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

Arsenic and the placenta: A review with emphasis on the immune system

Chronic arsenic exposure affects over 140 million people globally. While arsenic easily crosses the placenta, the specific mechanisms impacting placental immune cell populations and fetal health are unclear. Maternal arsenic exposure is epidemiologically linked to increased infection risk, mortality, and cancer susceptibility in offspring, emphasizing the importance of understanding placentally-mediated immune effects. This review explores the potential role of the placenta, a key organ for immune transfer to the developing fetus, in mediating chronic low-dose arsenic exposure effects. Examining three potential pathways-direct contaminant transfer, altered immune transfer from the mother, and indirect impact on fetal immune programming via maternal and placental signaling-the review highlights studies associating maternal arsenic levels with immune-related outcomes, including changes in cord blood T cell populations and increased placental inflammation. Placental gene expression analysis reveals alterations in pathways related to oxidative stress, proteasome activity, and aquaglyceroporin transporter expression. Impact on placental DNA methylation and microRNA regulation as well as on trophoblast dysfunction is discussed, with evidence suggesting inhibited trophoblast migration and placental growth factor expression. The complexity of mixtures, nutrition, and environmental interactions add challenges to investigating the placenta's role in immune programming. Despite inconsistent findings on placental morphology alterations, evidence suggests a potential link between arsenic exposure, placental anomalies, and adverse birth outcomes. Further research is crucial to comprehend the effects of prenatal arsenic exposure on trophoblasts, placental immune cells, and subsequent long-term consequences for fetal immune development and birth outcomes.

Maternal Exposure to Arsenic and Its Impact on Maternal and Fetal Health: A Review

Arsenic exposure is a significant public health issue, with harmful effects caused by its use in commercial products such as car batteries, pesticides, and herbicides. Arsenic has three main compounds: inorganic, organic, and arsine gas. Inorganic arsenic compounds in water are highly toxic. The daily intake of arsenic from food and beverages is between 20 and 300 mcg/day. Arsenic is known for its carcinogenic properties and is classified as a human carcinogen by different institutions. Exposure can lead to oxidative stress, DNA damage, and epigenetic deregulation, which can cause endocrine disorders, altered signal transduction pathways, and cell proliferation. In addition, arsenic can easily cross the placenta, making it a critical concern for maternal and fetal health. Exposure can lead to complications such as gestational diabetes, anemia, low birth weight, miscarriage, and congenital anomalies. Female babies are particularly vulnerable to the negative impact of arsenic exposure, with a higher risk of low weight for gestational age and congenital cardiac anomalies. Therefore, it is crucial to monitor and regulate the levels of arsenic in drinking water and food sources to prevent these adverse health outcomes. Further research is necessary to fully understand the impact of arsenic exposure on human health, especially during pregnancy and infancy, by implementing preventative measures and monitoring the levels of arsenic in the environment.

Anthropometric measures and arsenic methylation among pregnant women in rural northern Bangladesh

INTRODUCTION

Arsenic methylation converts inorganic arsenic (iAs) to monomethyl (MMA) and dimethyl (DMA) arsenic compounds. Body mass index (BMI) has been positively associated with arsenic methylation efficiency (higher DMA%) in adults, but evidence in pregnancy is inconsistent. We estimated associations between anthropometric measures and arsenic methylation among pregnant women in rural northern Bangladesh.

METHODS

We enrolled pregnant women (n = 784) (median [IQR] gestational week: 14 [13, 15]) in Gaibandha District, Bangladesh from 2018 to 2019. Anthropometric measures were BMI, subscapular and triceps skinfold thicknesses, and mid-upper arm circumference (MUAC), fat area (MUAFA), and muscle area (MUAMA). Arsenic methylation measures were urinary iAs, MMA, and DMA divided by their sum and multiplied by 100 (iAs%, MMA%, and DMA%), primary methylation index (MMA/iAs; PMI), and secondary methylation index (DMA/MMA; SMI). In complete cases (n = 765 [97.6%]), we fitted linear, beta, and Dirichlet regression models to estimate cross-sectional differences in iAs%, MMA%, DMA%, PMI, and SMI per IQR-unit difference in each anthropometric measure, adjusting for drinking water arsenic, age, gestational age, education, living standards index, and plasma folate, vitamin B12, and homocysteine.

RESULTS

Median (IQR) BMI, subscapular skinfold thickness, triceps skinfold thickness, MUAC, MUAFA, and MUAMA were 21.5 (19.4, 23.8) kg/m2, 17.9 (13.2, 24.2) mm, 14.2 (10.2, 18.7) mm, 25.9 (23.8, 28.0) cm, 15.3 (10.5, 20.3) cm2, and 29.9 (25.6, 34.2) cm2, respectively. Median (IQR) iAs%, MMA%, DMA%, PMI, and SMI were 12.0 (9.3, 15.2)%, 6.6 (5.3, 8.3)%, 81.0 (77.1, 84.6)%, 0.6 (0.4, 0.7), and 12.2 (9.3, 15.7), respectively. In both unadjusted and adjusted linear models, all anthropometric measures were negatively associated with iAs%, MMA%, and PMI and positively associated with DMA% and SMI. For example, fully adjusted mean differences (95% CI) in DMA% per IQR-unit difference in BMI, subscapular skinfolds thickness, triceps skinfold thickness, MUAC, MUAFA, and MUAMA were 1.72 (1.16, 2.28), 1.58 (0.95, 2.21), 1.74 (1.11, 2.37), 1.45 (0.85, 2.06), 1.70 (1.08, 2.31), and 0.70 (0.13, 1.27) pp, respectively.

CONCLUSIONS

Anthropometric measures were positively associated with arsenic methylation efficiency among pregnant women in the early second trimester.

The association of arsenic exposure with mortality due to cancer, diabetes, Alzheimer's and congenital anomalies using Poisson regression

The present study aims to determine the relationship between the concentration of arsenic in the groundwater of Hamadan province and the mortality rate due to various types of malignancies, congenital anomalies, diabetes mellitus and Alzheimer's. Mortality data due to various causes of death in Hamadan province were collected for five years (2016-2020). Sampling of drinking water was determined in the reference laboratory using polarography method. Poisson regression was used to investigate the relationship between arsenic level and the death rate due to various types of disease, at a significant level (p value < 0.05). According to the results of Poisson regression, among the various causes of death (N = 8042), Alzheimer's 5.94 (3.67-9.61), diabetes mellitus 4.05 (3.5-5.37), congenital malformations 2.98 (1.88-4.72), breast cancer 2.72 (1.56-4.71), leukemia 1.90 (1.24-2.92), stomach cancer 1.64 (1.28-2.10), Liver cancer 1.58 (1.58-2.30), other digestive organs 5.86 (3.38-10.16), meninges and brain cancer 1.57 (1.02-2.41) showed the highest relationship with arsenic contamination. The results of this study could be evidence for a positive and significant relationship between arsenic concentrations and mortality rates due to cancers, diabetes mellitus, Alzheimer disease, and congenital malformations. Therefore, it's necessary to use appropriate water treatment methods to remove arsenic at the source in contaminated areas.

Urinary arsenic and spontaneous pregnancy loss - a hypothesis-generating case-control investigation in western Romania

Arsenic occurs as a natural contaminant of drinking water supplies in arsenic endemic areas, posing a threat to public health. Our aim was to evaluate the relationship between urinary arsenic concentrations and spontaneous pregnancy loss in a population with low-moderate level drinking water arsenic exposure (mostly <10 μg/L). We enrolled 150 women with incident spontaneous pregnancy losses and 150 controls with ongoing pregnancies matched by gestational age. We measured arsenic species in urine using high performance liquid chromatography paired to inductively coupled plasma mass spectrometry. Urinary arsenic was not related to spontaneous pregnancy loss in conditional logistic regression models adjusted for confounding factors. However, a 10 μg/L increase in urinary arsenic (III + V) salt concentrations was associated with 8.00-fold (95% CI: 0.68, 3.35 × 105) greater odds of spontaneous loss among women using prenatal vitamins in an interaction model (P for interaction = 0.07), although the effect estimate was imprecise. In an additional interaction model, prenatal vitamin use was associated with lower odds of loss (OR = 0.30; 95% CI: 0.13, 0.66), although the association was diminished in the presence of a 10 μg/L increase in urinary inorganic arsenic (OR = 0.44; 95% CI: 0.70, 3.22). Total urinary arsenic was associated with 1.48-fold (95% CI: 0.20, 11.35) greater odds for loss among women with urinary cotinine >50 μg/L in another interaction model (P for interaction = 0.07). These results suggest a potential modest increase in the odds of pregnancy loss associated with increased total urinary arsenic among women smoking during pregnancy (urinary cotinine >50 μg/L). Prenatal vitamin use may act as a protective factor for arsenic exposure associated pregnancy loss, but appears to be less protective with increasing urinary inorganic arsenic concentrations.

Novel trace elements detected in multiple stages of pregnancy impact neonatal birth weight by affecting gestational age

Prenatal exposure to elements may be associated with birth weight via shortening of gestation. This study aimed to determine if prenatal exposure is associated with birth weight, and to explore the potential mediating role of gestational age in the association. Within an established Bangladesh prospective birth cohort (2008-2011), we analyzed the concentrations of 15 elements in maternal serum samples collected during the first (n = 780) and second (n = 610) trimesters using inductively coupled plasma mass spectrometry. Mediation analyses explored the relationships between these elements, gestational age, and birth weight. Serum concentrations of cobalt (Co) (first trimester: b = 56.5; 95% confidence interval [CI]: 13.5-99.0; false discovery rate [FDR]-q = 0.035; second trimester: b = 73.3; 95% CI: 20.4-130.2; FDR-q = 0.037) and antimony (Sb) in both trimesters (first trimester:b = 92.1; 95% CI: 66.0-118.9; FDR-q < 0.001; second trimester: b = 93.3; 95% CI: 67.3-118.4; FDR-q < 0.001), and strontium (Sr) in the first trimester (b = 142.4; 95% CI: 41.6-247.9; FDR-q = 0.035) were positively associated with birth weight, while negative associations were observed for barium (Ba) (first trimester: b = -154.8; 95% CI: -217.9 to 91.8; FDR-q <0.001; second trimester: b = -26.7; 95% CI: -44.9 to 10.2; FDR-q < 0.001). These elements act partially by affecting gestation age and appear to have heightened impact among smaller infants. Further research is needed to determine the biological underpinnings of these effects, which may inform strategies to avert low birth weight.

Chronic Community Exposure to Environmental Metal Mixtures Is Associated with Selected Cytokines in the Navajo Birth Cohort Study (NBCS)

Many tribal populations are characterized by health disparities, including higher rates of infection, metabolic syndrome, and cancer-all of which are mediated by the immune system. Members of the Navajo Nation have suffered chronic low-level exposure to metal mixtures from uranium mine wastes for decades. We suspect that such metal and metalloid exposures lead to adverse health effects via their modulation of immune system function. We examined the relationships between nine key metal and metalloid exposures (in blood and urine) with 11 circulating biomarkers (cytokines and CRP in serum) in 231 pregnant Navajo women participating in the Navajo Birth Cohort Study. Biomonitored levels of uranium and arsenic species were considerably higher in participants than NHANES averages. Each biomarker was associated with a unique set of exposures, and arsenic species were generally immunosuppressive (decreased cellular and humoral stimulating cytokines). Overall, our results suggest that environmental metal and metalloid exposures modulate immune status in pregnant Navajo women, which may impact long-term health outcomes in mothers and their children.

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.

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.

Effects of prenatal exposure to arsenic on neonatal birth size in Wujiang, China

To investigate prenatal exposure to arsenic and its effect on birth size, we conducted a cross-sectional study in Wujiang City, Jiangsu, China, from June 2009 to June 2010. A total of 1722 mother-infant pairs were included in the study. A questionnaire was administered to the pregnant women and umbilical cord blood(UCB) samples were collected. Arsenic concentration in UCB was detected by inductively coupled plasma emission mass spectroscopy (ICP-MS). The birth size included birth weight, birth body length and head circumference of the newborns. The effects of arsenic exposure on birth size were assessed by multiple linear regression analysis. Arsenic concentrations in UCB ranged from 0.11 to 30.36 μg/L, the median was 1.71 μg/L. In this range of exposure, arsenic concentration was significantly negatively associated with birth weight, especially among male infants. Our results showed that prenatal exposure to arsenic level was low in Wujiang City, China. However, low prenatal arsenic exposure could have negative effects on birth weight. Our research provided evidence for the adverse effects of prenatal low-level arsenic exposure on the intrauterine growth of the fetus.

Fate of arsenic in living systems: Implications for sustainable and safe food chains

Arsenic, a group 1 carcinogen for humans, is abundant as compared to other trace elements in the environment and is present mainly in the Earth's crust and soil. The arsenic distributions in different geographical regions are dependent on their geological histories. Anthropogenic activities also contribute significantly to arsenic release into the environment. Arsenic presents several complications to humans, animals, and plants. The physiology of plants and their growth and development are affected by arsenic. Arsenic is known to cause cancer and several types of organ toxicity, such as cardiotoxicity, nephrotoxicity, and hepatotoxicity. In the environment, arsenic exists in variable forms both as inorganic and organic species. From arsenic containing compartments, plants can absorb and accumulate arsenic. Crops grown on these contaminated soils pose several-fold higher toxicity to humans compared with drinking water if arsenic enters the food chain. Information regarding arsenic transfer at different trophic levels in food chains has not been summarized until now. The present review focuses on the food chain perspective of arsenic, which affects all components of the food chain during its course. The circumstances that facilitate arsenic accumulation in flora and fauna, as components of the food chain, are outlined in this review.

Child marriage, maternal serum metal exposure, and risk of preterm birth in rural Bangladesh: evidence from mediation analysis

BACKGROUND

The prevalence of preterm birth in Bangladesh is estimated to be 19.1%, the highest in the world. Although prenatal exposure to several metals has been linked with preterm birth, fewer prospective studies have investigated the socioeconomic factors that affect metal exposure, leading to preterm birth risk.

OBJECTIVE

We aim to identify novel metal biomarkers and their critical exposure windows, as well as the upstream socioeconomic risk factors for preterm birth in rural Bangladeshi, to shed light for future interventional strategies.

METHODS

This study included data from 780 mother-offspring pairs, who were recruited to participate in a prospective birth cohort in Bangladesh (2008-2011). Serum concentrations of 19 metals were measured in the first and second trimesters using inductively coupled plasma mass spectrometry. Mediation analysis was performed to explore the upstream socioeconomic factors that affect the risk of preterm birth mediated via metal exposure concentrations.

RESULTS

Early pregnancy exposure to serum zinc, arsenic, and strontium and mid-pregnancy exposure to barium were significantly associated with risk of preterm birth. Furthermore, younger marriage age was associated with an exponential increase in the risk of preterm birth, and women who married after 18 years old had a considerably lower risk of preterm birth. Mediation analysis indicated that these four elements mediated 30.2% of the effect of marriage age on preterm birth.

CONCLUSION

This study indicated that maternal serum metal exposure mediates the impact of child marriage on the increased risk of preterm birth via metal exposures. The findings shed light on the mechanisms underlying such association and provide insights into future interventional strategies.

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.