Maternal and cord blood manganese (Mn) levels and birth weight: The MIREC birth cohort study

The association of manganese levels with red cell distribution width: A population-based study

OBJECTIVES

Experimental and acute exposure studies imply that manganese affects red blood cell production. Nevertheless, the association between environmental exposure and red blood cell distribution width (RDW) has yet to be explored. This research sought to assess the correlation between blood manganese levels and RDW within the general population of the United States.

MATERIALS AND METHODS

Employing weighted multiple linear regression models, data from the 2011-2018 National Health and Nutrition Examination Survey (NHANES) were utilized to assess the correlation between manganese levels in the blood and RDW. Restricted cubic spline plots and two-piecewise linear regression models were also employed.

RESULT

The analysis included a total of 15882 participants in which we determined an independent positive relationship between blood manganese levels and RDW among participants(β = 0.079, P<0.001). Moreover, we identified a J-shaped association between blood manganese levels and RDW in total participants (inflection point for blood manganese: 7.32 ug/L) and distinct subgroups following adjusted covariates. Women exhibited a more pronounced association, even after controlling for adjusted covariates.

CONCLUSIONS

We determined a J-shaped relationship between blood manganese levels and RDW with an inflection point at 7.32 ug/L for blood manganese. Nevertheless, fundamental research and large sample prospective studies are needed to determine the extent to which blood manganese levels correlate with RDW.

Association of placental weight at birth with maternal whole blood concentration of heavy metals (cadmium, lead, mercury, selenium, and manganese): The Japan Environment and Children's Study (JECS)

BACKGROUND

Lifelong health is dependent on prenatal growth and development, influenced by the placental intrauterine environment. Charged with dual functions--exchange of oxygen and nutrients as well as a barrier against toxins--the placenta itself is susceptible to environmental exposure to heavy metals.

OBJECTIVE

To examine the use of placenta weight as a biomarker for heavy metal exposure using a large Japanese cohort of pregnant women.

METHODS

The placenta weight, as a biomarker of exposure to heavy metals (cadmium, lead, and mercury), was investigated using data from the Japan Environment and Children's Study (2011-2014). Selenium and manganese were included as factors directly affecting fetal growth or heavy metal toxicity. Maternal blood samples collected in the second or third trimester were used to measure heavy metal concentrations. The association between maternal blood metal concentrations and placenta weight was explored by applying Z scores and multivariable logistic regression analysis and classifying participants into quartiles (Q1, Q2, Q3, and Q4) according to metal concentrations.

RESULTS

This study included a total of 73,005 singleton pregnant women who delivered via live births and met the inclusion criteria. The median heavy metal concentrations in the maternal whole blood were 0.662 ng/g cadmium, 5.85 ng/g lead, 3.61 ng/g mercury, 168 ng/g selenium, and 15.3 ng/g manganese. Regression analysis revealed a significant correlation between placenta weight Z scores and maternal blood metal concentrations: cadmium, 0.0660 (standard error = 0.0074, p < 0.001); selenium, -0.3137 (standard error = 0.0276, p < 0.001); and manganese, 0.1483 (standard error = 0.0110, p < 0.001).

CONCLUSION

This study provides a robust examination of the association between heavy metal exposure and placenta weight. Cadmium and manganese showed a positive correlation with significant differences, whereas selenium showed a negative correlation. Essential elements notably affect placenta weight differently. No significant association was noted between lead or mercury and placenta weight.

Associations of plasma manganese with adverse pregnancy outcomes: Nested case-control studies in a Chinese birth cohort

Both insufficient and excessive manganese exposure are associated with adverse pregnancy outcomes. However, no systematic research has established a standardized reference range for manganese levels with the consideration of the associated health risks during pregnancy. To verify the associations of prenatal manganese exposure with adverse outcomes and to identify a proper reference range for manganese based on health risks, we designed three nested case-control studies on three adverse outcomes including hypertensive disorders of pregnancy (HDP), preterm birth (PTB), and low birth weight (LBW) to investigate the associations with manganese levels. Plasma manganese concentrations in early pregnancy were measured. Conditional logistic regression analyses were used to estimate the associations of manganese levels with adverse outcomes. Restricted cubic spline (RCS) models were used to characterize the dose-response relationship of manganese and each outcome. Nonlinear associations were observed for manganese and adverse outcomes. Compared with women in the middle tertile of plasma manganese, we found that those in the highest tertile had a significantly higher risk of HDP (OR = 1.72, 95% CI: 1.02 to 2.89), that women in the lowest tertile had almost a tripled risk of delivering LBW infants (OR = 2.93, 95% CI: 1.67 to 5.17), and that women both in the lowest and the highest tertiles had significantly higher risks of PTB [OR = 1.83 (95% CI: 1.14 to 2.95); OR = 1.70 (95% CI: 1.05 to 2.76)]. U-shaped associations were found between plasma manganese and risk of PTB and infant LBW. Based on the results of RCS models, we identified a proper plasma manganese range of 1.72-3.18 μg/L, with relatively lower risks of adverse pregnancy outcomes. In conclusion, our study found U-shaped associations between manganese exposure and adverse pregnancy outcomes, and provided an optimal range of manganese concentration for pregnant women, based on health risk considerations.

Particulate matter induces arrhythmia-like cardiotoxicity in zebrafish embryos by altering the expression levels of cardiac development- and ion channel-related genes

Air pollution is a risk factor that increases cardiovascular morbidity and mortality. In this study, we investigated the cardiotoxicity of particulate matter (PM) exposure using a zebrafish embryo model. We found that PM exposure induced cardiotoxicity, such as arrhythmia, during cardiac development. PM exposure caused cardiotoxicity by altering the expression levels of cardiac development (T-box transcription factor 20, natriuretic peptide A, and GATA-binding protein 4)- and ion-channel (scn5lab, kcnq1, kcnh2a/b, and kcnh6a/b)-related genes. In conclusion, this study showed that PM induces the aberrant expression of cardiac development- and ion channel-related genes, leading to arrhythmia-like cardiotoxicity in zebrafish embryos. Our study provides a foundation for further research on the molecular and genetic mechanisms of cardiotoxicity induced by PM exposure.

Content of selected heavy metals in the umbilical cord blood and anthropometric data of mothers and newborns in Poland: preliminary data

The ability to accumulate metals in organs and tissues leads to disturbances in the physiological functioning of the body, causing oxidative stress. This negatively affects the functioning of the placenta and may result in miscarriages, premature birth and fetal growth disorders. The aim of the study was to examine the relationship between the levels of selected heavy metals in umbilical cord blood and anthropometric parameters of mothers and the newborns. Content of elements in umbilical cord blood has been assessed by high-resolution inductively coupled plasma optical emission spectroscopy (ICP-OES). The study results were collected and statistically analyzed using IBM SPSS Statistics software (PS IMAGO). The Pearson correlation coefficient was used to test for associations between selected variables. Regression analysis was conducted to identify predictors of anthropometric parameters of studied women and newborns. The study group consisted of women aged 19-41, whose pregnancy was uncomplicated and were not exposed to heavy metals due to their work or smoking. The following metals were identified in all collected cord blood samples: lead (26.25 ± 9.32 µg/L), zinc (2025.24 ± 717.83 µg/L), copper (749.85 ± 203.86 µg/L), manganese (32.55 ± 13.58 µg/L), chromium (8.34 ± 2.16 µg/L) and selenium (158.46 ± 41.58 µg/L). The conducted statistical analysis indicated the relationship between the copper content in the umbilical cord blood and the weight gain of pregnant women. A significant relationship was observed between newborn head circumference and chromium content. In addition, significant positive correlations were found between the content of zinc and copper, manganese and lead, manganese and selenium, lead and selenium, and lead and chromium in umbilical cord blood. The ratio of zinc to copper concentrations was related to neonatal head circumference. Weight gain in pregnant women is positively correlated with the copper level in umbilical cord blood. There is an association between head circumference at birth and the chromium concentration in umbilical cord blood. Copper and zinc levels in umbilical cord blood are positively correlated with head circumference at birth.

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.

Prenatal polymetallic exposure and small for gestational age: A case-control study in Taiyuan, China

BACKGROUND

Studies focused on independent effects of metals on small for gestational age, failing to account for potential interdependence among metals.

METHODS

In this case-control study, we selected 187 pregnant women and 187 matched controls from the First Hospital of Shanxi Medical University. Determination of 12 elements in the venous blood of pregnant women before delivery by ICP-MS. Logistic regression, weighted quantile sum regression (WQSR) and Bayesian kernel machine regression (BKMR) were used to estimate the overall effect and identify important mixture components that drive the associations with SGA.

RESULTS

An increased risk of SGA was associated with As (OR= 1.06,95%CI: 1.01,1.12), Cd (OR= 1.24,95%CI: 1.04,1.47) and Pb (OR= 1.05,95%CI: 1.02,1.08), while Zn (OR= 0.58,95%CI: 0.45,0.76) and Mn (OR= 0.97,95%CI: 0.94,0.99) were protective factors for SGA. In the WQSR positive model, the mixture of heavy metals has a positive combined effect on SGA (OR= 1.74,95%CI: 1.15, 2.62), with Sb and Cd having the highest weights. The BKMR models confirmed that the metal mixture was associated with decreased risk of SGA when the concentration of 12 metals was between the 30th percentile and the 65th percentile, and Zn and Cd had the greatest independent effect. Zn and SGA may not be linearly correlated, higher Zn level may reduce the effect of Cd on the risk of SGA.

CONCLUSIONS

Our study suggested that exposure to multiple metals was associated with risk of SGA, and the observed association with multiple metals was dominated by Zn, Cd. Sb exposure during pregnancy may also increase the risk of SGA.

Individual, Independent, and Joint Associations of Toxic Metals and Manganese on Hypertensive Disorders of Pregnancy: Results from the MIREC Canadian Pregnancy Cohort

BACKGROUND

Toxic metals, such as lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg), may be associated with a higher risk of gestational hypertension and preeclampsia, whereas manganese (Mn) is an essential metal that may be protective.

OBJECTIVES

We estimated the individual, independent, and joint associations of Pb, Cd, As, Hg, and Mn on the risk of developing gestational hypertension and preeclampsia in a cohort of Canadian women.

METHODS

Metal concentrations were analyzed in first and third trimester maternal blood (n=1,560). We measured blood pressure after 20 wk gestation to diagnose gestational hypertension, whereas proteinuria and other complications defined preeclampsia. We estimated individual and independent (adjusted for coexposure) relative risks (RRs) for each doubling of metal concentrations and examined interactions between toxic metals and Mn. We used quantile g-computation to estimate the joint effect of trimester-specific exposures.

RESULTS

Each doubling of third trimester Pb (RR=1.54; 95% CI: 1.06, 2.22) and first trimester blood As (RR=1.25; 95% CI: 1.01, 1.58) was independently associated with a higher risk of developing preeclampsia. First trimester blood As (RR=3.40; 95% CI: 1.40, 8.28) and Mn (RR=0.63; 95% CI: 0.42, 0.94) concentrations were associated with a higher and lower risk, respectively, of developing gestational hypertension. Mn modified the association with As such that the deleterious association with As was stronger at lower concentrations of Mn. First trimester urinary dimethylarsinic acid concentrations were not associated with gestational hypertension (RR=1.31; 95% CI: 0.60, 2.85) or preeclampsia (RR=0.92; 95% CI: 0.68, 1.24). We did not observe overall joint effects for blood metals.

DISCUSSION

Our results confirm that even low blood Pb concentrations are a risk factor for preeclampsia. Women with higher blood As concentrations combined with lower Mn in early pregnancy were more likely to develop gestational hypertension. These pregnancy complications impact maternal and neonatal health. Understanding the contribution of toxic metals and Mn is of public health importance. https://doi.org/10.1289/EHP10825.

Multidimensional analysis of the essential elements in pregnant women's whole blood and characterization of maternal status by elemental pattern

BACKGROUND

During pregnancy, the fetus needs to obtain a lot of nutrients from the mother, but the micronutrient deficiencies in pregnancy are not clear at present, and there is no reliable basis for nutrient intake and supplement. The purpose of this study was to understand the levels of essential elements in whole blood of pregnant women during various pregnancy stages at different ages and in different regions, to evaluate the deficiency of essential elements in Chinese pregnant women, and to explore the feasibility of using the elemental pattern to characterize maternal status.

METHODS

Whole blood samples of 11222 healthy pregnant women enrolled in different areas of China from Jan-Dec 2019, were analyzed for concentrations of six essential elements including Mn, Cu, Zn, Ca, Mg, and Fe, using the inductively coupled plasma mass spectrometer. A retrospective comparative study during different pregnancy periods at different ages and in different regions in whole blood essential elements content from non-pregnant normal women and pregnant normal women was developed using multivariate statistical analysis. Principal component analysis evaluation elemental pattern was used to characterize pregnancy status of pregnant women.

RESULTS

In general, the levels of six essential elements in whole blood of pregnant women can satisfy the needs of normal physiological activities. With the development of pregnancy, the contents of Cu and Mn increased, while the contents of Fe and Mg decreased, and the contents of Zn and Ca have no noteworthy change. At the same gestation stage, the Cu content in whole blood of elderly pregnant women was higher. There were some differences in whole blood essential elements content of pregnant women in different regions. Principal component analysis and heat map analysis showed the feasibility of using bioinformatics research strategies to identify different pregnancies.

CONCLUSIONS

There are differences in the content of whole blood essential elements of women at different stages of pregnancy in different regions. It was found that there was no obvious deficiency in whole blood essential elements levels of pregnant women in recent years. The pattern of essential elements has a certain application potential in the evaluation of pregnancy and pregnant women's health status.

Birth Size Outcomes in Relation to Maternal Blood Levels of Some Essential and Toxic Elements

Exposures to toxic trace elements and deficiencies of essential trace elements during pregnancy may impact fetal growth. This study was conducted to determine the association between maternal blood levels of essential elements including manganese (Mn), copper (Cu), and zinc (Zn) and toxic elements including arsenic (As), cadmium (Cd), and lead (Pb) at the first trimester with neonatal anthropometric parameters. This cross-sectional study was conducted in 2019-2020 in Isfahan, Iran. Overall, 263 mother-infant pairs were recruited in the first trimester of pregnancy. Maternal whole blood was collected, and essential and toxic elements were determined by mass spectrometry (ICP-MS)-based method. Birth size measurements were performed according to standardized protocols. Geometric means and standard deviations of maternal blood concentrations of Mn, Cu, Zn, As, Cd, and Pb were 3.94 ± 0.82, 5.22 ± 0.57, 7.67 ± 0.58, 2.21 ± 0.77, - 0.59 ± 0.98, and 3.23 ± 0.72 µg/l, respectively. Mean age of mothers was 29.94 ± 5.22 years. Thirty-one (12.1%) neonates were preterm. Maternal blood Pb levels were negatively correlated with birth weight (β = - 0.22 (CI 95%: - 0.38, - 0.05) p = 0.010) and marginally with birth head circumference (β = - 0.14(CI 95%: - 0.29, 0.02), P = 0.094) after adjustment for potential confounder variables. There was no significant association between Mn, Cu, Zn, As, Cd, and birth size measurements. Reverse association was found between maternal blood Pb levels and birth weight and birth head circumference. There is limited evidence related to the association between essential and toxic elements during pregnancy with birth size measurements and pregnancy disorders. More studies are suggested to assess of the effect of the trace elements and birth outcomes.

Maternal exposure to heavy metals and risk for severe congenital heart defects in offspring

BACKGROUND

Congenital heart defects (CHDs) are the most common congenital malformations with a complex etiology, and environmental factors play an important role. Large epidemiology studies on prenatal exposure to selected heavy metals and their association with risk for CHDs are scarce and joint effects are not well understood.

OBJECTIVES

To examine the association between prenatal exposure to selected heavy metals and risk for CHDs.

METHODS

Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the maternal plasma concentrations of arsenic, cadmium, mercury, lead, and manganese were in 303 CHD cases and 303 healthy controls that were recruited in eight hospitals in China. Generalized linear mixed model (GLMM) and Bayesian kernel machine regression (BKMR) were fitted to evaluate the individual and joint effects of metal concentrations on CHDs.

RESULTS

In GLMM, two metals were each significantly associated with an increased risk for CHDs [adjusted odds ratio (95% confidence interval): mercury, 2.88 (1.22-6.77); lead, 2.74 (1.00-7.57)]. In BKMR, CHD risk increased with mixture levels of the five metals when their concentrations were at the 40th percentile or higher, compared to when all metals were below their 35th percentile, and mercury was the major metal that contributed to the mixture effect. The interaction between mercury and lead was observed in BKMR.

CONCLUSIONS

Using metal concentrations in maternal plasma obtained during the second or third trimester as exposure markers, we found that the risk of CHDs increased with the levels of the mixtures of As, Cd, Hg, Pb, and Mn, with Hg being the most important contributor to the mixture effect.

Prenatal Exposure to Mercury, Manganese, and Lead and Adverse Birth Outcomes in Suriname: A Population-Based Birth Cohort Study

Globally, adverse birth outcomes are increasingly linked to prenatal exposure to environmental contaminants, such as mercury, manganese, and lead. This study aims to assess an association between prenatal exposure to mercury, manganese, and lead and the occurrence of adverse birth outcomes in 380 pregnant women in Suriname. The numbers of stillbirths, preterm births, low birth weights, and low Apgar scores were determined, as well as blood levels of mercury, manganese, lead, and relevant covariates. Descriptive statistics were calculated using frequency distributions. The associations between mercury, manganese, and lead blood levels, on the one hand, and adverse birth outcomes, on the other hand, were explored using contingency tables, tested with the χ2-test (Fisher's exact test), and expressed with a p value. Multivariate logistic regression models were computed to explore independent associations and expressed as (adjusted) odds ratios (aOR) with 95% confidence intervals (CI). The findings of this study indicate no statistically significant relationship between blood mercury, manganese, or lead levels and stillbirth, preterm birth, low birth weight, and low Apgar score. However, the covariate diabetes mellitus (aOR 5.58, 95% CI (1.38-22.53)) was independently associated with preterm birth and the covariate hypertension (aOR 2.72, 95% CI (1.081-6.86)) with low birth weight. Nevertheless, the observed high proportions of pregnant women with blood levels of mercury, manganese, and lead above the reference levels values of public health concern warrants environmental health research on risk factors for adverse birth outcomes to develop public health policy interventions to protect pregnant Surinamese women and their newborns from potential long-term effects.

Examination of Trace Metals and Their Potential Transplacental Transfer in Pregnancy

With the ever-growing concern for human health and wellbeing, the prenatal period of development requires special attention since fetuses can be exposed to various metals through the mother. Therefore, this study explored the status of selected toxic (Pb, Cd, Ni, As, Pt, Ce, Rb, Sr, U) and essential trace metals (Mn, Co, Cu, Zn, Se) in the umbilical cord (UC) sera, maternal sera, and placental tissue samples of 92 healthy women with normal pregnancies. A further aim focuses on the potential transplacental transfer of these trace metals. Based on the obtained levels of investigated elements in clinical samples, it was observed that all of the trace metals cross the placental barrier and reach the fetus. Furthermore, statistical analysis revealed significant differences in levels of toxic Ni, As, Cd, U, Sr, Rb, and essential Mn, Cu, and Zn between all three types of analyzed clinical samples. Correlation analysis highlighted As to be an element with levels that differed significantly between all tested samples. Principal component analysis (PCA) was used to enhance these findings. PCA demonstrated that Cd, Mn, Zn, Rb, Ce, U, and Sr were the most influential trace metals in distinguishing placenta from maternal and UC serum samples. As, Co, and Cu were responsible for the clustering of maternal serum samples, and PCA demonstrated that the Pt level in UC sera was responsible for the clustering of these samples. Overall, the findings of this study could contribute to a better understanding of transplacental transfer of these trace metals, and shed a light on overall levels of metal exposure in the population of healthy pregnant women and their fetuses.

Cord Blood Manganese Concentrations in Relation to Birth Outcomes and Childhood Physical Growth: A Prospective Birth Cohort Study

Gestational exposure to manganese (Mn), an essential trace element, is associated with fetal and childhood physical growth. However, it is unclear which period of growth is more significantly affected by prenatal Mn exposure. The current study was conducted to assess the associations of umbilical cord-blood Mn levels with birth outcomes and childhood continuous physical development. The umbilical cord-blood Mn concentrations of 1179 mother-infant pairs in the Sheyang mini birth cohort were measured by graphite furnace atomic absorption spectrometry (GFAAS). The association of cord-blood Mn concentrations with birth outcomes, and the BMI z-score at 1, 2, 3, 6, 7 and 8 years old, were estimated separately using generalized linear models. The relationship between prenatal Mn exposure and BMI z-score trajectory was assessed with generalized estimating equation models. The median of cord-blood Mn concentration was 29.25 μg/L. Significantly positive associations were observed between Mn exposure and ponderal index (β, regression coefficient = 0.065, 95% CI, confidence interval: 0.021, 0.109; p = 0.004). Mn exposure was negatively associated with the BMI z-score of children aged 1, 2, and 3 years (β = -0.383 to -0.249, p < 0.05), while no significant relationships were found between Mn exposure and the BMI z-score of children at the age of 6, 7, and 8 years. Prenatal Mn exposure was related to the childhood BMI z-score trajectory (β = -0.218, 95% CI: -0.416, -0.021; p = 0.030). These results indicated that prenatal Mn exposure was positively related to the ponderal index (PI), and negatively related to physical growth in childhood, which seemed most significant at an early stage.

Correlation between concentrations of four heavy metals in cord blood and childhood blood of Jamaican children

This study investigated whether the concentrations of four metals [lead (Pb), mercury (Hg), manganese (Mn), and aluminum (Al)] are correlated in cord blood and childhood blood samples from Jamaican children. Cord blood samples were obtained from 21 pregnant women enrolled in the second Jamaican Birth Cohort Study from July 1, 2011 to September 30, 2011, and blood samples were drawn from their children who participated in a follow up study when the children were 4-8 years old. Correlations were assessed by the Pearson or the Spearman's rank correlation coefficient. The mean ages of children at the childhood visit and their mother at the child's birth were 5.5 years and 29.8 years, respectively. About 47.6% of children were male. Statistically significant correlations between cord blood and childhood blood concentrations of Pb (r_Spearman =0.45; P = 0.04) and Mn (r_Pearson=0.48; P = 0.03) were found, and these remained significant when adjusted for the child's sex, age, or both. For Al and Hg, r_Spearman=0.29 and 0.08, respectively, but the correlations were not statistically significant (both P ≥ 0.20). A significant correlation between cord blood and childhood blood Pb concentrations for children 4-8 years old has not been previously reported.

Performance of urine, blood, and integrated metal biomarkers in relation to birth outcomes in a mixture setting

BACKGROUND

Studies on the health effects of metal mixtures typically utilize biomarkers measured in a single biological medium, such as blood or urine. However, the ability to evaluate mixture effects are limited by the uncertainty whether a unified medium can fully capture exposure for each metal. Therefore, it is important to compare and assess metal mixtures measured in different media in epidemiology studies.

OBJECTIVES

The aim of this study was to examine the mixture predictive performance of urine and blood metal biomarkers and integrated multi-media biomarkers in association with birth outcomes.

METHODS

In our analysis of 847 women from the Puerto Rico PROTECT Cohort, we measured 10 essential and non-essential metals in repeated and paired samples of urine and blood during pregnancy. For each metal, we integrated exposure estimates from paired urine and blood biomarkers into multi-media biomarkers (MMBs), using intraclass-correlation coefficient (ICC) and weighted quantile sum (WQS) approaches. Using Ridge regressions, four separate Environmental risk scores (ERSs) for metals in urine, blood, MMBICC, and MMBWQS were computed as a weighted sum of the 10 metal concentrations. We then examined associations between urine, blood, and multi-media biomarker ERSs and birth outcomes using linear and logistic regressions, adjusting for maternal age, maternal education, pre-pregnancy body mass index (BMI), and second-hand smoke exposure. The performance of each ERS was evaluated with continuous and tertile estimates and 95% confidence intervals of the odds ratio of preterm birth using area under the curve (AUC).

RESULTS

Pb was the most important contributor of blood ERS as well as the two integrated multi-media biomarker ERSs. Individuals with high ERS (3rd tertile) showed increased odds of preterm birth compared to individuals with low ERS (1st tertile), with 2.8-fold (95% CI, 1.49 to 5.40) for urine (specific gravity corrected); 3.2- fold (95% CI, 1.68 to 6.25) for blood; 3.9-fold (95% CI, 1.72 to 8.66) for multi-media biomarkers composed using ICC; and 5.2-fold (95% CI, 2.34 to 11.42) for multi-media biomarkers composed using WQS. The four ERSs had comparable predictive performances (AUC ranging from 0.64 to 0.68) when urine is examined with specific gravity corrected concentrations.

CONCLUSIONS

Within a practical metal panel, measuring metals in either urine or blood may be an equally good approach to evaluate the metals as a mixture. Applications in practical study design require validation of these methods with other cohorts, larger panels of metals and within the context of other adverse health effects of interest.

Umbilical Cord Blood Metal Mixtures and Birth Size in Bangladeshi Children

BACKGROUND

Studies have evaluated environmental exposure to toxic metals such as arsenic (As), cadmium (Cd), manganese (Mn), or lead (Pb) on birth size; however, information on potential effects of exposures to metal mixtures is limited.

OBJECTIVES

We assessed the association between metal mixtures (As, Cd, Mn, Pb) in umbilical cord blood and neonate size in Bangladeshi children.

METHODS

In this birth cohort study, pregnant women who were ≥18 years of age with an ultrasound-confirmed singleton pregnancy of ≤16wk gestation were recruited from two Bangladesh clinics between 2008 and 2011. Neonate size metrics were measured at the time of delivery. Metals in cord blood were measured using inductively coupled plasma mass spectrometry. We employed multivariable linear regression and Bayesian kernel machine regression (BKMR) to estimate associations of individual metals and metal mixtures with birth size parameters.

RESULTS

Data from 1,088 participants was assessed. We found a significant negative association between metal mixture and birth length and head circumference when all metal concentrations were above the 60th and 55th percentiles, respectively, compared with the median. An interquartile range (IQR) increase in log Cd concentration {log[Cd (in micrograms per deciliter)] IQR=2.51} was associated with a 0.13-standard deviation (SD) decrease in mean birth length (95% CI: -0.25, -0.02) and a 0.17-SD decrease in mean head circumference (95% CI: -0.28, -0.05), based on linear regression models adjusted for covariates and the other metals. An IQR increase in log Mn concentration {log[Mn (in micrograms per deciliter)] IQR=0.69} was associated with a 0.07-SD decrease in mean birth weight (95% CI: -0.15, 0.002).

DISCUSSION

Metal mixtures in cord blood were associated with reduced birth size in Bangladeshi children. Results from linear regression models adjusted and the BKMR mixtures analyses suggest adverse effects of Cd and Mn, as individual metal exposures, on birth size outcomes. https://doi.org/10.1289/EHP7502.

Psychosocial status modifies the effect of maternal blood metal and metalloid concentrations on birth outcomes

BACKGROUND

Metal exposure and psychosocial stress in pregnancy have each been associated with adverse birth outcomes, including preterm birth and low birth weight, but no study has examined the potential interaction between them.

OBJECTIVES

We examined the modifying effect of psychosocial stress on the association between metals and birth outcomes among pregnant women in Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) birth cohort study.

METHODS

In our analysis of 682 women from the PROTECT study, we measured 16 essential and non-essential metals in blood samples at two time points. We administered questionnaires to collect information on depression, perceived stress, social support, and life experience during pregnancy. Using K-means clustering, we categorized pregnant women into one of two groups: "good" and "poor" psychosocial status. We then evaluated whether the effect of blood metals (geometric average) on adverse birth outcomes (gestational age, preterm birth [overall and spontaneous], birth weight z-score, small for gestation [SGA], large for gestation [LGA]) vary between two clusters of women, adjusting for maternal age, maternal education, pre-pregnancy body mass index (BMI), and second-hand smoke exposure.

RESULTS

Blood manganese (Mn) was associated with an increased odds ratio (OR) of overall preterm birth (OR/interquartile range [IQR] = 2.76, 95% confidence interval [CI] = 1.25, 6.12) and spontaneous preterm birth (OR/IQR: 3.68, 95% CI: 1.20, 6.57) only among women with "poor" psychosocial status. The association between copper (Cu) and SGA was also statistically significant only among women having "poor" psychosocial status (OR/IQR: 2.81, 95% CI: 1.20, 6.57). We also observed associations between nickel (Ni) and preterm birth and SGA that were modified by psychosocial status during pregnancy.

CONCLUSIONS

Presence of "poor" psychosocial status intensified the adverse associations between Mn and preterm birth, Cu and SGA, and protective effects of Ni on preterm. This provides evidence that prenatal psychosocial stress may modify vulnerability to metal exposure.

A Nonlinear Relation Between Maternal Red Blood Cell Manganese Concentrations and Child Blood Pressure at Age 6-12 y: A Prospective Birth Cohort Study

BACKGROUND

Although manganese (Mn) is an essential trace element and a common component of most multivitamins on the market, an adverse effect on blood pressure (BP) has been reported in adults. In addition, the longitudinal relation between prenatal Mn status and childhood BP is still unknown.

OBJECTIVE

This study investigated the association between prenatal Mn concentrations and risk of elevated BP at ages 3-12 y.

METHOD

The analyses included 1268 mother-child dyads who were enrolled at birth and followed prospectively at the Boston Medical Center. Maternal RBC Mn concentrations were measured by inductively coupled plasma mass spectrometry, using RBCs collected within 1-3 d after delivery (reflecting late-pregnancy Mn exposure). Child elevated BP was defined as systolic or diastolic BP ≥90th percentile for a given age, sex and height. Multivariate logistic regression models were conducted. Path analysis was applied to mediation estimation.

RESULTS

The median (IQR) maternal RBC Mn concentration was 37.5 (29.2-48.5) μg/L. The rate of child elevated BP at ages 3-12 y was 25%. Both the lowest and highest quartiles of maternal RBC Mn concentrations were associated with higher risk of elevated BP among children aged 6-12 y (OR: 1.52; 95% CI: 1.04, 2.21 and OR: 1.65; 95% CI: 1.13, 2.40, respectively) compared with those in the second and third quartiles. Gestational age and fetal growth mediated the association between low maternal RBC Mn (first quartile) and child elevated BP, explaining 25% of the association, but not for high (fourth quartile) maternal RBC Mn concentrations. No association was found between maternal RBC Mn concentrations and BP among children aged 3-5 y.

CONCLUSION

We found a nonlinear association between maternal RBC Mn concentrations and elevated BP among children aged 6-12 y from a high-risk, predominantly minority population. Our findings warrant further investigation.

Developmental toxicity of cadmium in infants and children: a review

Several millions of people are exposed to cadmium worldwide due to natural and anthropogenic activities that led to their widespread distribution in the environment and have shown potential adverse effects on the kidneys, liver, heart and nervous system. Recently human and animal-based studies have been shown that In utero and early life exposure to cadmium can have serious health issues that are related to the risk of developmental disabilities and other outcomes in adulthood. Since, cadmium crosses the placental barrier and reaches easily to the fetus, even moderate or high-level exposure of this metal during pregnancy could be of serious health consequences which might be reflected either in the children’s early or later stages of life. Mortality from various diseases including cancer, cardiovascular, respiratory, kidney and neurological problems, correlation with In utero or early life exposure to cadmium has been found in epidemiological studies. Animal studies with strong evidence of various diseases mostly support for the human studies, as well as suggested a myriad mechanism by which cadmium can interfere with human health and development. More studies are needed to establish the mechanism of cadmium-induced toxicity with environmentally relevant doses in childhood and later life. In this review, we provide a comprehensive examination of the literature addressing potential long- term health issues with In utero and early life exposure to cadmium, as well as correlating with human and animal exposure studies.

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.

Circulating metal concentrations, inflammatory cytokines and gestational weight gain: Shanghai MCPC cohort

OBJECTIVES

Based on a prospective birth cohort, we aimed to investigate the associations between maternal circulating metals exposure and gestational weight gain (GWG) across pregnancy, and explore whether maternal inflammatory cytokines could contribute to the GWG changes associated with metals exposure.

METHODS

A total of 234 pregnant women from the Shanghai Maternal-Child Pairs cohort were enrolled in this panel study. 547 blood and serum samples were collected from pregnant women during three follow-up visits, and the circulating concentrations of 27 metals were determined by using the ICP-MS method. Five inflammatory cytokines in serum samples were measured through multiplexed immunoassays. The linear mixed models were used to estimate the association between each ln-transformed metal concentration and GWG across pregnancy. Robust generalized linear regression models were used to estimate the associations among circulating metals, GWG, and inflammatory cytokines.

RESULTS

The GWG during pregnancy was 13.76 ± 1.40 kg. The concentrations Co, Zn, Mo, B, Ag and Te in second or third trimesters were significantly higher than those in early second trimester. The concentration of Mg decreased with the increase of pregnant weeks and no significant statistical differences were found in the concentrations of other metals in different trimesters. Among the detected 26 metals, Li and Sr concentrations were positively associated with GWG in the third trimester. The GWG increased by 0.100 kg (95% CI 0.005, 0.195) and 0.120 kg (95% CI 0.009, 0.232) with each one ln-concentration increase in circulating Li and Sr concentrations, respectively. Concentrations of Li and Sr in the third trimester were positively associated with tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6, but negatively associated with growth differentiation factor-15 (GDF-15) significantly. Besides, IL-6 and GDF-15 levels were associated with the increase or decrease of overall pregnancy GWG, respectively.

CONCLUSIONS

Results showed that maternal exposure to Li and Sr were associated with increased GWG, in which maternal IL-6 and GDF-15 could contribute to the associations between metal exposures and GWG in pregnant women.

Maternal blood metal and metalloid concentrations in association with birth outcomes in Northern Puerto Rico

BACKGROUND

In previous studies, exposures to heavy metals such as Pb and Cd have been associated with adverse birth outcomes; however, knowledge on effects at low levels of exposure and of other elements remain limited.

METHOD

We examined individual and mixture effects of metals and metalloids on birth outcomes among 812 pregnant women in the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) cohort. We measured 16 essential and non-essential metal(loid)s in maternal blood collected at 16-20 and 24-28 weeks gestation. We used linear and logistic regression to independently examine associations between geometric mean (GM) concentrations of each metal across visits and gestational age, birthweight z-scores, preterm birth, small for gestational age (SGA), and large for gestational age (LGA). We evaluated effect modification with infant sex*metal interaction terms. To identify critical windows of susceptibility, birth outcomes were regressed on visit-specific metal concentrations. Furthermore, average metal concentrations were divided into tertiles to examine the potential for non-linear relationships. We used elastic net (ENET) regularization to construct Environmental Risk Score (ERS) as a metal risk score and Bayesian Kernel Machine Regression (BKMR) to identify individual metals most critical to each outcome, accounting for correlated exposures.

RESULTS

In adjusted models, an interquartile range (IQR) increase in GM lead (Pb) was associated with 1.63 higher odds of preterm birth (95%CI = 1.17, 2.28) and 2 days shorter gestational age (95% CI = -3.1, -0.5). Manganese (Mn) and zinc (Zn) were also associated with higher odds of preterm birth and shorter gestational age; the associations were strongest among the highest tertile for Mn and among females for Zn. Mercury (Hg) was associated with higher risk of preterm birth at the later window of pregnancy. Ni measured later in pregnancy was associated with lower odds of SGA. ENET and BKMR models selected similar metals as "important" predictors of birth outcomes. The association between ERS and preterm birth was assessed and the third tertile of ERS was significantly associated with an elevated odds ratio of 2.13 (95% CI = 1.12, 5.49) for preterm birth compared to the first tertile.

CONCLUSION

As the PROTECT cohort has lower Pb concentrations (GM = 0.33 μg/dL) compared to the mainland US, our findings suggest that low-level prenatal lead exposure, as well as elevated Mn and Zn exposure, may adversely affect birth outcomes. Improved understanding on environmental factors contributing to preterm birth, together with sustainable technologies to remove contamination, will have a direct impact in Puerto Rico and elsewhere.

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.

Blood manganese levels during pregnancy and postpartum depression: A cohort study among women in Mexico

BACKGROUND

Occupational studies have shown an association between elevated Mn exposure and depressive symptoms. Blood Mn (BMn) naturally rises during pregnancy due to mobilization from tissues, suggesting it could contribute to pregnancy and postpartum depressive symptoms.

OBJECTIVES

To assess the association between BMn levels during pregnancy and postpartum depression (PPD), creating opportunities for possible future interventions.

METHODS

We studied 561 women from the reproductive longitudinal Programming Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) cohort in Mexico City. BMn was measured at the 2nd and 3rd trimesters, as well as delivery. The Edinburgh Postnatal Depression Scale (EPDS) was used to assess PPD symptoms at 12-months postpartum. We used a generalized linear model assuming a Poisson distribution to assess the association between BMn levels and PPD, with adjustments for age, stress and depressive symptoms during pregnancy, education, socioeconomic status, and contemporaneous blood lead levels.

RESULTS

The mean ± standard deviation (SD) EPDS score at 12-months postpartum was 6.51 ± 5.65, and 17.11% of women met the criteria for possible PPD (score ≥ 13). In adjusted models, BMn during the 3rd trimester (β: 0.13, 95% CI: 0.04-0.21) and BMn levels averaged at the 2nd and 3rd trimester (β: 0.14, 95% CI: 0.02-0.26) had a positive association with EPDS scores at 12 months postpartum. BMn at the 2nd trimester (β: 0.07, 95% CI: -0.09-0.22) and delivery (β: 0.03, 95% CI: -0.04-0.10) had a non-significant positive association with EPDS scores at 12-months postpartum. Stress and depressive symptoms during pregnancy was associated with higher EPDS scores at 12-months postpartum in all of the adjusted models but were only significant when either BMn during 3rd trimester or BMn averaged across 2nd and 3rd trimester was assessed as the exposure.

DISCUSSION

Our results demonstrate that elevated BMn levels during pregnancy predict PPD symptoms and could be a potential pathway for intervention and prevention of PPD.

Prenatal exposure to metal mixture and sex-specific birth outcomes in the New Hampshire Birth Cohort Study

BACKGROUND

In utero exposure to individual metals may impact fetal growth, though little is known about the effects of exposure to metal mixtures. Therefore, we investigated joint effects of in utero exposure to a mixture of As (arsenic), Mn (manganese), and Pb (lead) on newborn outcomes in a United States population.

METHODS

Concentrations of As, Mn, and Pb were determined in maternal postpartum toenail samples, a biomarker of in utero exposure, from 989 maternal-infant pairs (492 females and 497 males). Newborns' anthropometric characteristics, including head circumference, length, and weight, were obtained from medical records. The joint effects of the three metals were modeled using Bayesian kernel machine regression and linear regression. Both sex-combined and sex-stratified statistical analyses were performed.

RESULTS

We observed an inverted-U-shape association between maternal toenail Mn concentrations and newborn head circumference, particularly among female infants. Concentrations of Pb were related to reduced head circumference, weight, and length, especially among females at lower concentrations of the other metals. Overall, toenail As concentrations were related to reduced head circumference, especially among males, and an increase in birth length and weight among females. We found little evidence of As interactions with other metals within the mixture.

CONCLUSIONS

Our findings suggest that in utero metal mixture exposures may influence birth outcomes, and that such relations may differ by infant sex.

An Important Need to Monitor from an Early Age the Neurotoxins in the Blood or by an Equivalent Biomarker

An overwhelming amount of evidence now suggests that some people are becoming overloaded with neurotoxins. This is mainly from changes in their living environment and style, coupled with the fact that all people are different and display a broad distribution of genetic susceptibilities. It is important for individuals to know where they lie concerning their ability to either reject or retain toxins. Everyone is contaminated with a certain baseline of toxins that are alien to the body, namely aluminum, arsenic, lead, and mercury. Major societal changes have modified their intake, such as vaccines in enhanced inoculation procedures and the addition of sushi into diets, coupled with the ever-present lead, arsenic, and traces of manganese. It is now apparent that no single toxin is responsible for the current neurological epidemics, but rather a collaborative interaction with possible synergistic components. Selenium, although also a neurotoxin if in an excessive amount, is always present and is generally more present than other toxins. It performs as the body’s natural chelator. However, it is possible that the formation rates of active selenium proteins may become overburdened by other toxins. Every person is different and it now appears imperative that the medical profession establish an individual’s neurotoxicity baseline. Moreover, young women should certainly establish their baselines long before pregnancy in order to identify possible risk factors.

Prenatal manganese and cord blood mitochondrial DNA copy number: Effect modification by maternal anemic status

INTRODUCTION

Manganese (Mn) is an essential nutrient but also a toxicant at high exposures, when it can induce oxidative stress (OS). Mn uptake is inversely correlated with iron status, therefore anemic individuals may be more susceptible to Mn overload induced-OS, which can manifest as changes in mitochondrial DNA copy number (mtDNA CN). Our objectives were to: 1) determine stage-specific associations of prenatal Mn exposure with cord blood MtDNA CN; and 2) investigate effect modification by maternal anemia, ferritin, and mean corpuscular volume (MCV).

MATERIALS AND METHODS

We measured whole blood Mn, hemoglobin, serum ferritin, and MCV in the 2nd and 3rd trimester, in maternal blood at birth, and in cord blood from a prospective birth cohort in Mexico City, Mexico (n = 485). We then extracted DNA from cord blood leukocytes to determine mtDNA CN. We used robust regression to measure associations between Mn and mtDNA CN at each trimester and at birth. Anemia (hemoglobin ≤11 g/dL), iron deficiency (ferritin ≤15 ng/mL) and MCV (stratified at median), were examined as effect modifiers.

RESULTS

Mn levels increased throughout pregnancy, and Mn was inversely correlated with ferritin. We observed a positive association between Mn in the 3rd trimester and Mn in cord blood and mtDNA CN (β = 0.04-0.05; 95% CI = 0.01, 0.08). Anemia significantly modified the association between mtDNA CN and Mn in the 2nd trimester. We found a positive association between 2nd trimester Mn and mtDNA CN in mothers with normal hemoglobin, and a negative association in those with low hemoglobin. (βhigh = 0.06; 95% CI = 0.01, 0.11; p = 0.01 and βlow = -0.06; 95% CI = 0.03, -0.13; p = 0.06). No associations were detected between anemia, iron deficiency and MCV and mtDNA CN.

CONCLUSIONS

Maternal blood Mn in the 3rd trimester and in cord blood was positively associated with mtDNA CN, suggesting that higher late pregnancy prenatal Mn exposures can impact newborn mitochondria by promoting OS. Furthermore, 2nd trimester Mn was positively associated with mtDNA in non-anemic mother-child pairs but inversely associated in anemic individuals, indicating potential interactions between Mn and chronic anemia.

Associations between the Level of Trace Elements and Minerals and Folate in Maternal Serum and Amniotic Fluid and Congenital Abnormalities

Congenital birth defects may result in a critical condition affecting the baby, including severe fetal/neonatal handicap and mortality. Several studies have shown that genetic, nutritional, and environmental factors may have an impact on fetal development and neonatal health. The relevance of essential and toxic elements on fetal development has not yet been fully investigated, and the results of recent research indicate that these elements may be crucial in the assessment of the risk of malformations in neonates. We determined the association between essential and toxic elements and the level of folate in maternal serum (MS) and amniotic fluid (AF), along with neonatal abnormalities. A total of 258 pregnant Polish women in the age group of 17⁻42 years participated in this study. AF and MS were collected during vaginal delivery or during cesarean section. An inductively coupled plasma mass spectrometry technique was used to determine the levels of various elements in AF and MS. The results of this exploratory study indicate that the levels of essential and toxic elements are associated with fetal and newborn anatomical abnormalities and growth disorders.

Associations of blood metal exposure with thyroid hormones in Chinese pregnant women: A cross-sectional study

BACKGROUND

Few epidemiological studies have investigated associations of exposure to multiple metals with thyroid hormone homeostasis, especially for the pregnant women.

METHODS

Among all the 1644 participants enrolled in Hangzhou Birth Cohort Study (HBCS) at baseline, a total of 915 pregnant women with complete data of interest were analyzed. Eleven metals were measured in blood samples collected around 25 weeks gestation. Serum levels of thyroid hormones including free triiodothyronine (FT3), total triiodothyronine (TT3), free thyroxine (FT4), total thyroxine (TT4) and thyroid-stimulating hormone (TSH) were abstracted from the medical records. Relationships between tertiles of metal levels (setting the lowest tertile as the reference) and percent changes in thyroid hormones were estimated by multivariable adjusted linear regression models.

RESULTS

Five metals [arsenic (As), selenium (Se), manganese (Mn), nickel (Ni), antimony (Sb)] were significantly linked to decreased levels of one or more thyroid hormones based on trend tests in the single-metal models. Percent changes [95% confidence intervals (CIs)] in thyroid hormones for the third tertiles of metals remained significant between FT3 and As [-3.53% (-5.48%, -1.54%)]; and between TT3 and As [-4.19% (-7.00%, -1.31%)]; and between FT4 and Mn [-2.05% (-3.49%, -0.58%)], Sb [-1.99% (-3.44%, -0.52%)] in the multiple-metal models.

CONCLUSIONS

Thyroid hormone concentrations were reversely related to the levels of blood metals of As, Mn and Sb among Chinese pregnant women. Additional prospective studies are warranted to confirm the causality. Paper capsule: Exposure to multiple metals was reversely associated with one or more thyroid hormones in the Chinese pregnant women.