's intellectual functioning.

METHODS

This study enrolled 667 children at nine elementary schools in five South Korean cities. A cross-sectional examination of urine phthalate concentrations was performed, and scores on neuropsychological tests were obtained from both the children and their mothers.

RESULTS

We measured mono-2-ethylhexyl phthalate (MEHP) and mono(2-ethyl-5-oxohexyl)phthalate (MEOHP), both metabolites of di(2-ethylhexyl)phthalate (DEHP), and mono-n-butyl phthalate (MBP), a metabolite of dibutyl phthalate (DBP), in urine samples. The geometric mean (ln) concentrations of MEHP, MEOHP, and MBP were 21.3 microg/L [geometric SD (GSD) = 2.2 microg/L; range, 0.5-445.4], 18.0 microg/L (GSD = 2.4; range, 0.07-291.1), and 48.9 microg/L (GSD = 2.2; range, 2.1-1645.5), respectively. After adjusting for demographic and developmental covariates, the Full Scale IQ and Verbal IQ scores were negatively associated with DEHP metabolites but not with DBP metabolites. We also found a significant negative relationship between the urine concentrations of the metabolites of DEHP and DBP and children's vocabulary subscores. After controlling for maternal IQ, a significant inverse relationship between DEHP metabolites and vocabulary subscale score remained. Among boys, we found a negative association between increasing MEHP phthalate concentrations and the sum of DEHP metabolite concentrations and Wechsler Intelligence Scale for Children vocabulary score; however, among girls, we found no significant association between these variables.

CONCLUSION

Controlling for maternal IQ and other covariates, the results show an inverse relationship between phthalate metabolites and IQ scores; however, given the limitations in cross-sectional epidemiology, prospective studies are needed to fully explore these associations.

Prenatal phthalate exposure is associated with childhood behavior and executive functioning

BACKGROUND

Experimental and observational studies have reported biological consequences of phthalate exposure relevant to neurodevelopment.

OBJECTIVE

Our goal was to examine the association of prenatal phthalate exposure with behavior and executive functioning at 4-9 years of age.

METHODS

The Mount Sinai Children's Environmental Health Study enrolled a multiethnic prenatal population in New York City between 1998 and 2002 (n = 404). Third-trimester maternal urines were collected and analyzed for phthalate metabolites. Children (n = 188, n = 365 visits) were assessed for cognitive and behavioral development between the ages of 4 and 9 years.

RESULTS

In multivariate adjusted models, increased loge concentrations of low molecular weight (LMW) phthalate metabolites were associated with poorer scores on the aggression [beta = 1.24; 95% confidence interval (CI), 0.15- 2.34], conduct problems (beta = 2.40; 95% CI, 1.34-3.46), attention problems (beta = 1.29; 95% CI, 0.16- 2.41), and depression (beta = 1.18; 95% CI, 0.11-2.24) clinical scales; and externalizing problems (beta = 1.75; 95% CI, 0.61-2.88) and behavioral symptom index (beta = 1.55; 95% CI, 0.39-2.71) composite scales. Increased loge concentrations of LMW phthalates were also associated with poorer scores on the global executive composite index (beta = 1.23; 95% CI, 0.09-2.36) and the emotional control scale (beta = 1.33; 95% CI, 0.18- 2.49).

CONCLUSION

Behavioral domains adversely associated with prenatal exposure to LMW phthalates in our study are commonly found to be affected in children clinically diagnosed with conduct or attention deficit hyperactivity disorders.

Exposure to phthalates and breast cancer risk in northern Mexico

BACKGROUND

Phthalates, ubiquitous environmental pollutants that may disturb the endocrine system, are used primarily as plasticizers of polyvinyl chloride and as additives in consumer and personal care products.

OBJECTIVES

In this study, we examined the association between urinary concentrations of nine phthalate metabolites and breast cancer (BC) in Mexican women.

METHODS

We age-matched 233 BC cases to 221 women residing in northern Mexico. Sociodemographic and reproductive characteristics were obtained by direct interviews. Phthalates were determined in urine samples (collected pretreatment from the cases) by isotope dilution/high-performance liquid chromatography coupled to tandem mass spectrometry.

RESULTS

Phthalate metabolites were detected in at least 82% of women. The geometric mean concentrations of monoethyl phthalate (MEP) were higher in cases than in controls (169.58 vs. 106.78 microg/g creatinine). Controls showed significantly higher concentrations of mono-n-butyl phthalate, mono(2-ethyl-5-oxohexyl) phthalate, and mono(3-carboxypropyl) phthalate (MCPP) than did the cases. After adjusting for risk factors and other phthalates, MEP urinary concentrations were positively associated with BC [odds ratio (OR), highest vs. lowest tertile = 2.20; 95% confidence interval (CI), 1.33-3.63; p for trend < 0.01]. This association became stronger when estimated for premenopausal women (OR, highest vs. lowest tertile = 4.13; 95% CI, 1.60-10.70; p for trend < 0.01). In contrast, we observed significant negative associations for monobenzyl phthalate (MBzP) and MCPP.

CONCLUSIONS

We show for the first time that exposure to diethyl phthalate, the parent compound of MEP, may be associated with increased risk of BC, whereas exposure to the parent phthalates of MBzP and MCPP might be negatively associated. These findings require confirmation.

Transcriptional biomarkers of steroidogenesis and trophoblast differentiation in the placenta in relation to prenatal phthalate exposure

BACKGROUND

Phthalates can alter steroidogenesis and peroxisome proliferator-activated receptor gamma (PPARgamma)mediated transcription in rodent tissues. The placenta offers a rich source of biomarkers to study these relationships in humans.

OBJECTIVE

We evaluated whether gestational phthalate exposures in humans were associated with altered human placental steroidogenesis and trophoblast differentiation as measured by markers of mRNA transcription.

METHODS

We measured seven target genes in placentas collected from 54 Dominican and African-American women at delivery in New York City using quantitative real-time polymerase chain reaction (qPCR), normalized to 18S rRNA. qPCR results for the target genes were log-transformed, converted to Z-scores, and grouped into two functional pathways: steroidogenesis (aromatase, cholesterol side chain cleavage enzyme, 17beta-hydroxysteroid dehydrogenase type 1, and cytochrome P450 1B1) and trophoblast differentiation (PPARgamma, aryl hydrocarbon receptor, and human chorionic gonadotropin). Repeated measures models were used to evaluate the association of phthalate metabolites measured in third-trimester urine samples with each group of target genes, accounting for correlation among the genes within a pathway.

RESULTS

Higher urinary concentrations of five phthalate metabolites were associated with lower expression of the target genes reflecting trophoblast differentiation. Results were less consistent for genes in the steroidogenesis pathway and suggested a nonlinear dose-response pattern for some phthalate metabolites.

CONCLUSIONS

We observed a significant association between prenatal exposure to phthalates and placental gene expression within two pathways. Further studies are warranted to understand the significance of this association with respect to fetal development and placental function.

Intra- and inter-individual variability of urinary phthalate metabolite concentrations in Hmong women of reproductive age

The reproducibility of urinary phthalate metabolite concentrations has not been well characterized in non-pregnant women of reproductive age. Our primary study objectives were to describe the distribution of urinary phthalate metabolites concentrations among a population of Hmong women of reproductive age, and to evaluate intra- and inter-individual variability of phthalate metabolite concentrations. Ten phthalate metabolites were measured in first-morning urine samples collected from 45 women and 20 of their spouses, who were members of the Fox River Environment and Diet Study cohort in Green Bay, Wisconsin. Repeated first-morning urine samples were collected and analyzed from 25 women, who provided up to three samples over approximately 1 month. Measurement variability was assessed using intraclass correlations (ICCs) and surrogate category analysis. Linear mixed models were used to evaluate the associations between participant characteristics and phthalate metabolite concentrations. Nine of the 10 phthalate metabolites were detected in >80% of all analyzed samples, of which seven were detected in all samples. As a measure of reliability, ICCs were strongest for monobenzyl phthalate (0.64) and weakest for the metabolites of di(2-ethylhexyl)phthalate (DEHP) (ranging from 0.13 to 0.22). Similarly, surrogate category analysis suggested that a single urine sample characterized an average 1-month exposure with reasonable accuracy across low, medium and high tertiles for all metabolites, except the DEHP metabolites. Geometric mean concentrations of monoethyl phthalate increased with age, but patterns by education, income, body mass index, environmental tobacco smoke or season were not observed when measures were adjusted for urinary dilution. Our results suggest that the participant characteristics assessed in this study have limited influence on inter-individual variability of phthalate metabolite concentrations. With regard to intra-individual variability, our results suggest that urinary concentrations of some phthalate metabolites are more reproducible over time and are less subjected to exposure misclassification than others (e.g., metabolites of DEHP).

Environment and Obesity in the National Children's Study

We describe the approach taken by the National Children's Study (NCS) to understanding the role of environmental factors in the development of obesity. We review the literature with regard to the two core hypotheses in the NCS that relate to environmental origins of obesity and describe strategies that will be used to test each hypothesis. Although it is clear that obesity in an individual results from an imbalance between energy intake and expenditure, control of the obesity epidemic will require understanding of factors in the modern built environment and chemical exposures that may have the capacity to disrupt the link between energy intake and expenditure. Through its embrace of the life-course approach to epidemiology, the NCS will be able to study the origins of obesity from preconception through late adolescence, including factors ranging from genetic inheritance to individual behaviors to the social, built, and natural environment and chemical exposures. It will have sufficient statistical power to examine interactions among these multiple influences, including geneenvironment and geneobesity interactions. A major secondary benefit will derive from the banking of specimens for future analysis.