Arsenic exposure and measures of glucose tolerance in Bangladeshi adults: A cross-sectional study.

Background: Arsenic has been associated with diabetes and impaired glucose tolerance in many studies, although some reports have shown null findings. Methods: We conducted a cross-sectional study among 300 adults in Bangladesh. Participants were randomly selected from a roster of 1800 people who previously participated in studies of arsenic and skin lesions. We measured fasting glucose and insulin levels. We assessed drinking water arsenic concentration using graphite furnace atomic absorption spectrophotometry (GF-AAS) and toenail arsenic concentration using inductively coupled mass spectrometry (ICP-MS). We ran covariant-adjusted, linear regression and spline models to examine associations of arsenic concentrations with the homeostatic model assessment of insulin resistance (HOMA-IR), a marker of insulin resistance, and HOMA of beta-cell function (HOMA-ß), a marker of beta-cell function. Results: Among 285 participants with complete data, the median (IQR) arsenic concentration was 4.0 (6.9) µg/g in toenails and 39.0 (188.5) µg/L in drinking water. Arsenic concentrations were not associated with insulin resistance or beta-cell function. HOMA-IR was 0.67% lower and HOMA-ß was 0.28% lower per µg/g increment in toenail arsenic, but these effect estimates were small, and confidence intervals crossed the null value. Conclusions: Although arsenic exposure has been associated with diabetes, we found no evidence of an adverse effect on insulin resistance or beta-cell function.

Testing the Limit: Evaluating Drinking Water Arsenic Regulatory Levels Based on Adverse Pregnancy Outcomes in Bangladesh.

(1) Background: Arsenic (As) is a common drinking water contaminant that is regulated as a carcinogen. Yet, As is a systemic toxicant and there is considerable epidemiological data showing As adversely impacts reproductive health. This study used data from a birth cohort in Bangladesh (2008−2011) to examine associations between drinking water As levels and reproductive outcomes. (2) Methods: Pregnant individuals (n = 1597) were enrolled at <16 weeks gestation and drinking water As was measured. Participants with live births (n = 1130) were propensity score matched to participants who experienced miscarriage (n = 132), stillbirth (n = 72), preterm birth (n = 243), and neonatal mortality (n = 20). Logistic regression was used to examine drinking water As recommendations of 50, 10, 5, 2.5, and 1 µg/L on the odds of adverse birth outcomes. (3) Results: The odds of miscarriage were higher for pregnant women exposed to drinking water ≥2.5 versus <2.5 µg As/L [adjusted odds ratio (OR) 1.90, 95% Confidence Interval (CI): 1.07−3.38)]. (4) Conclusions: These preliminary findings suggest a potential threshold where the odds of miscarriage increases when drinking water As is above 2.5 µg/L. This concentration is below the World Health Organizations and Bangladesh's drinking water recommendations and supports the re-evaluation of drinking water regulations.

A prospective study of arsenic and manganese exposures and maternal blood pressure during gestation.

BACKGROUND: Pregnancy is a sensitive time for maternal cardiovascular functioning and exposures to arsenic or manganese may adversely affect blood pressure (BP). OBJECTIVES: This study examined the associations between arsenic and manganese exposures and maternal BP measured during pregnancy. Effect modification by pre-pregnancy body mass index (BMI) was evaluated. METHODS: Pregnant women (N = 1522) were recruited for a prospective cohort study in Bangladesh (2008-2011). Exposure to arsenic and manganese was measured in drinking water at <16 weeks gestation and toenails at one-month postpartum. Systolic and diastolic BP were measured monthly. Linear mixed models estimated mean BP and differences in mean BP over gestation for arsenic or manganese exposures and adjusted for covariates. RESULTS: Arsenic levels had an increasing dose-response association with maternal BP after 25 weeks gestation. Effect modification was observed for BMI. Participants with lower BMI (<23 kg/m2) exposed to 50 µg/L arsenic had 2.83 mmHg (95% CI:1.74-3.92) greater mean systolic and 1.96 mmHg (95% CI: 1.02-2.91 mmHg) diastolic BP compared to those exposed to ≤ 1 µg/L arsenic at 40 weeks gestation. Participants with higher BMI (≥23 kg/m2) showed a greater mean systolic BP of 5.72 mmHg (95% CI: 3.18-8.27 mmHg) and diastolic BP change of 6.09 mmHg (95% CI: 4.02-8.16 mmHg) at 40 weeks gestation when exposed to 50 µg/L compared to ≤ 1 µg/L arsenic. Participants with lower BMI exposed to drinking water manganese in the 2nd quartile (181-573 µg/L) had 1.04 mmHg higher mean diastolic BP (95% CI: 0.01-2.07 mmHg) at 40 weeks gestation compared to those in the 1st quartile (0.5-180 µg/L). CONCLUSION: Arsenic exposures during pregnancy were consistently associated with increased average maternal systolic and diastolic BP. The effect of manganese on BP was less consistent.

Household use of crop residues and fuelwood for cooking and newborn birth size in rural Bangladesh.

OBJECTIVES: We aimed to investigate the association between type of cooking biomass fuels (crop residues vs fuelwood) and newborn birth outcomes in Bangladeshi children. METHODS: In this birth cohort study, pregnant women who were 18 years or older with ultrasound confirmed singleton pregnancy of ≤16 weeks of gestation were enrolled from two Bangladesh clinics between January 2008 and June 2011. Exposure to cooking biomass fuels during pregnancy was assessed by an administered questionnaire. The newborn size metrics were measured at the time of delivery. We used multiple linear regression and logistic regression to assess the associations between the type of cooking biomass fuels and birth outcomes after adjusting for covariates. RESULTS: A total of 1137 participants were using biomass fuels, including crop residues (30.3%) and fuelwood (69.7%), respectively, for cooking. After adjusting for covariates, the use of crop residues for cooking was associated with a 0.13 SD decrease in birth length (95% CI 0.25 to -0.01), a 0.14 SD decrease in head circumference (95% CI -0.27 to -0.02), and increased risk of low birth weight (LBW, OR 1.52, 95% CI 1.07 to 2.15) compared with the use of fuelwood. CONCLUSION: The use of crop residues for cooking was associated with reduced birth size and increased risk for LBW in Bangladeshi children, implying that the use of crop residues during pregnancy may have a detrimental effect on fetal growth.

Umbilical Cord Blood Metal Mixtures and Birth Size in Bangladeshi Children.

BACKGROUND: Studies have evaluated environmental exposure to toxic metals such as arsenic (As), cadmium (Cd), manganese (Mn), or lead (Pb) on birth size; however, information on potential effects of exposures to metal mixtures is limited. OBJECTIVES: We assessed the association between metal mixtures (As, Cd, Mn, Pb) in umbilical cord blood and neonate size in Bangladeshi children. METHODS: In this birth cohort study, pregnant women who were ≥18 years of age with an ultrasound-confirmed singleton pregnancy of ≤16wk gestation were recruited from two Bangladesh clinics between 2008 and 2011. Neonate size metrics were measured at the time of delivery. Metals in cord blood were measured using inductively coupled plasma mass spectrometry. We employed multivariable linear regression and Bayesian kernel machine regression (BKMR) to estimate associations of individual metals and metal mixtures with birth size parameters. RESULTS: Data from 1,088 participants was assessed. We found a significant negative association between metal mixture and birth length and head circumference when all metal concentrations were above the 60th and 55th percentiles, respectively, compared with the median. An interquartile range (IQR) increase in log Cd concentration {log[Cd (in micrograms per deciliter)] IQR=2.51} was associated with a 0.13-standard deviation (SD) decrease in mean birth length (95% CI: -0.25, -0.02) and a 0.17-SD decrease in mean head circumference (95% CI: -0.28, -0.05), based on linear regression models adjusted for covariates and the other metals. An IQR increase in log Mn concentration {log[Mn (in micrograms per deciliter)] IQR=0.69} was associated with a 0.07-SD decrease in mean birth weight (95% CI: -0.15, 0.002). DISCUSSION: Metal mixtures in cord blood were associated with reduced birth size in Bangladeshi children. Results from linear regression models adjusted and the BKMR mixtures analyses suggest adverse effects of Cd and Mn, as individual metal exposures, on birth size outcomes. https://doi.org/10.1289/EHP7502.

Stunting and lead: using causal mediation analysis to better understand how environmental lead exposure affects cognitive outcomes in children.

BACKGROUND: Many children in Bangladesh experience poor nutritional status and environmental lead exposure, both of which are associated with lower scores on neurodevelopmental assessments. Recent studies have suggested that part of lead's adverse effects on neurodevelopment are caused in part by lead's effect on growth. New statistical methods are now available to evaluate potential causal pathways in observational studies. This study used a novel statistical method to test the hypothesis that stunting, a measure of linear growth related to poor nutrition, is a mediator and/or an effect modifier of the lead exposure's adverse effect on cognitive development. METHODS: Participants were 734 children from a longitudinal birth cohort established in rural Bangladesh to study the health effects of prenatal and early childhood environmental metal exposures. Lead exposure was estimated using umbilical cord blood samples obtained at birth and blood obtained via venipuncture at age 20-40 months. Stunting was determined using the World Health Organization's standards. Neurodevelopment was assessed at age 20-40 months years using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). We evaluated the effect of lead on stunting and whether the effect of lead on cognitive scores is modified by stunting status in multivariable regression analyses. We then conducted a novel 4-way mediation analysis that allows for exposure-mediator interaction to assess how much of the effect of lead on cognitive scores is explained by the pathway through stunting (mediation) and how much is explained by the interaction between lead and stunt (effect modification). RESULTS: Stunting was not a mediator of the effect of lead in our analyses. Results suggested effect modification by stunting. In an area of Bangladesh with lower lead exposures (median umbilical cord blood lead concentration, 1.7 µg/dL), stunting modified the relationship between prenatal blood lead concentrations and cognitive score at age 2-3 years. A 1-unit increase in natural log cord blood lead concentration in the presence of stunting was associated with a 2.1-unit decrease in cognitive scores (ß = - 2.10, SE = 0.71, P = 0.003). This interaction was not found in a second study site where lead exposures were higher (median umbilical cord blood lead concentration, 6.1 µg/dL, ß = - 0.45, SE = 0.49, P = 0.360). CONCLUSIONS: We used a novel method of mediation analysis to test whether stunting mediated the adverse effect of prenatal lead exposure on cognitive outcomes in Bangladesh. While we did not find that stunting acted as mediator of lead's effect on cognitive development, we found significant effect modification by stunting. Our results suggest that children with stunting are more vulnerable to the adverse effects of low-level lead exposure.

A prospective cohort study of in utero and early childhood arsenic exposure and infectious disease in 4- to 5-year-old Bangladeshi children.

BACKGROUND: Previous research found that infants who were exposed to high levels of arsenic in utero had an increased risk of infectious disease in the first year of life. This prospective study examined the association between arsenic exposures during gestation, and respiratory, diarrheal, and febrile morbidity in children 4-5 years of age. METHODS: A cohort of pregnant women was recruited in 2008-2011 in Bangladesh. Their children (N = 989) were followed, and household drinking water samples were collected during pregnancy, toddlerhood (12-40 months of age), and childhood (4-5 years of age). We actively surveyed mothers every 2 weeks regarding their children's infectious diseases symptoms from 4 to 5 years of age. Poisson regression models were used to estimate the association between arsenic exposure and respiratory and febrile illness. RESULTS: Median drinking water arsenic was 4.6, 8.8, and 4.2 µg/L in pregnancy, toddlerhood, and childhood, respectively. We observed 0.01, 1.2, and 1.0 cases per 100 person-days of diarrhea, respiratory, and febrile illness, respectively. The incident rate ratios (IRRs) for each doubling of drinking water arsenic during pregnancy were 1.10 (95% confidence interval [CI] = 1.00, 1.22) and 0.93 (95% CI = 0.82, 1.05) for respiratory and febrile illness, respectively, after adjusting for covariates. The association between arsenic exposure measured during toddlerhood and childhood was attenuated and not significantly associated with either outcome. Diarrheal disease was too infrequent to assess. CONCLUSIONS: Drinking water arsenic exposure during pregnancy was associated with a higher risk of acute respiratory infections in children 4-5 years old in Bangladesh.

Evaluating the effects between metal mixtures and serum vaccine antibody concentrations in children: a prospective birth cohort study.

BACKGROUND: Many populations are exposed to arsenic, lead, and manganese. These metals influence immune function. We evaluated the association between exposure to single and multiple metals, including arsenic, lead, and manganese, to humoral immunity as measured by antibody concentrations to diphtheria and tetanus toxoid among vaccinated Bangladeshi children. Additionally, we examined if this association was potentially mediated by nutritional status. METHODS: Antibody concentrations to diphtheria and tetanus were measured in children's serum at age 5 (n = 502). Household drinking water was sampled to quantify arsenic (W-As) and manganese (W-Mn), whereas lead was measured in blood (B-Pb). Exposure samples were taken during pregnancy, toddlerhood, and early childhood. Multiple linear regression models (MLRs) with single or combined metal predictors were used to determine the association with antibody outcomes. MLR results were transformed to units of percent change in outcome per doubling of exposure to improve interpretability. Structural equation models (SEMs) were used to further assess exposure to metal mixtures. SEMs regressed a latent exposure variable (Metals), informed by all measured metal variables (W-As, W-Mn, and B-Pb), on a latent outcome variable (Antibody), informed by measured antibody variables (diphtheria and tetanus). Weight-for-age z-score (WFA) at age 5 was evaluated as a mediator. RESULTS: Diphtheria antibody was negatively associated with W-As during pregnancy in MLR, but associations were attenuated after adjusting for W-Mn and B-Pb (- 2.9% change in diphtheria antibody per doubling in W-As, 95% confidence interval [CI]: - 7%, 1.5%). Conversely, pregnancy levels of B-Pb were positively associated with tetanus antibody, even after adjusting for W-As and W-Mn (13.3%, 95% CI: 1.7%, 26.3%). Overall, null associations were observed between W-Mn and antibody outcomes. Analysis by SEMs showed that the latent Metals mixture was significantly associated with the latent Antibody outcome (ß = - 0.16, 95% CI: - 0.26, - 0.05), but the Metals variable was characterized by positive and negative loadings of W-As and B-Pb, respectively. Sex-stratified MLR and SEM analyses showed W-As and B-Pb associations were exclusive to females. Mediation by WFA was null, indicating Metals only had direct effects on Antibody. CONCLUSIONS: We observed significant modulation of vaccine antibody concentrations among children with pregnancy and early life exposures to drinking water arsenic and blood lead. We found distinct differences by child sex, as only females were susceptible to metal-related modulations in antibody levels. Weight-for-age, a nutritional status proxy, did not mediate the association between the metal mixture and vaccine antibody.

Cord blood DNA methylation of DNMT3A mediates the association between in utero arsenic exposure and birth outcomes: Results from a prospective birth cohort in Bangladesh.

BACKGROUND: Fetal epigenetic programming plays a critical role in development. DNA methyltransferase 3 alpha (DNMT3A), which is involved in de novo DNA methylation (DNAm), is a prime candidate gene as a mediator between prenatal exposures and birth outcomes. We evaluated the relationships between in utero arsenic (As) exposure, birth outcomes, and DNMT3A DNAm. METHODS: In a prospective Bangladeshi birth cohort, cord blood DNAm of three DNMT3A CpGs was measured using bisulfite pyrosequencing. Maternal toenail As concentrations at birth were measured to estimate in utero exposure. Among vaginal births (N = 413), structural equation models (SEMs) were used to evaluate relationships between DNMT3A methylation, log2 (toenail As), birth weight, and gestational age. RESULTS: In an adjusted SEM including birth weight and gestational age, maternal toenail As levels were associated with DNMT3A DNAm (B = 0.40; 95% CI: 0.15, 0.66) and gestational age (B = -0.19 weeks; 95% CI: 0.36, -0.03). DNMT3A DNAm was associated with gestational age (B = -0.10 weeks; 95% CI: 0.16, -0.04) and birth weight (B = -11.0 g; 95% CI: 21.5, 0.4). There was an indirect effect of As on gestational age mediated through DNMT3A DNAm (B = -0.04; 95% CI: 0.08, -0.01), and there were indirect effects of maternal toenail As levels on birth weight through pathways including gestational age (B = -14.4 g; 95% CI: 29.2, -1.9), DNMT3A DNAm and gestational age (B = -3.1 g; 95% CI: 6.6, -0.8), and maternal weight gain and gestational age (B = -5.1 g; 95% CI: 9.6, -1.5). The total effect of a doubling in maternal toenail As concentration is a decrease in gestational age of 2.1 days (95% CI: 0.9, 3.3) and a decrease in birth weight of 29 g (95% CI: 14, 46). CONCLUSIONS: DNMT3A plays a critical role in fetal epigenetic programming. In utero arsenic exposure was associated with greater methylation of CpGs in DNMT3A which partially mediated associations between prenatal As exposure and birth outcomes. Additional studies are needed to verify this finding.

Determinants of arsenic methylation efficiency and urinary arsenic level in pregnant women in Bangladesh.

BACKGROUND: Prenatal inorganic arsenic (iAs) exposure is associated with pregnancy outcomes. Maternal capabilities of arsenic biotransformation and elimination may influence the susceptibility of arsenic toxicity. Therefore, we examined the determinants of arsenic metabolism of pregnant women in Bangladesh who are exposed to high levels of arsenic. METHODS: In a prospective birth cohort, we followed 1613 pregnant women in Bangladesh and collected urine samples at two prenatal visits: one at 4-16 weeks, and the second at 21-37 weeks of pregnancy. We measured major arsenic species in urine, including iAs (iAs%) and methylated forms. The proportions of each species over the sum of all arsenic species were used as biomarkers of arsenic methylation efficiency. We examined the difference in arsenic methylation using a paired t-test between first and second visits. Using linear regression, we examined determinants of arsenic metabolism, including age, BMI at enrollment, education, financial provider income, arsenic exposure level, and dietary folate and protein intake, adjusted for daily energy intake. RESULTS: Comparing visit 2 to visit 1, iAs% decreased 1.1% (p <  0.01), and creatinine-adjusted urinary arsenic level (U-As) increased 21% (95% CI: 15, 26%; p <  0.01). Drinking water arsenic concentration was positively associated with iAs% at both visits. When restricted to participants with higher adjusted urinary arsenic levels (adjusted U-As > 50 µg/g-creatinine) gestational age at measurement was strongly associated with DMA% (ß = 0.38, p <  0.01) only at visit 1. Additionally, DMA% was negatively associated with daily protein intake (ß = - 0.02, p <  0.01) at visit 1, adjusting for total energy intake and other covariates. CONCLUSIONS: Our findings indicate that arsenic metabolism and adjusted U-As level increase during pregnancy. We have identified determinants of arsenic methylation efficiency at visit 1.

Association of prenatal pesticide exposures with adverse pregnancy outcomes and stunting in rural Bangladesh.

BACKGROUND: Pesticide exposure during pregnancy is thought to adversely affect fetal growth, which in turn may impact child growth, but results have been inconsistent across studies and few have explored these effects in developing countries. OBJECTIVES: To quantify urinary concentrations of pesticide biomarkers in early pregnancy (<16 weeks' gestation), and to estimate the association of these concentrations with preterm birth, low birth weight, small for gestational age, and stunting at ~1 and 2 years of age. METHODS: Eight pesticide biomarkers were quantified in urine collected from 289 pregnant women (aged 18-40 years) participating in a birth cohort study in Bangladesh. Anthropometry measurements were conducted on the index child at birth and approximately 1 and 2 years of age. A directed acyclic graph was used to identify minimal sufficient adjustment sets. Log-binomial regression was used to estimate the relative risk (RR) with 95% confidence intervals (CI). RESULTS: 3,5,6-trichloro-2-pyridinol (TCPY), a metabolite of chlorpyrifos and chlorpyrifos methyl, and 4-nitrophenol, a metabolite of parathion and methyl parathion, were detected in nearly all women with geometric mean (95% CI) values of 3.17 (2.82-3.56) and 18.66 (17.03-20.46) µg/g creatinine, respectively. 3-phenoxybenzoic acid (3-PBA), a non-specific metabolite of several pyrethroids, and 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMPY), a diazinon metabolite, were detected in 19.8% and 16.1% of women, respectively. The remaining four pesticide biomarkers were detected in <10% of women. Women in the highest quartile of 4-nitrophenol were more than 3 times more likely to deliver preterm than women in the lowest quartile: unadjusted RR (95% CI), 3.57 (1.65, 7.73). Women in the highest quartile of 4-nitrophenol were also at increased risk of having a child born small for gestational age: RR (95% CI) adjusted for household income, maternal education, and maternal total energy and meat intake, 3.81 (1.10, 13.21). Women with detectable concentrations of IMPY were at increased risk of having a child born with low birth weight compared to women with non-detectable concentrations: adjusted RR (95% CI), 2.13 (1.12, 4.08). We observed no association between any of the pesticide biomarkers and stunting at 1 or 2 years of age. DISCUSSION: Exposure to the insecticides parathion and diazinon during early pregnancy may increase the risk of adverse birth outcomes.

Exosomal MALAT1 derived from hepatic cells is involved in the activation of hepatic stellate cells via miRNA-26b in fibrosis induced by arsenite.

In the liver microenvironment, interactions among diverse types of hepatic cells are involved in liver fibrosis. In fibrotic tissues, exosomes act as transporters in intercellular communication. Long non-coding RNAs (lncRNAs) are involved in the activation of hepatic stellate cells (HSCs), which are participants in liver fibrosis. However, the functions of exosomal lncRNAs in liver fibrosis induced by arsenite are undefined. The purposes of the present study were (a) to determine if lncRNAs secreted from human hepatic (L-02) cells exposed to arsenite are shuttled to hepatic stellate LX-2 cells and (b) to establish their effects on LX-2 cells. In mice, MALAT1 was overexpressed in the progression of liver fibrosis induced by arsenite as well as in L-02 cells exposed to arsenite. Co-cultures with arsenite-treated L-02 cells induced the activation of LX-2 cells and overexpression of MALAT1. Arsenite-treated L-02 cells transported MALAT1 into LX-2 cells. Downregulation of MALAT1, which reduced the MALAT1 levels in exosomes derived from arsenite-treated L-02 cells, inhibited the activation of LX-2 cells. Additionally, exosomal MALAT1 derived from arsenite-treated L-02 cells promoted the activation of LX-2 cells via microRNA-26b regulation of COL1A2. Furthermore, circulating exosomal MALAT1 was up-regulated in people exposed to arsenite. In sum, exosomes derived from arsenite-treated hepatic cells transferred MALAT1 to HSCs, which induced their activation. These findings support the concept that, during liver fibrosis induced by arsenite, exosomal lncRNAs are involved in cell-cell communication.

Arsenic exposure and serum antibody concentrations to diphtheria and tetanus toxoid in children at age 5: A prospective birth cohort in Bangladesh.

BACKGROUND: Arsenic can impair immune function. Timing of exposure can influence potential immunotoxicity of arsenic exposure. We examined the association between drinking water arsenic concentrations (W-As) measured repeatedly during different exposure windows in early life and serum concentrations of IgG antibodies against diphtheria and tetanus toxoids (diphtheria and tetanus antibody). METHODS: A prospective cohort of pregnant women was recruited in Bangladesh (2008-2011). Averaged W-As levels were calculated for: pregnancy (W-Aspregnancy): ≤16 weeks gestation and <1 month; toddlerhood (W-Astoddlerhood): 12 and 20-40 months; and early childhood (W-Aschildhood): 4-5 years. Serum was collected from 502 vaccinated children at age 5 and concentrations of diphtheria and tetanus toxoid IgG (i.e. antibody) were quantified. Antibody concentrations >0.1 IU/mL were considered clinically sufficient for protection. Associations were estimated using linear and logistic regression models. RESULTS: Inverse associations were observed between W-Aspregnancy and serum diphtheria antibody levels, while null associations were observed between W-As and tetanus antibody. Children within the highest versus lowest tertile of W-Aspregnancy had 91% greater odds of having clinically insufficient concentrations of diphtheria antibody (Odds ratio:1.91, 95% confidence interval (CI): 1.03, 3.56). Among females, a doubling in W-Aspregnancy was associated with 12.3% (95%CI: -20.1%, -4.5%) lower median concentrations of diphtheria antibody. Tetanus antibody was only associated with W-Aspregnancy among females (percent change in median: -9.5%, 95%CI: -17.6%, -1.3%). Among children who were stunted or underweight, a doubling in W-Aspregnancy was associated with decreased diphtheria antibody of 19.8% (95%CI: -32%, -7.5%) and 14.3% (95%CI: -26.7%, -2%), respectively. CONCLUSIONS: Among vaccinated children, W-As measured during pregnancy was associated with decreased diphtheria antibody levels, but not tetanus antibody. However, W-As measured during toddlerhood and early childhood were not associated with either antibody outcome. Children's sex and malnutrition status were important effect modifiers of W-As for both diphtheria and tetanus antibody levels, highlighting the importance of these factors and the timing of the exposure when evaluating the effect of arsenic on humoral immunity.

A case-control analysis of maternal diet and risk of neural tube defects in Bangladesh.

OBJECTIVES: Mothers need a nutrient-rich diet for healthy neural tube development. Neural tube defect risk can be reduced through fortifying grain products with folic acid and taking folic acid supplements. Fortification is not required in Bangladesh. Maternal supplement use rates are low, similar to other countries. This study evaluates maternal dietary intake during pregnancy to identify possible interventions. METHODS: A food frequency questionnaire (FFQ) assessed maternal diet. The primary aim compared dietary intake (calories, fat, carbohydrate, protein, fiber, vitamins, and minerals) between mothers of infants with myelomeningocele (cases) and mothers of controls. Secondary aims included (i) comparing foods consumed and (ii) evaluating if rice intake correlated with arsenic exposure. Paired t-tests, Wilcoxon signed rank tests, McNemar's chi-squared test, and linear regression were used. RESULTS: This study included 110 matched mother-infant pairs (55 cases/55 controls). Mothers of cases and mothers of controls had similar caloric intake [median 2406 kcal/day vs. 2196 kcal/day (p = 0.071)]. Mothers in both groups consumed less than half the daily recommended 600 µg of folate. Diets were potentially deficient in vitamins A, D, E, potassium, sodium, and iron. Steamed rice was the primary food consumed for both groups, and this rice intake was not associated with toenail arsenic. CONCLUSIONS: Dietary interventions should increase folate, vitamins A, D, E, potassium, sodium, and iron intake in Bangladeshi mothers. Folic acid fortification of grain products maybe the only viable strategy to achieve adequate folate intake for mothers. Given the central role of rice to the Bangladeshi diet, fortifying rice may be a viable option.

Gene-environment interaction and maternal arsenic methylation efficiency during pregnancy.

BACKGROUND: Single nucleotide polymorphisms (SNPs) may influence arsenic methylation efficiency, affecting arsenic metabolism. Whether gene-environment interactions affect arsenic metabolism during pregnancy remains unclear, which may have implications for pregnancy outcomes. OBJECTIVE: We aimed to investigate main effects as well as potential SNP-arsenic interactions on arsenic methylation efficiency in pregnant women. METHOD: We recruited 1613 pregnant women in Bangladesh, and collected two urine samples from each participant, one at 4-16 weeks, and the second at 21-37 weeks of pregnancy. We determined the proportions of each arsenic metabolite [inorganic As (iAs)%, monomethylarsonic acid (MMA)%, and dimethylarsinic acid (DMA)%] from the total urinary arsenic level of each sample. A panel of 63 candidate SNPs was selected for genotyping based on their reported associations with arsenic metabolism (including in As3MT, N6AMT1, and GSTO2 genes). We used linear regression models to assess the association between each SNP and DMA% with an additive allelic assumption, as well as SNP-arsenic interaction on DMA%. These analyses were performed separately for two urine collection time-points to capture differences in susceptibility to arsenic toxicity. RESULT: Intron variants for As3MT were associated with DMA%. rs9527 (ß = -2.98%, PFDR = 0.008) and rs1046778 (ß = 1.64%, PFDR = 0.008) were associated with this measure in the early gestational period; rs3740393 (ß = 2.54%, PFDR = 0.002) and rs1046778 (ß = 1.97%, PFDR = 0.003) in the mid-to-late gestational period. Further, As3MT, GSTO2, and N6AMT1 polymorphisms showed different effect sizes on DMA% conditional on arsenic exposure levels. However, SNP-arsenic interactions were not statistically significant after adjusting for false discovery rate (FDR). rs1048546 in N6AMT1 had the highest significance level in the SNP-arsenic interaction test during mid-to-late gestation (ß = -1.8% vs. 1.4%, PGxE_FDR = 0.075). Finally, As3MT and As3MT/CNNM2 haplotypes were associated with DMA% at both time points. CONCLUSION: We found that not all genetic associations reported in arsenic methylation efficiency replicate in pregnant women. Arsenic exposure level has a limited effect in modifying the association between genetic variation and arsenic methylation efficiency.

Regulation of gasdermin D by miR-379-5p is involved in arsenite-induced activation of hepatic stellate cells and in fibrosis via secretion of IL-1ß from human hepatic cells.

Arsenic is an environmental toxicant and human carcinogen. The liver is the main site of arsenic storage and metabolism. Exposure to excessive arsenic causes liver damage and release of pro-inflammatory factors, which in turn lead to liver fibrosis. Gasdermin D (GSDMD), a mediator of pyroptosis, has low expression in hepatic tumor cells. In L-02 cells, arsenite caused increases of GSDMD and cleaved caspase-1 levels and decreases of caspase-1 and miR-379-5p levels. It also promoted the release of IL-1ß in a concentration- and time-dependent manner. Luciferase reporter assays showed that GSDMD was a direct target of miR-379-5p. In L-02 cells, the over-expression of miR-379-5p blocked the arsenite-induced increases of GSDMD levels and the release of IL-1ß, effects that were reversed by up-regulation of GSDMD. LX-2 cells, cultured in the media from arsenite-treated L-02 cells, showed elevated levels of proliferating cell nuclear antigen (PCNA), collagen I, vimentin, and α-smooth muscle actin (α-SMA), which indicated activation of these cells. Activation of LX-2 cells by media from arsenite-treated L-02 cells was inhibited by IL-1ß neutralizing antibody. The media from arsenite-treated L-02 cells transfected with an miR-379-5p mimic inhibited the activation of LX-2 cells, a process that was reversed by up-regulation of GSDMD and by co-treatment with human recombinant IL-1ß. Chronic exposure to arsenite induced, in liver tissue of mice, morphological damage, collagen deposition, and activation of hepatic stellate cells (HSCs). In liver tissue of arsenite-exposed mice, the levels of miR-379-5p were lower, but the levels of GSDMD and cleaved caspase-1 were elevated, and in sera from arsenite-exposed mice, the IL-1ß levels were elevated. These results indicate that, by elevating the secretion of IL-1ß, miR-379-5p regulation of GSDMD is involved in arsenite-induced activation of HSCs and in hepatic fibrosis. This establishes a previously unknown molecular mechanism for arsenite-induced liver damage, inflammation, and fibrosis.

A Prospective Cohort Study Examining the Associations of Maternal Arsenic Exposure With Fetal Loss and Neonatal Mortality.

Arsenic crosses the placenta, possibly increasing the risk of adverse reproductive outcomes. We aimed to examine the association between maternal arsenic exposure and fetal/neonatal survival using data from a prospective cohort study of 1,616 maternal-infant pairs recruited at a gestational age of ≤16 weeks in Bangladesh (2008-2011). Arsenic concentration in maternal drinking water was measured at enrollment. Extended Cox regression (both time-dependent coefficients and step functions) was used to estimate the time-varying association between maternal arsenic exposure and fetal/neonatal death (all mortality between enrollment and 1 month after birth). In a sensitivity analysis, we assessed gestational arsenic exposure using maternal urine samples taken at enrollment. We observed 203 fetal losses and 20 neonatal deaths. Higher arsenic exposure was associated with a slightly decreased mortality rate up to the middle of the second trimester, and then the mortality rate switched directions around 20 weeks' gestation. In the step function model, the hazard ratios for combined mortality (fetal loss and neonatal death) per unit increase in the natural log of drinking water arsenic concentration (µg/L) ranged from 1.35 (95% CI: 1.08, 1.69) in weeks 25-28 to 0.81 (95% CI: 0.65, 1.02) in weeks 9-12. This nonlinear association suggests that arsenic may exert survival pressure on developing fetuses, potentially contributing to survival bias, and may also indicate that arsenic toxicity differs by fetal developmental stage.

Lead in Air in Bangladesh: Exposure in a Rural Community with Elevated Blood Lead Concentrations among Young Children.

Previous evaluations of a birth cohort in the Munshiganj District of Bangladesh had found that over 85% of 397 children aged 2⁻3 years had blood lead concentrations above the United States Centers for Disease Control and Prevention's reference level of 5 µg/dL. Studies in urban areas of Bangladesh have found elevated levels of lead in the air due to industries and remaining contamination from the historic use of leaded gasoline. Sources of lead in rural areas of Bangladesh remain unknown. We conducted air sampling in both residential and industrial sites in Munshiganj to determine whether children are exposed to elevated lead concentrations in the air and study the association between the children's blood lead levels and sampled air lead concentrations. Residential and industrial air samples in Munshiganj were found to have elevated lead concentrations (mean 1.22 µg/m³) but were not found to be associated with the observed blood lead concentrations. Lead in air is an important environmental health exposure risk to the for children in Munshiganj, and further research may shed light on specific sources to inform exposure prevention and mitigation programs.

DNA methylation in cord blood as mediator of the association between prenatal arsenic exposure and gestational age.

Prenatal arsenic exposure is associated with adverse birth outcomes and disease risk later in life, which could be mediated through epigenetic dysregulation. We evaluated the association between arsenic and gestational age (GA) that was mediated through DNA methylation (DNAm) using data from a Bangladeshi birth cohort. Arsenic exposure was measured in maternal drinking water at ≤16 weeks GA and maternal toenails collected ≤1 month postpartum. Cord blood DNAm was measured using Infinium HumanMethylation450 arrays (n = 44, discovery phase). Top loci identified in the discovery phase were then pyrosequenced in a second group (n = 569, validation phase). Structural equation models (SEM) evaluated the direct and indirect effects of arsenic and DNAm on GA. In the discovery phase, arsenic was associated with differential DNAm of 139 loci that were associated with GA (P < 1.10X10-6; |ß regression|>0.10). Each doubling in water arsenic concentration decreased GA by 2 days, which was fully mediated through the main principal component of the top-ten CpGs (P < 0.001). In the validation phase, there were direct and indirect effects of miR214-3 and MCC DNAm on GA. In an adjusted SEM model, mediation of the association between arsenic and GA by miR124-3 was borderline significant (P = 0.061). This study therefore identified DNAm at specific loci in cord blood that mediated the effect of arsenic exposure on GA. Specifically, prenatal arsenic exposure was associated with lower methylation of miR124-3 that mediated the exposure-response of arsenic on GA. Future research should evaluate if these epigenetic changes are persistent and associated with disease risk.

Growth parameters at birth mediate the relationship between prenatal manganese exposure and cognitive test scores among a cohort of 2- to 3-year-old Bangladeshi children.

Background: Our previous study demonstrated that prenatal manganese exposure is associated with cognitive test scores among a cohort of 2- to 3-year-old Bangladeshi children. This study tested the hypothesis that the adverse effects of manganese are mediated through poor prenatal growth. Methods: Pregnant mothers were enrolled in a birth cohort in Bangladesh between 2008 and 2011, and children were followed at birth and age 20-40 months. Manganese concentration was measured in umbilical cord blood. Anthropometric measurements (weight, length, head circumference) were assessed at delivery. Children's cognitive development was assessed at age 20-40 months using the Bayley Scales of Infant and Toddler Development-Third Edition. Using recently developed statistical approaches that estimate mediation and interaction effects simultaneously, we evaluated whether the association between cord blood manganese and cognitive score was mediated through anthropometric measures at birth. Results: This analysis included 764 mother-child pairs. Higher manganese concentration was associated with lower cognitive score [ß=-0.61, standard error (SE)=0.23, p = 0.009]. Among the birth measures, we found a significant indirect effect only through birth length (ß =-0.10, SE = 0.03, p = 0.001). We also found evidence of mediated interaction (both mediation and interaction, ß =-0.03, SE = 0.01, p = 0.01) with birth length in the association between cord blood manganese and cognitive score. The overall proportion mediated by birth length was 33% (p = 0.02) and the proportion attributed to interaction was 11% (p = 0.04). We did not find evidence of a mediating effect through birth weight or head circumference. Conclusions: Our findings confirm that prenatal growth, particularly birth length, contributes to the overall effect of environmental manganese exposure on a child's cognitive development.