Association Between Placental Polycyclic Aromatic Hydrocarbons (PAHS), Oxidative Stress, and Preterm Delivery: A Case-Control Study

Urinary polycyclic aromatic hydrocarbon metabolites in Chinese pregnant women: Concentrations, variability, predictors, and association with oxidative stress biomarkers

Polycyclic aromatic hydrocarbons (PAHs) are a class of pervasive contaminants having adverse health effects. Urinary monohydroxylated PAHs (OH-PAHs) are commonly employed as biomarkers to estimate PAH exposure levels in humans. However, little is understood about the variability in OH-PAHs among pregnant women across trimesters and their relationship with oxidative stress biomarkers (OSBs). Based on a prospective birth cohort study conducted in Wuhan, China, we selected 644 women who donated (spot) urine samples across different trimesters and measured the urinary concentrations of eight OH-PAHs and three selected OSBs (8-OHG, 8-OHdG, and HNEMA) to explore the relationship between the OH-PAHs and OSBs. Pregnant women were found to be ubiquitously exposed to the PAHs, with detection rates of the OH-PAHs ranging from 86.3% to 100%. 2-Hydroxynaphthalene (2-OH-Nap) had the highest urinary concentrations among the OH-PAHs during the three trimesters (specific gravity-adjusted median values for the first, second, and third trimesters: 1.86, 2.39, and 2.20 ng/mL, respectively). However, low reproducibility of the OH-PAHs was observed across the three trimesters with intraclass correlation coefficients ranged between 0.02 and 0.22. Most urinary OH-PAHs had the highest concentrations at the first trimester and the lowest at the third trimester. Some OH-PAH concentrations were higher in pregnant women with lower educational level [2-hydroxyphenanthrene (2-OH-Phen) and 3-hydroxyphenanthrene (3-OH-Phen)], those who were overweight [2-OH-Nap, 2/3-hydroxyfluorene (2/3-OH-Fluo), 2-OH-Phen, and 4-hydroxyphenanthrene (4-OH-Phen)], those who were unemployed during pregnancy [1-hydroxynaphthalene, 1/9-hydroxyphenanthrene, and 4-OH-Phen], and the samples donated in summer (most OH-PAHs, except for 2-OH-Nap). In multivariable linear mixed-effects model analyses, every OH-PAH was found to be significantly associated with increased levels of the three OSBs. For example, each interquartile range-fold increase in 2/3-OH-Fluo concentration was associated with the largest increase in 8-OHdG (65.4%) and 8-OHG (49.1%), while each interquartile range-fold increase in 3-OH-Phen concentration was associated with the largest increase in HNEMA (76.3%). Weighted quantile sum regression models, which were used to examine the joint effect of OH-PAH mixture on the OSBs, revealed positive associations between the OH-PAH mixture exposure and the OSBs. Specifically, 2/3-OH-Fluo and 2-OH-Nap were the major contributors in the association with oxidative damage of nucleic acids (8-OHdG and 8-OHG), while hydroxyphenanthrenes and 1-hydroxypyrene were the major contributors in the association with oxidative damage of lipid (HNEMA). Further work is required to examine the potential mediating role of oxidative stress in the relationship of adverse health outcomes with elevated PAH exposure among pregnant women.

Adverse neurodevelopment in children associated with prenatal exposure to fine particulate matter (PM2.5) - Possible roles of polycyclic aromatic hydrocarbons (PAHs) and mechanisms involved

Prenatal exposure to ambient fine particles (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) has been associated with adverse birth outcomes including neurodevelopmental effects with cognitive and/or behavioral implications in early childhood. As a background we first briefly summarize human studies on PM2.5 and PAHs associated with adverse birth outcomes and modified neurodevelopment. Next, we add more specific information from animal studies and in vitro studies and elucidate possible biological mechanisms. More specifically we focus on the potential role of PAHs attached to PM2.5 and explore whether effects of these compounds may arise from disturbance of placental function or more directly by interfering with neurodevelopmental processes in the fetal brain. Possible molecular initiating events (MIEs) include interactions with cellular receptors such as the aryl hydrocarbon receptor (AhR), beta-adrenergic receptors (βAR) and transient receptor potential (TRP)-channels resulting in altered gene expression. MIE linked to the binding of PAHs to cytochrome P450 (CYP) enzymes and formation of reactive electrophilic metabolites are likely less important. The experimental animal and in vitro studies support the epidemiological findings and suggest steps involved in mechanistic pathways explaining the associations. An overall evaluation of the doses/concentrations used in experimental studies combined with the mechanistic understanding further supports the hypothesis that prenatal PAHs exposure may cause adverse outcomes (AOs) linked to human neurodevelopment. Several MIEs will likely occur simultaneously in various cells/tissues involving several key events (KEs) which relative importance will depend on dose, time, tissue, genetics, other environmental factors, and neurodevelopmental endpoint in study.

Prenatal exposure to Benzo[a]pyrene affects maternal-fetal outcomes via placental apoptosis

Prenatal exposure to Benzo[a]pyrene (BaP) has been suggested to increase the risk of adverse pregnancy outcomes. However, the role of placental apoptosis on BaP reproductive toxicity is poorly understood. We conducted a maternal animal model of C57BL/6 wild-type (WT) and transformation-related protein 53 (Trp53) heterozygous knockout (p53KO) mice, as well as a nested case-control study involving 83 women with PB and 82 term birth from a birth cohort on prenatal exposure to BaP and preterm birth (PB). Pregnant WT and p53KO mice were randomly allocated to BaP treatment and control groups, intraperitoneally injected of low (7.8 mg/kg), medium (35 mg/kg), and high (78 mg/kg) doses of 3,4-BaP per day and equal volume of vegetable oil, from gestational day 10.5 until delivery. Results show that high-dose BaP treatment increased the incidence of preterm birth in WT mice. The number of fetal deaths and resorptions increased with increasing doses of BaP exposure in mice. Notably, significant reductions in maternal and birth weights, increases in placental weights, and decrease in the number of livebirths were observed in higher-dose BaP groups in dose-dependent manner. We additionally observed elevated p53-mediated placental apoptosis in higher BaP exposure groups, with altered expression levels of p53 and Bax/Bcl-2. In case-control study, the expression level of MMP2 was increased among women with high BaP exposure and associated with the increased risk of all PB and moderate PB. Our study provides the first evidence of BaP-induced reproductive toxicity and its adverse effects on maternal-fetal outcomes in both animal and population studies.

Cell type-dependent response to benzo(a)pyrene exposure of human placental cell lines under normoxic, hypoxic, and pro-inflammatory conditions

Benzo(a)pyrene (BaP) can be detected in the human placenta. However, little is known about the effects of BaP exposure on different placental cells under various conditions. In this study, we aimed to investigate the effects of BaP on mitochondrial function, pyrin domain-containing protein 3 (NLRP3) inflammasome, and apoptosis in three human trophoblast cell lines under normoxia, hypoxia, and inflammatory conditions. JEG-3, BeWo, and HTR-8/SVneo cell lines were exposed to BaP under normoxia, hypoxia, or inflammatory conditions for 24 h. After treatment, we evaluated cell viability, apoptosis, aryl hydrocarbon receptor (AhR) protein and cytochrome P450 (CYP) gene expression, mitochondrial function, including mitochondrial DNA copy number (mtDNAcn), mitochondrial membrane potential (ΔΨm), intracellular adenosine triphosphate (iATP), and extracellular ATP (eATP), nitric oxide (NO), NLPR3 inflammasome proteins, and interleukin (IL)-1β. We found that BaP upregulated the expression of AhR or CYP genes to varying degrees in all three cell lines. Exposure to BaP alone increased ΔΨm in all cell lines but decreased NO in BeWo and HTR-8/SVneo, iATP in HTR-8/SVneo, and cell viability in JEG-3, without affecting apoptosis. Under hypoxic conditions, BaP did not increase the expression of AhR and CYP genes in JEG-3 cells but increased CYP gene expression in two others. Pro-inflammatory conditions did not affect the response of the 3 cell lines to BaP with respect to the expression of CYP genes and changes in the mitochondrial function and NLRP3 inflammasome proteins. In addition, in HTR-8/SVneo cells, BaP increased IL-1β secretion in the presence of hypoxia and poly(I:C). In conclusion, our results showed that BaP affected mitochondrial function in trophoblast cell lines by increasing ΔΨm. This increased ΔΨm may have rescued the trophoblast cells from activation of the NLRP3 inflammasome and apoptosis after BaP treatment. We also observed that different human trophoblast cell lines had cell type-dependent responses to BaP exposure under normoxia, hypoxia, or pro-inflammatory conditions.

The Maternal and Infant Environmental Health Riskscape study of perinatal disparities in greater Houston: rationale, study design and participant profiles

Introduction

The Maternal and Infant Environmental Health Riskscape (MIEHR) Center was established to address the interplay among chemical and non-chemical stressors in the biological, physical, social, and built environments that disproportionately impact perinatal health among Black pregnant people in a large and diverse urban area with documented disparities in the U.S.

Methods

The MIEHR cohort is recruiting non-Hispanic Black and non-Hispanic white pregnant people who deliver their infants at major obstetric hospitals in Houston, Texas. At enrollment, all participants are asked to provide urine samples for chemical [metals, cotinine, and polycyclic aromatic hydrocarbons (PAHs)] analyses and blood samples. A subset of the cohort is asked to provide oral and vaginal swabs, and fecal samples. Questionnaire and electronic health record data gather information about residential address history during pregnancy, pregnancy history and prenatal care, sociodemographic and lifestyle factors, experiences of discrimination and stress, and sources of social support. Using information on where a participant lived during their pregnancy, features of their neighborhood environment are characterized. We provide summaries of key individual- and neighborhood-level features of the entire cohort, as well as for Black and white participants separately.

Results

Between April 2021 and February 2023, 1,244 pregnant people were recruited. Nearly all participants provided urine samples and slightly less than half provided blood samples. PAH exposure patterns as assessed on 47% of participants thus far showed varying levels depending on metabolite as compared to previous studies. Additionally, analyses suggest differences between Black and white pregnant people in experiences of discrimination, stress, and levels of social support, as well as in neighborhood characteristics.

Discussion

Our findings to date highlight racial differences in experiences of discrimination, stress, and levels of support, as well as neighborhood characteristics. Recruitment of the cohort is ongoing and additional neighborhood metrics are being constructed. Biospecimens will be analyzed for metals and PAH metabolites (urine samples), miRNAs (plasma samples) and the microbiome (oral swabs). Once enrollment ends, formal assessments are planned to elucidate individual- and neighborhood-level features in the environmental riskscape that contribute to Black-White disparities in perinatal health.

Modulatory effects of quercetin on histological changes, biochemical and oxidative stress of rat placenta induced by inhalation exposure to crude oil vapor

The inhalation exposure to crude oil vapor (COV) has been shown to have adverse effects on the placenta and fetal development. The modulatory effects of quercetin (QUE) as a natural phenolic compound with antioxidant properties are promising for the protection of placental structure. This study aimed to investigate the modulatory role of QUE in mitigating histopathological damage, oxidative stress, and biochemical alteration in the placenta of COV-exposed pregnant rats. Forty-eight pregnant rats were divided into eight groups (days 15 and 20) as follows: 1-2) Control groups, 3-4) COV groups, 5-6) COV+QUE groups, and 7-8) QUE-treated groups (50 mg/kg). The inhalation method was used to expose pregnant rats to COV, and QUE was administered orally. On the 15th and 20th days of gestation, placental tissue was analyzed using PAS and H&E staining and immunohistochemistry. The expression of the caspase-3 gene and oxidative stress biomarkers including TAC, CAT, MDA, GPx, and SOD were investigated in the placental tissue. The COV significantly decreased the weight, diameter, and thickness of the placenta as well as the thickness of the junctional zone and labyrinth and the number of trophoblast giant cells in 15- and 20-day-old placentas (P<0.05). Also, COV significantly increased placental expression of caspase-3 and the oxidative stress biomarkers (P<0.05). The administration of QUE along with exposure to COV reduced morphometric and histological alteration, oxidative stress, and caspase-3 expression (P<0.05). Our findings indicated that QUE in COV-exposed pregnant rats can prevent placental histopathological alternations by increasing the activity of the antioxidant system.

Repeated measurements and mixture effects of urinary bisphenols, parabens, polycyclic aromatic hydrocarbons, and other chemicals on biomarkers of oxidative stress in pre- and postpartum women

The association between oxidative stress and exposure to bisphenols, parabens, phenols, polycyclic aromatic hydrocarbons (PAH), and volatile organic compounds (VOCs) has been investigated by many in vitro and in vivo studies. However, most of these findings are based on cross-sectional studies, as a result of which the combined effects of these compounds have been rarely analyzed. In this study, our objective was to assess urinary bisphenols, parabens, PAHs, and VOCs, in relation to oxidative stress during pre-and postpartum periods, analyze the association between these chemicals and oxidative stress via repeated measurements using a linear mixed model (LMM), and evaluate the combined effects exerted by these chemicals on oxidative stress using Bayesian Kernel Machine Regression (BKMR). A total 529 urine samples were collected from 242 pregnant women during the 1st and 2nd trimesters, as well as postpartum follow-ups. Three bisphenols, four parabens, benzopheone-3 (BP-3), triclosan (TCS), four PAHs, two VOCs, and 3- phenoxy-benzoic acid (3-PBA) were analyzed. We also measured 8-hydroxydeoxyguanosine (8-OHdG) and malondialdehyde (MDA), which serve as oxidative stress biomarkers in maternal urine samples. During this period, 8-OHdG decreased steadily, whereas MDA increased during pregnancy and decreased after childbirth. LMM indicated that Bisphenol A, Prophyl-paraben, BP-3, and 1-hydroxypyrene (1-OHP) showed a significant association with increased MDA levels. The BKMR models revealed that the mixture effect exerted by these 16 chemicals had changed MDA levels, which indicate oxidative stress, and that both Butyl Paraben (BP) and 1-hydroxypyrene (1-OHP) had contributed to such oxidative stress. Mixtures of each subgroup (bisphenols, parabens, and PAHs) were associated with increased MDA levels. These findings suggest that exposure to some phenols and PAHs during pre- and post-partum stages may cause oxidative stress, and that exposure to these chemicals should be minimized during this period.

The association between exposure to polycyclic aromatic hydrocarbons and birth outcomes: A systematic review and meta-analysis of observational studies

Exposure to polycyclic aromatic hydrocarbons (PAHs) has been linked to adverse birth outcomes; however, to date, the available studies on such relations, with the exception of birth weight, has not been systematically synthesized. We conducted a systematic review and meta-analysis of the available observational studies on the association of maternal exposure to PAHs and their metabolites during pregnancy with indicators of fetal growth and gestational age at delivery. We searched Web of Science, PubMed and Scopus systematically for all relevant published papers in English until 13 January 2023. Random effects meta-analysis was applied to synthesize the association estimates. Publication bias was assessed using Egger's regression. A total of 31 articles were included in our review (n = 703,080 participants). Our quality assessment of reviewed papers showed that 19 research had excellent, nine had good, and three had fair quality. Most of the reviewed studies on exposure to PAHs and their metabolites with gestational age and preterm birth (seven studies) reported no statistically significant association. Eight studies were eligible for our meta-analysis. Results of the meta-analysis indicated that higher levels of maternal urinary 1-OHP was associated with lower birth weight, birth length and head circumference and a higher risk of low birth weight (LBW). However, these associations were not statistically significant. Similarly, the combined association between maternal urinary 1-OHP and newborn's Ponderal index (PI) and Cephalization index were not statistically significant. Overall, our systematic review and meta-analysis suggested a potential adverse impact of exposure to PAHs on LBW, HC, and CC; however, further studies are required to be able to draw concrete conclusions on such associations.

Prenatal exposure to crude oil vapor reduces differentiation potential of rat fetal mesenchymal stem cells by regulating ERK1/2 and PI3K signaling pathways: Protective effect of quercetin

It has been indicated that crude oil vapor (COV) induces tissue damage by several molecular mechanisms. Quercetin (QT) as an important component of food with antioxidant properties has a protective role against cell toxicity caused by many pollutants. However, data related to the adverse effects of crude oil vapor (COV) on stem cell fate and differentiation and the role of quercetin (QT) in protecting stem cells against the toxicity caused by these pollutants is very limited. This study aimed to explore the protective effect of QT against the adverse effects of COV on fetal mesenchymal stem cells (fMSCs) differentiation. Twenty-four pregnant Wistar rats were categorized into 4 groups including the control, COV, COV+QT, and QT. Rats were exposed to COV from gestational day (GD) 0-15 and received QT by gavage. The fMSCs were isolated from fetuses, and cell proliferation, differentiation potential, expression of osteogenesis and adipogenesis-related genes, and phosphorylation of PI3K and ERK1/2 signaling proteins were evaluated. The results showed that COV reduced the proliferation and differentiation of fMSCs through the activation of PI3K and ERK1/2 signaling pathways. Also, COV significantly decreased the expression of osteonectin, ALP, BMP-6, Runx-2, PPARγ, and CREBBP genes in differentiated cells. QT treatment increased the proliferation and differentiation of fMSCs in COV-exposed rats. In conclusion, our findings suggest that prenatal exposure to COV impaired fMSCs differentiation and QT reduced the adverse effects of COV by regulating ERK1/2 and PI3K signaling pathways.

Effects of polycyclic aromatic hydrocarbons (PAHs) on pregnancy, placenta, and placental trophoblasts

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants that are carcinogenic, mutagenic, endocrine-toxic, and immunotoxic. PAHs can be found in maternal and fetal blood and in the placenta during pregnancy. They may thus affect placental and fetal development. Therefore, the exposure levels and toxic effects of PAHs in the placenta deserve further study and discussion. This review aims to summarize current knowledge on the effects of PAHs and their metabolites on pregnancy and birth outcomes and on placental trophoblast cells. A growing number of epidemiological studies detected PAH-DNA adducts as well as the 16 high-priority PAHs in the human placenta and showed that placental PAH exposure is associated with adverse fetal outcomes. Trophoblasts are important cells in the placenta and are involved in placental development and function. In vitro studies have shown that exposure to either PAH mixtures, benzo(a)pyrene (BaP) or BaP metabolite benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) affected trophoblast cell viability, differentiation, migration, and invasion through various signaling pathways. Furthermore, similar effects of BPDE on trophoblast cells could also be observed in BaP-treated mouse models and were related to miscarriage. Although the current data show that PAHs may affect placental trophoblast cells and pregnancy outcomes, further studies (population studies, in vitro studies, and animal studies) are necessary to show the specific effects of different PAHs on placental trophoblasts and pregnancy outcomes.

Impacts of PAH accumulation on reproductive hormones, indices of oxidative stress and BPDE-albumin adduct in women with recurrent pregnancy loss

Chronic exposure to Poly aromatic hydrocarbons (PAHs) may be associated with adverse pregnancy outcomes. Disruption of hormonal and redox balance by toxic PAH metabolites may interfere with successful pregnancy leading to miscarriage. The association of exposure to PAH contaminated mussel via the dietary route with perturbations in reproductive hormones, biomarkers of oxidative stress, and PAH metabolites were assessed in women with recurrent pregnancy loss (RPL). Furthermore, an analysis of the concentration of PAHs in environmentally relevant bivalve animals was performed to preliminary get insights into the levels of these pollutants in the environment. Seventy-six women (20-35 years) were categorized into 18 fertile women without RPL (control), and Groups I, II, and III comprising 24, 18, and 16 women with RPL (2, 3, and > 3 abortions respectively) were studied. Whole blood samples were collected for the estimation of malondialdehyde (MDA), catalase, reduced glutathione (GSH), glutathione-S-transferase (GST), progesterone (P4), follicle-stimulating hormone (FSH), benzo[a]pyren-7,8-dihydrodiol-9,10-epoxide-albumin adduct (BPDE-albumin) and urine for α-naphthol and β-naphthol. Two species of mussel Donax trunculus and Andar aduloii samples were collected for the estimation of 16 priority PAHs. The concentration of PAHs exceeding the maximum limits was observed in the two species of mussels studied. Higher levels of BPDE-albumin, MDA, GST, α and β-naphthol and lower GSH, catalase, FSH, and P4 were observed in women with RPL (Groups I-III) compared to controls (p =  < 0.001). Negative associations were observed between BPDE-albumin and catalase (r = - 0.276, p = 0.036), and GSH (r = - 0.331, p = - 0.011) only in women with RPL. Collectively, our findings indicate a possible association of chronic PAH accumulation with recurrent pregnancy loss in women.

Graphical abstract

High PAH exposure in pregnant women is associated with 10-epoxide-albumin adduct formation and high MDA levels in their sera. On the other hand, PAH exposure in those women led to a decrease in their GSH, catalase, P4, and FSH sera levels. These findings indicate that PAH exposure can exert different physiological effects in pregnant women leading to a high level of abortion in those women.

Association of the urinary polycyclic aromatic hydrocarbons with sex hormones stratified by menopausal status older than 20 years: a mixture analysis

We examined the relationships between exposure to polycyclic aromatic hydrocarbons (PAH) metabolites and sex hormones in pre- and postmenopausal women from the 2013-2016 National Health and Nutrition Examination Survey. The study comprised 648 premenopausal and 370 postmenopausal women (aged 20 years or older) with comprehensive data on PAH metabolites and sex steroid hormones. To evaluate the correlations between individual or mixture of the PAH metabolites and sex hormones stratified by menopausal status, we used linear regression and Bayesian kernel machine regression (BKMR). After controlling for confounders, 1-Hydroxynaphthalene (1-NAP) was inversely associated with total testosterone (TT), and 1-NAP, 3-Hydroxyfluorene (3-FLU), and 2-Hydroxyfluorene (2-FLU) were inversely associated with estradiol (E2). 3-FLU was positively associated with sex hormone-binding globulin (SHBG) and TT/E2, whereas 1-NAP and 2-FLU were inversely associated with free androgen index (FAI). In the BKMR analyses, chemical combination concentrations at or above the 55th percentile were inversely connected to E2, TT, and FAI values but positively correlated with SHBG when compared with the matching 50th percentile. In addition, we only found that mixed exposure to PAHs was positively associated with TT and SHBG in premenopausal women. Exposure to PAH metabolites, either alone or as a mixture, was negatively associated with E2, TT, FAI, and TT/E2 but positively associated with SHBG. These associations were stronger among postmenopausal women.

Cellular mechanisms linking to outdoor and indoor air pollution damage during pregnancy

Pregnancies are a critical window period for environmental influences over the mother and the offspring. There is a growing body of evidence associating indoor and outdoor air pollution exposure to adverse pregnancy outcomes such as preterm birth and hypertensive disorders of pregnancy. Particulate matter (PM) could trigger oxi-inflammation and could also reach the placenta leading to placental damage with fetal consequences. The combination of strategies such as risk assessment, advise about risks of environmental exposures to pregnant women, together with nutritional strategies and digital solutions to monitor air quality can be effective in mitigating the effects of air pollution during pregnancy.

Placental transcriptomic signatures of prenatal exposure to Hydroxy-Polycyclic aromatic hydrocarbons

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants originating from petrogenic and pyrogenic sources. PAH compounds can cross the placenta, and prenatal PAH exposure is linked to adverse infant and childhood health outcomes.

OBJECTIVE

In this first human transcriptomic assessment of PAHs in the placenta, we examined associations between prenatal PAH exposure and placental gene expression to gain insight into mechanisms by which PAHs may disrupt placental function.

METHODS

The ECHO PATHWAYS Consortium quantified prenatal PAH exposure and the placental transcriptome from 629 pregnant participants enrolled in the CANDLE study. Concentrations of 12 monohydroxy-PAH (OH-PAH) metabolites were measured in mid-pregnancy urine using high performance liquid chromatography tandem mass spectrometry. Placental transcriptomic data were obtained using paired-end RNA sequencing. Linear models were fitted to estimate covariate-adjusted associations between maternal urinary OH-PAHs and placental gene expression. We performed sex-stratified analyses to evaluate whether associations varied by fetal sex. Selected PAH/gene expression analyses were validated by treating HTR-8/SVneo cells with phenanthrene, and quantifying expression via qPCR.

RESULTS

Urinary concentrations of 6 OH-PAHs were associated with placental expression of 8 genes. Three biological pathways were associated with 4 OH-PAHs. Placental expression of SGF29 and TRIP13 as well as the vitamin digestion and absorption pathway were positively associated with multiple metabolites. HTR-8/SVneo cells treated with phenanthrene also exhibited 23 % increased TRIP13 expression compared to vehicle controls (p = 0.04). Fetal sex may modify the relationship between prenatal OH-PAHs and placental gene expression, as more associations were identified in females than males (45 vs 28 associations).

DISCUSSION

Our study highlights novel genes whose placental expression may be disrupted by OH-PAHs. Increased expression of DNA damage repair gene TRIP13 may represent a response to double-stranded DNA breaks. Increased expression of genes involved in vitamin digestion and metabolism may reflect dietary exposures or represent a compensatory mechanism to combat damage related to OH-PAH toxicity. Further work is needed to study the role of these genes in placental function and their links to perinatal outcomes and lifelong health.

Urinary profile of PAHs and related compounds in women working in beauty salons

Polycyclic aromatic hydrocarbons (PAHs) are a group of chemical compounds which interest to human biological monitoring researches because of their potential carcinogenic, mutagenic, and teratogenic properties. However, the exposure of female beauticians to these contaminants is not well-reported. For biomonitoring of potential exposure of female cosmeticians to PAHs in beauty salons, urine samples were taken from cosmetologist women (n = 50.00) and housewives (n = 35.00) as the exposure group (EG) and control group (CG), respectively. Next, unmetabolized PAHs levels as well as the concentration of - 1-hydroxypyrene (1-OHP) were analyzed in these specimens. In addition, since benzene has some common source with PAHs, in this study t, t'-Muconic acid (TTMA) level was also determined as the metabolite and indicator of exposure to benzene. The results indicated a high detection frequency of the target compounds (PAHs, 1-OHP and TTMA) in the urine specimens of beauticians. The results also showed that there is a significant difference between the concentration of these pollutants in the urine specimens of the exposure and control groups. The median concentration of ΣPAHs, 1-OHP, and TTMA in the before exposure (BE) specimens collected from the exposure group were 337.42 ng/L, 593.92 ng/L, and 247.90 μg/L, respectively. However, a higher concentration of these contaminants was observed in the after exposure specimens with a median concentration of 423.29 ng/L, 745.03 ng/L, and 310.97 μg/L, respectively. In terms of contribution of PAHs compounds in total toxic equivalents, DahA, BaP, and IndP with 59.03, 28.73, and 2.86 % had the largest share. In this study, it was also observed that some kidney damage biomarkers as well as some oxidative stress injury biomarkers are positively and significantly correlated with the urinary values of ∑PAHs. Thus, it can be concluded that high health risks threaten the female beauticians regarding kidney injury and DNA oxidative stress.

Prenatal exposure to polycyclic aromatic hydrocarbons and gestational age at birth

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous chemicals with mechanisms of toxicity that include endocrine disruption. We examined associations of prenatal urinary PAH with spontaneous preterm birth (PTB) and gestational age (GA) at birth. We also assessed whether infant sex modifies the association of PAH exposure with spontaneous PTB and GA at birth.

METHODS

Participants included 1,677 non-smoking women from three cohorts (CANDLE, TIDES, and GAPPS) in the ECHO PATHWAYS Consortium. Twelve monohydroxylated-PAHs were measured in second trimester maternal urine. Seven metabolites with >60% overall detection were included in analyses: 1-hydroxynaphthalene [1-OH-NAP], 2-hydroxynaphthalene [2-OH-NAP], 2-hydroxyphenanthrene [2-OH-PHEN], 3-hydroxyphenanthrene [3-OH-PHEN], 1/9-hydroxyphenanthrene [1/9-OH-PHEN], 2/3/9-hydroxyfluorene [2/3/9-OH-FLUO], and 1-hydroxypyrene [1-OH-PYR]. Logistic and linear regression models were fit for spontaneous PTB and GA among births ≥34 weeks, respectively, with log₁₀-transformed OH-PAH concentrations as the exposure, adjusted for specific gravity and suspected confounders. Effect modification by infant sex was assessed using interaction terms and marginal estimates.

RESULTS

Percent detection was highest for 2-OH-NAP (99.8%) and lowest for 1-OH-PYR (65.2%). Prevalence of spontaneous PTB was 5.5% (N = 92). Ten-fold higher 2-OH-NAP exposure was associated with 1.60-day (95% CI: -2.92, -0.28) earlier GA at birth. Remaining associations in the pooled population were null. Among females, we observed significant inverse associations between 1-OH-PYR and PTB (OR: 2.65 [95% CI: 1.39, 5.05]); and 2-OH-NAP with GA: -2.46 days [95% CI: -4.15, -0.77]). Among males, we observed an inverse association between 2/3/9-OH-FLUO and PTB (OR = 0.40 [95% CI: 0.17,0.98]). ORs for PTB were higher among females than males for 2-OH-PHEN (p = 0.02) and 1-OH-PYR (p = 0.02).

DISCUSSION

We observed inverse associations of 2-OH-NAP exposure with GA and null associations of remaining OH-PAHs with GA and PTB. Females may be more susceptible to spontaneous PTB or shorter GA following prenatal exposure to some OH-PAHs. This study is the first to assess sex-specific OH-PAH toxicity in relation to spontaneous PTB and GA.

Effects of Benzo[a]pyrene-DNA adducts, dietary vitamins, folate, and carotene intakes on preterm birth: a nested case-control study from the birth cohort in China

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) and its DNA adducts has been suggested to increase the risk of preterm birth (PB). Yet, few studies have been conducted to investigate this association, and the role of dietary nutrients intakes including vitamins, folate, and carotene during pre- and post-conception on this association has not been studied.

METHODS

Building upon a birth cohort in Taiyuan China, we conducted a nested case control study including 83 PB and 82 term births. Benzo[a]pyrene (BaP)-DNA adducts were measured by an improved LC-MC/MC analytic method. Dietary nutrient intakes were estimated from food frequency questionnaire using the Chinese Standard Tables of Food Consumption. Multivariable logistic regression model was used to examine the associations.

RESULTS

Increased risk of PB was observed as per interquartile increase in maternal BaP-DNA adduct level (OR = 1.27, 95%CI 0.95-1.67). Compared to low level (below mean) of maternal adducts, high level (above mean) of adducts was associated with the risk of PB (OR = 2.05, 95%CI 1.05-4.01). After stratified by dietary nutrients intakes, high adducts levels were associated with approximately 2-fourfold times increases in risk of PB among women with low vitamin A, C, E, folate, and carotene intakes during pre- and/or post-conception. Stronger stratified associations were consistently seen during preconception. Similar patterns were observed after additional adjustment for supplementation.

CONCLUSIONS

Our study supports the hypothesis that high level of maternal PAHs exposure was significantly associated with increased risk of PB, and provides the first evidence that dietary vitamins, carotene, and folate intake levels may modify this association during different pregnancy windows. Our findings are relevant to identify recommendation for environment management and prenatal nutrition regarding pregnant women and newborns. Further investigation in other populations is warranted.

Prenatal exposure to polycyclic aromatic hydrocarbons and effects on neonatal anthropometric indices and thyroid-stimulating hormone in a Middle Eastern population

Prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) evokes extensive concerns regarding public health. Monitoring the pregnant women's exposure can be considered a suitable alternative to assess the fetus's exposure. This study aimed to monitor pregnant women's exposure (n = 126) to PAHs using a biomonitoring approach to evaluate effects on anthropometric indices and neonatal thyroid-stimulating hormone (TSH) in Shiraz, Iran. PAHs priority compounds were measured by gas chromatography-mass spectrometry (GC-MS) after separating blood serum and liquid-liquid extraction (LLE) method. Information on anthropometric indices, neonatal TSH levels, and data from the respondents was obtained from medical records and questionnaires. The mean PAHs concentrations ranged from 0.29 to 327.91 ng/g lipid. There was no significant difference between the measured PAHs in maternal serum at the seventh month and pregnancy termination except for ACY (p-Value<0.05). Regression analysis results showed a significant correlation (p-value<0.05) between exposure to passive smoke and total PAHs concentrations. There was no significant relationship between exposure to PAHs and weight, height, head circumference, and Apgar score of newborns. The results showed TSH decreased by 0.99 units as ACE increased per unit (β = -0.001). This study is the first to evaluate relationships between prenatal exposure to PAHs and effects on newborn health indicators, including TSH levels in a Middle Eastern population. Future studies are suggested to perform detailed assessments of PAHs intake sources, especially in vulnerable populations such as pregnant women and children.

Prenatal polycyclic aromatic hydrocarbon (PAH) exposure in relation to placental corticotropin releasing hormone (pCRH) in the CANDLE pregnancy cohort

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous endocrine-disrupting combustion by-products that have been linked to preterm birth. One possible mechanism is through disruption of placental corticotropin releasing hormone (pCRH), a key hormone implicated in parturition. As an extension of recent research identifying pCRH as a potential target of endocrine disruption, we examined maternal PAH exposure in relation to pCRH in a large, diverse sample. Participants, drawn from the CANDLE cohort, part of the ECHO-PATHWAYS Consortium, completed study visits at 16-29 weeks (V1) and 22-39 weeks (V2) gestation (n=812). Seven urinary mono-hydroxylated PAH metabolites (OH-PAHs) were measured at V1 and serum pCRH at V1 and V2. Associations between individual log-transformed OH-PAHs (as well as two summed PAH measures) and log(pCRH) concentrations across visits were estimated using mixed effects models. Minimally-adjusted models included gestational age and urinary specific gravity, while fully-adjusted models also included sociodemographic characteristics. We additionally evaluated effect modification by pregnancy complications, fetal sex, and maternal childhood trauma history. We observed associations between 2-OH-Phenanthrene (2-OH-PHEN) and rate of pCRH change that persisted in fully adjusted models (β=0.0009, 0.00006, 0.0017), however, positive associations with other metabolites (most notably 3-OH-Phenanthrene and 1-Hydroxypyrene) were attenuated after adjustment for sociodemographic characteristics. Associations tended to be stronger at V1 compared to V2 and we observed no evidence of effect modification by pregnancy complications, fetal sex, or maternal childhood trauma history. In conclusion, we observed modest evidence of association between OH-PAHs, most notably 2-OH-PHEN, and pCRH in this sample. Additional research using serial measures of PAH exposure is warranted, as is investigation of alternative mechanisms that may link PAHs and timing of birth, such as inflammatory, epigenetic, or oxidative stress pathways.

Mixture Analysis of Associations between Occupational Exposure to Polycyclic Aromatic Hydrocarbons and Sperm Oxidative DNA Damage

OBJECTIVE

This study aimed to determine (i) associations between levels of the polycyclic aromatic hydrocarbon (PAH) mixture with 16 targeted PAH compounds in the personal breathing zone area and sperm oxidative DNA damage, (ii) associations between levels of individual PAH compounds and sperm oxidative DNA damage, (iii) oxidative stress as the mode of action for the genotoxic effects on sperm, and (iv) any dose-response relationship between exposure to the PAH mixture and/or individual PAH compounds and sperm oxidative DNA damage.

METHODS

Sixteen targeted PAH compounds in the personal breathing zone area of 38 coke-oven workers and 24 control subjects were quantified using gas chromatography-mass spectrometry. Sperm oxidative damage and status were evaluated by measuring levels of sperm 7,8-dihydro-8-oxoguanie (8-oxodGuo), seminal malondialdehyde (MDA) and seminal reactive oxygen species (ROS). Bayesian kernel machine regression with hierarchical variable selection process was employed to determine associations of the PAH mixture and the biomarkers of sperm oxidative damage. A novel grouping approach needed for the hierarchical variable selection process was developed based on PAH bay region and molecular weight.

RESULTS

The PAH mixture exhibited a positive trend with increased sperm 8-oxodGuo levels at their lower percentiles (25th-50th). The exposure of the PAH mixture was associated with increased MDA levels in sperm. Bay and bay-like regions of the PAH mixture were the most important group for estimating the associations between the PAH mixture and sperm oxidative stress status. Benzo[a]anthracene was the main individual PAH compound that was associated with increased MDA levels.

CONCLUSION

Sperm oxidative DNA damage induced by occupational exposure to the PAH mixture had a suggestive association with increased MDA levels in coke-oven workers. Finally, the study identified that the individual PAH compound, benzo[a]anthracene, was the primary driver for the suggestive association between the PAH mixture and sperm oxidative damage.

Placental weight mediates association between prenatal exposure to cooking oil fumes and preterm birth

Background: There are some reports on association between maternal prenatal cooking oil fume (COF) exposure and preterm birth (PTB), but its mechanism remains poorly understood. Therefore, this study aims to assess whether placental weight mediates their associations.Method: We enrolled 619 pregnant women delivering PTB newborns as cases and 1701 delivering full-term appropriate for gestational age newborns as controls. They were inquired with a self-reported questionnaire about prenatal COF exposure, socio-demographics and obstetric characteristics at Women and Children's Hospitals of Shenzhen and Foshan. After controlling for the potential confounders, a series of logistic and linear regressions were conducted to assess associations among COF exposure, placental weight and PTB, and the mediation of placental weight in the association between COF exposure and PTB.Results: Maternal prenatal COF exposure was significantly associated with PTB and the frequency of prenatal COF exposure was negatively associated with placental weight. Compared with mother who never cooked, those cooking occasionally, sometimes or often increased the risk of PTB, and similarly, those cooking between half to an hour was also showed a higher risk of PTB. Typical Chinese cooking methods including stir-frying, pan-frying and deep-frying were also associated with PTB. Different oil types mainly used, including peanut oil, corn oil and animal oil were associated with PTB as well. Mediation analysis illustrated that placental weight partially mediated 13.60% (95% CI = 10.62-33.20%) of the effects on the association between the frequency of maternal prenatal COF exposure and PTB.Conclusion: Maternal cooking during pregnancy and the frequency of prenatal COF exposure might increase the risk of PTB, in which placenta might play mediation role.

A review of human and animals exposure to polycyclic aromatic hydrocarbons: Health risk and adverse effects, photo-induced toxicity and regulating effect of microplastics

Polycyclic aromatic hydrocarbons (PAHs) are one of the most widely distributed persistent organic pollutants (POPs) in the environmental media. PAHs have been widely concerned due to their significant health risk and adverse effects to human and animals. Currently, the main sources of PAHs in the environment are the incomplete combustion of fossil fuels, as well as municipal waste incineration and agricultural non-surface source emissions. In this work, the scope of our attention includes 16 typical PAHs themselves without involving their metabolites and industrial by-products. Exposure of human and animals to PAHs can lead to a variety of adverse effects, including carcinogenicity and teratogenicity, genotoxicity, reproductive- and endocrine-disrupting effects, immunotoxicity and neurotoxicity, the type and severity of which depend on a variety of factors. On the other hand, the regulatory effect of microplastics (MPs) on the bio-toxicity and bioaccumulation capacity of PAHs has now gradually attracted attention. We critically reviewed the adsorption capacity and mechanisms of MPs on PAHs as well as the effects of MPs on PAHs toxicity, thus highlighting the importance of paying attention to the joint bio-toxicity caused by PAHs-MPs interactions. In addition, due to the extensive nature of the common exposure pathway of PAHs and ultraviolet ray, an accurate understanding of biological processes exposed to both PAHs and UV light is necessary to develop effective protective strategies. Finally, based on the above critical review, we highlighted the research gaps and pointed out the priority of further studies.

Praegnatio Perturbatio-Impact of Endocrine-Disrupting Chemicals

The burden of adverse pregnancy outcomes such as preterm birth and low birth weight is considerable across the world. Several risk factors for adverse pregnancy outcomes have been identified. One risk factor for adverse pregnancy outcomes receiving considerable attention in recent years is gestational exposure to endocrine-disrupting chemicals (EDCs). Humans are exposed to a multitude of environmental chemicals with known endocrine-disrupting properties, and evidence suggests exposure to these EDCs have the potential to disrupt the maternal-fetal environment culminating in adverse pregnancy and birth outcomes. This review addresses the impact of maternal and fetal exposure to environmental EDCs of natural and man-made chemicals in disrupting the maternal-fetal milieu in human leading to adverse pregnancy and birth outcomes-a risk factor for adult-onset noncommunicable diseases, the role lifestyle and environmental factors play in mitigating or amplifying the effects of EDCs, the underlying mechanisms and mediators involved, and the research directions on which to focus future investigations to help alleviate the adverse effects of EDC exposure.

Impact of gestational exposure to endocrine disrupting chemicals on pregnancy and birth outcomes

With the advent of industrialization, humans are exposed to a wide range of environmental chemicals, many with endocrine disrupting potential. As successful maintenance of pregnancy and fetal development are under tight hormonal control, the gestational exposure to environmental endocrine disrupting chemicals (EDC) have the potential to adversely affect the maternal milieu and support to the fetus, fetal developmental trajectory and birth outcomes. This chapter summarizes the impact of exposure to EDCs both individually and as mixtures during pregnancy, the immediate and long-term consequences of such exposures on the mother and fetus, the direct and indirect mechanisms through which they elicit their effects, factors that modify their action, and the research directions to focus future investigations.

Polycyclic aromatic hydrocarbon exposure results in altered CRH, reproductive, and thyroid hormone concentrations during human pregnancy

Polycyclic aromatic hydrocarbons (PAHs) are byproducts of incomplete combustion reactions and are ubiquitous in the environment, leading to widespread human exposure via inhalation and ingestion pathways. PAHs have been implicated as endocrine disrupting compounds in previous animal and in vitro studies, but human studies are currently lacking. Pregnant women and their developing fetuses are particularly susceptible populations to environmental contaminants, in part because alterations in hormone physiology during gestation can have adverse consequences on the health of the pregnancy. We utilized data on 659 pregnant women from the PROTECT longitudinal birth cohort in Puerto Rico to assess associations between repeated measures of 8 urinary hydroxylated PAH (OH-PAH) metabolites and 9 serum hormones during gestation. Urine samples were collected at 3 study visits (median gestational ages of 18, 22, and 26 weeks at each visit, respectively) and serum samples were collected at the first and third study visits. Linear mixed effects models were used to ascertain longitudinal associations between OH-PAHs and hormones, and sensitivity analyses were employed to assess potential nonlinearity and differences in associations on the basis of fetal sex and timing of biomarker measurement. Among the multiple positive associations we observed between OH-PAHs and CRH, estriol, progesterone, T3, and the ratio of T3 to T4, and inverse associations with testosterone, the most notable are a 24.3% increase (95% CI: 13.0, 36.7) in CRH with an interquartile range (IQR) increase in 1-hydroxyphenanthrene and a 17.2% decrease (95% CI: 8.13, 25.4) in testosterone with an IQR increase in 1-hydroxynapthalene. Many associations observed were dependent on fetal sex, and some relationships showed evidence of nonlinearity. These findings demonstrate the importance of studying PAH exposures during pregnancy and highlight the potential complexity of their impacts on the physiology of human pregnancy.

Benchmark dose estimation for coke oven emissions based on oxidative damage in Chinese exposed workers

Coke oven emissions (COEs) can cause oxidative stress of the body, which in turn induces the occupational lung disease and also increases the risk of other diseases. COEs are the major occupational hazard factors for coke oven workers. The aim of the study is to explore the influences of COEs exposure on oxidative damage and estimate the benchmark dose (BMD) of COEs. A group of 542 workers exposed to COEs and 237 healthy controls from the same city were recruited in this study. The corresponding measuring kits were used to determine the plasma biomarkers of oxidative damage level. Generalized linear models and trend tests were used to analyze the relationship between COEs exposure and biomarkers. EPA Benchmark Dose Software was performed to calculate BMD and the lower confidence limit of the benchmark dose (BMDL) of COEs exposure. A significant association was observed between COEs exposure and oxidative damage with T-AOC as a biomarker. The BMD of COEs exposure were 2.83 mg/m³ and 1.39 mg/m³ for males and females, respectively, and the corresponding BMDL were 1.47 mg/m³ and 0.75 mg/m³, respectively. Our results suggested that the exposure level of COEs below the current national occupational exposure limits (OELs) would induce oxidative damage, and the OEL of COEs based on the T-AOC damage was suggested at 0.03 mg/m³ in this study.

Placental levels of polycyclic aromatic hydrocarbons (PAHs) and their association with birth weight of infants

As an alarming group of pollutants, polycyclic aromatic hydrocarbons (PAHs) gather much public health concern not only because of their carcinogenic or co-carcinogenic risk but also by interfering with hormone systems or by causing oxidative damage, henceforth liable to toxic actions on reproduction. Accordingly, the present study was aimed to explore the association between in-utero exposure to PAHs by evaluating their placental levels and infant birth weight among 110 healthy and nonsmoking pregnant women. Placental tissue samples were collected instantly after delivery and were analyzed for the presence of sixteen Environmental Protection Agency (EPA) listed PAHs with the help of Gas chromatography equipped with flame ionization detector (GC-FID). Chrysene and benzo(k)fluoranthene were the predominant PAHs detected in tissue samples. To assess the source of origin of PAHs in placenta tissue samples, the ratio of low molecular weight PAHs to high molecular weight (∑LMW/∑HMW PAHs) was calculated, showing the predominance of pyrogenic sources of PAHs possibly responsible for the exposure of the studied population. Results of regression analysis demonstrated the inverse although not significant association of naphthalene (Nap), acenaphthylene (Acy), anthracene (Anth), pyrene (Pyr), benzo(b)fluoranthene (BbF), benzo(k)Fluoranthene (BkF), benzo(a)pyrene (BaP), indeno (123 cd pyrene (IcdP), dibenzo(ah)anthracene (DahA) and benzo(ghi)Perylene (BghiP) with birth weight of neonates. Additionally, the regression model lay light upon the significant association of fluoranthene (Fla) (coefficient= -1.41 gram, p < 0.05) to the depletion trend of birth weight after adjusting for potential covariates. These findings suggest the possible role of an environmental contaminants like PAHs on impairment of fetal growth.

Predicting risk of low birth weight offspring from maternal features and blood polycyclic aromatic hydrocarbon concentration

Prenatal exposure to organic pollutants increases the risk of low birth weight (LBW) offspring. Women involved in the plucking of tea leaves can be exposed to polycyclic aromatic hydrocarbons (PAHs) during pregnancy through inhalation and diet. Therefore, the aim of the study was to investigate the association of maternal socio-demographic features and blood PAH concentration with LBW; also to develop a model for predicting LBW risk. The study was performed by recruiting 55 women who delivered LBW and 120 women with NBW (normal birth weight) babies from Assam Medical College. The placental tissue, maternal and cord blood samples were collected. A total of sixteen PAHs and cotinine were analysed by HPLC and GC-MS. Association of PAH concentration with weight was determined using correlation and multiple logistic regression analyses. Predictive model was developed using SVM^light and Weka software. Maternal features such as age, education, food habits, occupation, etc. were found to be associated with LBW deliveries (p-value<0.05). Overall, 9 PAHs and cotinine were detected in the samples. A multiple logistic regression depicted an increased likelihood of LBW by exposure to PAHs (pyrene, di-benzo (a,h) anthracene, fluorene and fluoranthene) and cotinine. Models based on the features and PAHs/ cotinine predicted LBW offspring with 84.35% sensitivity and 74% specificity. LBW prediction models are available at http://dev.icmr.org.in/plbw/ webserver. With machine learning gaining more importance in medical science; our webserver could be instrumental for researchers and clinicians to predict the state of the fetus.

Organochlorine pesticides residue in placenta and their influence on anthropometric measures of infants

The objective of this study is to evaluate the influence of placental concentrations of some organochlorine pesticides on newborn's anthropometric measurements (height, weight, head circumference & ponderal index). For this study, we have collected 90 placental tissue samples for the measurement of Dichlorodiphenyltrichloroethane (DDT) & Hexachlocyclohexane (HCH) by Gas Chromatography equipped with Electron Capture Detector (GC-ECD). Regression analysis were performed between outcome variables such as birth weight, birth height, head circumference, ponderal index and independent variable i.e., organochlorine pesticide concentrations. In case of birth weight, there was a substantial decrease of 5.81, 1.94, 4.71, and 2.64 g for 1 ppb (μg/L) increase in placental α-HCH, β-HCH, γ-HCH, and total HCH concentrations respectively. Significant decrease of 2.02 and 0.43 kg/m³ in ponderal index was found with 1 μg/L increase of total-HCH and total DDT concentrations in placenta. The results of this study support an association between environmental exposure to organochlorine pesticides and anthropometric development of the fetus leading to a significant reduction in its birth weight and ponderal index, slight and non-significant reduction in birth height and head circumference. Efforts should be made to reduce exposure of women of reproductive age in relation to long-term impact on health.

Oxidative stress - Related spontaneous preterm delivery challenges in causality determination, prevention and novel strategies in reduction of the sequelae

Spontaneous preterm birth (PTB) is one of the major complications of pregnancy and the main cause of neonatal mortality and morbidity. Despite the efforts devoted to the understanding of this obstetrical syndrome and improved medical care, there has been a tendency for the PTB rate to increase in the last decades globally. The costs of the screening for spontaneous PTB, its management, and treatment of the sequelae represent a major burden to the health service economy of high-income countries. In this scenario, it has been widely acknowledged that oxidative stress (OS) plays an important role in the pathogenicity of human disease in wide range of areas of medicine. There is an emerging evidence that an imbalance between pro-and-antioxidants may be associated with spontaneous PTB. However, there are still many controversies on the mechanisms by which OS are involved in the pathogenesis of prematurity. Moreover, the crucial question whether the OS is the cause or consequence of the disease is yet to be answered. The purpose of this article is to briefly summarize the current knowledge and controversies on oxidative stress-related spontaneous PTB and to give a critical approach on future perspectives on this topic as a classical example of translational medicine. Placenta-mediated pregnancy adverse outcome associated with OS leading to iatrogenic PTB (e.g. pre-eclampsia, intrauterine growth restriction, gestational diabetes) will not be discussed.

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.

Associations of urinary polycyclic aromatic hydrocarbons with age at natural menopause in U.S. women aged 35-65, NHANES 2003-2012

Polycyclic aromatic hydrocarbons (PAHs) mediated ovarian toxicity has been demonstrated in animal experiments. However, this issue has not been assessed in humans. Based on the National Health and Nutrition Examination Survey (NHANES) 2003-2012, data analysis was restricted to 1221 general U.S. women aged 35-65 years with complete data of interest. Levels of nine PAH metabolites in spot urine specimens were measured by isotope dilution gas chromatography/tandem mass spectrometry (GC-MS/MS). Self-reported information on the menopause status and age at menopause were obtained during interview. Cox proportional hazards regression was employed to assess the associations between PAH levels and natural menopause. Compared with women in the first quartile, subjects in the highest quartile of 1-Hydroxynapthalene [hazard ratio (HR) = 1.46, 95% confidence interval (CI) = 1.06 to 2.01], 2-Hydroxynapthalene (HR = 1.51, 95% CI = 1.12 to 2.05) and 3-Hydroxyfluorene (HR = 1.51, 95% CI = 1.06 to 2.16), or in the second quartile of 9-Hydroxyfluorene (HR = 1.53, 95% CI = 1.05 to 2.22), had elevated risks of earlier onset of natural menopause. Our findings suggested positive associations between urinary PAH levels and earlier age at natural menopause in the general U.S. women. Prospective studies are warranted to confirm the causality in the future.