Endocrine disruptors and childhood social impairment

Considerable exposure to the endocrine disrupting chemicals phthalates and bisphenol-A in intensive care unit (ICU) patients

Critical care medicine has largely benefited from plastic-containing medical devices. However, bisphenol-A (BPA) and phthalates present in the plastics can leach from such devices. We hypothesized that intensive care unit (ICU) patients are exposed to BPA and phthalates through (plastic) medical devices. Serum (n = 118) and urine (n= 102) samples of adult ICU patients (n = 35) were analyzed for total BPA and phthalate metabolites (PMs). Our results showed that adult ICU patients are continuously exposed to phthalates, such as di(2-ethylhexyl)phthalate (DEHP), as well as to BPA, albeit to a lesser extent. This exposure resulted in detectable high serum and urinary levels in almost every patient and at every studied time point. Moreover, these levels were significantly higher than in controls or compared to referenced literature. The chronology of exposure was demonstrated: pre-operative urinary and serum levels of the DEHP metabolites were often below the detection limit. Plastic-containing medical devices were the main source of DEHP exposure: post-operative patients on hemofiltration, extracorporeal membrane oxygenation or both showed serum levels 100-or 1000-fold higher than the levels in the general population reported in the literature. The serum and some of the urinary levels of the DEHP metabolites are the highest ever reported in humans; some at biologically highly relevant concentrations of ≥ 10-50 μM. Despite the continuously tightening regulations, BPA and DEHP appear to be still present in (some) medical devices. Because patient safety is a concern in the ICU, further research into the (possibly toxic and clinical) effects of these chemicals released from medical devices is imperiously necessary.

Using Sibling Designs to Understand Neurodevelopmental Disorders: From Genes and Environments to Prevention Programming

Neurodevelopmental disorders represent a broad class of childhood neurological conditions that have a significant bearing on the wellbeing of children, families, and communities. In this review, we draw on evidence from two common and widely studied neurodevelopmental disorders-autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD)-to demonstrate the utility of genetically informed sibling designs in uncovering the nature and pathogenesis of these conditions. Specifically, we examine how twin, recurrence risk, and infant prospective tracking studies have contributed to our understanding of genetic and environmental liabilities towards neurodevelopmental morbidity through their impact on neurocognitive processes and structural/functional neuroanatomy. It is suggested that the siblings of children with ASD and ADHD are at risk not only of clinically elevated problems in these areas, but also of subthreshold symptoms and/or subtle impairments in various neurocognitive skills and other domains of psychosocial health. Finally, we close with a discussion on the practical relevance of sibling designs and how these might be used in the service of early screening, prevention, and intervention efforts that aim to alleviate the negative downstream consequences associated with disorders of neurodevelopment.

Lessons learned from the application of BEES-C: Systematic assessment of study quality of epidemiologic research on BPA, neurodevelopment, and respiratory health

Epidemiologic studies evaluating associations between biomarkers of exposure to short-lived chemicals and health endpoints in humans face special challenges. Perhaps the most critical challenges are the need to determine the type and optimal number of samples, and the proper timing of specimen collection. Further, as many short-lived chemicals are ubiquitous in the environment, utmost care is required to avoid sample contamination. A separate set of challenges is associated with appropriate interpretation and reporting of results from multiple simultaneous analyses, which are becoming increasingly feasible. The Biomonitoring, Environmental Epidemiology, and Short-Lived Chemicals (BEES-C) instrument is specifically designed to evaluate the quality of epidemiologic studies that measure biomarkers of chemicals with short physiologic half-lives. The instrument provides systematic guidance for evaluating 14 different aspects of study quality divided into three broad categories: 1) biomarker selection and measurement, 2) strategy and execution of exposure assessment, and 3) general considerations of study design and reporting. We evaluated the utility of the BEES-C instrument using epidemiologic studies of exposure to bisphenol A and its association with neurodevelopmental and respiratory health indicators. Each BEES-C element was assessed with respect to needed modifications and concordance among reviewers using professional, scientific judgment. Based on this first use of the BEES-C instrument, we found that most of its elements were effective in comparing the quality of available studies, with reviews generally concordant and justifications consistent. However, we note that certain elements would be improved with slight adjustments and that one of the elements appeared redundant and should be removed.

Phthalate concentrations in house dust in relation to autism spectrum disorder and developmental delay in the CHildhood Autism Risks from Genetics and the Environment (CHARGE) study

BACKGROUND

Phthalates are endocrine-disrupting chemicals that influence thyroid hormones and sex steroids, both critical for brain development.

AIM

We studied phthalate concentrations in house dust in relation to the risks of developing autism spectrum disorder (ASD) or developmental delay (DD).

METHODS

Participants were a subset of children from the CHARGE (CHildhood Autism Risks from Genetics and the Environment) case-control study. ASD and DD cases were identified through the California Department of Developmental Services system or referrals; general population controls were randomly sampled from state birth files and frequency-matched on age, sex, and broad geographic region to ASD cases. All children (50 ASD, 27 DD, 68 typically developing (TD)) were assessed with Mullen Scales of Early Learning, Vineland Adaptive Behavior Scales (VABS) and Aberrant Behavior Checklist. We measured 5 phthalates in dust collected in the child's home using a high volume small surface sampler.

RESULTS

None of the phthalates measured in dust was associated with ASD. After adjustment, we observed greater di(2-ethylhexyl) phthalate (DEHP) and butylbenzyl phthalate (BBzP) concentrations in indoor dust from homes of DD children: Odds ratios (OR) were 2.10 (95% confidence interval (CI); 1.10; 4.09) and 1.40 (95% CI; 0.97; 2.04) for a one-unit increase in the ln-transformed DEHP and BBzP concentrations, respectively. Among TD children, VABS communication, daily living, and adaptive composite standard scores were lower, in association with increased diethyl phthalate (DEP) concentrations in dust. Participants with higher dibutyl phthalate (DBP) concentrations in house dust also trended toward reduced performance on these subscales. Among ASD and DD boys, higher indoor dust concentrations of DEP and DBP were associated with greater hyperactivity-impulsivity and inattention.

DISCUSSION AND CONCLUSION

House dust levels of phthalates were not associated with ASD. The inability to distinguish past from recent exposures in house dust and the fact that house dust does not capture exposure from all sources, limit the interpretation of both positive and null findings and further work is needed. However, the associations observed for DEP and DBP with impairments in several adaptive functions and greater hyperactivity, along with evidence for increased risk of DD raise concerns that these chemicals may affect neurodevelopment in children.

Influence of Low-Level Prenatal Exposure to PCDD/Fs and PCBs on Empathizing, Systemizing and Autistic Traits: Results from the Duisburg Birth Cohort Study

BACKGROUND

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are assumed to act as endocrine disruptor chemicals. Prenatal exposure to these pollutants might influence fetal steroid hormone levels, which are thought to be related to sex-typical development and autistic traits.

OBJECTIVES

We examined associations of prenatal levels of PCDD/Fs and PCBs with autism traits and sex-typical behaviour in childhood.

METHODS

We measured levels of PCDD/Fs and PCBs in maternal blood samples during pregnancy using gas chromatography/high-resolution mass spectrometry. Sex-typical behaviour was assessed at 9 years of age (n = 96) and autistic traits at 10 years of age using the Social Responsiveness Scale (SRS; n = 100). Multiple regression analyses were conducted to estimate the associations between prenatal exposure and outcome variables.

RESULTS

Blood concentrations (WHO2005-TEq) of ƩPCDD/Fs ranged from 2.93-46.45 pg/g lipid base (median = 12.91 pg/g lipid base) and concentrations of ƩPCBs were in the range of 1.24-25.47 pg/g lipid base (median = 6.85 pg/g lipid base) which is within the range of German background exposure. We found significant negative associations between PCDD/F levels in maternal blood and SRS scores in the whole group (β = -6.66, p < .05), in girls (β = -10.98, p < .05) and, in one SRS subscale, in boys (β = -6.86, p < .05). For PCB levels, associations with one SRS subscale were significant for the whole study group as were associations with two subscales in girls. We did not find significant associations between PCDD/F or PCB levels and sex-typical behaviour for either sex.

CONCLUSIONS

In an earlier part of this study, prenatal exposure to PCDD/Fs and PCBs was found to be associated with lower testosterone levels, therefore, our findings are consistent with the idea that autism spectrum conditions are related to fetal androgen levels. Several possible mechanisms, through which PCDD/Fs and PCBs might influence autistic behaviour, are discussed.

Bisphenol A Exposure in Children With Autism Spectrum Disorders

The etiology of autism spectrum disorders (ASD) is believed to involve genetic and environmental components. This study focused on the plasticizer, Bisphenol-A (BPA). The major pathway for BPA metabolism and excretion is via glucuronidation. To determine whether there was a relationship between BPA exposure and ASD, urine specimens were collected from 46 children with ASD and 52 controls. Free and total BPA concentrations were determined by mass spectrometry. The fraction glucuronidated was calculated from the difference. A metabolomics study was done to investigate metabolite distribution in the urine. (i) Most of the BPA excreted in the urine was as the glucuronide; (ii) about 20% of the ASD children had BPA levels beyond the 90th percentile (>50 ng/mL) of the frequency distribution for the total sample of 98 children; (iii) Mann-Whitney U tests and multiple regression analyses found significant differences (P < 0.05) between the groups in total and % bound BPA; and (iv) the metabolomics analyses showed the number of absolute partial correlations >|0.30| between metabolite concentrations and total BPA was ∼3 times greater with the ASD group than the controls (P < 0.001), and the number of absolute partial correlations > |0.30| for % bound BPA was ∼15 times higher with ASD (P < 0.001). The results suggest there is an association between BPA and ASD.

Elucidating the links between endocrine disruptors and neurodevelopment

Recent data indicate that approximately 12% of children in the United States are affected by neurodevelopmental disorders, including attention deficit hyperactivity disorder, learning disorders, intellectual disabilities, and autism spectrum disorders. Accumulating evidence indicates a multifactorial etiology for these disorders, with social, physical, genetic susceptibility, nutritional factors, and chemical toxicants acting together to influence risk. Exposure to endocrine-disrupting chemicals during the early stages of life can disrupt normal patterns of development and thus alter brain function and disease susceptibility later in life. This article highlights research efforts and pinpoints approaches that could shed light on the possible associations between environmental chemicals that act on the endocrine system and compromised neurodevelopmental outcomes.

Modulation of the genome and epigenome of individuals susceptible to autism by environmental risk factors

Diverse environmental factors have been implicated with the development of autism spectrum disorders (ASD). Genetic factors also underlie the differential vulnerability to environmental risk factors of susceptible individuals. Currently the way in which environmental risk factors interact with genetic factors to increase the incidence of ASD is not well understood. A greater understanding of the metabolic, cellular, and biochemical events involved in gene x environment interactions in ASD would have important implications for the prevention and possible treatment of the disorder. In this review we discuss various established and more alternative processes through which environmental factors implicated in ASD can modulate the genome and epigenome of genetically-susceptible individuals.

Neurobehavioral deficits, diseases, and associated costs of exposure to endocrine-disrupting chemicals in the European Union

CONTEXT

Epidemiological studies and animal models demonstrate that endocrine-disrupting chemicals (EDCs) contribute to cognitive deficits and neurodevelopmental disabilities.

OBJECTIVE

The objective was to estimate neurodevelopmental disability and associated costs that can be reasonably attributed to EDC exposure in the European Union.

DESIGN

An expert panel applied a weight-of-evidence characterization adapted from the Intergovernmental Panel on Climate Change. Exposure-response relationships and reference levels were evaluated for relevant EDCs, and biomarker data were organized from peer-reviewed studies to represent European exposure and approximate burden of disease. Cost estimation as of 2010 utilized lifetime economic productivity estimates, lifetime cost estimates for autism spectrum disorder, and annual costs for attention-deficit hyperactivity disorder. Setting, Patients and Participants, and Intervention: Cost estimation was carried out from a societal perspective, ie, including direct costs (eg, treatment costs) and indirect costs such as productivity loss.

RESULTS

The panel identified a 70-100% probability that polybrominated diphenyl ether and organophosphate exposures contribute to IQ loss in the European population. Polybrominated diphenyl ether exposures were associated with 873,000 (sensitivity analysis, 148,000 to 2.02 million) lost IQ points and 3290 (sensitivity analysis, 3290 to 8080) cases of intellectual disability, at costs of €9.59 billion (sensitivity analysis, €1.58 billion to €22.4 billion). Organophosphate exposures were associated with 13.0 million (sensitivity analysis, 4.24 million to 17.1 million) lost IQ points and 59 300 (sensitivity analysis, 16,500 to 84,400) cases of intellectual disability, at costs of €146 billion (sensitivity analysis, €46.8 billion to €194 billion). Autism spectrum disorder causation by multiple EDCs was assigned a 20-39% probability, with 316 (sensitivity analysis, 126-631) attributable cases at a cost of €199 million (sensitivity analysis, €79.7 million to €399 million). Attention-deficit hyperactivity disorder causation by multiple EDCs was assigned a 20-69% probability, with 19 300 to 31 200 attributable cases at a cost of €1.21 billion to €2.86 billion.

CONCLUSIONS

EDC exposures in Europe contribute substantially to neurobehavioral deficits and disease, with a high probability of >€150 billion costs/year. These results emphasize the advantages of controlling EDC exposure.

Impact of hospital-based environmental exposures on neurodevelopmental outcomes of preterm infants

PURPOSE OF REVIEW

Over 300,000 infants are hospitalized in a neonatal intensive care unit (NICU) in the United States annually during a developmental period critical to later neurobehavioral function. Environmental exposures during the fetal period and infancy have been shown to impact long-term neurobehavioral outcomes. This review summarizes evidence linking NICU-based environmental exposures to neurodevelopmental outcomes of children born preterm.

RECENT FINDINGS

Preterm infants experience multiple exposures important to neurodevelopment during the NICU hospitalization. The physical layout of the NICU, management of light and sound, social interactions with parents and NICU staff, and chemical exposures via medical equipment are important to long-term neurobehavioral outcomes in this highly vulnerable population.

SUMMARY

Existing research documents NICU-based exposure to neurotoxic chemicals, aberrant light, excess sound, and restricted social interaction. In total, this creates an environment of co-existing excesses (chemicals, light, sound) and deprivation (touch, speech). The full impact of these co-exposures on the long-term neurodevelopment of preterm infants has not been adequately elucidated. Research into the importance of the NICU from an environmental health perspective is in its infancy, but could provide understanding about critical modifiable factors impacting the neurobehavioral health of hundreds of thousands of children each year.

Exposure to free and conjugated forms of bisphenol A and triclosan among pregnant women in the MIREC cohort

BACKGROUND

Bisphenol A (BPA) and triclosan (TCS) are two nonpersistent chemicals that have been frequently measured in spot urine samples from the general population but less so in pregnant women; however, data are limited on the free (bioactive) and conjugated forms of these phenols.

OBJECTIVES

The Maternal-Infant Research on Environmental Chemicals (MIREC) Study addressed these data gaps by utilizing stored maternal urine samples from a large multicenter cohort study of Canadian pregnant women.

METHODS

Concentrations of free and conjugated forms of BPA and TCS were measured in about 1,890 first-trimester urine samples by ultra performance liquid chromatography-tandem mass spectrometry using isotope dilution.

RESULTS

The glucuronides of BPA and TCS were the predominant forms of these chemicals measured (detected in 95% and 99% of samples, respectively), whereas the free forms were detected in 43% and 80% of samples, respectively. The geometric mean urinary concentrations for glucuronides of BPA and TCS were 0.80 μg/L (95% CI: 0.75, 0.85) and 12.30 μg/L (95% CI: 11.08, 13.65), respectively. Significant predictors of BPA included maternal age < 25 vs. ≥ 35 years, current smoking, low vs. high household income, and low vs. high education. For TCS, urinary concentrations were significantly higher in women ≥ 25 years of age, never vs. current smokers, and women with high household income and high education.

CONCLUSIONS

The results from this study represent the largest national-level data on urinary concentrations of free and conjugated forms of BPA and TCS in pregnant women and suggest that maternal characteristics predicting elevated urinary concentrations of these phenols largely act in opposite directions.

Multifactorial Origin of Neurodevelopmental Disorders: Approaches to Understanding Complex Etiologies

A significant body of evidence supports the multifactorial etiology of neurodevelopmental disorders (NDDs) affecting children. The present review focuses on early exposure to environmental chemicals as a risk factor for neurodevelopment, and presents the major lines of evidence derived from epidemiological studies, underlying key uncertainties and research needs in this field. We introduce the exposome concept that, encompassing the totality of human environmental exposures to multiple risk factors, aims at explaining individual vulnerability and resilience to early chemical exposure. In this framework, we synthetically review the role of variable gene backgrounds, the involvement of epigenetic mechanisms as well as the function played by potential effect modifiers such as socioeconomic status. We describe laboratory rodent studies where the neurodevelopmental effects of environmental chemicals are assessed in the presence of either a “vulnerable” gene background or adverse pregnancy conditions (i.e., maternal stress). Finally, we discuss the need for more descriptive and “lifelike” experimental models of NDDs, to identify candidate biomarkers and pinpoint susceptible groups or life stages to be translated to large prospective studies within the exposome framework.

Bisphenol A and phthalate endocrine disruption of parental and social behaviors

Perinatal exposure to endocrine disrupting chemicals (EDCs) can induce promiscuous neurobehavioral disturbances. Bisphenol A and phthalates are two widely prevalent and persistent EDCs reported to lead to such effects. Parental and social behaviors are especially vulnerable to endocrine disruption, as these traits are programmed by the organizational-activational effects of testosterone and estrogen. Exposure to BPA and other EDCs disrupts normal maternal care provided by rodents and non-human primates, such as nursing, time she spends hunched over and in the nest, and grooming her pups. Paternal care may also be affected by BPA. No long-term study has linked perinatal exposure to BPA or other EDC and later parental behavioral deficits in humans. The fact that the same brain regions and neural hormone substrates govern parental behaviors in animal models and humans suggests that this suite of behaviors may also be vulnerable in the latter. Social behaviors, such as communication, mate choice, pair bonding, social inquisitiveness and recognition, play behavior, social grooming, copulation, and aggression, are compromised in animal models exposed to BPA, phthalates, and other EDCs. Early contact to these chemicals is also correlated with maladaptive social behaviors in children. These behavioral disturbances may originate by altering the fetal or adult gonadal production of testosterone or estrogen, expression of ESR1, ESR2, and AR in the brain regions governing these behaviors, neuropeptide/protein hormone (oxytocin, vasopressin, and prolactin) and their cognate neural receptors, and/or through epimutations. Robust evidence exists for all of these EDC-induced changes. Concern also exists for transgenerational persistence of such neurobehavioral disruptions. In sum, evidence for social and parental deficits induced by BPA, phthalates, and related chemicals is strongly mounting, and such effects may ultimately compromise the overall social fitness of populations to come.

Maternal and infant exposure to environmental phenols as measured in multiple biological matrices

BACKGROUND

Results of recent national surveys have shown the high prevalence of exposure to bisphenol A (BPA) and triclosan (TCS) among the general population; however biomonitoring data for pregnant women and infants are limited.

METHODS

Women (n=80) were recruited from early prenatal clinics and asked to collect urine samples multiple times during pregnancy and once 2-3 months post-partum. Samples of infant urine and meconium as well as breast milk and infant formula were also collected. Biospecimens were analyzed by GC-MS/MS for BPA, TCS and triclocarban (TCC).

RESULTS

Triclosan was detected in over 80% of the maternal urines (geometric mean (GM): 21.61 μg/L), 60% of the infant urines (GM: 2.8 μg/L), 46% of the breast milk and 80% of the meconium samples. Triclocarban was rarely detected in any of the biospecimens. Median total BPA concentrations were 1.21 and 0.24 μg/L in maternal and infant urines, respectively. Free BPA was detected in only 11% of infant urine samples. The meconium of female infants had significantly higher concentrations of total BPA and TCS than those of males, while no differences were observed in infant urine concentrations by sex.

CONCLUSIONS

We found widespread exposure among pregnant women and infants to environmental phenols, with large inter-individual variability in exposure to triclosan. These data will contribute to the risk assessment of these chemicals, especially in susceptible sub-populations.

Chemicals eluting from disposable plastic syringes and syringe filters alter neurite growth, axogenesis and the microtubule cytoskeleton in cultured hippocampal neurons

Cultures of dissociated hippocampal neurons are often used to study neuronal cell biology. We report that the development of these neurons is strongly affected by chemicals leaching from commonly used disposable medical-grade syringes and syringe filters. Contamination of culture medium by bioactive substance(s) from syringes and filters occurred with multiple manufacturing lots and filter types under normal use conditions and resulted in changes to neurite growth, axon formation and the neuronal microtubule cytoskeleton. The effects on neuronal morphology were concentration dependent and significant effects were detected even after substantial dilution of the contaminated medium. Gas chromatography-mass spectrometry analyses revealed many chemicals eluting from the syringes and filters. Three of these chemicals (stearic acid, palmitic acid and 1,2-ethanediol monoacetate) were tested but showed no effects on neurite growth. Similar changes in neuronal morphology were seen with high concentrations of bisphenol A and dibutyl phthalate, two hormonally active plasticisers. Although no such compounds were detected by gas chromatography–mass spectrometry, unknown plasticisers in leachates may affect neurites. This is the first study to show that leachates from laboratory consumables can alter the growth of cultured hippocampal neurons. We highlight important considerations to ensure leachate contamination does not compromise cell biology experiments.

Low-dose exposure to bisphenol A and replacement bisphenol S induces precocious hypothalamic neurogenesis in embryonic zebrafish

Bisphenol A (BPA), a ubiquitous endocrine disruptor that is present in many household products, has been linked to obesity, cancer, and, most relevant here, childhood neurological disorders such as anxiety and hyperactivity. However, how BPA exposure translates into these neurodevelopmental disorders remains poorly understood. Here, we used zebrafish to link BPA mechanistically to disease etiology. Strikingly, treatment of embryonic zebrafish with very low-dose BPA (0.0068 μM, 1,000-fold lower than the accepted human daily exposure) and bisphenol S (BPS), a common analog used in BPA-free products, resulted in 180% and 240% increases, respectively, in neuronal birth (neurogenesis) within the hypothalamus, a highly conserved brain region involved in hyperactivity. Furthermore, restricted BPA/BPS exposure specifically during the neurogenic window caused later hyperactive behaviors in zebrafish larvae. Unexpectedly, we show that BPA-mediated precocious neurogenesis and the concomitant behavioral phenotype were not dependent on predicted estrogen receptors but relied on androgen receptor-mediated up-regulation of aromatase. Although human epidemiological results are still emerging, an association between high maternal urinary BPA during gestation and hyperactivity and other behavioral disturbances in the child has been suggested. Our studies here provide mechanistic support that the neurogenic period indeed may be a window of vulnerability and uncovers previously unexplored avenues of research into how endocrine disruptors might perturb early brain development. Furthermore, our results show that BPA-free products are not necessarily safer and support the removal of all bisphenols from consumer merchandise.

Bisphenol A exposure during early development induces sex-specific changes in adult zebrafish social interactions

Developmental bisphenol A (BPA) exposure is associated with adverse behavioral effects, although underlying modes of action remain unclear. Because BPA is a suspected xenoestrogen, the objective was to identify sex-based changes in adult zebrafish social behavior developmentally exposed to BPA (0.0, 0.1, or 1 μM) or one of two control compounds (0.1 μM 17β-estradiol [E2], and 0.1 μM GSK4716, a synthetic estrogen-related receptor γ ligand). A test chamber was divided lengthwise so each arena held one fish unable to detect the presence of the other fish. A mirror was inserted at one end of each arena; baseline activity levels were determined without mirror. Arenas were divided into three computer-generated zones to represent different distances from mirror image. Circadian rhythm patterns were evaluated at 1-3 (= AM) and 5-8 (= PM) h postprandial. Adult zebrafish were placed into arenas and monitored by digital camera for 5 min. Total distance traveled, percent of time spent at mirror image, and number of attacks on mirror image were quantified. E2, GSK4716, and all BPA treatments dampened male activity and altered male circadian activity patterns; there was no marked effect on female activity. BPA induced nonmonotonic effects (response curve changes direction within range of concentrations examined) on male percent of time at mirror only in AM. All treatments produced increased percent of time at the mirror during PM. Male attacks on the mirror were reduced by BPA exposure only during AM. There were sex-specific effects of developmental BPA on social interactions, and time of day of observation affected results.

Role of environmental contaminants in the etiology of Alzheimer's disease: a review

Alzheimer's dis ease (AD) is a leading cause of mortality in the developed world with 70% risk attributable to genetics. The remaining 30% of AD risk is hypothesized to include environmental factors and human lifestyle patterns. Environmental factors possibly include inorganic and organic hazards, exposure to toxic metals (aluminium, copper), pesticides (organochlorine and organophosphate insecticides), industrial chemicals (flame retardants) and air pollutants (particulate matter). Long term exposures to these environmental contaminants together with bioaccumulation over an individual's life-time are speculated to induce neuroinflammation and neuropathology paving the way for developing AD. Epidemiologic associations between environmental contaminant exposures and AD are still limited. However, many in vitro and animal studies have identified toxic effects of environmental contaminants at the cellular level, revealing alterations of pathways and metabolisms associated with AD that warrant further investigations. This review provides an overview of in vitro, animal and epidemiological studies on the etiology of AD, highlighting available data supportive of the long hypothesized link between toxic environmental exposures and development of AD pathology.

Di-(2-ethylhexyl) phthalate exposure is negatively correlated with trait anxiety in girls but not with trait anxiety in boys or anxiety-like behavior in male mice

The authors aimed to study the effects of postnatal exposure to phthalate on anxiety-like behavior in mice and anxiety proneness in children. Male Imprinting Control Region (ICR) mice aged 4 weeks were administered 20 to 540 mg/kg of di-(2-ethylhexyl) phthalate (DEHP) or vehicle and assessed in the Open Field Test. A group of 277 children aged 8-11 years (150 males) was recruited from South Korea. A cross-sectional examination of urinary DEHP and dibutylphthalate metabolite concentrations was conducted, and the children were scored on the Trait Anxiety Inventory for Children (TAIC). DEHP metabolite concentrations in the urine were significantly and negatively correlated with TAIC scores in the female population but not in the male population. There were no significant group differences in the percentage of distance moved or time spent in the central area in male mice treated with DEHP or vehicle. Our results suggest a sex-dependent effect of DEHP on anxiety proneness in childhood.

Neurological Effects of Bisphenol A and its Analogues

The endocrine disrupting chemical bisphenol A (BPA) is widely used in the production of polycarbonate plastics and epoxy resins. The use of BPA-containing products in daily life makes exposure ubiquitous, and the potential human health risks of this chemical are a major public health concern. Although numerous in vitro and in vivo studies have been published on the effects of BPA on biological systems, there is controversy as to whether ordinary levels of exposure can have adverse effects in humans. However, the increasing incidence of developmental disorders is of concern, and accumulating evidence indicates that BPA has detrimental effects on neurological development. Other bisphenol analogues, used as substitutes for BPA, are also suspected of having a broad range of biological actions. The objective of this review is to summarize our current understanding of the neurobiological effects of BPA and its analogues, and to discuss preventive strategies from a public health perspective.

Prenatal bisphenol A exposure and maternally reported behavior in boys and girls

Prenatal exposure to gonadal hormones plays a major role in the normal development of the male and female brain and sexually dimorphic behaviors. Hormone-dependent differences in brain structure and function suggest that exposure to exogenous endocrine disrupting chemicals may be associated with sex-specific alterations in behavior. Bisphenol A (BPA) is an environmental chemical that has been shown to alter estrogen, androgen, and thyroid hormone signaling pathways. Epidemiological and experimental studies suggest associations between prenatal exposure to BPA and child behavior, however data are inconsistent, and few studies have examined school age children. We examined BPA concentration in spot urine samples from women at mean 27 weeks of pregnancy in relation to child behavior assessed at age 6-10 years using the parent-completed Child Behavior Checklist (CBCL). We report associations between maternal BPA urinary concentrations and several CBCL scores in 153 children (77 boys and 76 girls). We observed a significant interaction between maternal urinary BPA and sex for several behaviors (externalizing, aggression, Anxiety Disorder, Oppositional/Defiant Disorder and Conduct Disorder traits), but no significant associations between BPA and scores on any CBCL scales. However in analyses restricted to children of mothers with detectable prenatal urinary BPA (n=125), BPA was associated with moderately increased internalizing and externalizing behaviors, withdrawn/depressed behavior, somatic problems, and Oppositional/Defiant Disorder traits in boys. In addition we observed a significant interaction between BPA and sex for several behaviors (externalizing, withdrawn/depressed, rule-breaking, Oppositional/Defiant Disorder traits, and Conduct Disorder traits). These results suggest that prenatal exposure to BPA may be related to increased behavior problems in school age boys, but not girls.

Environmental chemical exposures and autism spectrum disorders: a review of the epidemiological evidence

In the past decade, the number of epidemiological publications addressing environmental chemical exposures and autism has grown tremendously. These studies are important because it is now understood that environmental factors play a larger role in causing autism than previously thought and because they address modifiable risk factors that may open up avenues for the primary prevention of the disability associated with autism. In this review, we covered studies of autism and estimates of exposure to tobacco, air pollutants, volatile organic compounds and solvents, metals (from air, occupation, diet, dental amalgams, and thimerosal-containing vaccines), pesticides, and organic endocrine-disrupting compounds such as flame retardants, non-stick chemicals, phthalates, and bisphenol A. We included studies that had individual-level data on autism, exposure measures pertaining to pregnancy or the 1st year of life, valid comparison groups, control for confounders, and adequate sample sizes. Despite the inherent error in the measurement of many of these environmental exposures, which is likely to attenuate observed associations, some environmental exposures showed associations with autism, especially traffic-related air pollutants, some metals, and several pesticides, with suggestive trends for some volatile organic compounds (e.g., methylene chloride, trichloroethylene, and styrene) and phthalates. Whether any of these play a causal role requires further study. Given the limited scope of these publications, other environmental chemicals cannot be ruled out, but have not yet been adequately studied. Future research that addresses these and additional environmental chemicals, including their most common routes of exposures, with accurate exposure measurement pertaining to several developmental windows, is essential to guide efforts for the prevention of the neurodevelopmental damage that manifests in autism symptoms.

A comparison of temporal trends in United States autism prevalence to trends in suspected environmental factors

BACKGROUND

The prevalence of diagnosed autism has increased rapidly over the last several decades among U.S. children. Environmental factors are thought to be driving this increase and a list of the top ten suspected environmental toxins was published recently.

METHODS

Temporal trends in autism for birth years 1970-2005 were derived from a combination of data from the California Department of Developmental Services (CDDS) and the United States Individuals with Disabilities Education Act (IDEA). Temporal trends in suspected toxins were derived from data compiled during an extensive literature survey. Toxin and autism trends were compared by visual inspection and computed correlation coefficients. Using IDEA data, autism prevalence vs. birth year trends were calculated independently from snapshots of data from the most recent annual report, and by tracking prevalence at a constant age over many years of reports. The ratio of the snapshot:tracking trend slopes was used to estimate the "real" fraction of the increase in autism.

RESULTS

The CDDS and IDEA data sets are qualitatively consistent in suggesting a strong increase in autism prevalence over recent decades. The quantitative comparison of IDEA snapshot and constant-age tracking trend slopes suggests that ~75-80% of the tracked increase in autism since 1988 is due to an actual increase in the disorder rather than to changing diagnostic criteria. Most of the suspected environmental toxins examined have flat or decreasing temporal trends that correlate poorly to the rise in autism. Some, including lead, organochlorine pesticides and vehicular emissions, have strongly decreasing trends. Among the suspected toxins surveyed, polybrominated diphenyl ethers, aluminum adjuvants, and the herbicide glyphosate have increasing trends that correlate positively to the rise in autism.

CONCLUSIONS

Diagnosed autism prevalence has risen dramatically in the U.S over the last several decades and continued to trend upward as of birth year 2005. The increase is mainly real and has occurred mostly since the late 1980s. In contrast, children's exposure to most of the top ten toxic compounds has remained flat or decreased over this same time frame. Environmental factors with increasing temporal trends can help suggest hypotheses for drivers of autism that merit further investigation.

A longitudinal study of urinary phthalate excretion in 58 full-term and 67 preterm infants from birth through 14 months

BACKGROUND

Some phthalates have shown antiandrogenic effects in rat offspring. Premature infants may be exposed to high amounts of specific phthalates during hospitalization, and thus are potentially at risk.

OBJECTIVE

We evaluated longitudinal phthalate exposure and metabolism in full-term (FT) and preterm (PT) infants.

METHODS

Fifty-eight FT and 67 PT (gestational age, 24.7-36.6 weeks) infants were recruited at birth and followed until 14 months (nine times). Urinary concentrations of metabolites of diethyl phthalate (DEP), dibutyl phthalate isomers (DiBP and DnBP), butylbenzyl phthalate (BBzP), di(2-ethylhexyl) phthalate (DEHP), and diisononyl phthalate (DiNP) were measured in 894 samples. Daily intake and a hazard index for antiandrogenic effects were estimated, and excretion patterns of DEHP and DiNP metabolites were analyzed.

RESULTS

Metabolites of BBzP, DiNP, and DEHP were 5-50 times higher at day 7 (D7) and month 1 (M1) in PT than in FT infants. Thereafter, metabolite concentrations were similar between the two groups. The estimated hazard index for combined DiBP, DnBP, BBzP, and DEHP exposures 7 days after birth exceeded the antiandrogenic threshold in > 80% of PT and > 30% of FT infants, and after M2, in 30% of all infants. The excretion pattern of DEHP and DiNP metabolites changed with age.

CONCLUSION

Most PT infants and approximately one-third of healthy FT newborns were exposed to phthalates during early life at a potentially harmful level according to the European Food Safety Authority's recommended limits of daily exposure. Changes in the relative proportions of secondary phthalate metabolites over time were consistent with maturation of infant metabolic pathways during the first year of life. Further research is needed on the health effects of phthalate exposures and the influence of changes in metabolic capacity in neonates and infants.

Phthalate exposure and child development: the Polish Mother and Child Cohort Study

BACKGROUND

Widespread phthalate exposure has prompted investigations concerning their potential adverse health effects.

AIM

The objective of this study was to evaluate the impact of pre and early postnatal phthalate exposure on child psychomotor development based on the data from the prospective Polish Mother and Child Cohort Study (REPRO PL).

STUDY DESIGN, SUBJECTS AND OUTCOME MEASURES

Phthalate exposure was determined by measuring 11 phthalate metabolites (MEP, MiBP, MnBP, 3OH-MnBP, MBzP, MEHP, 5OH-MEHP, 5oxo-MEHP, OH-MiNP, oxo-MiNP, and MnOP) in the urine collected from mothers during the third trimester of pregnancy (prenatal exposure) and from their children at the 24th month of age (postnatal exposure). The analysis was performed by the HPLC-MS/MS method. Psychomotor development was assessed in children at the age of 2years by the Bayley Scales of Infant and Toddler Development.

RESULTS

Child motor development was inversely associated with natural log concentrations (μg/g creatinine) of 3OH-MnBP (β= -2.3; 95% CI -4.0 to -0.6), 5OH-MEHP (β= -1.2; 95% CI -2.2 to -0.3), 5oxo-MEHP (β= -1.8; 95% CI -3.3 to -0.2) and sum of DEHP metabolites (β= -2.2; 95% CI -3.6 to -0.8), DnBP metabolites (β= -1.9; 95% CI -3.4 to -0.4), and high molecular weight phthalates (β= -2.5; 95% CI -4.1 to -0.9) in the urine collected from mothers during pregnancy after adjustment for a variety of potential confounders. Additional adjustment for postnatal phthalate exposure did not change the results. Postnatal child exposure to phthalates was not associated with any of the measured scores of child psychomotor development.

CONCLUSIONS

The study findings add further support to the possibility that prenatal phthalate exposure may be detrimental to child neurodevelopment and underscore the importance of policies and public health interventions aiming at reduction of such exposure.

Personal care product use and urinary phthalate metabolite and paraben concentrations during pregnancy among women from a fertility clinic

Parabens and phthalates are potential endocrine disruptors frequently used in personal care/beauty products, and the developing fetus may be sensitive to these chemicals. We measured urinary butyl-paraben (BP), methyl-paraben, propyl-paraben, mono-n-butyl phthalate (MBP), and monoethyl phthalate (MEP) concentrations up to three times in 177 pregnant women from a fertility clinic in Boston, MA. Using linear mixed models, we examined the relationship between self-reported personal care product use in the previous 24 h and urinary paraben and phthalate metabolite concentrations. Lotion, cosmetic, and cologne/perfume use were associated with the greatest increases in the molar sum of phthalate metabolite and paraben concentrations, although the magnitude of individual biomarker increases varied by product used. For example, women who used lotion had BP concentrations 111% higher (95% confidence interval (CI): 41%, 216%) than non-users, whereas their MBP concentrations were only 28% higher (CI: 2%, 62%). Women using cologne/perfume had MEP concentrations 167% (CI: 98%, 261%) higher than non-users, but BP concentrations were similar. We observed a monotonic dose-response relationship between the total number of products used and urinary paraben and phthalate metabolite concentrations. These results suggest that questionnaire data may be useful for assessing exposure to a mixture of chemicals from personal care products during pregnancy.

Early exposure to bisphenol A alters neuron and glia number in the rat prefrontal cortex of adult males, but not females

Previous work has shown that exposure to bisphenol A (BPA) during early development can alter sexual differentiation of the brain in rodents, although few studies have examined effects on areas of the brain associated with cognition. The current study examined if developmental BPA exposure alters the total number of neurons and glia in the medial prefrontal cortex (mPFC) in adulthood. Pregnant Long-Evans rats were orally exposed to 0, 4, 40, or 400-μg/kg BPA in corn oil throughout pregnancy. From postnatal days 1 to 9, pups were given daily oral doses of oil or BPA, at doses corresponding to those given during gestation. Brains were examined in adulthood, and the volume of layers 2/3 and layers 5/6 of the mPFC was parcellated. The density of neurons and glia in these layers was quantified stereologically with the optical disector, and density was multiplied by volume for each animal. Males exposed to 400-μg/kg BPA were found to have increased numbers of neurons and glia in layers 5/6. Although there were no significant effects of BPA in layers 2/3, the pattern of increased neuron number in males exposed to 400-μg/kg BPA was similar to that seen in layers 5/6. No effects of BPA were seen in females or in males exposed to the other doses of BPA. This study indicates that males are more susceptible to the long-lasting effects of BPA on anatomy of the mPFC, an area implicated in neurological disorders.

Pop, heavy metal and the blues: secondary analysis of persistent organic pollutants (POP), heavy metals and depressive symptoms in the NHANES National Epidemiological Survey

OBJECTIVES

Persistent environmental pollutants, including heavy metals and persistent organic pollutants (POPs), have a ubiquitous presence. Many of these pollutants affect neurobiological processes, either accidentally or by design. The aim of this study was to explore the associations between assayed measures of POPs and heavy metals and depressive symptoms. We hypothesised that higher levels of pollutants and metals would be associated with depressive symptoms.

SETTING

National Health and Nutrition Examination Survey (NHANES).

PARTICIPANTS

A total of 15 140 eligible people were included across the three examined waves of NHANES.

PRIMARY AND SECONDARY OUTCOME MEASURES

Depressive symptoms were assessed using the nine-item version of the Patient Health Questionnaire (PHQ-9), using a cut-off point of 9/10 as likely depression cases. Organic pollutants and heavy metals, including cadmium, lead and mercury, as well as polyfluorinated compounds (PFCs), pesticides, phenols and phthalates, were measured in blood or urine.

RESULTS

Higher cadmium was positively associated with depression (adjusted Prevalence Ratios (PR)=1.48, 95% CI 1.16 to 1.90). Higher levels of mercury were negatively associated with depression (adjusted PR=0.62, 95% CI 0.50 to 0.78), and mercury was associated with increased fish consumption (n=5500, r=0.366, p<0.001). In addition, several PFCs (perfluorooctanoic acid, perfluorohexane sulfonic acid, perfluorodecanoic acid and perfluorononanoic acid) were negatively associated with the prevalence of depression.

CONCLUSIONS

Cadmium was associated with an increased likelihood of depression. Contrary to hypotheses, many of persistent environmental pollutants were not associated or negatively associated with depression. While the inverse association between mercury and depressive symptoms may be explained by a protective role for fish consumption, the negative associations with other pollutants remains unclear. This exploratory study suggests the need for further investigation of the role of various agents and classes of agents in the pathophysiology of depression.

Association between urine phthalate levels and poor attentional performance in children with attention-deficit hyperactivity disorder with evidence of dopamine gene-phthalate interaction

Although there is some evidence supporting the existence of an association between prenatal maternal or postnatal child’s urine phthalate metabolite concentrations and poor attentional performances, the interaction between urine phthalate metabolite levels and genetic variation for neuropsychological deficit of attention-deficit hyperactivity disorder (ADHD) has not been examined. The aim of this study was to determine whether phthalate metabolites in urine are associated with poor neuropsychological performance in children with ADHD, and whether such association is affected by genotype-phthalate interaction. A cross-sectional examination of urine phthalate metabolite concentrations and the continuous performance test (CPT) were performed in 179 Korean children with ADHD recruited from department of psychiatry of university hospital. Correlations between urine phthalate metabolite concentrations and the CPT scores were investigated, and the interaction of phthalate metabolite levels with the selected polymorphisms at major candidate genes for ADHD, namely dopamine receptor D4 (DRD4), dopamine transporter, α-2A-adrenergic receptor, and norepinephrine transporter genes. For the subjects with the DRD4 4/4 genotype, there were significant associations of the urine phthalate metabolite concentrations with the number of omission errors, the number of commission errors, and the response time variability scores on the CPT. However, for the subjects without the DRD4 4/4 genotype, no significant associations were found. The results of this study suggest a possible association between phthalate metabolite concentrations and poor attentional performances of ADHD as well as a genetic influence on this association. Further prospective and epigenetic studies are needed to investigate causality and pathophysiological mechanisms.

Intake estimates of phthalate esters for South Delhi population based on exposure media assessment

An indirect estimation method was followed to derive exposure levels of fifteen phthalate congeners in urban population of Delhi, India. The exposure media samples were collected from Jawaharlal Nehru University (JNU) campus and Okhla industrial area. GC-MS analysis of the samples indicated di(2-ethylhexyl) phthalate (DEHP) to be the most abundant congener and its estimated total daily intake level reached upto 70 μg kg(-1) d(-1). Out of the studied congeners, intake doses for di-n-butyl phthalate (DnBP) and DEHP, reached levels near or above the established exposure limit. In JNU, DEHP, dimethyl phthalate (DMP) and butyl benzyl phthalate (BBP) had 69% share in combined daily intake of Σ15 phthalates (CDI15); whereas, in Okhla, DEHP, diethyl phthalate (DEP), diisobutyl phthalate (DIBP), DnBP and DMP shared 64% of the CDI15. Food was found to be the major source of exposure contributing 67% and 74% of the estimated CDI15 at JNU and Okhla respectively.

Parabens. From environmental studies to human health

Parabens are a group of substances commonly employed as preservatives, mainly in personal care products, pharmaceuticals and food. Scientific reports concerning their endocrine disrupting potential and the possible link with breast cancer raised wide discussion about parabens' impact and safety. This paper provides holistic overview of paraben usage, occurrence in the environment, methods of their degradation and removal from aqueous solution, as well as hazards related to their endocrine disrupting potential and possible involvement in carcinogenesis.

Gestational exposure to endocrine-disrupting chemicals and reciprocal social, repetitive, and stereotypic behaviors in 4- and 5-year-old children: the HOME study

BACKGROUND

Endocrine-disrupting chemicals (EDCs) may be involved in the etiology of autism spectrum disorders, but identifying relevant chemicals within mixtures of EDCs is difficult.

OBJECTIVE

Our goal was to identify gestational EDC exposures associated with autistic behaviors.

METHODS

We measured the concentrations of 8 phthalate metabolites, bisphenol A, 25 polychlorinated biphenyls (PCBs), 6 organochlorine pesticides, 8 brominated flame retardants, and 4 perfluoroalkyl substances in blood or urine samples from 175 pregnant women in the HOME (Health Outcomes and Measures of the Environment) Study (Cincinnati, OH). When children were 4 and 5 years old, mothers completed the Social Responsiveness Scale (SRS), a measure of autistic behaviors. We examined confounder-adjusted associations between 52 EDCs and SRS scores using a two-stage hierarchical analysis to account for repeated measures and confounding by correlated EDCs.

RESULTS

Most of the EDCs were associated with negligible absolute differences in SRS scores (≤ 1.5). Each 2-SD increase in serum concentrations of polybrominated diphenyl ether-28 (PBDE-28) (β = 2.5; 95% CI: -0.6, 5.6) or trans-nonachlor (β = 4.1; 95% CI: 0.8-7.3) was associated with more autistic behaviors. In contrast, fewer autistic behaviors were observed among children born to women with detectable versus nondetectable concentrations of PCB-178 (β = -3.0; 95% CI: -6.3, 0.2), β-hexachlorocyclohexane (β = -3.3; 95% CI: -6.1, -0.5), or PBDE-85 (β = -3.2; 95% CI: -5.9, -0.5). Increasing perfluorooctanoate (PFOA) concentrations were also associated with fewer autistic behaviors (β = -2.0; 95% CI: -4.4, 0.4).

CONCLUSIONS

Some EDCs were associated with autistic behaviors in this cohort, but our modest sample size precludes us from dismissing chemicals with null associations. PFOA, β-hexachlorocyclohexane, PCB-178, PBDE-28, PBDE-85, and trans-nonachlor deserve additional scrutiny as factors that may be associated with childhood autistic behaviors.

Bisphenol A and human chronic diseases: current evidences, possible mechanisms, and future perspectives

Bisphenol-A (BPA) is one of the highest volume chemicals produced worldwide, with over 6billion pounds produced and over 100t released into the atmosphere each year. Recent extensive literature has raised concerns about its possible implication in the etiology of some human chronic diseases such as diabetes, obesity, reproductive disorders, cardiovascular diseases, birth defects, chronic respiratory and kidney diseases and breast cancer. In this review, we present the highlighted evidences on the relationship between BPA exposure and human chronic diseases and we discuss its eventual mechanisms of action, especially genetic, epigenetic and endocrine disruption mechanisms with the possible involvement of oxidative stress, mitochondrial dysfunction and cell signaling.

Neurobehavioural effects of developmental toxicity

Neurodevelopmental disabilities, including autism, attention-deficit hyperactivity disorder, dyslexia, and other cognitive impairments, affect millions of children worldwide, and some diagnoses seem to be increasing in frequency. Industrial chemicals that injure the developing brain are among the known causes for this rise in prevalence. In 2006, we did a systematic review and identified five industrial chemicals as developmental neurotoxicants: lead, methylmercury, polychlorinated biphenyls, arsenic, and toluene. Since 2006, epidemiological studies have documented six additional developmental neurotoxicants-manganese, fluoride, chlorpyrifos, dichlorodiphenyltrichloroethane, tetrachloroethylene, and the polybrominated diphenyl ethers. We postulate that even more neurotoxicants remain undiscovered. To control the pandemic of developmental neurotoxicity, we propose a global prevention strategy. Untested chemicals should not be presumed to be safe to brain development, and chemicals in existing use and all new chemicals must therefore be tested for developmental neurotoxicity. To coordinate these efforts and to accelerate translation of science into prevention, we propose the urgent formation of a new international clearinghouse.

Maternal lifestyle and environmental risk factors for autism spectrum disorders

BACKGROUND

Over the past 10 years, research into environmental risk factors for autism has grown dramatically, bringing evidence that an array of non-genetic factors acting during the prenatal period may influence neurodevelopment.

METHODS

This paper reviews the evidence on modifiable preconception and/or prenatal factors that have been associated, in some studies, with autism spectrum disorder (ASD), including nutrition, substance use and exposure to environmental agents. This review is restricted to human studies with at least 50 cases of ASD, having a valid comparison group, conducted within the past decade and focusing on maternal lifestyle or environmental chemicals.

RESULTS

Higher maternal intake of certain nutrients and supplements has been associated with reduction in ASD risk, with the strongest evidence for periconceptional folic acid supplements. Although many investigations have suggested no impact of maternal smoking and alcohol use on ASD, more rigorous exposure assessment is needed. A number of studies have demonstrated significant increases in ASD risk with estimated exposure to air pollution during the prenatal period, particularly for heavy metals and particulate matter. Little research has assessed other persistent and non-persistent organic pollutants in association with ASD specifically.

CONCLUSIONS

More work is needed to examine fats, vitamins and other maternal nutrients, as well as endocrine-disrupting chemicals and pesticides, in association with ASD, given sound biological plausibility and evidence regarding other neurodevelopmental deficits. The field can be advanced by large-scale epidemiological studies, attention to critical aetiological windows and how these vary by exposure, and use of biomarkers and other means to understand underlying mechanisms.

Environmental toxicants and autism spectrum disorders: a systematic review

Although the involvement of genetic abnormalities in autism spectrum disorders (ASD) is well-accepted, recent studies point to an equal contribution by environmental factors, particularly environmental toxicants. However, these toxicant-related studies in ASD have not been systematically reviewed to date. Therefore, we compiled publications investigating potential associations between environmental toxicants and ASD and arranged these publications into the following three categories: (a) studies examining estimated toxicant exposures in the environment during the preconceptional, gestational and early childhood periods; (b) studies investigating biomarkers of toxicants; and (c) studies examining potential genetic susceptibilities to toxicants. A literature search of nine electronic scientific databases through November 2013 was performed. In the first category examining ASD risk and estimated toxicant exposures in the environment, the majority of studies (34/37; 92%) reported an association. Most of these studies were retrospective case-control, ecological or prospective cohort studies, although a few had weaker study designs (for example, case reports or series). Toxicants implicated in ASD included pesticides, phthalates, polychlorinated biphenyls (PCBs), solvents, toxic waste sites, air pollutants and heavy metals, with the strongest evidence found for air pollutants and pesticides. Gestational exposure to methylmercury (through fish exposure, one study) and childhood exposure to pollutants in water supplies (two studies) were not found to be associated with ASD risk. In the second category of studies investigating biomarkers of toxicants and ASD, a large number was dedicated to examining heavy metals. Such studies demonstrated mixed findings, with only 19 of 40 (47%) case-control studies reporting higher concentrations of heavy metals in blood, urine, hair, brain or teeth of children with ASD compared with controls. Other biomarker studies reported that solvent, phthalate and pesticide levels were associated with ASD, whereas PCB studies were mixed. Seven studies reported a relationship between autism severity and heavy metal biomarkers, suggesting evidence of a dose-effect relationship. Overall, the evidence linking biomarkers of toxicants with ASD (the second category) was weaker compared with the evidence associating estimated exposures to toxicants in the environment and ASD risk (the first category) because many of the biomarker studies contained small sample sizes and the relationships between biomarkers and ASD were inconsistent across studies. Regarding the third category of studies investigating potential genetic susceptibilities to toxicants, 10 unique studies examined polymorphisms in genes associated with increased susceptibilities to toxicants, with 8 studies reporting that such polymorphisms were more common in ASD individuals (or their mothers, 1 study) compared with controls (one study examined multiple polymorphisms). Genes implicated in these studies included paraoxonase (PON1, three of five studies), glutathione S-transferase (GSTM1 and GSTP1, three of four studies), δ-aminolevulinic acid dehydratase (one study), SLC11A3 (one study) and the metal regulatory transcription factor 1 (one of two studies). Notably, many of the reviewed studies had significant limitations, including lack of replication, limited sample sizes, retrospective design, recall and publication biases, inadequate matching of cases and controls, and the use of nonstandard tools to diagnose ASD. The findings of this review suggest that the etiology of ASD may involve, at least in a subset of children, complex interactions between genetic factors and certain environmental toxicants that may act synergistically or in parallel during critical periods of neurodevelopment, in a manner that increases the likelihood of developing ASD. Because of the limitations of many of the reviewed studies, additional high-quality epidemiological studies concerning environmental toxicants and ASD are warranted to confirm and clarify many of these findings.

Association between urinary levels of bisphenol-A and estrogen metabolism in Korean adults

Bisphenol-A (BPA) possesses estrogenic properties both in vitro and in vivo as an endocrine disrupting chemical. Humans experience a long-term and cumulative exposure to BPA. BPA was detectable in 97.3% of 1904 urine specimens from Korean adults. We investigated urinary estrogen concentrations in subjects with low and high BPA concentrations and its possible association with estrogen metabolism. Urine samples were collected from a high BPA concentration group (BPA-H; n=100, 11.05 ± 20.47 μg/g creatinine) and a low BPA concentration group (BPA-L; n=100, 0.70 ± 0.22 μg/g creatinine) from Korea Biomonitoring Program of Hazardous Materials Survey 2009-2010. Urinary estrogens were enzymatically hydrolyzed, extracted, and then derivatized for quantitative analysis by gas chromatography-mass spectrometry. Estrogen levels were higher in the BPA-H group than in the BPA-L group. Concentrations of estrone, 17β-estradiol, and their hydroxylated metabolites in both men and women were significantly higher in the BPA-H group than in the BPA-L group (p<0.04). Furthermore, in the BPA-H group, estrogen metabolism to 4-hydroxy-estrone and 4-hydroxy-17β-estradiol was more active than that to 2-hydroxy-estrone and 2-hydroxy-17β-estradiol. Although single measurement and/or single spot urine samples limit the measurement of long-term exposure to BPA, we found significant differences of estrogen metabolism in the BPA-H and the BPA-L groups. The increase of hydroxyestrogens, especially 4-hydroxyestrogens, can be an important factor resulting negative effects of prolonged exposure to BPA.

Environment and Autism: Current State of the Science

Research into environmental risk factors for autism has grown dramatically over the past 10 years, providing evidence that non-genetic factors acting during the prenatal period may influence the underlying neurodevelopmental processes. This paper reviews the evidence on modifiable preconception and/or prenatal factors that have been associated with autism spectrum disorder (ASD), including only human studies with at least 50 cases of ASD, having a valid comparison group, conducted within the past decade, and focusing on maternal lifestyle or environmental chemicals. Consistent results have been reported for an association of higher maternal intake of certain nutrients and supplements with reduction in ASD risk, with the strongest evidence for folic acid supplements. A number of studies have demonstrated significant increases in ASD risk with estimated exposure to air pollution during the prenatal period, particularly for heavy metals and particulate matter. A few studies suggest a link with organophosphate pesticides. More rigorous ascertainment of exposure is needed for studies of substance use; most investigations adjusting for potential confounders, but relying on self-reported use, have shown no links between maternal smoking or alcohol consumption and ASD. Little research has assessed other persistent and non-persistent organic chemical pollutants, such as are found in common household or personal care products, in association with ASD specifically. More work is needed to examine fats, vitamins, and other maternal nutrients, as well as endocrine-disrupting chemicals and pesticides, in association with ASD, given sound biological plausibility and evidence regarding other neurodevelopmental outcomes. In addition, the field could be advanced by the use of large-scale epidemiologic studies, attention to critical etiologic windows and how these vary by exposure, interactions with genetic susceptibility, and a focus on underlying mechanisms.

Phthalates induce neurotoxicity affecting locomotor and thermotactic behaviors and AFD neurons through oxidative stress in Caenorhabditis elegans

Background

Phthalate esters are ubiquitous environmental contaminants and numerous organisms are thus exposed to various levels of phthalates in their natural habitat. Considering the critical, but limited, research on human neurobehavioral outcomes in association with phthalates exposure, we used the nematode Caenorhabditis elegans as an in vivo model to evaluate phthalates-induced neurotoxicity and the possible associated mechanisms.

Principal Findings

Exposure to phthalates (DEHP, DBP, and DIBP) at the examined concentrations induced behavioral defects, including changes in body bending, head thrashing, reversal frequency, and thermotaxis in C. elegans. Moreover, phthalates (DEHP, DBP, and DIBP) exposure caused toxicity, affecting the relative sizes of cell body fluorescent puncta, and relative intensities of cell bodies in AFD neurons. The mRNA levels of the majority of the genes (TTX-1, TAX-2, TAX-4, and CEH-14) that are required for the differentiation and function of AFD neurons were decreased upon DEHP exposure. Furthermore, phthalates (DEHP, DBP, and DIBP) exposure at the examined concentrations produced elevated intracellular reactive oxygen species (ROS) in C. elegans. Finally, pretreatment with the antioxidant ascorbic acid significantly lowered the intracellular ROS level, ameliorated the locomotor and thermotactic behavior defects, and protected the damage of AFD neurons by DEHP exposure.

Conclusions

Our study suggests that oxidative stress plays a critical role in the phthalate esters-induced neurotoxic effects in C. elegans.

Transgenerational effects of prenatal bisphenol A on social recognition

Bisphenol A (BPA) is a man-made endocrine disrupting compound used to manufacture polycarbonate plastics. It is found in plastic bottles, canned food linings, thermal receipts and other commonly used items. Over 93% of people have detectable BPA levels in their urine. Epidemiological studies report correlations between BPA levels during pregnancy and activity, anxiety, and depression in children. We fed female mice control or BPA-containing diets that produced plasma BPA concentrations similar to concentrations in humans. Females were mated and at birth, pups were fostered to control dams to limit BPA exposure to gestation in the first generation. Sibling pairs were bred to the third generation with no further BPA exposure. First (F1) and third (F3) generation juveniles were tested for social recognition and in the open field. Adult F3 mice were tested for olfactory discrimination. In both generations, BPA exposed juvenile mice displayed higher levels of investigation than controls in a social recognition task. In F3 BPA exposed mice, dishabituation to a novel female was impaired. In the open field, no differences were noted in F1 mice, while in F3, BPA lineage mice were more active than controls. No impairments were detected in F3 mice, all were able to discriminate different male urine pools and urine from water. No sex differences were found in any task. These results demonstrate that BPA exposure during gestation has long lasting, transgenerational effects on social recognition and activity in mice. These findings show that BPA exposure has transgenerational actions on behavior and have implications for human neurodevelopmental behavioral disorders.