Levels of PAH-DNA adducts in cord blood and cord tissue and the risk of fetal neural tube defects in a Chinese population

Biomonitoring of polycyclic aromatic hydrocarbons in Brazilian pregnant women: Urinary levels and health risk assessment

Over the years, humans have been continuously exposed to several compounds directly generated by industrial processes and/or present in consumed products. Polycyclic aromatic hydrocarbons (PAHs) are legacy pollutants ubiquitous in the environment and represent the main chemical pollutants in urban areas. Worldwide, studies that aim to understand the impacts of exposure to these chemicals have gained increasing prominence due to their potential toxicity profile, mainly concerning genotoxicity and carcinogenicity. Human biomonitoring (HB) is an analytical approach to monitoring population exposure to chemicals; however, these studies are still limited in Brazil. Thus, this work aimed to evaluate the exposure of Brazilian pregnant women to PAHs through HB studies. Besides, the risk characterization of this exposure was performed. For this purpose, urine samples from 358 Brazilian pregnant women were used to evaluate 11 hydroxylated metabolites of PAHs employing gas chromatography coupled to mass spectrometry. The 1OH-naphthol and 2OH-naphthol were detected in 100% of the samples and showed high levels, corresponding to 16.99 and 3.62 μg/g of creatinine, respectively. 2OH-fluorene (8.12 μg/g of creatinine) and 9OH-fluorene (1.26 μg/g of creatinine) were detected in 91% and 66% of the samples, respectively. Benzo(a)pyrene (BaP) metabolites were detected in more than 50% of the samples (0.58-1.26 μg/g of creatinine). A hazard index of 1.4 and a carcinogenic risk above 10-4 were found for BaP metabolites in the risk characterization. Therefore, our findings may indicate that exposure to PAHs poses a potential risk to pregnant women's health and a high probability of carcinogenic risk due to their exposure to BaP. Finally, this work shows the need for more in-depth studies to determine the sources of exposure and the implementation of health protection measures regarding the exposure of the Brazilian population to PAHs.

Polycyclic aromatic hydrocarbons (PAHs): Updated aspects of their determination, kinetics in the human body, and toxicity

Polycyclic aromatic hydrocarbons (PAHs) are legacy pollutants of considerable public health concern. Polycyclic aromatic hydrocarbons arise from natural and anthropogenic sources and are ubiquitously present in the environment. Several PAHs are highly toxic to humans with associated carcinogenic and mutagenic properties. Further, more severe harmful effects on human- and environmental health have been attributed to the presence of high molecular weight (HMW) PAHs, that is PAHs with molecular mass greater than 300 Da. However, more research has been conducted using low molecular weight (LMW) PAHs). In addition, no HMW PAHs are on the priority pollutants list of the United States Environmental Protection Agency (US EPA), which is limited to only 16 PAHs. However, limited analytical methodologies for separating and determining HMW PAHs and their potential isomers and lack of readily available commercial standards make research with these compounds challenging. Since most of the PAH kinetic data originate from animal studies, our understanding of the effects of PAHs on humans is still minimal. In addition, current knowledge of toxic effects after exposure to PAHs may be underrepresented since most investigations focused on exposure to a single PAH. Currently, information on PAH mixtures is limited. Thus, this review aims to critically assess the current knowledge of PAH chemical properties, their kinetic disposition, and toxicity to humans. Further, future research needs to improve and provide the missing information and minimize PAH exposure to humans.

Association between fetal exposure to polycyclic aromatic hydrocarbons and low birth weight: a case-control study in Shenzhen, China

The potential hazards of polycyclic aromatic hydrocarbons (PAHs) on fetus development have raised widespread concerns in recent years, although current epidemiological findings are conflicting. The aim of this case-control study was to investigate the relationship between PAH concentrations in maternal serum and low birth weight (LBW). A questionnaire survey was conducted among 144 (72 pairs) neonates with normal or LBW and their mothers at four different hospitals in Shenzhen, China. Peripheral blood from primiparas and umbilical cord blood from neonates were collected. Concentrations of PAHs were determined by gas chromatography-mass spectrometry. The detection frequencies of PAHs were relatively higher in the peripheral blood samples, while levels of low molecular weight PAHs were greater than high molecular weight PAHs in both peripheral and umbilical cord blood samples. Phenanthrene was frequently detected in blood samples from the case and control groups. Logistic regression analysis showed that acenaphthene in peripheral blood was positively associated with LBW (p < 0.05). This study found a relationship between exposure to certain PAHs and LBW, although future studies are needed to confirm these results.

Birth defects and unconventional natural gas developments in Texas, 1999-2011

Unconventional natural gas developments (UNGD) may release air and water pollutants into the environment, potentially increasing the risk of birth defects. We conducted a case-control study evaluating 52,955 cases with birth defects and 642,399 controls born between 1999 and 2011 to investigate the relationship between UNGD exposure and the risk of gastroschisis, congenital heart defects (CHD), neural tube defects (NTDs), and orofacial clefts in Texas. We calculated UNGD densities (number of UNGDs per area) within 1, 3, and 7.5 km of maternal address at birth and categorized exposure by density tertiles. For CHD subtypes with large case numbers, we also performed time-stratified analyses to examine temporal trends. We calculated adjusted odds ratios (aOR) and 95% confidence intervals (CI) for the association with UNGD exposure, accounting for maternal characteristics and neighborhood factors. We also included a bivariable smooth of geocoded maternal location in an additive model to account for unmeasured spatially varying risk factors. Positive associations were observed between the highest tertile of UNGD density within 1 km of maternal address and risk of anencephaly (aOR: 2.44, 95% CI: 1.55, 3.86), spina bifida (aOR: 2.09, 95% CI: 1.47, 2.99), gastroschisis among older mothers (aOR: 3.19, 95% CI: 1.77, 5.73), aortic valve stenosis (aOR: 1.90, 95% CI: 1.33, 2.71), hypoplastic left heart syndrome (aOR: 2.00, 95% CI: 1.39, 2.86), and pulmonary valve atresia or stenosis (aOR: 1.36, 95% CI: 1.10, 1.66). For CHD subtypes, results did not differ substantially by distance from maternal address or when residual confounding was considered, except for atrial septal defects. We did not observe associations with orofacial clefts. Our results suggest that UNGDs were associated with some CHDs and possibly NTDs. In addition, we identified temporal trends and observed presence of spatial residual confounding for some CHDs.

Neural Tube Defects and ZIC4 Hypomethylation in Relation to Polycyclic Aromatic Hydrocarbon Exposure

Background

Epigenetic dysregulation is one of the postulated underlying mechanisms of neural tube defects (NTDs). Polycyclic aromatic hydrocarbons (PAHs), a group of environmental pollutants that are reported as a risk factor of NTDs, may cause decreased genome-wide DNA methylation. With DNA extracted from neural tissues, this study identified gene(s) whose hypomethylation was related to elevated risk for NTDs and examined whether its hypomethylation is related to PAH exposure.

Results

Using data profiled by Infinium HumanMethylation450 BeadChip array from 10 NTD cases and eight controls, ZIC4, CASP8, RAB32, RARA, and TRAF6 were identified to be the top five genes in NTD-related hypomethylated gene families. Among all identified genes, ZIC4 had the largest number of differently methylated CpG sites (n = 13) in the promoter region and 5′ UTR. Significantly decreased methylation in the ZIC4 promoter region and 5′ UTR was verified in an independent cohort of 80 cases and 32 controls (p < 0.001) utilizing the Sequenom EpiTYPER platform. Hypomethylation of ZIC4 was associated with a higher risk of NTDs [adjusted OR = 1.08; 95% confidence interval (CI): 1.03, 1.13] in a logistic regression model. Mean methylation levels in the promoter region and 5′ UTR of ZIC4 tended to be inversely associated with levels of high-molecular-weight PAHs in fetal liver among NTD fetuses (β [95% CI]: −0.045 [−0.091, 0.001], p = 0.054). Six and three CpG sites in the ZIC4 promoter region and 5′ UTR were inversely correlated with antioxidant indicators and protein oxidation markers (ρ: −0.45 to −0.75, p < 0.05) in fetal neural tissues, respectively. In a whole-embryo cultured mouse model, hypomethylation of the Zic4 promoter region and 5′ UTR and upregulation of Zic4 were observed, coupled with increased NTD rates after BaP exposure. The antioxidant N-acetyl-L-cysteine normalized the changes observed in the BaP exposure group.

Conclusion

Hypomethylation of the ZIC4 promoter region and 5′ UTR may increase the risk for NTDs; oxidative stress is likely to play a role in the methylation change of Zic4 in response to PAH exposure in NTD formation.

Insights into biomonitoring of human exposure to polycyclic aromatic hydrocarbons with hair analysis: A case study in e-waste recycling area

In this study, 96 pairs of hair and urine samples were collected from e-waste (EW) dismantling workers of an industrial park, as well as residents living in surrounding areas. The concentrations of polycyclic aromatic hydrocarbons (PAHs) and hydroxylated PAH metabolites (OH-PAHs) were analyzed . The results show that concentrations of Σ₁₅PAHs ranged from 6.24 to 692 ng/g dry weight (dw) and Σ₁₂OH-PAHs from undetected to 187 ng/g dw in hair external (hair-Ex), and ranged from 31.7 to 738 ng/g dw and 21.6 to 1887 ng/g dw in hair internal (hair-In). There was no significant difference in exposure levels between EW dismantling workers and residents of the surrounding area. For the parent PAHs, the concentrations of Σ₁₅PAHs of hair-In were comparable with those of hair-Ex for all populations except for the child residents. On the contrary, for the OH-PAHs, the concentrations of Σ₁₂OH-PAHs of hair-In were 9-37 times higher than those of hair-Ex for populations. Moreover, the congener profiles of OH-PAHs of hair-In were different from those of hair-Ex, but similar to that of urine. Particularly, 3-OH-Bap, which is a carcinogenic metabolite, was only detected in the hair-In. These results indicate that OH-PAHs in hair-In, just like in urine, are mainly derived from endogenous metabolism and could be considered as reliable biomarkers for PAHs exposure. However, there was almost no significant correlations between hair-In and urine for OH-PAHs. This indicates that more attention should be paid to OH-PAHs when conducting PAHs exposure risk assessment using hair, which will help to obtain more reliable and comprehensive information on health risk assessments.

Recovery and reactivity of polycyclic aromatic hydrocarbons collected on selected sorbent tubes and analyzed by thermal desorption-gas chromatography/mass spectrometry

This article describes the optimization of methodology for extending the measurement of volatile organic compounds (VOCs) to increasingly heavier polycyclic aromatic hydrocarbons (PAHs) with a detailed focus on recent sorbent tube technology. Although PAHs have lower volatility than compounds such as benzene, toluene, ethylbenzene and xylenes, these semi-volatile compounds can be detected in air and breath samples. For this work, PAHs were captured on sorbent tubes and subsequently analyzed using automated thermal desorption gas chromatography - mass spectrometry (ATD-GC/MS). While many different sorbent tubes are commercially available, optimization for airborne PAH sampling using sorbent tubes has not been previously considered. Herein, several commercially available sorbent tubes, including Carbograph 2 TD/1TD, Tenax TA, XRO-440, and inert-coated PAH tubes are compared to determine the relative recovery for eight PAHs commonly found in the environment. Certain types of sorbent materials were found to be better suited for PAH recovery during thermal desorption, and PAH reaction products were observed on several types of sorbent tubes, including graphitized carbon black sorbents with stainless steel tube materials. As such, selection of sorbent tube media should be carefully considered prior to embarking on a PAH study.

Association between elevated placental polycyclic aromatic hydrocarbons (PAHs) and PAH-DNA adducts from Superfund sites in Harris County, and increased risk of preterm birth (PTB)

The preterm birth (PTB) rate in Harris County, Texas, exceeds the U.S. rate (11.4% vs.9.6%), and there are 15 active Superfund sites in Harris County. Polycyclic aromatic hydrocarbons (PAHs) are contaminants of concern (COC) at Superfund sites across the nation. In this investigation, we tested the hypothesis that higher levels of exposure to PAHs and PAH-DNA adducts in placenta of women living near Superfund sites contribute to the increased rate of PTBs. Levels of benzo[a]pyene (BP), benzo[b]fluorene (BbF) and dibenz[a,h]anthracene (DBA), were higher in placentae from preterm deliveries compared with term deliveries in women living near Superfund sites, whereas this was not the case for women living in non-Superfund site areas. Among the PAHs, DBA levels were significantly higher than BP or BbF, and DBA levels were inversely correlated with gestational age at delivery and birth weight. Bulky PAH-DNA adducts are more prevalent in placental tissue from individuals residing near Superfund sites. Expression of Ah receptor (AHR) and NF-E2-related factor 2 (NRF2) was decreased in preterm deliveries in subjects residing near Superfund sites. Unbiased metabolomics revealed alterations in pathways involved in pentose phosphate, inositol phosphate and starch and sucrose metabolism in preterm subjects in Superfund site areas. In summary, this is the first report showing an association between PAH levels, DNA adducts, and modulation of endogenous metabolic pathways with PTBs in subjects residing near Superfund sites, and further studies could lead to novel strategies in the understanding of the mechanisms by which PAHs contribute to PTBs in women.

Decreased global DNA hydroxymethylation in neural tube defects: Association with polycyclic aromatic hydrocarbons

5-Hydroxymethylcytosine (5hmC), a distinct epigenetic marker that plays a role in DNA active demethylation, has been reported to be important for embryonic development and may respond to environmental exposure. No studies have evaluated the association between DNA hydroxymethylation and the risk for fetal neural tube defects (NTDs), with consideration of prenatal exposure to polycyclic aromatic hydrocarbons (PAHs), a risk factor for NTDs. We measured the global levels of 5hmC% in neural tissue from 92 terminated NTD cases and 33 terminated non-malformed fetuses. A lower level of 5hmC% was found in the NTD cases (median [interquartile range]: 0.25 [0.12-0.39]) compared to the controls (0.45 [0.19-1.00]). After adjusting for periconceptional folate supplementation, risk for NTDs increased with decreasing tertiles of 5hmC% (odds ratio: 7.89, 95% confidence interval: 2.32, 26.86, for the lowest tertile relative to the top tertile; p_{for trend} = 0.002). Linear regression revealed that concentrations of high-molecular-weight PAHs (H_PAHs) in fetal liver tissue were negatively associated with log2-transformed 5hmC%. Superoxide dismutase activity and 5hmC% were positively correlated in fetal neural tissue (r_s = 0.64; p < 0.05). A mouse whole-embryo culture model was used for further validation. Decreased levels of 5hmC% and increased levels of reactive oxygen species were found in mouse embryos treated with BaP, a well-studied PAH. Taken together, levels of 5hmC% in fetal neural tissue were inversely associated with the risk for NTDs, and this association may be related to oxidative stress induced by exposure to PAHs.

Casp8 hypomethylation and neural tube defects in association with polycyclic aromatic hydrocarbon exposure

Background

Epidemiological studies have found that prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) is associated with increased risk for neural tube defects (NTDs). Aberrant DNA methylation, excessive apoptosis, and oxidative stress have been implied as the mechanism underlying the association between PAH exposure and NTDs, respectively. However, the role of DNA methylation aberration of apoptotic initiator CASP8 (caspase-8, apoptosis-related cysteine peptidase) in the formation of NTDs in association with PAH exposure is not known. By combining a case–control study and mouse model, we aimed to explore the full spectrum of the links from PAH exposure, oxidative stress, CASP8 methylation change, caspase-8 activation, apoptosis, to NTD formation.

Results

Hypomethylation of CASP8 promoter was noticed in the microarray profiled by Infinium HumanMethylation450 BeadChip using neural tissues from 10 terminated NTD fetuses and 8 terminated non-malformed fetuses (14 CpG sites, with β difference ranging between 8.8 and 26.3%), and was validated in a larger case–control sample performed with neural tissues from 80 NTD cases and 32 non-malformed fetuses, using the Sequenom MassARRAY system (7 CpG sites). Hypomethylation of CASP8 was a risk factor for NTDs (aOR = 1.11; 95% CI, 1.05–1.17) based on the logistic regression model. According to Pearson’s correlation, methylation levels of CASP8 were inversely correlated with PAH concentrations in maternal serum and with oxidative stress markers in fetal neural tissues (p < 0.05). In the animal study, increased NTD rates (13.5% frequency), Casp8 hypomethylation, caspase-8 upregulation, increased caspase-8 cleavage, and excessive apoptosis were found in mouse embryos cultured with benz(a)pyrene (BaP) in vitro. Antioxidant N-acetyl-L-cysteine (NAC) and BaP co-treatment attenuated the changes found in BaP treatment group.

Conclusions

Hypomethylation of Casp8 promoter is associated with the formation of NTDs, and Casp8 hypomethylation may be induced by oxidative stress that resulted from exposure to PAHs.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0673-6) contains supplementary material, which is available to authorized users.

MGMT is down-regulated independently of promoter DNA methylation in rats with all-trans retinoic acid-induced spina bifida aperta

O6-methylguanine DNA methyltransferase (MGMT), a DNA repair enzyme, has been reported in some congenital malformations, but it is less frequently reported in neural tube defects. This study investigated MGMT mRNA expression and methylation levels in the early embryo and in different embryonic stages, as well as the relationship between MGMT and neural tube defects. Spina bifida aperta was induced in rats by a single intragastric administration of all-trans retinoic acid on embryonic day (E) 10, whereas normal control rats received the same amount of olive oil on the same embryonic day. DNA damage was assessed by detecting γ-H2A.X in spina bifida aperta rats. Real time-polymerase chain reaction was used to examine mRNA expression of MGMT in normal control and spina bifida aperta rats. In normal controls, the MGMT mRNA expression decreased with increasing embryonic days, and was remarkably reduced from E11 to E14, reaching a minimum at E18. In the spina bifida aperta model, γ-H2A.X protein expression was increased, and mRNA expression of MGMT was markedly decreased on E14, E16, and E18. Bisulfite sequencing polymerase chain reaction for MGMT promoter methylation demonstrated that almost all CpG sites in the MGMT promoter remained unmethylated in both spina bifida aperta rats and normal controls, and there was no significant difference in methylation level between the two groups on either E14 or E18. Our results show that DNA damage occurs in spina bifida aperta rats. The mRNA expression of MGMT is downregulated, and this downregulation is independent of promoter DNA methylation.

Fetal toxicology

Toxic chemicals, either from natural sources or man-made, are ubiquitous in our environment. Many of the synthetic chemicals make life more comfortable and therefore production continues to grow. Simultaneously with the increase in production, an increase in neurodevelopmental disorders has been observed. Some chemicals are not biodegradable or have a very long half-life time and, despite the fact that production of a number of those chemicals has been severely reduced, they are still ubiquitous in the environment. Fetal exposure to toxic chemicals is dependent on maternal exposure to those chemicals and the developing stage of the fetus. Human evidence from epidemiologic studies is described with regard to the effect of prenatal exposure to various groups of neurotoxicants (alcohol, particulate fine matter, metals, and endocrine disrupting chemicals) on neurobehavior development. Data indicate that prenatal exposure to alcohol, polycyclic aromatic hydrocarbons, lead, methylmercury (MeHg), organophosphate pesticides (OPPs), and polychlorinated biphenyl ethers (PBDEs) impair cognitive development, whereas exposure to alcohol, MeHg, organochlorine pesticides and OPPs, polychlorinated biphenyls, PBDEs, and bisphenol A increases the risk of developing either attention deficit/hyperactivity and/or autism spectrum disorders. Psychomotor development appears to be less affected. However, data are not conclusive, which may depend on the assessment of exposure and the exposure level, among other factors.

Oxidative Stress and Apoptosis in Benzo[a]pyrene-Induced Neural Tube Defects

Neural tube defects (NTDs) are among the most common and severe congenital malformations and result from incomplete closure of the neural tube during early development. Maternal exposure to polycyclic aromatic hydrocarbons (PAHs) has been suggested to be a risk factor for NTDs and previous studies imply that the mechanism underlying the association between PAH exposure and NTDs may involve oxidative stress and apoptosis. The objectives of this study were to investigate whether there is a direct effect of maternal benzo[α] pyrene (BaP) exposure on the closure of the neural tube in mice, and to examine the underlying mechanisms by combining animal experiments and human subject studies. We found that intraperitoneal injection of BaP from embryonic day 7 at a dose of 250 mg kg^-1 induced NTDs (13.3% frequency) in ICR mice. BaP exposure significantly increased expression of genes associated with oxidative stress, Cyp1a1, Sod1 and Sod2, while repressing Gpx1. Elevated apoptosis and higher protein expression of cleaved caspase-3 in the neuroepithelium of treated embryos were observed. Pre-treatment with vitamin E, added to food, significantly protected against BaP-induced NTDs (1.4% frequency) (P < 0.05). Vitamin E also partly normalized oxidative stress related gene expression and excess apoptosis in BaP-treated embryos. Examination of human neural tissues revealed that increased levels of protein carbonyl and apoptosis were related with maternal exposure to PAHs and the risk of NTDs. Collectively, these results suggest that BaP exposure could induce NTDs and that this may involve increased oxidative stress and apoptosis, while vitamin E may have a protective effect.

Distribution and predictors of urinary polycyclic aromatic hydrocarbon metabolites in two pregnancy cohort studies

Pregnant women and their fetuses represent susceptible populations to environmental contaminants. Exposure to polycyclic aromatic hydrocarbons (PAHs) among pregnant women may contribute to adverse birth outcomes such as preterm birth. Multiple previous studies have assessed airborne sources of PAHs among pregnant women but few have measured urinary PAH metabolites which can capture total exposure through multiple routes. The aim of this study was to bridge this knowledge gap by assessing longitudinal urinary PAH metabolite concentrations over two time points in pregnancy cohorts in Boston (N = 200) and Puerto Rico (N = 50) to better understand exposure distributions throughout pregnancy and how they relate to demographic factors. Urine samples were analyzed for 1-NAP, 2-NAP, 2-FLU, 1-PHE, 2,3-PHE, 4-PHE, 9-PHE, and 1-PYR. Concentrations of 2-NAP, 1-PYR, and 4-PHE were higher in Puerto Rico, while all other metabolites were present in higher concentrations in Boston. In Puerto Rico, intraclass correlation coefficients (ICC) were weak to moderate, ranging from 0.06 to 0.42. PAH metabolite concentrations were significantly higher among younger, heavier (except 1-NAP and 9-PHE), and less educated individuals in Boston only. Consistent significant associations between PAH concentrations and measured covariates were not found in Puerto Rico. Our results suggest that potentially important differences in PAH exposure exist between these two populations. Additionally, our results indicate that multiple urinary measurements are required to accurately assess PAH exposure throughout pregnancy.

Biomarkers used in studying air pollution exposure during pregnancy and perinatal outcomes: a review

PURPOSE

This review focuses on studies among pregnant women that used biomarkers to assess air pollution exposure, or to understand the mechanisms by which it affects perinatal outcomes.

METHODS

We searched PubMed and Google scholar databases to find articles.

RESULTS AND CONCLUSIONS

We found 29 articles, mostly consisting of cohort studies. Interpolation models were most frequently used to assess exposure. The most consistent positive association was between polycyclic aromatic hydrocarbon (PAH) exposure during entire pregnancy and cord blood PAH DNA adducts. Exposure to particulate matter (PM) and nitrogen dioxide (NO₂) showed consistent inverse associations with mitochondrial DNA (mtDNA) content, particularly in the third trimester of pregnancy. No single pollutant showed strong associations with all the biomarkers included in this review. C-reactive proteins (CRPs) and oxidative stress markers increased, whereas telomere length decreased with increasing air pollution exposure. Placental global DNA methylation and mtDNA methylation showed contrasting results with air pollution exposure, the mechanism behind which is unclear. Most studies except those on PAH DNA adducts and mtDNA content provided insufficient evidence for characterizing a critical exposure window. Further research using biomarkers is warranted to understand the relationship between air pollution and perinatal outcomes.

Transplacental transfer of polycyclic aromatic hydrocarbons in paired samples of maternal serum, umbilical cord serum, and placenta in Shanghai, China

Prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) is a high-priority public health concern. However, maternal to fetal transplacental transfer of PAHs has not been systematically studied. To investigate the transplacental transfer of PAHs from mother to fetus and determine the influence of lipophilicity (octanol-water partition coefficient, K_OW) on transfer process, in the present study, we measured the concentrations of 15 PAHs in 95 paired maternal and umbilical cord serum, and placenta samples (in total 285 samples) collected in Shanghai, China. The average concentration of total PAHs was the highest in maternal serums (1290 ng g^-1 lipid), followed by umbilical cord serums (1150 ng g^-1 lipid). The value was the lowest in placenta samples (673 ng g^-1 lipid). Low molecular weight PAHs were the predominant compounds in the three matrices. Increases in fish and meat consumption did not lead to increases in maternal PAH levels, and no obvious gender differences in umbilical cord serums were observed. The widespread presence of PAHs in umbilical cord serums indicated the occurrence of transplacental transfer. The ratios of PAH concentrations in umbilical cord serum to those in maternal serum (F/M) and the concentrations in placenta to those in maternal serum (P/M) of paired samples were analyzed to characterize the transfer process of individual PAHs. Most F/M ratios on lipid basis were close to one (range: 0.79 to 1.36), which suggested that passive diffusion may control the transplacental transfer of PAHs from maternal serum to the fetal circulation. The P/M and F/M values calculated on lipid basis showed that PAHs with lower K_OW were more likely to transfer from mother to fetus via the placenta.

Environmental exposure to polycyclic aromatic hydrocarbons (PAHs): The correlation with and impact on reproductive hormones in umbilical cord serum

Polycyclic aromatic hydrocarbons (PAHs) are a type of ubiquitous pollutant with the potential ability to cause endocrine disruption that would have an adverse health impact on the general population. To assess the maternal exposure to PAHs in neonates and evaluate the possible impact of PAHs on reproductive hormone levels, the concentration of PAHs and reproductive hormone levels in the umbilical cord serum of 98 mother-infant pairs in the Shengsi Islands were investigated. The median concentration of total PAHs was determined to be 164 (Inter-Quartile Range, IQR 93.6-267) ng g^-1 lipid, and 68% of the PAHs were lower-molecule congeners. The highest level was found for pyrene (PYR) and naphthalene (NAP), which contributed 54.6% of all the PAHs present in the samples. The exposure to PAHs negatively affected estradiol (E2) and Anti-Mullerian hormones (AMH) and positively affected FSH in the umbilical cord serum. The result expanded the database of the human burden of PAHs and suggested that PAHs can act as a type of Endocrine-Disrupting Chemical (EDC). These results may help to understand the complex pathways involved in disorders of human reproductive health associated with prenatal exposure to PAHs.

Air pollution, a rising environmental risk factor for cognition, neuroinflammation and neurodegeneration: The clinical impact on children and beyond

Air pollution (indoors and outdoors) is a major issue in public health as epidemiological studies have highlighted its numerous detrimental health consequences (notably, respiratory and cardiovascular pathological conditions). Over the past 15 years, air pollution has also been considered a potent environmental risk factor for neurological diseases and neuropathology. This review examines the impact of air pollution on children's brain development and the clinical, cognitive, brain structural and metabolic consequences. Long-term potential consequences for adults' brains and the effects on multiple sclerosis (MS) are also discussed. One challenge is to assess the effects of lifetime exposures to outdoor and indoor environmental pollutants, including occupational exposures: how much, for how long and what type. Diffuse neuroinflammation, damage to the neurovascular unit, and the production of autoantibodies to neural and tight-junction proteins are worrisome findings in children chronically exposed to concentrations above the current standards for ozone and fine particulate matter (PM2.5), and may constitute significant risk factors for the development of Alzheimer's disease later in life. Finally, data supporting the role of air pollution as a risk factor for MS are reviewed, focusing on the effects of PM10 and nitrogen oxides.