The critical fetal stage for maternal manganese exposure

Couples' preconception urinary essential trace elements concentration and spontaneous abortion risk: A nested case-control study in a community population

BACKGROUND

Previous studies have indicated a correlation between maternal imbalances in essential trace elements during pregnancy and the occurrence of spontaneous abortion (SA). Nonetheless, the impact of these elements from both partners and during the preconception period remains unexplored.

OBJECTIVE

This study sought to evaluate the relationship between preconception essential trace elements and spontaneous abortion (SA) based on husband-wife dyads.

METHODS

This study selected 390 couples with spontaneous abortion (SA) and 390 matched couples with live births from a preconception cohort of 33,687 couples. Urine samples collected prior to pregnancy were analyzed for ten essential trace elements (Se, Cr, Mo, Cu, Zn, Fe, Mn, V, Co, and Ni) using inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Multivariate conditional logistic regression analysis identified that elevated concentrations of Zn (OR = 0.73) and Ni (OR = 0.69) in couples were associated with a reduced risk of SA, whereas elevated levels of Cr (OR = 1.30) and Mn (OR = 1.39) were linked to an increased risk. Restricted cubic spline models suggested a U-shaped association between couples' Cu and Co concentrations and SA. Bayesian Kernel Machine Regression further supported a U-shaped relationship between the mixture of ten elements and SA, showing significant protection at the 50th and 55th percentiles compared to the 10th percentile. Additionally, the effects of Cr, Zn, Mn, and Ni on SA varied when the concentrations of the other nine elements were held constant at their 25th, 50th, and 75th percentiles. Stratified analysis revealed that maternal Cu (OR = 0.43) and Fe (OR = 0.63) reduced the risk of SA when paternal Cu and Fe were in the lower quartile. Conversely, maternal Cu (OR = 2.03) and Fe (OR = 1.77) increased the risk of SA when paternal concentrations were in the higher quartile. Similar patterns were observed for Cr, Mn, Co, and Zn.

CONCLUSION

Elevated urinary concentrations of Zn and Ni in couples were associated with a reduced risk of SA, while higher levels of Cr and Mn were linked to an increased risk. Cu, Co, and a mixture of ten essential trace elements exhibited a U-shaped relationship with SA. The impact of certain essential trace elements (Cu, Fe, Cr, Mn, Co, and Zn) on SA in one partner was influenced by their concentrations in the other partner.

Interaction of prenatal maternal selenium and manganese levels on child neurodevelopmental trajectories-the Shanghai birth cohort study

OBJECTIVE

The fetal brain is particularly plastic, and may be concurrently affected by chemical exposure and malnutritional factors. Selenium is essential for the developing brain, and excess manganese exposure may exert neurotoxic effects. However, few epidemiological studies have evaluated the interaction of manganese and selenium assessed in different prenatal stages on postnatal neurodevelopmental trajectories.

METHODS

This study contained 1024 mother-child pairs in the Shanghai-birth-cohort study from 2013 to 2016 recruited since early/before pregnancy with complete data on manganese and selenium levels in different prenatal stages and infant neurodevelopmental trajectories. Whole blood manganese and selenium in early pregnancy and around birth were measured by inductively-coupled-plasma-mass-spectrometry (ICP-MS), children's cognitive development was evaluated at 6, 12, and 24 months of age using Age & Stage-Questionnaire (ASQ)-3 and Bayley-III. Multiple linear regression was used to investigate the interaction of prenatal selenium and manganese on neurodevelopmental trajectories.

RESULTS

The prenatal manganese and selenium levels were 1.82 ± 0.98 μg/dL and 13.53 ± 2.70 μg/dL for maternal blood in early pregnancy, and 5.06 ± 1.67 μg/dL and 11.81 ± 3.35 μg/dL for umbilical cord blood, respectively. Higher prenatal Se levels were associated with better neurocognitive performances or the consistently-high-level trajectory (P < 0.05), with more significant associations observed in early pregnancy than around birth. However, such positive relationships became non-significant or even adverse in high (vs. low) manganese status, and the effect differences between low and high manganese were more significant in early pregnancy.

CONCLUSIONS

Prenatal Selenium was positively associated with child neurodevelopment, but prenatal high manganese may mitigate such favorable effects. The effects were mainly observed in earlier prenatal stage.

Exposure to heavy metals and trace elements among pregnant women with twins: levels and association with twin growth discordance

Background

Twin growth discordance is one of the leading causes of perinatal mortality in twin pregnancies. Whether prenatal exposure to heavy metals and trace elements is associated with twin growth discordance has not been studied yet.

Objective

To evaluate the prenatal level of heavy metals and trace elements in twin pregnancy and its relationship with twin growth discordance.

Methods

This study involving 60 twin pairs and their mothers was conducted in Zhejiang Province, China, in 2020-2021. The concentration of heavy metals and trace elements in maternal blood, umbilical cord, and placenta were collected at delivery and measured by inductively coupled plasma tandem mass spectrometer. The association of prenatal level with twin growth discordance was evaluated using conditional logistic regression.

Results

High levels of heavy metal elements (thallium in maternal blood and umbilical cord blood of larger twins, vanadium in the placenta of larger twins) and trace elements (iodine in the placenta of larger twins) during pregnancy, as well as low levels of heavy metal elements (strontium in the umbilical cord blood of larger twins, strontium and chromium in the umbilical cord blood of smaller twins, strontium in the placenta of larger twins, molybdenum and lead in the placenta of smaller twins and difference of molybdenum in the placenta of twins), are associated with intertwin birthweight discordance. Univariate regression analyses showed a significant effect of gestational age at delivery and eleven trace element data on intertwin birthweight discordance. Multivariable logistic regression analysis with transformed variables as dichotomous risk factors combined with baseline demographic characteristics showed Tl in maternal blood as an independent risk factor. The model constructed by combining Tl in maternal blood (OR = 54.833, 95% CI, 3.839-83.156) with the gestational week (OR = 0.618, 95% CI, 0.463-0.824) had good predictive power for intertwin birthweight discordance (AUC = 0.871). The sensitivity analysis results indicate that the effect of maternal blood thallium on intertwin birthweight discordance is stable and reliable.

Conclusion

To our knowledge, ours is the first case-control study to investigate the association between elevated maternal thallium levels before delivery and twin growth discordance.

Associations of intrauterine exposure to manganese with fetal and early-childhood growth: a prospective prenatal cohort study

Prenatal manganese (Mn) exposure may be related to poor birth outcomes; however, there are few relevant epidemiological reports on the effects of intrauterine Mn levels on intrauterine fetal and early childhood growth. From 2013 to 2016, 2082 pairs of mothers and infants were recruited in Wuhan, China, who provided an entire set of urine samples during their first, second, and third trimesters. Fetal head circumference (HC), abdominal circumference (AC), femoral length (FL), and estimated fetal weight (EFW) were obtained by ultrasound at the 16, 24, and 31 weeks of pregnancy. When the children were born, 6 months old, 12 months old, and 24 months old, their weight, height, weight-for-height, and BMI were measured. We used generalized linear models, generalized estimated equations, and restricted cubic spline curves (RCS) to investigate the linear and nonlinear relationships between antenatal Mn levels and fetal and early childhood growth. In all fetuses, Mn exposure during the 1st and 2nd gestation was associated with decreased fetal AC, FL, and EFW at 24 weeks (e.g., for each doubling of urinary Mn concentrations during the 1st and 2nd gestation, the SD score of EFW at 24 weeks decreased by - 4.16% (95% CI, - 6.22%, - 2.10%) and - 3.78% (95% CI, - 5.86%, - 1.70%)). Mn concentrations in the highest tertile group of the 1st and 2nd gestation were related to decreased fetus growth parameters compared to the lowest tertile group. For each doubling of the average Mn concentrations during pregnancy, the z-scores of weight, weight-for-height, and BMI at 12 months decreased, with percentage changes of - 2.93% (95% CI, - 5.08%, - 0.79%), - 3.25% (95% CI, - 5.56%, - 0.94%), and - 3.09% (95% CI, - 5.44%, - 0.73%). In the RCS model, we found a reverse U-shaped association between 1st trimester Mn concentration and fetal FL at 16 weeks and HC at 31 weeks in male fetuses and a non-linear association between mean Mn concentration during pregnancy and girls' weight-for-height and BMI at 6 months. Intrauterine exposure to Mn may be related to restricted growth in the fetus and early childhood, especially in fetuses at 24 weeks of gestation and children at 12 months of age. Also, meaningful curvilinear relationships were found in the sex stratification.

Low concentrations of ethylene bisdithiocarbamate pesticides maneb and mancozeb impair manganese and zinc homeostasis to induce oxidative stress and caspase-dependent apoptosis in human hepatocytes

The worldwide and intensive use of phytosanitary compounds results in environmental and food contamination by chemical residues. Human exposure to multiple pesticide residues is a major health issue. Considering that the liver is not only the main organ for metabolizing pesticides but also a major target of toxicities induced by xenobiotics, we studied the effects of a mixture of 7 pesticides (chlorpyrifos-ethyl, dimethoate, diazinon, iprodione, imazalil, maneb, mancozeb) often detected in food samples. Effects of the mixture was investigated using metabolically competent HepaRG cells and human hepatocytes in primary culture. We report the strong cytotoxicity of the pesticide mixture towards hepatocytes-like HepaRG cells and human hepatocytes upon acute and chronic exposures at low concentrations extrapolated from the Acceptable Daily Intake (ADI) of each compound. Unexpectedly, we demonstrated that the manganese (Mn)-containing dithiocarbamates (DTCs) maneb and mancozeb were solely responsible for the cytotoxicity induced by the mixture. The mechanism of cell death involved the induction of oxidative stress, which led to cell death by intrinsic apoptosis involving caspases 3 and 9. Importantly, this cytotoxic effect was found only in cells metabolizing these pesticides. Herein, we unveil a novel mechanism of toxicity of the Mn-containing DTCs maneb and mancozeb through their metabolization in hepatocytes generating the main metabolite ethylene thiourea (ETU) and the release of Mn leading to intracellular Mn overload and depletion in zinc (Zn). Alteration of the Mn and Zn homeostasis provokes the oxidative stress and the induction of apoptosis, which can be prevented by Zn supplementation. Our data demonstrate the hepatotoxicity of Mn-containing fungicides at very low doses and unveil their adverse effect in disrupting Mn and Zn homeostasis and triggering oxidative stress in human hepatocytes.

Role of placental barrier on trace element transfer in maternal fetal system and hypertensive disorders complicating pregnancy and gestational diabetes mellitus

BACKGROUND

Hypertensive disorders complicating pregnancy (HDCP) and gestational diabetes mellitus (GDM) can affect the placental barrier function to varying degrees. However, current studies show that the transfer and distribution characteristics of trace elements in the maternal-fetal system are still unclear. This study investigated the effect of the placental barrier on the transfer of trace elements from mother to fetus and its relationship with HDCP and GDM.

METHODS

A case-control method was used in this study. 140 pairs of samples were collected; 60 were from healthy pregnant women, and 80 were from patients with pregnancy complications. The contents of trace elements in paired samples were determined by inductively coupled plasma-mass spectrometry (ICP-MS). SPSS software was used to analyze the differences in trace element levels in matched samples of each group. The correlations were analyzed based on Pearson's correlation factor (r).

RESULTS

The distribution characteristics of Fe content in the pathological group (HDCP group and GDM group) were the same as those in the normal group (umbilical cord blood > maternal blood > placenta), but there was no significant difference in the iron content in maternal blood and cord blood of pathological group. The distribution characteristics of Mn content in the pathological group (placenta > umbilical cord blood > maternal blood) were changed compared with those in the normal group (placenta > maternal blood > umbilical cord blood). In addition, the placental Cr content and cord blood Cr and Ni content of the pathological group were higher than those of the normal group. HDCP placental Cr and GDM placental Fe levels were significantly correlated with the Apgar score.

CONCLUSIONS

The transfer of Fe and Mn and the placental barrier function of Cr and Ni in the maternal-fetal system of HDCP and GDM are significantly altered, which directly or indirectly increases the maternal and fetal health risk.

Association between gestational levels of toxic metals and essential elements and cerebral palsy in children

Introduction

Cerebral palsy (CP) is the most common motor disability in childhood, but its causes are only partly known. Early-life exposure to toxic metals and inadequate or excess amounts of essential elements can adversely affect brain and nervous system development. However, little is still known about these as perinatal risk factors for CP. This study aims to investigate the associations between second trimester maternal blood levels of toxic metals, essential elements, and mixtures thereof, with CP diagnoses in children.

Methods

In a large, population-based prospective birth cohort (The Norwegian Mother, Father, and Child Cohort Study), children with CP diagnoses were identified through The Norwegian Patient Registry and Cerebral Palsy Registry of Norway. One hundred forty-four children with CP and 1,082 controls were included. The relationship between maternal blood concentrations of five toxic metals and six essential elements and CP diagnoses were investigated using mixture approaches: elastic net with stability selection to identify important metals/elements in the mixture in relation to CP; then logistic regressions of the selected metals/elements to estimate odds ratio (OR) of CP and two-way interactions among metals/elements and with child sex and maternal education. Finally, the joint effects of the mixtures on CP diagnoses were estimated using quantile-based g-computation analyses.

Results

The essential elements manganese and copper, as well as the toxic metal Hg, were the most important in relation to CP. Elevated maternal levels of copper (OR = 1.40) and manganese (OR = 1.20) were associated with increased risk of CP, while Hg levels were, counterintuitively, inversely related to CP. Metal/element interactions that were associated with CP were observed, and that sex and maternal education influenced the relationships between metals/elements and CP. In the joint mixture approach no significant association between the mixture of metals/elements and CP (OR = 1.00, 95% CI = [0.67, 1.50]) was identified.

Conclusion

Using mixture approaches, elevated levels of copper and manganese measured in maternal blood during the second trimester could be related to increased risk of CP in children. The inverse associations between maternal Hg and CP could reflect Hg as a marker of maternal fish intake and thus nutrients beneficial for foetal brain development.

Metals and per- and polyfluoroalkyl substances mixtures and birth outcomes in the New Hampshire Birth Cohort Study: Beyond single-class mixture approaches

We aimed to investigate the joint, class-specific, and individual impacts of (i) PFAS, (ii) toxic metals and metalloids (referred to collectively as "metals"), and (iii) essential elements on birth outcomes in a prospective pregnancy cohort using both established and recent mixture modeling approaches. Participants included 537 mother-child pairs from the New Hampshire Birth Cohort Study. Concentrations of 6 metals and 5 PFAS were measured in maternal toenail clippings and plasma, respectively. Birth weight, birth length, and head circumference at birth were abstracted from medical records. Joint, index-wise, and individual associations of the metals and PFAS concentrations with birth outcomes were evaluated using Bayesian Kernel Machine Regression (BKMR) and Bayesian Multiple Index Models (BMIM). After controlling for potential confounders, the metals-PFAS mixture was associated with a larger head circumference at birth, which was driven by manganese. When using BKMR, the difference in the head circumference z-score when changing manganese from its 25th to 75th percentiles while holding all other mixture components at their medians was 0.22 standard deviations (95% posterior credible interval [CI]: -0.02, 0.46). When using BMIM, the posterior mean of index weight estimates assigned to manganese for head circumference z-score was 0.72 (95% CI: 0, 0.99). Prenatal exposure to the metals-PFAS mixture was not associated with birth weight or birth length by either BKMR or BMIM. Using both traditional and new mixture modeling approaches, prenatal exposure to manganese was associated with a larger head circumference at birth after accounting for exposure to PFAS and multiple toxic and essential metals.

Maternal Exposure to Potentially Toxic Metals and Birth Weight: Preliminary Results from the DSAN-12M Birth Cohort in the Recôncavo Baiano, Brazil

Prenatal exposure to potentially toxic metals (PTM) may impair fetal growth (FG). We investigated the relationship between maternal exposure to lead (Pb), cadmium (Cd) and manganese (Mn) and birth weight (BW) of 74 newborns. Blood was collected during the second trimester of pregnancy to determine Pb (PbB) and Cd (CdB), while hair (MnH) and toenails (MnTn) were used for Mn. Samples were analyzed by graphite furnace atomic absorption spectrophotometry (GFAAS). Sociodemographic and BW data were collected from questionnaires and maternity records, respectively. The medians (P25th-P75th) of PbB, CdB, MnH, and MnTn were, respectively, 0.9 (0.5-1.8) µg/dL; 0.54 (0.1-0.8) µg/L; 0.18 (0.1-0.4) µg/g; and 0.65 (0.37-1.22) µg/g. The means (standard deviation) of birth weight according to sex were 3067 (426.3) and 3442 (431) grams, respectively, for girls and boys. MnTn presented an inverse correlation with the BW/gestational age ratio for girls (rho = -0.478; p = 0.018), suggesting the effect of sex modification. Although BW correlation with CdB was not statistically significant, hierarchical linear regression (beta = -2.08; 95% CI-4.58 to 0.41) suggested a fetotoxic effect. These results confirmed the threat PTMs may represent and the need for more extensive research to elucidate their role in inadequate FG in developing countries.

Human biomonitoring reference values, exposure distribution, and characteristics of metals in the general population of Taiwan: Taiwan environmental survey for Toxicants (TESTs), 2013-2016

Human biomonitoring (HBM) provides information to identify chemicals that need to be assessed regarding potential health risks to human populations. We established a population-representative sample in Taiwan, namely the Taiwan Environmental Survey for Toxicants (TESTs) in 2013-2016. In total, 1871 participants (aged 7-97 years) were recruited from throughout Taiwan. A questionnaire survey was applied to obtain individuals' demographic characteristics, and urine samples were obtained to assess metal concentrations. Inductively coupled plasma-mass spectrometry was used to determine concentrations of urinary As (total), Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Ni, Pb, Se, Sr, Tl, and Zn. The purpose of this study was to establish the human urinary reference levels (RVs) for metals in the general population of Taiwan. We found that median concentrations of urinary Cu, Fe, Pb, and Zn in males were statistically significant (p < 0.05) higher than in females (Cu: 11.48 vs. 10.00 μg/L; Fe: 11.48 vs. 10.46 μg/L; Pb: 0.87 vs. 0.76 μg/L; and Zn: 448.93 vs. 348.35 μg/L). On the contrary, Cd and Co were significantly lower in males than in females (Cd: 0.61 vs. 0.64 μg/L; and Co: 0.27 vs. 0.40 μg/L). Urinary Cd levels in the ≥18-year-old group (0.69 μg/L) were significantly higher than those in the 7-17-year-old group (0.49 μg/L, p < 0.001). Among the investigated metals, most were significantly higher in the 7-17-year-old group than in the ≥18-year-old group, except for Cd, Ga, and Pb. Participants who lived in central Taiwan had higher median levels of urinary Cd, Cu, Ga, Ni, and Zn than those in other regions. Median levels of urinary As, Cd, Pb, and Se were significantly higher in participants who lived in harbor (94.12 μg/L), suburban (0.68 μg/L), industrial (0.92 μg/L), and rural (50.29 μg/L) areas, respectively, than the others who lived in other areas. RV₉₅ percentiles of urinary metals (ng/mL) for 7-17/≥18-year-old groups were As (346.9/370.0), Cd (1.41/2.21), Co (2.30/1.73), Cr (0.88/0.88), Cu (28.02/22.78), Fe (42.27/42.36), Ga (0.13/0.12), In (0.05/0.04), Mn (3.83/2.91), Ni (8.09/6.17), Pb (8.09/5.75), Se (122.4/101.9), Sr (556.5/451.3), Tl (0.57/0.49), and Zn (1314.6/1058.8). In this study, we have highlighted the importance of As, Cd, Pb, and Mn exposure in the general population of Taiwan. The established RV₉₅ of urinary metals in Taiwanese would be fundamental information to promote the reduction of metal exposure or policy intervention. We concluded that urinary levels of exposure to certain metals in the general Taiwanese population varied by sex, age, region, and urbanization level. References of metal exposure in Taiwan were established in the current study.

Association of Maternal Plasma Manganese with the Risk of Spontaneous Preterm Birth: A Nested Case–Control Study Based on the Beijing Birth Cohort Study (BBCS) in China

We performed this study to clarify the dynamic changes in maternal manganese (Mn) concentration during pregnancy and its association with spontaneous preterm birth (SPB). A nested case–control study was conducted based on the Beijing Birth Cohort Study (BBCS) from 2018 to 2020. Singleton pregnancy women aged 18–44 (n = 488) were involved in the study, including 244 cases of SPB and 244 controls. All of the participants provided blood samples twice (in their first and third trimesters). Inductively coupled plasma mass spectrometry (ICP-MS) was used for the laboratory analysis, and unconditional logistic regression was used for the statistical analysis. We found that the maternal Mn levels were significantly higher in the third trimester than those in the first trimester (median: 1.23 vs. 0.81 ng/mL). The SPB risk was increased to 1.65 (95% CI: 1.04–2.62, p = 0.035) in the highest Mn level (third tertile) in the third trimester, especially in normal-weight women (OR: 2.07, 95% CI: 1.18–3.61, p = 0.011) or non-premature rupture of membrane (PROM) women (OR: 3.93, 95% CI: 2.00–7.74, p < 0.001). Moreover, a dose-dependent relationship exists between the SPB risk and maternal Mn concentration in non-PROM women (P trend < 0.001). In conclusion, dynamic monitoring of maternal Mn level during pregnancy would be helpful for SPB prevention, especially in normal-weight and non-PROM women.

Plasma Concentration of Essential and Toxic Trace Elements After Brazil Nut Intake: Results from a Randomized Controlled Trial

Brazil nut (BN) is a good source of essential nutrients, but little is known about the content of other components, such as toxic elements. Moreover, the high consumption of BN could probably contribute to increased levels of toxic and essential elements in the blood. Thus, this study aimed to evaluate the concentration of essential and toxic trace elements in BN and their concentration in plasma of obese women after regular intake of BN. A randomized controlled clinical trial was carried out with 55 subjects that were randomly assigned to either the Brazil nut group (BN) (n = 29) or the control group (CO) (n = 26) and followed up for 2 months. The BN group consumed one unit of Brazil nut per day, and the CO group did not receive any intervention. The concentration of essential elements (zinc, copper, manganese, and cobalt) and toxic (barium, lead, and cadmium) in BN samples and plasma of obese women (before and after the intervention) were determined by inductively coupled plasma mass spectrometry. Barium followed by copper, and manganese were the trace elements present in higher amounts in Brazil nuts. After the BN intervention period was observed an increase in plasma cadmium (p = 0.002) and a reduction of plasma manganese (p < 0.001) levels. In conclusion, our findings suggest that the regular consumption of BN from the Brazilian Amazon rainforest contributes to the intake of essential trace elements and can be considered safe regarding the content of heavy metals.

Sex-specific differences in early renal impairment associated with arsenic, lead, and cadmium exposure among young adults in Taiwan

Exposure to a single metal has been reported to damage renal function in humans. However, information regarding the association between multiple-metal exposure and markers for early renal impairment in different sexes among the young adult Taiwanese population is scarce. We assessed the association between exposure to arsenic (As), cadmium (Cd), and lead (Pb), and early renal impairment markers using urinary microalbumin (MA), β2-microglobulin (β2MG), and N-acetyl-beta-D-glucosaminidase (NAG) by analyzing 157 young adults aged 20‒29 years, in Taiwan. Inductively coupled plasma mass spectrometry was used to determine urinary As, Cd, and Pb levels. Regression models were applied to different sex groups. The results showed that after adjusting for potential confounding factors and each metal, urinary Cd levels were significantly positively associated with urinary MA (β = 0.523, 95% CI: 0.147-0.899) and β2MG (β = 1.502, 95% CI: 0.635-2.370) in males. However, the urinary Cd level was significantly positively associated with only urinary NAG (β = 0.161, 95% CI: 0.027-0.296) in females. This study thus indicates that the effect of exposure to metals (especially Cd) on early renal impairment among young adults in Taiwan is sex-specific. Our study results could contribute toward developing early intervention programs for decreasing the incidence of renal dysfunction. Further studies are warranted to confirm our findings and clarify the potential mechanisms involved.

Pregnancy Outcome in Women Exposed to Metal Fume in Welding: A Canadian Cohort Study

OBJECTIVES

Welding is a physically demanding job that entails exposure to metal fume and particles. There is little information on the effect of welding exposures on the outcome of a pregnancy conceived during a period when a woman was employed as a welder.

METHODS

Women welders recruited to the Workers Health in Apprenticeship Trades-Metal and Electrical (WHAT-ME) study were followed-up every 6 months for up to 5 years (January 2011-August 2018), and every pregnancy recorded. At the first 6-month follow-up, a detailed questionnaire was completed for the most recent day in welding, and this information was collected again at each follow-up and also from questionnaires completed during pregnancy. The date of conception was estimated for each pregnancy and the job at that date identified. Exposures to ergonomic factors, work schedule and perceptions of noise, heat and cold were extracted for the job at conception. Exposures to metals (aluminum, chromium, manganese, and nickel) and particles in welding fume were estimated from previously validated exposure algorithms reflecting the welding process, base metal and consumables of the job at the conception date. The effects of exposures were estimated in multilevel multivariable models allowing for confounding.

RESULTS

There were 242 pregnancies conceived by a welder working in her trade, 87 were before the first follow-up, 3 were after first follow-up but detailed information was not collected, 22 of those potentially included in the assessment group were in-trade but not welding leaving 122 pregnancies in 90 welders for analysis. Of these 91 resulted in a live birth and 31 in a fetal loss (27 miscarriages and 4 stillbirths). Mean birth weight for live births was 3365 g and gestation 39.4 weeks. Final models showed that risk of fetal loss increased with manipulating heavy objects [odds ratio (OR) = 5.13, 95% confidence interval (CI) 2.04-12.92], whole-body vibration (OR = 5.86, 95% CI 1.81-18.92), a higher rating for noise exposure intensity (OR = 1.52, 95% CI 1.24-1.85), and decreased with use of local exhaust ventilation (OR = 0.20, 95% CI 0.03-1.18). Gestation decreased with perceived heat intensity (β = -0.15, 95% CI -0.29 to -0.02) and number of previous pregnancies (β = -0.35, 95% CI -0.65 to -0.05). Birth weight was lower in those reporting whole-body vibration (β = -596 g, 95% CI -924 to -267) and increased with the welder's body mass index (β = 36 g, 95% CI 12-61). Estimates of exposure to metals and particles were unrelated to gestation or birth weight. In a bivariate analysis, allowing for the same welder reporting >1 pregnancy, estimated airborne aluminum exposure (and to a lesser degree exposure to nickel and particles) was related to greater risk of fetal loss (OR = 1.52, 95% CI 1.04-2.24) but neither aluminum nor the other estimated elements of welding fume added to the final model.

CONCLUSIONS

In this group of women actively engaged in welding during the time surrounding conception, the outcome of pregnancy was strongly related to work exposures, particularly vibration (reported in grinding tasks), manipulation of heavy objects, and perceived intensity of noise and heat. The study was unable to show an independent effect of exposure to metal fume constituents.

Early pregnancy exposure to metal mixture and birth outcomes - A prospective study in Project Viva

BACKGROUND

Prenatal exposure to metals has been individually associated with birth outcomes. However, little is known about the effect of metal mixture, particularly at low exposure levels.

OBJECTIVES

To estimate individual and joint effects of metal mixture components on birth outcomes.

METHODS

We used data from 1,391 mother-infant pairs in Project Viva (1999-2002). We measured 11 metals in maternal 1st trimester erythrocyte; abstracted birth weight from medical records; calculated gestational age from last menstrual period or ultrasound; and obtained birth length (n = 729) and head circumference (n = 791) from research measurements. We estimated individual and joint effects of metals using multivariable linear and Bayesian kernel machine regressions.

RESULTS

In both single metal and metal mixture analyses, exposure to higher concentrations of arsenic was associated with lower birth weight in males, zinc with higher head circumference in females, and manganese with higher birth length in sex-combined analysis. We also observed sex-specific metal interactions with birth outcomes. Arsenic and manganese showed a synergistic association with birth weight in males, in whom an interquartile range (IQR) increase in arsenic was associated with 25.3 g (95% CI: -79.9, 29.3), 47.9 g (95% CI: -98.0, 2.1), and 72.2 g (95% CI: -129.8, -14.7) lower birth weight when manganese concentrations were at 25th, 50th, and 75th percentiles, respectively. Lead and zinc showed an antagonistic association with head circumference in males, where an IQR increase in lead was associated with 0.18 cm (95% CI: -0.35, -0.02), 0.10 cm (95% CI: -0.25, 0.04), 0.03 cm (95% CI: -0.2, 0.14) smaller head circumference when zinc concentrations were at 25th, 50th, and 75th percentiles, respectively. Exposure to higher concentrations of arsenic was also associated with lower gestational age in males when concentrations of manganese and lead were higher.

DISCUSSION

Maternal erythrocyte concentrations of arsenic, manganese, lead, and zinc were individually and interactively associated with birth outcomes. The associations varied by infant sex and exposure level of other mixture components.

Placental chemical elements concentration in small fetuses and its relationship with Doppler markers of placental function

INTRODUCTION

In this study, we aimed at quantifying placental concentrations of 22 chemical elements in small fetuses (SGA) as compared with normally grown fetuses (AGA), and to assess the relationship with Doppler markers of placental function.

METHODS

Prospective cohort study, including 71 SGA fetuses (estimated fetal weight < 10th percentile) and 96 AGA fetuses (estimated fetal weight > 10th percentile), recruited in the third trimester of gestation. The placental concentration of 22 chemical elements was determined by inductively coupled plasma optical emission spectrophotometer (ICP-OES, ICAP 6500 Duo Thermo): aluminum (Al), beryllium (Be), bismuth (Bi), calcium (Ca), cadmium (Cd), cobalt (Co), chrome (Cr), copper (Cu), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), phosphorus (P), lead (Pb), rubidium (Rb), sulfur (S), strontium (Sr), titanium (Ti), thallium (Tl), antimony (Sb), selenium (Se), and zinc (Zn). Placental function was assessed by measuring the following fetal-maternal parameters: Uterine artery Pulsatility Index (UtA PI), Umbilical artery Pulsatility Index (UA PI) and Middle Cerebral artery Pulsatility Index (MCA PI). The association between the chemical elements concentration and study group and the association with Doppler measures were evaluated.

RESULTS

SGA was associated with significantly (p < 0.05) lower concentrations of Al (AGA 21.14 vs SGA 0.51 mg/kg), Cr (AGA 0.17 vs SGA 0.12 mg/kg), Cu (AGA 0.89 vs SGA 0.81 mg/kg), Mg (AGA 0.007 vs SGA 0.006 g/100g), Mn (AGA 0.60 vs SGA 0.47 mg/kg), Rb (AGA 1.68 vs SGA 1.47 mg/kg), Se (AGA 0.02 vs SGA 0.01 mg/kg), Ti (AGA 0.75 vs SGA 0.05 mg/kg) and Zn (AGA 9.04 vs SGA 8.22 mg/kg). Lower placental concentrations of Al, Cr, Mn, Se, Ti were associated with abnormal UtA, UA and MCA Doppler.

DISCUSSION

Lower placental concentrations of Al, Cr, Cu, Mn, Rb, Se, Ti and Zn are associated with SGA fetuses and abnormal fetal-maternal Doppler results. Additional studies are required to further understand how chemical elements affect fetal growth and potentially find strategies to prevent SGA.

Association between maternal urinary manganese concentrations and newborn telomere length: Results from a birth cohort study

OBJECTIVE

Telomere length (TL) is a biomarker for biological aging, and the initial setting of TL at birth is a determinant factor of TL in later life. Newborn TL is sensitive to maternal metals concentrations, while study about the association between maternal manganese (Mn) concentrations and newborn TL was not found. Our study aimed to investigate whether newborn TL is related to maternal Mn concentrations.

METHODS

Data were collected from a birth cohort study of 762 mother-newborn pairs conducted from November 2013 to March 2015 in Wuhan, China. We measured the Mn concentrations in spot urine samples collected during three trimesters by inductively coupled plasma mass spectrometry (ICP-MS) and relative cord blood TL by quantitative real-time polymerase chain reaction (qPCR). We applied multiple informant models to investigate the associations between maternal Mn concentrations and cord blood TL.

RESULTS

The geometric mean of creatinine-corrected urinary Mn concentrations were 1.58 μg/g creatinine, 2.53 μg/g creatinine, and 2.62 μg/g creatinine in the first, second, and third trimester, respectively. After adjusting for potential confounders, a doubling of maternal urinary Mn concentration during the second trimester was related to a 2.10% (95% CI: 0.25%, 3.99%) increase in cord blood TL. Mothers with the highest tertile of urinary Mn concentrations during the second trimester had a 9.67% (95% CI: 2.13%, 17.78%) longer cord blood TL than those with the lowest tertile. This association was more evident in male infants. No relationship was found between maternal urinary Mn concentrations and cord blood TL during the first and third trimesters in our study.

CONCLUSIONS

Our findings suggested that maternal Mn concentration during the second trimester was positively associated with newborn TL. These results might provide an epidemiology evidence on the protective role of maternal Mn for newborn TL and offer clues for the early prevention of telomere shortening related diseases.

Association of biomarkers of exposure to metals and metalloids with maternal hormones in pregnant women from Puerto Rico

BACKGROUND

Metal(loid)s have been associated to adverse birth outcomes in experimental and epidemiological studies, but the underlying mechanism(s) are not well understood. Endocrine disruption may be a mechanism by which the metal(loid)s impact birth outcomes.

METHODS

Pregnant women were recruited through the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT). Urine, blood, demographic and pregnancy-related data were collected at recruitment and subsequent visits. Sixteen metal(loid)s were analyzed in urine and blood samples, while nine maternal hormones (corticotropin-releasing hormone (CRH), sex-hormone binding globulin (SHBG), estriol (E3), progesterone, testosterone, thyroid-stimulating hormone (TSH), total triiodothyronine (T3), total thyroxine (T4), and free thyroxine (fT4)) were measured in serum samples from 815 singleton pregnancies. Linear mixed models with random intercepts were used to examine associations between metal(loid)s in blood and urine with hormone concentrations.

RESULTS

Arsenic blood concentrations were significantly associated with increased levels in CRH (%Δ: 23.0, 95%CI: 8.4-39.6) and decreased levels in testosterone (%Δ: ^-16.3, 95%CI: ^-26.2-^-5.1). Cobalt, manganese, and lead blood concentrations were associated with small increases in SHBG (%Δ range: 3.3-4.2), E3 (%Δ range: 3.9-8.7) and progesterone (%Δ range: 4.1-6.3) levels, respectively. Nickel blood concentration was inversely associated with testosterone levels (%Δ ^-13.3, 95%CI: ^-18.7-^-7.6). Significant interactions were detected for the association between nickel and study visit in relation to CRH (p < 0.02) and testosterone levels (p < 0.01).

CONCLUSION

Our analysis suggests that metal(loid)s may act as endocrine disruptors by altering prenatal hormone levels. This disruption may depend on specific windows of exposure during pregnancy. Additionally, some essential metal(loid)s such as managense and cobalt may be contributors to adverse maternal and fetal outcomes. The study of metal(loid)s as endocrine disruptors is in the early stages of epidemiological research and future studies are needed to further investigate these associations.

Fasting Plasma Glucose Mediates the Prospective Effect of Maternal Metal Level on Birth Outcomes: A Retrospective and Longitudinal Population-Based Cohort Study

OBJECTIVE

Previously, we found that the presence of maternal serum metals before the 24th week of gestation prospectively increased fasting plasma glucose (FPG) at 24-28 weeks. We further explored the prospective association between levels of metals and neonatal outcomes and assessed the mediating effects of FPG on these relationships.

METHODS

A total of 7,644 pregnant women were included in a retrospective cohort study, and the relationships between metals [manganese (Mn), copper (Cu), lead (Pb), zinc (Zn), and magnesium (Mg)] and birth outcomes were explored. Quantile and linear regressions were performed to detect the shifts and associations between metals and neonatal size distribution focused on the 10th, 50th, and 90th percentiles. Mediation analysis was performed to assess the mediating effect of FPG on metals and birth outcomes.

RESULTS

After adjustment, a 50% increase in Mn and Zn levels was related to a 0.136-cm (95% CI: 0.067-0.205) and 0.120-cm (95% CI: 0.046-0.193) increase in head circumference, respectively. Based on head circumference distribution, the magnitude of the association with Mn was smaller at the upper tail, while the magnitude of correlation with Zn was greater at the upper tail. A 50% increase in Mn and Zn levels was related to a 0.135-cm (95% CI: 0.058-0.212) and 0.095-cm (95% CI: 0.013-0.178) increase in chest circumference, respectively. The magnitude of the association with Mn increased with increasing chest circumference, while the magnitude of correlation with Zn decreased with increasing chest circumference. FPG explained 10.00% and 17.65% of the associations of Mn with head and chest circumference. A positive indirect effect of Zn associated with head circumference (0.004, 95% CI: 0.002-0.006) and chest circumference (0.005, 95% CI: 0.003-0.008) through FPG was also observed, and the estimated proportion of the mediating effect was 13.79% and 26.32%, respectively.

CONCLUSION

Maternal serum Mn and Zn levels before the 24th week of gestation may prospectively increase the circumference of the neonatal head and chest. FPG at 24-28 weeks had positive mediating effects on these relationships. Further research is needed to identify a balance between maternal blood glucose and birth size.

Characterization of trace elements exposure in pregnant women in the United States, NHANES 1999-2016

OBJECTIVE

The objective of the current study is to report on urine, blood and serum metal concentrations to characterize exposures to trace elements and micronutrient levels in both pregnant women and women of child-bearing age in the U.S. National Health and Nutrition Examination Survey (NHANES) years 1999-2016.

METHODS

Urine and blood samples taken from NHANES participants were analyzed for thirteen urine metals, three blood metals, three serum metals, speciated mercury in blood and speciated arsenic in urine. Adjusted and unadjusted least squares geometric means and 95% confidence intervals were calculated for all participants among women aged 15-44 years. Changes in exposure levels over time were also examined. Serum cotinine levels were used to adjust for smoke exposure, as smoking is a source of metal exposure.

RESULTS

Detection rates for four urine metals from the ATSDR Substance Priority List: arsenic, lead, mercury and cadmium were ~83-99% for both pregnant and non-pregnant women of child bearing age. A majority of metal concentrations were higher in pregnant women compared to non-pregnant women. Pregnant women had higher mean urine total arsenic, urine mercury, and urine lead; however, blood lead and mercury were higher in non-pregnant women. Blood lead, cadmium, mercury, as well as urine antimony, cadmium and lead in women of childbearing age decreased over time, while urine cobalt increased over time.

CONCLUSIONS

Pregnant women in the US have been exposed to several trace metals, with observed concentrations for some trace elements decreasing since 1999.

Selenium, Zinc, and Manganese Status in Pregnant Women and Its Relation to Maternal and Child Complications

Micronutrients, as essential components of prenatal care, are important to reduce the risk for maternal and child morbidity and mortality by lowering pregnancy-related complications. The present study aimed to investigate the status of the trace elements, i.e., selenium, zinc, and manganese in pregnant and non-pregnant women from a developing country and to evaluate its relationship with maternal and child complications. Selenium, zinc, and manganese concentrations were measured in the blood serum of 80 pregnant women and compared with 40 non-pregnant healthy controls. The quantitative analyses of trace elements were performed by using the inductively coupled plasma–optical emission spectrometry (ICP-OES) method. The information about the dietary habits of the study participants was recorded by using a food frequency questionnaire. The results showed significant lower selenium and zinc levels in pregnant women as compared to the controls (2.26 ± 1.09 vs. 2.76 ± 1.15 µmol/L, p = 0.031; 21.86 ± 7.21 vs. 29.54 ± 7.62 µmol/L, p < 0.001) respectively, with no difference in manganese concentrations (1.40 ± 0.09 vs.1.38 ± 0.09 log₁₀ nmol/L, p = 0.365). Regarding maternal and child complications, higher manganese levels were associated with an increased odds ratio for maternal complications (OR = 3.175, CI (95%) 1.631−6.181; p = 0.038). Consumption of dairy products was associated with lower selenium and manganese values. Pregnant women showed a lower serum selenium and zinc status, and in addition elevated serum manganese concentrations, which might be associated with a higher risk for maternal pregnancy/birth complications, although more studies are necessary to evaluate this association.

Effects of Methcathinone Exposure during Prenatal and Lactational Periods on the Development and the Learning and Memory Abilities of Rat Offspring

This study aimed to investigate the effects of prenatal and lactational methcathinone exposure on the development and the learning and memory abilities of rat offspring using a Sprague-Dawley rat model. Pregnant and lactating rats were administered a consecutive daily dose of methcathinone (0.37 mg/kg) or an equivalent volume of saline by injection on gestational days 7-20 and postnatal days 2-15, respectively. The physical development and neurobehavioral test results of rat pups were recorded throughout the lactation period. Morris water maze (MWM) and novel object recognition (NOR) tests were performed from postnatal day 35 to day 42 to assess the learning and memory abilities of rat offspring in adolescence. The occurrence of hair growth and developments in neurological reflexes, such as improvements in limb grasp, righting reflex, and gait, were delayed in pups after perinatal methcathinone exposure compared with that in the control. Results from MWM and NOR tests indicate that perinatal methcathinone exposure induced deficits in spatial memory, learning ability, and novel object exploration in the adolescent offspring compared with that in the control. The impairment of spatial learning and memory was greater in the prenatal exposure group, while the impairment of novel object exploration was greater in the lactational exposure group. These data show that the prenatal and lactational methcathinone exposure induced the delay of physical and neurological reflex development and impaired learning and memory in rat offspring.

Children's environmental health based on birth cohort studies of Asia (2) - air pollution, pesticides, and heavy metals

The life style and child raising environment in Asia are quite different compared with Western countries. Besides, the children's environmental threats and difficulties in conducting studies could be different. To address children's environmental health in Asia area, the Birth Cohort Consortium of Asia (BiCCA) was co-established in 2011. We reviewed the mercury, polychlorinated biphenyls, perfluoroalkyl substances, phthalates, and environmental tobacco smoke in pervious based on birth cohort studies in Asia. The aim of this study was to summarize the traditional environmental pollution and the target subjects were also based on the birth cohort in Asia area. Environmental pollutants included air pollutants, pesticides focusing on organochlorine pesticides, diakylphosphates, and pyrethroid, and heavy metals including lead, arsenic, cadmium, manganese, vanadium, and thallium. Fetal growth and pregnancy outcomes, childhood growth and obesity, neurodevelopment and behavioral problems, and allergic disease and immune function were classified to elucidate the children's health effects. In total, 106 studies were selected in this study. The evidences showed air pollution or pesticides may affect growth during infancy or childhood, and associated with neurodevelopmental or behavioral problems. Prenatal exposure to lead or manganese was associated with neurodevelopmental or behavioral problems, while exposure to arsenic or cadmium may influence fetal growth. In addition to the harmonization and international collaboration of birth cohorts in Asia; however, understand the whole picture of exposure scenario and consider more discipline in the research are necessary.

Serum levels of copper, iron, and manganese in women with pregnancy, miscarriage, and primary infertility

BACKGROUND

Iron (Fe), copper (Cu), and manganese (Mn) play a significant role in female reproduction and fetal development. At the same time, high levels of metals may exert toxic effects. Correspondingly, both excess and deficiency of essential trace elements were shown to be associated with female infertility and adverse pregnancy outcome, although the existing data are rather contradictory. Therefore, the objective of the present study was to reveal the potential role of altered iron, copper, and manganese status in female reproductive health problems through assessment of serum metal levels in healthy non-pregnant and pregnant women, as well as patients with miscarriage and primary infertility.

METHODS

A total of 150 healthy controls, 169 pregnant women (II trimester of pregnancy), 75 women with miscarriage, and 91 patients with primary infertility were enrolled. Serum metal levels were assessed using ICP-MS.

RESULTS

Pregnant women are characterized by a significant increase in serum Cu an Mn levels by 40% (p < 0.001) and 16% (p = 0.043) as compared to the controls, respectively. Serum Cu levels in women with miscarriage and infertility were 30% and 35% lower than those in pregnant women (p < 0.001). No significant difference in serum iron levels were observed between the control and pregnant women. Women who had miscarriage were characterized by 13% (p = 0.042) higher serum Fe levels as compared to the pregnant ones. Multiple regression analysis demonstrated that serum copper levels was significantly associated both with pregnancy (β = 0.436; p < 0.001) and reproductive health problems in women (β = -0.272; p < 0.001). The latter was improved significant after adjustment for serum Fe and Mn levels, age, and BMI (β = -0.431; p < 0.001). The model incorporating serum Cu, Fe, Mn, and anthropometric parameters accounted for 23% of variability in reproductive status (p < 0.001).

CONCLUSIONS

It is proposed that the lack of pregnancy-associated increase in metal levels in miscarriage and infertility may be indicative of at least partial role of metal insufficiency in impaired pregnancy and reproductive function in general. However, detailed clinical studies as well as experimental investigations are required for assessment of the potential causes and mechanisms of the observed associations.

Blood mercury, lead, cadmium, manganese and selenium levels in pregnant women and their determinants: the Japan Environment and Children's Study (JECS)

The Japan Environment and Children's Study (JECS) is a birth-cohort study of 100,000 mother-child dyads that aims to investigate the effect of the environment on child health and development. Mercury (Hg), lead (Pb), cadmium (Cd), manganese (Mn) and selenium (Se) are considered to be important co-exposures when examining the effect of other chemical substances on child development. The levels of these elements in the blood of 20,000 randomly selected mid/late-term pregnant women from the whole JECS cohort were analysed using inductively coupled plasma-mass spectrometry. The median concentrations (interquartile ranges) for Pb, Hg, Cd, Mn and Se were 0.63 (0.51-0.78) µg dl^-1, 3.83 (2.70-5.43) µg l^-1, 0.70 (0.52-0.95) µg l^-1, 16.1 (13.2-19.6) µg l^-1 and 178 (165-192) µg l^-1, respectively. Hg and Se correlated positively with each other (Spearman's ρ = 0.287), as did Pb and Cd (ρ = 0.239) and Cd and Mn (ρ = 0.267). The blood Pb levels decreased by 5-10-fold over the past 25 years. The main predictors of the blood levels of each element were fish consumption for Hg, maternal age and non-alcoholic beverage consumption for Pb, maternal age and smoking for Cd, gestational age at sampling for Mn and serum protein levels for Se. These results revealed the historical trends and current predictors of the blood levels of these elements in pregnant Japanese women.

Association between blood manganese level during pregnancy and birth size: The Japan environment and children's study (JECS)

BACKGROUND

Manganese (Mn) is both an essential element and a potential toxicant. Although a few studies have suggested a nonlinear relationship between the maternal whole blood Mn level at delivery and infant birth weight, little is known about the effects of Mn levels during pregnancy on fetal growth, particularly with regard to sex-specific differences.

METHODS

In this nationwide birth cohort study, we examined the association of maternal blood Mn level during pregnancy with infant birth weight, length, and head circumference in 16,473 mother-infant pairs. Pregnant women living in 15 regions across Japan were recruited between January 2011 and March 2014. The analysis of birth size (8,484 males and 7,989 females) was conducted using a nonlinear spline, followed by the use of quadratic regression or linear regression models. The analysis of small-for-gestational-age (SGA) (6,962 males and 6,528 females born vaginally) was conducted using multivariate logistic regression. Additionally, subgroup analysis was conducted according to the timing of blood sampling.

RESULTS

The median maternal blood Mn level during pregnancy (i.e., 2nd and 3rd trimesters) was 16.2 µg/L (range, 4.3-44.5 µg/L). A positive linear association between the log blood Mn level and head circumference was observed in both male and female infants. However, a nonlinear relationship between the log blood Mn level and birth weight was observed only in male infants, such that the birth weight increased up to a blood Mn level of 18.6 µg/L. In the subgroup analysis stratified by the timing of maternal blood sampling, this nonlinear relationship was obvious only when sampling was performed in the 3rd trimester. Male infants in the lowest blood Mn level quartile (≤ 13.2 µg/L) faced an increased risk of SGA (odds ratio [95% confidence interval] = 1.35 [1.04-1.74]), as did those in the highest blood Mn level quartile (≥ 21.0 µg/L) when sampling was performed during the 3rd trimester (odds ratio [95% confidence interval] = 1.62 [1.10 to 2.39]), compared to those in the third blood Mn level quartile (the category including 18.6 µg/L). No association of blood Mn level with birth weight was observed among female infants, and blood Mn level was not associated with birth length in either male or female infants.

CONCLUSION

A low blood Mn level during pregnancy or a high blood Mn level during the 3rd trimester was associated with a lower birth weight and increased risk of SGA in male infants, but not in female infants. A low blood Mn level was found to correlate slightly with a small head circumference among infants of both sexes.

In utero metal exposures measured in deciduous teeth and birth outcomes in a racially-diverse urban cohort

A growing number of studies have examined associations of metal exposures with birth outcomes, however, results from these studies have been inconsistent, and hampered by methodological limitations. We measured direct fetal exposure to three metals (lead, manganese and zinc) during the second and third trimester and examined its association with birth weight and gestational age at delivery. Participants in the Wayne County Health, Environment, Allergy and Asthma Longitudinal Study (WHEALS), a population-based birth cohort established between September 2003 and December 2007, were invited to donate teeth to the study. Lead, manganese and zinc during the second and third trimesters were measured via high-resolution microspatial mapping of dentin growth rings, a validated biomarker for prenatal metal exposure. Gestational age at delivery and infant birth weight were obtained from the delivery medical record. A total of 145 children had tooth metal measurements and birth outcome data. Mean birth weight was 3431 ± 472 g and mean gestational age at delivery was 39.0 ± 1.3 weeks. Overall, there was a positive association between second (β = 0.21, 95% CI: 0.05, 0.37, P = 0.01) and third trimester (β = 0.21, 95% CI: 0.05, 0.37, P = 0.01) tooth manganese and birth weight Z-score; this remained statistically significant after covariate adjustment. There was also a negative association between second trimester tooth lead level and birth weight Z-score (β = -0.20, 95% CI: -0.38, -0.02, P = 0.02), however, this was attenuated after adjusting for covariates. Mixture analysis revealed similar findings. There was evidence for a sex-specific effect of manganese with birth weight Z-score, with the association stronger in female compared to male infants. Overall, we found evidence suggesting that higher in utero manganese is associated with larger birth weight Z-scores and that these associations may vary by infant sex.

Trace element profiles in pregnant women's sera and umbilical cord sera and influencing factors: Repeated measurements

In utero exposure to toxic heavy metals and deficient or excessive essential trace elements during pregnancy may have adverse effects on pregnant women and their offsprings, which are of great concern. The objective of the present study was to characterize serum concentrations of multiple trace elements at multiple time points during pregnancy in Chinese women. Three thousand four hundred and sixteen pregnant women in total were included from MABC (Ma'anshan Birth Cohort) study. Fasting sera in the morning and questionnaires were obtained at three separate follow-up visits. Nineteen trace elements from serum samples were analyzed, including aluminum (Al), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), barium (Ba), thallium (Tl), lead (Pb), calcium (Ca), magnesium (Mg), mercury (Hg) and molybdenum (Mo). The total detection rates for most elements were 100% rather than Ni (99.98%), As (99.97%), Cd (99.6%), Ba (99.9%), Pb (99.8%), Hg (99.8%). The concentration distributions of 19 elements varied vastly. Median concentrations for all trace elements ranged from 38.5 ng/L to 102.9 mg/L. The moderate interclass correlation coefficients (ICCs) were observed for Co, Cu, Se and Hg, ranging from 0.40 to 0.62; the lower ICCs, ranging from 0.13 to 0.32 were for Fe, Zn, Cd, Ba, Tl, Mg and Mo. The intraclass correlation effects were not observed for the remaining elements, such as Al, V, Cr, Mn, Ni, As and Pb. The concentrations of each element between three time points were significantly different; significant differences were also found between any two time points except for Ni, Cd and Mo. Many factors could affect the levels of trace elements, and a very important factor of them was season. Consequently, a single measurement of elements in sera seems not enough to describe exposure levels throughout pregnancy; additionally, season affected exposure levels of trace elements with moderate ICCs showed certain regularity. Future analyses should take sampling seasons into consideration carefully.

Placental metal concentrations and birth outcomes: The Environment and Childhood (INMA) project

OBJECTIVE

To examine the association of placental levels of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), manganese (Mn), and chromium (Cr) with birth outcomes (birth weight, length, and head circumference, low birth weight [LBW], gestational age, preterm delivery, and small for gestational age [SGA]) in mother-child pairs from the Environment and Childhood (INMA) Project in Spain.

METHODS

Metal concentrations were measured in placenta tissue samples randomly selected from five INMA cohorts. Data on birth outcomes were obtained from medical records. Associations were assessed in a sub-sample of 327 mother-infant pairs by regression models adjusted for confounding factors and for all metals simultaneously. Effect modification by sex was also evaluated.

RESULTS

Elevated placental Cd levels (>5.79 vs. <3.30 ng/g) were associated with reduced birth weight (-111.8 g, 95%CI = -215.6; -8.06, p-trend = 0.01) and length (-0.62 cm, 95%CI = -1.20; -0.04, p-trend = 0.02), while a 10% increase in Cd was associated with 1.21-fold increased odds (95%CI = 1.01; 1.43) of LBW in the global sample but with 14% lower odds (95%CI = 0.78; 0.96) of preterm delivery in males (P_interaction = 0.10). Detected (vs. undetected) Hg was associated with reduced head circumference (-0.49 cm, 95%CI = -1.00; 0.03) in females (P_interaction = 0.03). A 10% increase in placental Mn was associated with slight increases in gestational age (0.04 weeks, 95%CI = 0.01; 0.07) in the global sample and in head circumference (0.05 cm, 95%CI = -0.01; 0.10) in females (P_interaction = 0.03). Elevated Cr levels (>99.6 vs. <56.1 ng/g) were associated with reduced birth length (-0.68 cm, 95%CI = -1.33; -0.04, p-trend = 0.02) and slightly increased gestational age (0.35 weeks, 95%CI = -0.07; 0.77, p-trend = 0.08) in the global sample. As and Pb were detected in few placentas (27% and 13%, respectively) and were not associated with any studied birth outcome.

CONCLUSIONS

Data suggest that in utero exposure to Cd, Hg, and Cr could adversely affect fetal growth, whereas Mn and Cr appear to have a positive effect on gestational age. Given the relatively small number of subjects, sex-specific associations should be interpreted with caution.

Critical Windows for Associations between Manganese Exposure during Pregnancy and Size at Birth: A Longitudinal Cohort Study in Wuhan, China

BACKGROUND

Prenatal overexposure to manganese (Mn), an essential micronutrient, is related to impaired fetal growth and development. Fetuses appear to be highly sensitive to Mn during short periods of gestation. However, little is known about the critical windows of susceptibility to Mn for humans.

OBJECTIVES

Our objective was to estimate trimester-specific associations of exposure to Mn with size at birth.

METHODS

Urine samples of 3,022 women were collected repeatedly in the first, second, and third trimesters in Wuhan, China. Urinary concentrations of Mn and other toxic metals were measured using an inductively coupled plasma mass spectrometry. Trimester-specific associations of specific gravity–adjusted urinary Mn concentrations with birth weight, birth length, and ponderal index were estimated using multivariable linear regressions with generalized estimating equations. Linear mixed models were applied to evaluate the windows of susceptibility to Mn exposure by comparing the pattern of Mn exposure among newborns with restricted size at birth to those without.

RESULTS

When compared with the third quintile of urinary Mn concentrations, both higher and lower quintiles of urinary Mn concentrations in the second and third trimesters were related to reduced birth weight, birth length, and ponderal index. But the observed associations for higher quintiles were stronger and more likely to be statistically significant [e.g., for women who were in the fifth quintile of Mn concentration in the third trimester, the reduction in birth weight was [Formula: see text] (95% CI: [Formula: see text], [Formula: see text]) g and in birth length was [Formula: see text] (95% CI: [Formula: see text], 0.00) cm]. Moreover, newborns with restricted size at birth, compared with those without, had higher levels of Mn exposure in the second and third trimesters.

CONCLUSIONS

This prospective prenatal cohort study revealed an association of exposure to Mn during pregnancy, especially late pregnancy, with restricted size at birth. Replications are needed. https://doi.org/10.1289/EHP3423.

Water metal contaminants in a potentially mineral-deficient population of Haiti

This study aimed to characterize metal contaminant concentrations and assess temporal and spatial variability in the main drinking water sources of Cap-Haïtien, Haiti. Water sources from five communities were sampled in two seasons, June (2014) and October (2014), and analysed for a suite of metals. A geographic information system was used to examine the spatial distribution of sampling points. Metal concentrations were below the US Environmental Protection Agency (USEPA) primary drinking water standards. Mean manganese concentrations were comparatively higher in wells (254.5 µg/L), exceeding the USEPA secondary drinking water standard (50 µg/L). Higher mean Mg/Ca and Ba/Ca ratios (range 2.3-3.4) may indicate different interactions between seawater and groundwater throughout the year. Although metal concentrations were within the limits of the USEPA drinking water standards, emerging contaminants, such as manganese, showed concentrations in excess of recommended limits. These metals may interact with background nutritional status with potential implications for growth and development.

Associations between urinary total arsenic levels, fetal development, and neonatal birth outcomes: A cohort study in Taiwan

BACKGROUND

Arsenic exposure is a global health concern. Several studies have focused on chronic arsenic exposure in adults; however, limited data are available regarding the potential adverse effects of prenatal exposure on fetuses and neonates.

OBJECTIVES

To assess which time point maternal arsenic exposure may influence the fetus during pregnancy and birth outcomes.

METHODS

In this study, total arsenic concentrations were analyzed in urine samples collected from 130 women with singleton pregnancies (22-45years old) in Taiwan from March to December of 2010. All fetal biometric measurements in each trimester period and birth outcomes at delivery were obtained. We applied a generalized estimating equation model and multivariate regression models to evaluate the associations between maternal urinary total arsenic (UtAs) exposure during pregnancy, fetal biometric measurements, and neonatal birth outcomes.

RESULTS

We observed statistically significant correlations between maternal UtAs levels and the fetal biparietal diameter over all three trimesters (β=-1.046mm, p<0.05). Multiple regression analyses showed a negative association between maternal UtAs levels and chest circumference in the first trimester (β=-0.721cm, p<0.05), and second-trimester UtAs exposure was associated with decreases in birth weight (β=-173.26g, p<0.01), head circumference (β=-0.611cm, p<0.05), and chest circumference (β=-0.654cm, p<0.05). Dose-response relationships were also observed for maternal UtAs exposure and birth outcomes.

CONCLUSIONS

We identified a negative relationship between maternal UtAs levels during pregnancy, fetal development, and neonatal birth outcomes. These findings should be confirmed in future studies with large sample sizes.

Maternal and fetal exposure to cadmium, lead, manganese and mercury: The MIREC study

Given the susceptibility of the fetus to toxicants, it is important to estimate their exposure. Approximately 2000 pregnant women were recruited in 2008-2011 from 10 cities across Canada. Cd, Pb, Mn and total Hg were measured in maternal blood from the 1st and 3rd trimesters, umbilical cord blood, and infant meconium. Nutrient intakes of vitamin D, iron, and calcium (Ca) were assessed using a food frequency questionnaire and a dietary supplement questionnaire. Median concentrations in 1st trimester maternal blood (n = 1938) were 0.20, 8.79 and 0.70 μg/L for Cd, Mn and Hg, respectively, and 0.60 μg/dL for Pb. While the median difference between the paired 1st and 3rd trimester concentrations of Cd was 0, there was a significant decrease in Pb (0.04 μg/dL) and Hg (0.12 μg/L) and an increase in Mn (3.30 μg/L) concentrations over the course of the pregnancy. While Cd was rarely detected in cord blood (19%) or meconium (3%), median Pb (0.77 μg/dL), Mn (31.87 μg/L) and Hg (0.80 μg/L) concentrations in cord blood were significantly higher than in maternal blood. Significant negative associations were observed between estimated Ca intake and maternal Cd, Pb, Mn and Hg, as well as cord blood Pb. Vitamin D intake was associated with lower maternal Cd, Pb, and Mn as well as Pb in cord blood. Even at current metal exposure levels, increasing dietary Ca and vitamin D intake during pregnancy may be associated with lower maternal blood Pb and Cd concentrations and lower Pb in cord blood.

Maternal urinary manganese and risk of low birth weight: a case-control study

BACKGROUND

Manganese (Mn) is an essential element for humans, but exposure to high levels has been associated with adverse developmental outcomes. Early epidemiological studies evaluating the effect of Mn on fetal growth are inconsistent.

METHODS

We investigated the association between maternal urinary Mn during pregnancy and the risk of low birth weight (LBW). Mn concentrations in maternal urine samples collected before delivery were measured in 816 subjects (204 LBW cases and 612 matched controls) recruited between 2012 and 2014 in Hubei Province, China.

RESULTS

The median Mn concentration in maternal urine was 0.69 μg/g creatinine. Compared to the medium tertile of Mn levels, an increased risk of LBW was observed for the lowest tertile (≤0.30 μg/g creatinine) [adjusted odds ratio (OR) = 1.28; 95 % confidence interval (CI) = 0.67, 2.45], and a significantly increased risk of LBW was observed for the highest tertile (≥1.16 μg/g creatinine) [adjusted OR = 2.04; 95 % CI = 1.12, 3.72]. A curvilinear relationship between maternal urinary Mn and risk of LBW was observed, showing that the concentration at 0.43 μg/g creatinine was the point of inflection. Similar associations were observed among the mothers with female infants and among the younger mothers < 28 years old. However, among the mothers with male infants or the older mothers ≥ 28 years old, only higher levels of Mn were positively associated with LBW.

CONCLUSIONS

Lower or higher levels of maternal urinary Mn are associated with LBW, though only the association of LBW risk and higher levels of Mn was statistically significant. The findings also show that the associations may vary by maternal age and infant sex, but require confirmation in other populations.