Moderate Prenatal Cadmium Exposure and Adverse Birth Outcomes: a Role for Sex-Specific Differences?

Associations between prenatal metal exposure and growth rate in children: Based on Hangzhou Birth Cohort Study

BACKGROUND

It has been reported that prenatal metal exposure is associated with child anthropometry. However, studies focusing on the growth rate of anthropometry among children have not been conducted. This study aimed to examine associations between the exposure of multiple metals during pregnancy and the growth rate of anthropometry among offspring.

METHODS

743 mother-child pairs from the Hangzhou Birth Cohort Study (HBCS) were included. Levels of eleven metals in mother's blood during pregnancy were measured. Offspring had a mean of 5.7 measurements on anthropometric indicators including weight, length/height, head circumference, and body mass index (BMI) within 1.5 years of birth. Generalized estimating equation (GEE) model was used to investigate the associations between maternal metal exposure and growth rate of anthropometric indicators in children. Stratification analysis by sex was also examined.

RESULTS

Levels of selenium (Se, β = 0.213, 95 % CI = 0.017 to 0.409, P = 0.033) were positively associated with length/height gain per month in children. Levels of chromium (Cr, β = 0.025, 95 % CI = 0.018 to 0.033, P < 0.001) were positively associated with the rate of weight gain. Levels of manganese (Mn, β = -0.030, 95 % CI = -0.052 to -0.008, P = 0.009) and cobalt (Co, β = -0.012, 95 % CI = -0.024 to -0.000, P = 0.044) were inversely associated with growth rate of head circumference. Children with higher maternal Mn levels had a lower BMI change rate. Associations between metals and growth rate were stronger in girls than in boys. Besides, significant associations between metal mixtures and growth rate were found.

CONCLUSION

Prenatal exposure to Se, Cr, Mn, and Co was associated with growth rate in children, with sex-specific disparities. Our results suggested important effects of maternal exposure to multiple metals on development in offspring.

Prenatal air pollution exposure in relation to the telomere-mitochondrial axis of aging at birth: A systematic review

BACKGROUND

Telomere length (TL) and mitochondrial DNA (mtDNA) are central markers of vital biological mechanisms, including cellular aging. Prenatal air pollution exposure may impact molecular markers of aging leading to adverse health effects.

OBJECTIVE

To perform a systematic review on human population-based studies investigating the association between prenatal air pollution exposure and TL or mtDNA content at birth.

METHODOLOGY

Searches were undertaken on PubMed and Web of Science until July 2023. The framework of the review was based on the PRISMA-P guidelines.

RESULTS

Nineteen studies studied prenatal air pollution and TL or mtDNA content at birth. Studies investigating TL or mtDNA content measured at any other time or did not evaluate prenatal air pollution were excluded. Twelve studies (including 4381 participants with study sample range: 97 to 743 participants) investigated newborn TL and eight studies (including 3081 participants with study sample range: 120 to 743 participants) investigated mtDNA content at birth. Seven studies focused on particulate matter (PM2.5) exposure and newborn TL of which all, except two, showed an inverse association in at least one of the gestational trimesters. Of the eight studies on mtDNA content, four focused on PM2.5 air pollution with two of them reporting an inverse association. For PM2.5 exposure, observations on trimester-specific effects were inconsistent. Current literature showing associations with other prenatal air pollutants (including nitrogen oxides, sulfur dioxide, carbon monoxide and ozone) is inconsistent.

CONCLUSION

This review provides initial evidence that prenatal PM2.5 exposure impacts the telomere-mitochondrial axis of aging at birth. The current evidence did not reveal harmonious observations for trimester-specific associations nor showed consistent effects of other air pollutants. Future studies should elucidate the specific contribution of prenatal exposure to pollutants other than PM in relation to TL and mtDNA content at birth, and the potential later life health consequences.

Cadmium as an ovarian toxicant: A review

Cadmium (Cd) is a ubiquitous heavy metal toxicant with no biological function in the human body. Considerably, because of its long biological half-life and very low excretion rate, Cd is inclined to accumulate and cause deleterious effects on various body organs (e.g., liver, kidney, and ovary) in humans and animals. Ovaries are the most vulnerable targets of Cd toxicity. Cd has been shown to induce oxidative stress, follicular atresia, hormonal imbalance, and impairment of oocyte growth and development. Moreover, Cd toxicity has been associated with increasing incidences of menstrual disorders, pregnancy loss, preterm births, delayed puberty, and female infertility. Therefore, it is crucial to understand how Cd poisoning impacts specific ovarian processes for the development of preventive interventions to enhance female fertility. The current review attempts to collate the recent findings on Cd-induced oxidative stress, follicular apoptosis, steroid synthesis inhibition, and teratogenic toxicity, along with their possible mechanisms in the ovarian tissue of different animal species. Additionally, the review also summarizes the studies related to the use of many antioxidants, medicinal herbs, and other compounds as remedial approaches for managing Cd-induced ovarian toxicity.

Effects of heavy metal exposure during pregnancy on birth outcomes

Exposure to heavy metals such as lead, cadmium, and mercury poses serious health risks to pregnant women because of their high toxicity. In this study, we investigated the associations of heavy metal exposure with birth outcomes of Korean infants. Data of 5,215 women between 2015 and 2019 were analyzed. This study was part of the Korean Children's Environmental Health (Ko-CHENS) study. Linear regression and logistic regression analyses were used to examine effects of concentrations of lead, cadmium, and mercury on birth weight, small for gestational age, and large for gestational age after adjusting for maternal age groups, parity, infant sex, education, income, smoking, drinking, body mass index, stillbirth, premature birth, diabetes, hypertension, and gestational diabetes. Besides adjusting for these covariates, each metal was mutually adjusted to estimate birth weight and large for gestational age status. Maternal cadmium concentrations during early pregnancy (β =  - 39.96; 95% confidence interval (CI): - 63.76, - 16.17) and late pregnancy (β =  - 37.24; 95% CI - 61.63, - 12.84) were significantly associated with birth weight. Cadmium levels during early pregnancy (adjusted OR = 0.637; 95% CI 0.444, 0.912) were also associated with large for gestational age status. Our findings suggest that prenatal cadmium exposure, even at a low level of exposure, is significantly associated with low birth weight.

Prenatal Exposure to Heavy Metals and Adverse Birth Outcomes: Evidence From an E-Waste Area in China

Electronic waste that has not been properly treated can lead to environmental contamination including of heavy metals, which can pose risks to human health. Infants, a sensitive group, are highly susceptible to heavy metals exposure. The aim of this study was to investigate the association between prenatal heavy metal exposure and infant birth outcomes in an e-waste recycling area in China. We analyzed cadmium (Cd), chromium (Cr), manganese (Mn), lead (Pb), copper (Cu), and arsenic (As) concentrations in 102 human milk samples collected 4 weeks after delivery. The results showed that 34.3% of participants for Cr, which exceeds the World Health Organization (WHO) guidelines, as well as the mean exposure of Cr exceeded the WHO guidelines. We collected data on the birth weight (BW) and length of infants and analyzed the association between metal concentration in human milk and birth outcomes using multivariable linear regression. We observed a significant negative association between the Cd concentration in maternal milk and BW in female infants (β = -162.72, 95% CI = -303.16, -22.25). In contrast, heavy metals did not associate with birth outcomes in male infants. In this study, we found that 34.3% of participants in an e-waste recycling area had a Cr concentration that exceeded WHO guidelines, and there was a significant negative association between prenatal exposure to the Cd and infant BW in females. These results suggest that prenatal exposure to heavy metals in e-waste recycling areas may lead to adverse birth outcomes, especially for female infants.

Placental BCRP transporter reduces cadmium accumulation and toxicity in immortalized human trophoblasts

Cadmium (Cd) is a ubiquitous environmental metal detectable in most pregnant women. Animal and human studies demonstrate that in utero exposure to Cd reduces birth weight and impairs perinatal growth due to placental toxicity. BCRP is a prominent transporter that can efflux xenobiotics from the placenta. This study sought to investigate Cd transport and toxicity in cultured human BeWo trophoblasts with reduced expression and function of the placental barrier transporter BCRP. Knockdown (KD) of BCRP protein expression and function in BeWo trophoblasts increased the intracellular accumulation of Cd by 100% following treatment with 1 μM CdCl2. No change in the expression of Cd uptake transporters was observed between control and BCRP-KD cells. Reduced BCRP expression impaired viability of BeWo cells exposed to CdCl2 for 48 hr (BCRP-KD IC50: 11 μM, control cells IC50: 18 μM). Moreover, BCRP-KD cells were more sensitive to CdCl2-induced cytotoxicity compared to control BeWo cells. CdCl2 treatment strongly induced the expression of the metal-binding protein metallothionein (MT) in both control and BCRP-KD cells, with significantly greater MT upregulation in Cd-treated BCRP-KD cells. These data suggest that the BCRP transporter reduces Cd accumulation in syncytiotrophoblasts, which may be one mechanism to reduce subsequent toxicity to the placenta and developing fetus.

Prenatal Cadmium Exposure and Maternal Sex Steroid Hormone Concentrations across Pregnancy

Cadmium exposure has been associated with adverse perinatal outcomes. One possible mechanism is endocrine disruption. Studies of non-pregnant adults suggest that cadmium impacts androgen production; here, we examined these associations during pregnancy. Participants in the Understanding Pregnancy Signals and Infant Development (UPSIDE) cohort provided biospecimens and questionnaire data in each trimester (n = 272). We quantified urinary cadmium, serum total testosterone (TT), estrone, estradiol, and estriol and serum free testosterone (fT). In adjusted longitudinal models, we examined sex steroid concentrations across pregnancy in relation to specific gravity-adjusted, ln-transformed cadmium concentrations. Additionally, we examined trimester-specific associations and stratified models by fetal sex. Results are presented as percent change (%∆) in hormone concentrations. In longitudinal models, higher cadmium concentrations were associated with lower fT across pregnancy (%∆ = -5.19, 95%CI: -8.33, -1.93), with no differences in other hormones observed. In trimester-specific models, higher cadmium concentrations were associated with lower TT in trimester 2 (%∆ = -15.26, 95%CI: -25.15, -4.06) and lower fT in trimester 3 (%∆ = -14.35, 95%CI: -19.75, -8.59). Associations with TT were stronger in pregnancies carrying female fetuses. Maternal cadmium exposure may be associated with reduced testosterone in pregnancy. Additional work is necessary to understand how alterations in gestational testosterone activity may impact pregnancy and child health.

LncRNA Tuna is activated in cadmium-induced placental insufficiency and drives the NRF2-mediated oxidative stress response

Cadmium (Cd) is a toxic heavy metal found throughout the environment and one of the top ten toxicants of major public health concern identified by the World Health Organization. In utero Cd exposure causes fetal growth restriction, malformation, and spontaneous abortion; however, the mechanisms by which Cd impacts these outcomes are poorly understood. Cd accumulates in the placenta, suggesting that these negative outcomes may be a consequence of disrupted placental function and placental insufficiency. To understand the impact of Cd on gene expression within the placenta, we developed a mouse model of Cd-induced fetal growth restriction through maternal consumption of CdCl2 and performed RNA-seq on control and CdCl2 exposed placentae. The top differentially expressed transcript was the Tcl1 Upstream Neuron-Associated (Tuna) long non-coding RNA, which was upregulated over 25-fold in CdCl2 exposed placentae. Tuna has been shown to be critical for neural stem cell differentiation. However, within the placenta, there is no evidence that Tuna is normally expressed or functional at any developmental stage. To determine the spatial expression of Cd-activated Tuna within the placenta, we used in situ hybridization as well as placental layer-specific RNA isolation and analysis. Both methods confirmed the absence of Tuna expression in control samples and determined that Cd-induced Tuna expression is specific to the junctional zone. Since many lncRNAs regulate gene expression, we hypothesized that Tuna forms part of the mechanism of Cd-induced transcriptomic changes. To test this, we over-expressed Tuna in cultured choriocarcinoma cells and compared gene expression profiles to those of control and CdCl2 exposed cells. We demonstrate significant overlap between genes activated by Tuna overexpression and genes activated by CdCl2 exposure, with enrichment in the NRF2-mediated oxidative stress response. Herein we analyze the NRF2 pathway and show that Tuna increases NRF2/NRF2 both at the transcript and protein levels. Tuna drives increased NRF2 target gene expression, a result that is abrogated with the use of an NRF2 inhibitor, confirming that Tuna activates oxidative stress response genes through this pathway. This work identifies the lncRNA Tuna as a potential novel player in Cd-induced placental insufficiency.

Protective role of the placental efflux transporter BCRP/ABCG2 in the relationship between prenatal cadmium exposure, placenta weight, and size at birth

BACKGROUND AND AIM

Placental efflux transporter proteins, such as BCRP, reduce the placental and fetal toxicity of environmental contaminants but have received little attention in perinatal environmental epidemiology. Here, we evaluate the potential protective role of BCRP following prenatal exposure to cadmium, a metal that preferentially accumulates in the placenta and adversely impacts fetal growth. We hypothesized that individuals with a reduced function polymorphism in ABCG2, the gene encoding BCRP, would be most vulnerable to the adverse impacts of prenatal cadmium exposure, notably, smaller placental and fetal size.

METHODS

We measured cadmium in maternal urine samples at each trimester and in term placentas from UPSIDE-ECHO study participants (NY, USA; n = 269). We fit adjusted multivariable linear regression and generalized estimating equation models to examine log-transformed urinary and placental cadmium concentrations in relation to birthweight, birth length, placental weight, and fetoplacental weight ratio (FPR) and stratified models by ABCG2 Q141K (C421A) genotype.

RESULTS

Overall 17% of participants expressed the reduced-function ABCG2 C421A variant (AA or AC). Placental cadmium concentrations were inversely associated with placental weight (β = -19.55; 95%CI: -37.06, -2.04) and trended towards higher FPR (β = 0.25; 95%CI: -0.01, 0.52) with stronger associations in 421A variant infants. Notably, higher placental cadmium concentrations in 421A variant infants were associated with reduced placental weight (β = -49.42; 95%CI: 98.87, 0.03), and higher FPR (β = 0.85, 95%CI: 0.18, 1.52), while higher urinary cadmium concentration was associated with longer birth length (β = 0.98; 95%CI: 0.37, 1.59), lower ponderal index (β = -0.09; 95%CI: 0.15, -0.03), and higher FPR (β = 0.42; 95%CI: 0.14, 0.71).

CONCLUSIONS

Infants with reduced function ABCG2 polymorphisms may be particularly vulnerable to the developmental toxicity of cadmium as well as other xenobiotics that are BCRP substrates. Additional work examining the influence of placental transporters in environmental epidemiology cohorts is warranted.

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.

Association of paternal cadmium and other heavy metal exposure to birth outcomes using propensity score matching

BACKGROUND

Human exposure to cadmium has various effects on health, especially on male reproductive organs. Although it is widely known that prenatal maternal cadmium exposure can affect birth outcomes, the effect of paternal exposure to cadmium remains unclear.

OBJECTIVES

This study aimed to evaluate the effect of paternal cadmium exposure on fetal growth by considering maternal cadmium exposure and exposure to other heavy metals, namely mercury and lead.

METHODS

The Mothers and Children's Environmental Health (MOCEH) study is a prospective birth cohort study in Korea. Overall, 1313 families (father-mother-child triple) without child abnormalities and who completed paternal whole blood cadmium assessments were included in this study. Families were divided into two subgroups based on the blood sampling periods, namely early and late pregnancy. Subjects were selected as follows: one family triple with a high level of paternal cadmium and two triples with low levels of paternal cadmium, using the method of propensity score matching. And linear regression analyses were performed.

RESULTS

The group with high paternal cadmium exposure (80% or more; 1.93 μg/L) had lower birth weight infants compared to the group with low cadmium concentrations (β(se) = -0.21(0.10); p-value = 0.0283). After stratification by infant sex, prenatal paternal cadmium exposure significantly reduced the birth weight of females in subgroups of different sampling times, namely early pregnancy (β(se) = -0.52 (0.22); p-value = 0.0170) and late pregnancy (β(se) = -0.43 (0.18); p-value = 0.0160). Finally, after performing propensity score matching in the early pregnancy measurement group, it was found that the prenatal exposure of father to cadmium significantly reduced birth weight in females (β(se) = -0.72(0.25); p-value = 0.0047).

CONCLUSION

This study assessed the effect of paternal cadmium exposure on birth outcomes in family units consisting of a father, mother, and child. Prenatal paternal cadmium exposure negatively affected birth weight, especially that of female, considering covariates and other heavy metals exposure, namely mercury and lead.

First Trimester of Pregnancy as the Sensitive Period for the Association between Prenatal Mosquito Coil Smoke Exposure and Preterm Birth

Mosquito coils are efficient mosquito repellents and mosquito coil smoke (MCS) contributes to indoor air pollution. However, no prior population-based study has investigated whether prenatal MCS exposure is a risk factor for preterm birth (PTB) and whether exposure to MCS in different trimesters of pregnancy is associated with different levels of risk. The sample involved 66,503 mother-child dyads. Logistic regression models were used to examine the relationships between prenatal MCS exposure during different trimesters of pregnancy and PTB. We found that prenatal MCS exposure was associated with a greater likelihood of PTB (OR = 1.12, 95%CI: 1.05-1.20). The prenatal MCS exposure during the first trimester was associated with 1.17 (95%CI: 1.09-1.25) times the odds of being PTB, which was higher than exposure during the second trimester (OR = 1.11, 95%CI: 1.03-1.19) and during the third trimester (OR = 1.08, 95%CI: 1.01-1.16). In the stratified analysis, prenatal MCS exposure significantly increased PTB risk among girls but not among boys. Our results indicated that maternal MCS exposure during pregnancy was associated with PTB and that the first trimester might be the sensitive period. In light of these findings, public health interventions are needed to reduce prenatal exposure to MCS, particularly during the first trimester of pregnancy.

Maternal and fetal exposure to metal (loid)s, maternal nutrition status, and impact on prenatal growth in an energy rich zone and an urban area along the Persian Gulf

The main purposes of the study were to determine whether maternal and cord blood (MB and CB) levels of metal (loid)s (MLs) are different between industrial and urban areas. Subjects were derived from the petrochemical and gas area (PGA) of Asaluyeh County and the urban area (UA) of Bushehr County in Iran. Adjusted models revealed significant differences between the PGA and UA for maternal Fe, Cu, Mg, Cd, Zn, Ni, V and Pb levels, likewise cord Cu, V, Pb and Ni levels, which were higher in the PGA. Unadjusted models revealed there were decreases in neonatal weight and head circumference by 16.550 g and 0.059 cm, respectively for each Ln unit increase in maternal Cr levels. The mean blood levels of MLs significantly associated with food consumption frequency. The MLs were detected at higher levels in the body's fetuses and their mothers who resided in the PGA than those from the UA. So, the fetuses of mothers living in an industrial areas may be at higher risk from anthropometric measures. The impact of prenatal exposure to MLs on prenatal growth should be considered for better understanding in the further studies.

Maternal exposure to cadmium during pregnancy is associated with changes in DNA methylation that are persistent at 9 years of age

BACKGROUND

Cadmium (Cd) exposure during gestation has been associated with altered DNA methylation at birth, but it is not known if the changes in methylation persist into childhood.

OBJECTIVES

To evaluate whether gestational Cd-related changes of DNA methylation persist from birth to 9 years of age.

METHODS

We studied mother-child dyads in a longitudinal cohort in rural Bangladesh. Cadmium concentrations in maternal blood (erythrocyte fraction; Ery-Cd) at gestational week 14 and in child urine (U-Cd, long-term exposure marker) at 9 years were measured using inductively coupled plasma mass spectrometry. The epigenome-wide DNA methylation was measured in mononuclear cells (PBMCs) prepared from cord blood and peripheral blood at 9 years in 71 children (hereafter referred to as the explorative group) by Infinium HumanMethylation450K BeadChip. Replication of one differentially methylated region (DMR; 9 CpG sites) was performed in PBMCs of 160 9-year-old children (validation group) by EpiTyper MALDI-TOF mass spectrometry.

RESULTS

The median maternal Ery-Cd concentration was 1.24 µg/kg (range 0.35, 4.55) in the explorative group and 0.83 µg/kg (0.08, 2.97) in the validation group. The median U-Cd concentration in the 9-year-old children was 0.26 µg/L (0.09, 1.06) in the explorative group and 0.32 µg/L (0.07, 1.33) in the validation group. In the explorative group, we identified ten DMRs, both in cord blood and in PBMCs at 9 years, that were associated with maternal Ery-Cd. Eight out of the ten DMRs were hypomethylated and three of the hypomethylated DMRs were located in the HLA region on chromosome 6. One of the DMRs (hypomethylated) in the HLA region (upstream of the zinc finger protein 57 homolog, ZFP57 gene) was replicated in the validation group, and we found that it was hypomethylated in relation to maternal Ery-Cd, but not child U-Cd.

CONCLUSION

Gestational exposure to Cd appears to be associated with regional changes, especially hypomethylated, in DNA methylation that linger from birth up to prepubertal age.

Association between placental toxic metal exposure and NICU Network Neurobehavioral Scales (NNNS) profiles in the Rhode Island Child Health Study (RICHS)

BACKGROUND

Prenatal exposure to heavy metals has been linked to a variety of adverse outcomes in newborn health and later life. Toxic metals such as cadmium (Cd), manganese (Mn) and lead (Pb) have been implicated to negatively affect newborn neurobehavior. Placental levels of these metals may provide additional understandings on the link between prenatal toxic metal exposures and neurobehavioral performances in newborns.

OBJECTIVE

To evaluate associations between placental concentrations of toxic metals and newborn neurobehavioral performance indicated through the NICU Network Neurobehavioral Scales (NNNS) latent profiles.

METHOD

In the Rhode Island Child Health Study cohort (n = 625), newborn neurobehavioral performance was assessed with NNNS, and a latent profile analysis was used to define five discrete neurobehavioral profiles based on summary scales. Using multinomial logistic regression, we determined whether increased levels of placental toxic metals Cd, Mn and Pb associated with newborns assigned to the profile demonstrating atypical neurobehavioral performances.

RESULTS

Every doubling in placenta Cd concentration was associated with increased odds of newborns belonging to the atypical neurobehavior profile (OR: 2.72, 95% CI [1.09, 6.79]). Detectable placental Pb also demonstrated an increased odds of newborns assignment to the atypical profile (OR: 3.71, 95% CI [0.97, 13.96]) compared to being in the typical neurobehavioral profile.

CONCLUSIONS

Toxic metals Cd and Pb measured in placental tissue may adversely impact newborn neurobehavior. Utilizing the placenta as a prenatal toxic metal exposure biomarker is useful in elucidating the associated impacts of toxic metals on newborn health.

Prenatal metal(loid) mixtures and birth weight for gestational age: A pooled analysis of three cohorts participating in the ECHO program

BACKGROUND

A growing number of studies have identified both toxic and essential metals which influence fetal growth. However, most studies have conducted single-cohort analyses, which are often limited by narrow exposure ranges, and evaluated metals individually. The objective of the current study was to conduct an environmental mixture analysis of metal impacts on fetal growth, pooling data from three geographically and demographically diverse cohorts in the United States participating in the Environmental Influences on Child Health Outcomes program.

METHODS

The pooled sample (N = 1,002) included participants from the MADRES, NHBCS, and PROTECT cohorts. Associations between seven metals (antimony, cadmium, cobalt, mercury, molybdenum, nickel, tin) measured in maternal urine samples collected during pregnancy (median: 16.0 weeks gestation) and birth weight for gestational age z-scores (BW for GA) were investigated using Bayesian Kernel Machine Regression (BKMR). Models were also stratified by cohort and infant sex to investigate possible heterogeneity. Chromium and uranium concentrations fell below the limits of detection for most participants and were evaluated separately as binary variables using pooled linear regression models.

RESULTS

In the pooled BKMR analysis, antimony, mercury, and tin were inversely and linearly associated with BW for GA, while a positive linear association was identified for nickel. The inverse association between antimony and BW for GA was observed in both males and females and for all three cohorts but was strongest for MADRES, a predominantly low-income Hispanic cohort in Los Angeles. A reverse j-shaped association was identified between cobalt and BW for GA, which was driven by female infants. Pooled associations were null for cadmium, chromium, molybdenum, and uranium, and BKMR did not identify potential interactions between metal pairs.

CONCLUSIONS

Findings suggest that antimony, an understudied metalloid, may adversely impact fetal growth. Cohort- and/or sex-dependent associations were identified for many of the metals, which merit additional investigation.

Maternal urinary cadmium concentrations in early pregnancy in relation to prenatal and postpartum size of offspring

BACKGROUND

The impacts of environmental cadmium (Cd) exposure on birth size parameters including weight, length and head circumference (HC) have been reported in multiple studies. However, little remains known of the impacts of maternal Cd exposure during pregnancy on size during in utero development and during early childhood. The aim of this study was to comprehensively investigate impacts of maternal Cd exposure during pregnancy on the size of offspring in utero (from 24 weeks pregnancy) until six months of age.

METHODS

Pregnant mothers were recruited as part of an ongoing prospective birth cohort study based in Guangdong, China. Maternal urine samples were collected in the first and third trimesters of pregnancy, in which Cd concentrations were measured by inductively couple plasma mass spectrometry (ICPMS). In utero size indicators at 24 and 32 week of gestation, including biparietal diameter (BPD), abdominal circumference (AC), femur length (FL) and HC were derived from ultrasound examinations. Anthropometric measures of weight, height and HC at birth and one, three and six months of age were also collected. Associations of size measures at the various time points with maternal urinary Cd concentrations were assessed using linear regression models.

RESULTS

The median urinary Cd concentration was 1.00 and 0.98 μg/g creatinine in the first and third trimesters respectively. In univariate analysis, increased maternal Cd levels in the first trimester were associated with decreased HC (-0.17 cm/ug/g urinary Cd) at birth, and the association was particularly pronounced among males (-0.30 cm/ug/g urinary Cd). First trimester Cd exposure was also found to be significantly associated with decreased infant weight at three and six months of age among girls (-101 g/ug/g and -97 g/ug/g urinary Cd, respectively). Associations of similar magnitude were observed after adjustment for various maternal factors. No significant associations were observed with infant size measures or with measures of Cd in the third trimester.

CONCLUSIONS

Our detailed study suggests that the first trimester is particularly critical window of susceptibility to sex-specific effects of Cd on size parameters at birth, with some effects persisting to six months of age. These compelling sex-dependent effects on HC and body weight warrant future studies examining longer-term health effects of pregnancy-related Cd exposures.

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.

Environmental metal exposure and growth to 10 years of age in a longitudinal mother-child cohort in rural Bangladesh

BACKGROUND

Early-life exposure to arsenic (As), cadmium (Cd), and lead (Pb) has been linked to smaller birth and early childhood anthropometry, but little is known beyond the first years in life.

OBJECTIVES

To evaluate the impact of gestational and childhood exposures to As, Cd, and Pb on growth up to 10 years of age.

METHODS

We studied 1530 mother-child dyads from a nested sub-cohort of the MINIMat trial in rural Matlab, Bangladesh. Metal concentrations in maternal erythrocytes during pregnancy and in children's urine at 10y were measured by inductively coupled plasma mass spectroscopy. Child height and weight were measured at 19 occasions from birth until 10y and converted to height-for-age Z-scores (HAZ) and weight-for-age Z-scores (WAZ). Associations between log₂-transformed metal concentrations and growth parameters were assessed with multivariable-adjusted regression models.

RESULTS

Children's concurrent urinary Cd (median 0.24 µg/L), reflecting long-term exposure, was inversely associated with WAZ (B: -0.072; 95% confidence interval (CI): -0.12, -0.020; p = 0.007), and possibly HAZ (B: -0.046; 95% CI: -0.096, 0.0014; p = 0.057), at 10y. The association with WAZ was stronger in boys than in girls. Maternal erythrocyte Cd (median 0.90 µg/kg) during pregnancy was inversely associated with WAZ during childhood only in boys (B: -0.071, 95% CI: -0.14, -0.0047, p = 0.036). Concurrent urinary Pb (median 1.6 µg/L) was inversely associated with WAZ (B: -0.084; 95% CI: -0.16, -0.0085; p = 0.029) and HAZ (B: -0.087; 95% CI: -0.15, -0.021; p = 0.010) in boys, but not in girls. Neither gestational nor childhood As exposure (median maternal erythrocyte As 4.3 µg/kg and children's urinary As 57 µg/L) was associated with growth up to 10y.

CONCLUSIONS

While all effect estimates were small, environmental exposure to Cd and Pb is common and impaired growth is of public health concern, especially for children already at risk of reduced growth due to malnutrition. Gender differences in susceptibility need further investigation.

Sex-specific neurotoxic effects of heavy metal pollutants: Epidemiological, experimental evidence and candidate mechanisms

The heavy metals lead (Pb), mercury (Hg), and cadmium (Cd) are ubiquitous environmental pollutants and are known to exert severe adverse impacts on the nervous system even at low concentrations. In contrast, the heavy metal manganese (Mn) is first and foremost an essential nutrient, but it becomes neurotoxic at high levels. Neurotoxic metals also include the less prevalent metalloid arsenic (As) which is found in excessive concentrations in drinking water and food sources in many regions of the world. Males and females often differ in how they respond to environmental exposures and adverse effects on their nervous systems are no exception. Here, we review the different types of sex-specific neurotoxic effects, such as cognitive and motor impairments, that have been attributed to Pb, Hg, Mn, Cd, and As exposure throughout the life course in epidemiological as well as in experimental toxicological studies. We also discuss differential vulnerability to these metals such as distinctions in behaviors and occupations across the sexes. Finally, we explore the different mechanisms hypothesized to account for sex-based differential susceptibility including hormonal, genetic, metabolic, anatomical, neurochemical, and epigenetic perturbations. An understanding of the sex-specific effects of environmental heavy metal neurotoxicity can aid in the development of more efficient systematic approaches in risk assessment and better exposure mitigation strategies with regard to sex-linked susceptibilities and vulnerabilities.

Consequences of a short-term exposure to a sub lethal concentration of CdO nanoparticles on key life history traits in the fruit fly (Drosophila melanogaster)

Nanoparticles of cadmium oxide (CdO NPs) are among the most common industrial metal oxide nanoparticles. Early adulthood (P1) fruit flies (D. melanogaster) were exposed for 7 days to a sub lethal concentration (0.03 mg CdO NPs/mL, which was 20% of the LC₅₀), spiked into food media to test whether short episodes of CdO NPs exposures early in adult life have long-lasting effects on life history traits such as fecundity well beyond exposure times. All studied life history traits, as well as climbing behavior were adversely affected by exposure to CdO NPs. A blistered wing phenotype was also observed in the non-exposed progeny (F1) of adult flies (P1) and their fecundity was significantly decreased (-50%) compared to the fecundity of non-exposed (control) F1 flies. Expressions of antioxidant enzymes encoding genes; catalase and superoxide dismutase (SOD2) were significantly up regulated in P1 flies compared to control. Expression of metallothionein encoding genes (MTn A-D) were significantly up-regulated in both parent flies (P1) and their progeny (F1) after exposure of P1 flies to CdO NPs compared to non-exposed control flies, suggesting long-term potential effects. Taken together, these findings indicate that short-term exposure to a sub-lethal CdO NP concentration is sufficient to have long-lasting, adverse effects on fruit flies.

Exposure to toxic metals and per- and polyfluoroalkyl substances and the risk of preeclampsia and preterm birth in the United States: a review

Preeclampsia and preterm birth are among the most common pregnancy complications and are the leading causes of maternal and fetal morbidity and mortality in the United States. Adverse pregnancy outcomes are multifactorial in nature and increasing evidence suggests that the pathophysiology behind preterm birth and preeclampsia may be similar-specifically, both of these disorders may involve abnormalities in placental vasculature. A growing body of literature supports that exposure to environmental contaminants in the air, water, soil, and consumer and household products serves as a key factor influencing the development of adverse pregnancy outcomes. In pregnant women, toxic metals have been detected in urine, peripheral blood, nail clippings, and amniotic fluid. The placenta serves as a "gatekeeper" between maternal and fetal exposures, because it can reduce or enhance fetal exposure to various toxicants. Proposed mechanisms underlying toxicant-mediated damage include disrupted placental vasculogenesis, an up-regulated proinflammatory state, oxidative stressors contributing to prostaglandin production and consequent cervical ripening, uterine contractions, and ruptured membranes and epigenetic changes that contribute to disrupted regulation of endocrine and immune system signaling. The objective of this review is to provide an overview of studies examining the relationships between environmental contaminants in the US setting, specifically inorganic (eg, cadmium, arsenic, lead, and mercury) and organic (eg, per- and polyfluoroalkyl substances) toxicants, and the development of preeclampsia and preterm birth among women in the United States.

Cadmium exposure and risk of adverse pregnancy and birth outcomes: a systematic review and dose-response meta-analysis of cohort and cohort-based case-control studies

BACKGROUND

There are several inconsistencies in the epidemiological literature on the strength of the association between cadmium exposure and adverse pregnancy and birth outcomes, and the threshold dose of adverse effect.

OBJECTIVES

We therefore conducted a systematic review and dose-response meta-analysis to evaluate the available evidence to influence clinical decision making and better tailor public health interventions.

METHODS

PubMed and Scopus databases were searched up to January, 2019. Eighteen prospective studies satisfied the inclusion criteria. Random effects model was used to compute summary-effect estimates.

RESULTS

Cadmium exposure resulted in 42.11 g (95% confidence interval [CI]: -69.03, -15.18) reduction in birth weight, and 0.105 cm (95% CI: -0.181, -0.029) reduction in head circumference per 1 µg/l increment in blood/urine cadmium levels. Cadmium exposure also resulted in 21% (RR = 1.21; 95% CI: 1.02, 1.43), 32% (RR = 1.32; 95% CI: 1.05, 1.67) and 10% (RR = 1.10; 95% CI: 0.96, 1.27) increased risk of low birth weight (LBW), preterm birth (PTB), and small-for-gestational age (SGA), respectively. Risk for all outcomes decreased with decreasing exposure. In fixed effects dose-response meta-regression analyses, we found no evidence of association of cadmium exposure with LBW and SGA. For PTB, a 1 µg/l increment in cadmium exposure corresponded to 0.5% (OR = 1.005, 95% CI: 1.003, 1.007) increase in PTB risk.

CONCLUSIONS

Cadmium exposure was associated with risk of adverse birth outcomes. Regarding PTB, the formal dose-response meta-analyses suggests a causal association.

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.

Comprehensive Review of Cadmium Toxicity Mechanisms in Male Reproduction and Therapeutic Strategies

Cadmium (Cd) has been widely studied as an environmental pollutant for many years. Numerous studies have reported that Cd exposure causes damage to the heart, liver, kidneys, and thyroid in vivo. The emerging evidence suggests that Cd exposure induces damage on male reproductive system, which is related to oxidative stress, inflammation, steroidogenesis disruption, and epigenetics. Current preclinical animal studies have confirmed a large number of proteins and intracellular signaling pathways involved in the pathological process of Cd-induced male reproductive damage and potential measures for prophylaxis and treatment, which primarily include antioxidants, anti-inflammatory agents, and essential ion supplement. However, explicit pathogenesis and effective treatments remain uncertain. This review collects data from the literatures, discusses the underlying mechanisms of Cd-induced toxicity on male reproductive function, and summarizes evidence that may provide guidance for the treatment and prevention of Cd-induced male reproductive toxicity.

Low-level maternal exposure to cadmium, lead, and mercury and birth outcomes in a Swedish prospective birth-cohort

Observational studies have indicated that low-to-moderate exposure to cadmium (Cd), lead (Pb), and mercury (Hg) adversely affects birth anthropometry, but results are inconclusive. The aim of this study was to elucidate potential impact on birth anthropometry of exposure to Cd, Pb, and Hg in pregnant women, and to identify the main dietary sources. In the NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment) birth-cohort in northern Sweden, blood and urine were collected from pregnant women in early third trimester. Cd, Pb and Hg were measured in erythrocytes (n = 584), and Cd also in urine (n = 581), by inductively coupled plasma mass spectrometry. Dietary data were collected through a semi-quantitative food frequency questionnaire administered in mid-third trimester. Birth anthropometry data were extracted from hospital records. In multivariable-adjusted spline regression models, a doubling of maternal erythrocyte Cd (median: 0.29 μg/kg) above the spline knot of 0.50 μg/kg was associated with reduced birth weight (B: -191 g; 95% CI: -315, -68) and length (-0.67 cm; -1.2, -0.14). The association with birth weight remained when the analysis was restricted to never-smokers. Likewise, a doubling of erythrocyte Hg (median 1.5 μg/kg, mainly MeHg) above 1.0 μg/kg, was associated with decreased birth weight (-59 g; -115, -3.0), and length (-0.29 cm; -0.54, -0.047). Maternal Pb (median 11 μg/kg) was unrelated to birth weight and length. Erythrocyte Cd was primarily associated with intake of plant derived foods, Pb with game meat, tea and coffee, and Hg with fish. The results indicated that low-level maternal Cd and Hg exposure were associated with poorer birth anthropometry. Further prospective studies in low-level exposed populations are warranted.

Implications for prenatal cadmium exposure and adverse health outcomes in adulthood

Cadmium is a ubiquitous, non-essential metal that has earned a spot on the World Health Organizations top 10 chemicals of major public health concern. The mechanisms of cadmium-induced adverse health outcomes, such as cardiovascular disease, renal toxicity and cancer, are well studied in adults. However, the implications for early life exposures to low-level cadmium leading to increased risk of developing diseases in adulthood remains elusive. Epidemiological investigation of the long term implications of cadmium-associated adverse birth outcomes are limited and studies do not extend into adulthood. This review will summarize the literature on the non-lethal, adverse health effects associated with prenatal and early life exposure to cadmium and the implications of these exposures in the development of diseases later in life. In addition, this review will highlight possible mechanisms responsible for these outcomes as well as address the inconsistencies in the literature. More recent studies have addressed sex as a biological variable, showing prenatal cadmium exposure elicits sex-specific outcomes that would otherwise be masked by pooling male and female data. Furthermore, researchers have begun to investigate the role of prenatal and early life cadmium exposures in the development of diet-induced diseases with evidence of altered essential metal homeostasis as a likely mechanism for cadmium-enhanced, diet-induced diseases. Although novel experimental models are beginning to be established to study the association between prenatal cadmium exposure and adverse health outcomes in adulthood, the studies are few, highlighting a major need for further investigation.

Placenta as a target of trichloroethylene toxicity

Trichloroethylene (TCE) is an industrial solvent and a common environmental contaminant detected in thousands of hazardous waste sites. Risk of exposure is a concern for workers in occupations that use TCE as well as for residents who live near industries that use TCE or who live near TCE-contaminated sites. Although renal, hepatic and carcinogenic effects of TCE have been documented, less is known about TCE impacts on reproductive functions despite epidemiology reports associating maternal TCE exposure with adverse pregnancy outcomes. Toxicological evidence suggests that the placenta mediates at least some of the adverse pregnancy outcomes associated with TCE exposure. Toxicology studies show that the TCE metabolite, S-(1,2-dichlorovinyl)-l-cysteine (DCVC) generates toxic effects such as mitochondrial dysfunction, apoptosis, oxidative stress, and release of prostaglandins and pro-inflammatory cytokines in placental cell lines. Each of these mechanisms of toxicity have significant implications for placental functions and, thus, ultimately the health of mother and developing child. Despite these findings there remain significant gaps in our knowledge about effects of TCE on the placenta, including effects on specific placental cell types and functions as well as sex differences in response to TCE exposure. Due to the critical role that the placenta plays in pregnancy, future research addressing some of these knowledge gaps could lead to significant gains in public health.

Combined effects of multiple prenatal exposure to pollutants on birth weight: The Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

Increasing evidence shows that prenatal environmental exposures is a risk factor for restricted intrauterine growth. However, only a few studies have examined the effects of multiple environmental exposures on fetal growth.

OBJECTIVE

To investigate the effects of prenatal exposure on multiple environmental pollutants (heavy metals, bisphenol, phthalates, and air pollutants) on birth weight.

METHODS

The Mothers and Children's Environmental Health study is a prospective birth cohort comprising a total of 719 mother-child pairs, including 466 pairs undergoing early pregnancy exposure and 542 pairs of late pregnancy exposure. The concentrations of three heavy metals (mercury, lead, and cadmium) in the maternal blood samples were measured. The concentrations of three phthalate metabolites [mono(2-ethyl-5-hydroxyhexyl) phthalate, mono(2-ethyl-5-oxohexyl) phthalate, and mono-n-butyl phthalate] and bisphenol A in maternal urine samples were measured. Daily exposure to ambient particulate matter (PM10) and nitrogen dioxide (NO2) exposure was estimated based on residence and averaged by gestational age. To assess the combined effect of multiple pollutants, principal components analysis (PCA) and supervised principal components analysis (SCPA) were conducted.

RESULTS

Based on PCA, the components representing PM10 and NO2 exposure during early pregnancy were significantly associated with birth weight of -32.68 g (95% CI: -64.45 g to -0.91 g) per unit increase of the corresponding component. In SCPA model, the components representing NO2 exposure during early pregnancy and the combined exposure to mercury and lead during late pregnancy were negatively associated with birth weight of -46.63 g (95% CI: -90.65 g to -2.62 g) and -55.32 g (95% CI: -99.01 g to -11.64 g), respectively, per unit increase of the corresponding component.

CONCLUSION

Based on our multi-pollutant model, PM10 and NO2 exposure in early pregnancy and the combined effect of Pb and Hg in late pregnancy were associated with reduced birth weight. Our results suggest that exposure to various pollutants during pregnancy has a significant cumulative effect on birth weight, even if each pollutant is at a level below the concentration required for direct effect.

Cadmium toxicity: effects on human reproduction and fertility

Background Cadmium (Cd) is a non-essential toxic heavy metal, an environmental toxicant, and toxic at a low concentration, and it has no known beneficial role in the human body. Its exposure induces various health impairments including hostile reproductive health. Objective The present review discusses the information on exposure to Cd and human reproductive health impairments including pregnancy or its outcome with respect to environmental and occupational exposure. Methods The present review provides current information on the reproductive toxic potential of Cd in humans. The data were collected using various websites and consulting books, reports, etc. We have included recent data which were published from 2000 onward in this review. Results Cd exposure affects human male reproductive organs/system and deteriorates spermatogenesis, semen quality especially sperm motility and hormonal synthesis/release. Based on experimental and human studies, it also impairs female reproduction and reproductive hormonal balance and affects menstrual cycles. Based on the literature, it might be concluded that exposure to Cd at low doses has adverse effects on both human male and female reproduction and affects pregnancy or its outcome. Further, maternal prenatal Cd exposure might have a differential effect on male and female offspring especially affecting more female offspring. Hence, efforts must be made to prevent exposure to Cd. Conclusion Cd affects both male and female reproduction, impairs hormone synthesis/regulation and deteriorates pregnancy rate or its outcome even at lower doses.

Coal smoke, gestational cadmium exposure, and fetal growth

BACKGROUND

Gestational cadmium exposure may impair fetal growth. Coal smoke has largely been unexplored as a source of cadmium exposure. We investigated the relationship between gestational cadmium exposure and fetal growth, and assessed coal smoke as a potential source of airborne cadmium, among non-smoking pregnant women in Ulaanbaatar, Mongolia, where coal combustion in home heating stoves is a major source of outdoor and indoor air pollution.

METHODS

This observational study was nested within the Ulaanbaatar Gestation and Air Pollution Research (UGAAR) study, a randomized controlled trial of portable high efficiency particulate air (HEPA) filter air cleaner use during pregnancy, fetal growth, and early childhood development. We measured third trimester blood cadmium concentrations in 374 out of 465 participants who had a live birth. We used multiple linear and logistic regression to assess the relationships between log₂-transformed maternal blood cadmium concentrations and birth weight, length, head circumference, ponderal index, low birth weight, small for gestational age, and preterm birth in crude and adjusted models. We also evaluated the relationships between log₂-transformed blood cadmium concentrations and the density of coal-burning stoves within 5000 m of each participant's apartment as a proxy of coal smoke emissions from home heating stoves.

RESULTS

The median (25th,75th percentile) blood cadmium concentration was 0.20 (0.15, 0.29) μg/L. A doubling of blood cadmium was associated with a 95 g (95% CI: 34, 155 g) reduction in birth weight in adjusted models. An interquartile range increase in coal stove density (from 3.4 to 4.9 gers/hectare) surrounding participants' apartments was associated with a 12.2% (95% CI: 0.3, 25.6%) increase in blood cadmium concentrations.

CONCLUSIONS

Gestational cadmium exposure was associated with reduced birth weight. In settings where coal is a widely used fuel, cadmium may play a role in the putative association between air pollution and impaired fetal growth.

Association between ambient air pollution exposure and infants small for gestational age in Huangshi, China: a cross-sectional study

Small for gestational age (SGA) is defined as intrauterine growth retardation or small sample, referring to the 10th percentile of birth weight lower or two standard deviations less than the average weight at the same gestational age. SGA infants bring great economic and psychological burdens to families and society. The association between exposure to air pollution and SGA in underdeveloped cities with poor air quality remains unclear. Thus, this study is conducted to estimate the effects of maternal exposure to air pollutants on SGA numbers. Birth information was collected from the Huangshi Maternity and Children's Health Hospital from January 1st to December 31st in 2017. Data of pregnancy exposure were accessed using stationary monitors. These data included particulate matter less than or equal to 10 μm in aerodynamic diameter (PM₁₀), particulate matter less than or equal to 2.5 μm in aerodynamic diameter (PM_2.5), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂). Multivariate logistic regression models were performed to estimate the association between ambient air pollution and the risk of SGA during different exposure windows. It was found that a 1 μg/m³ increase in air pollution concentrations during the entire pregnancy was associated with a higher risk of SGA, with an adjusted odds ratio (OR) and 95% confidence interval (CI) of 1.055 (1.035-1.076), 1.084 (1.053-1.116), 1.000 (0.953-1.049), and 1.051 (0.968-1.141) for PM₁₀, PM_2.5, NO₂, and SO₂, respectively. Thus, it is suggested that exposure to air pollution is associated with an increased risk of SGA. The effects of PM₁₀ and PM_2.5 were more stable than NO₂ and SO₂.

The effects of long-term exposure to low doses of cadmium on the health of the next generation of mice

Cadmium (Cd) is an important toxic chemical due to its increasing levels in the environment and bioaccumulation in humans and animals. The present study was performed to evaluate the effects of long-term exposure to 1, 10, or 100 μg/L Cd in drinking water on the development, reproduction and neurotoxicity of offspring when administered to mice from parental puberty to postnatal 10 weeks in offspring. The development parameters measured in offspring included physical development, reflex ontogeny, body weight and body size. The reproductive indices measured consisted of anogenital distances (AGDs), estrous cycle, sperm quality, specific gene expression in Leydig or Sertoli cells, seminiferous epithelium cycle, sex hormone levels, histological morphology and apoptosis in testis or ovary, and the levels of oxidative stress. The determination of neurotoxicity included learning and memory ability, anxiety, and related serum indicators. In addition, blood lipid level, liver and kidney function were also determined by serum biochemical assays. The results showed that exposure to Cd in the present model had no adverse effects on development, but had some reproductive toxicity and neurotoxicity, including alteration of spermatogenic epithelial staging in testis and inducing anxiety in offspring. Furthermore, the levels of total protein, globulins, total bile acid and direct bilirubin were also significantly altered, especially in female offspring. The present study suggested that long-term exposure to low doses of Cd had adverse effects on the health of the next generation, and some harmful effects showed gender differences in offspring. The present study demonstrated that attention should be paid to Cd pollution in the environment, especially before pregnancy.

Heavy Metals Can either Aid or Oppose the Protective Function of the Placental Barrier

BACKGROUND:

In developing countries, toxic heavy metals are a threatening catastrophe to human health, particularly in the vulnerable group of pregnant mothers and their fetuses. Fortunately, the placenta can be a protective barrier to the fetuses.

AIM:

To explore the relationship between serum lead, cadmium and arsenic levels in pregnant mothers and their newborns, to address the placental barrier in this situation.

METHODS:

A cross-sectional study was conducted on 100 pregnant mothers at the time of labour and their newborns. Serum cadmium, lead, and arsenic levels were measured using the Inductively Coupled Plasma Mass Spectrometry.

RESULTS:

All the studied heavy metals concentrations showed a significant elevation in the maternal blood relative to the cord blood. There was a significant association between the maternal lead and both fetal lead and arsenic. Meanwhile, a negative but insignificant correlation was recorded between the maternal cadmium and each of the fetal cadmium, lead, and arsenic.

CONCLUSION:

The study findings indicated a weak relation between maternal and fetal blood heavy metals, except for the influence of maternal lead, so it can be assumed that the placental barriers are partially protective against those toxic pollutants, putting into consideration the influence of their different natures.

The association between prenatal cadmium exposure and birth weight: A systematic review and meta-analysis of available evidence

We conducted a meta-analysis to evaluate the association between prenatal cadmium (Cd) exposure and birth weight. PubMed, Embase, China National Knowledge Infrastructure (CNKI), and Wanfang databases were searched for studies published before March 2019. We used a model-based method, standardizing effect size from linear regression models to include a maximum number of studies during our quantitative evaluations. As a result, 11 articles from the general population, containing 10 birth cohorts and one cross-sectional study, were included. Our meta-analysis demonstrated that a 50% increase of maternal urine Cd (UCd) would be associated with a 6.15 g decrease in neonatal birth weight (β = -6.15 g, 95% CI: -10.81, -1.49) as well as a 50% increase of maternal blood Cd (BCd) would be associated with an 11.57 g decrease (β = -11.57 g; 95% CI: -18.85, -4.30). Stratified analysis of UCd data indicated that the results of female newborns were statistically significant (β = -8.92 g, 95% CI: -17.51, -0.34), as was the first trimester (β = -11.34 g, 95% CI: -19.54, -3.14). Furthermore, increased UCd levels were associated with a higher rate of low birth weight (LBW) risk (OR = 1.12, 95% CI: 1.03, 1.22). This meta-analysis demonstrated that elevated maternal Cd levels are associated with decreased birth weight and higher LBW risk.

Placental metal concentrations in relation to placental growth, efficiency and birth weight

The quality of the intrauterine environment, in which the placenta plays a critical role, affects birth outcomes and lifelong health. The effect of metal contaminants on the growth and functioning of the placenta have not been widely reported but may provide insights into how metal exposures lead to these outcomes. We examined relationships between placental concentrations of cadmium (Cd), arsenic (As), mercury (Hg) and lead (Pb) and measures of placental growth and functioning (placental weight, placental efficiency (the log ratio of placental weight and birth weight), chorionic disc area and disc eccentricity) as part of the New Hampshire Birth Cohort Study (N = 1159). We additionally examined whether these associations were modified by placental concentrations of essential elements zinc (Zn) and selenium (Se). Associations were evaluated using generalized linear models. Multivariable-adjusted differences in placental weight were - 7.81 g (95% CI: -15.42, -2.48) with every ng/g increase in the Cd concentration of placenta (p-Value = 0.0009). Greater decrements in placental weight and efficiency associated with placental Cd were observed for females. For placentae with below median Zn and Se concentrations, decrements in placental weight were - 8.81 g (95% CI: -16.85, -0.76) and - 13.20 g (95% CI: -20.70, -5.70) respectively. The Cd concentration of placenta was also associated with reductions in placental efficiency both overall, and in Zn- and Se-stratified models. No appreciable differences were observed with other elements (As, Hg or Pb) and with other placental measures (chorionic disc area and disc eccentricity). In structural equation models, placental weight was a mediator in the relation between placental Cd concentration and reduced birth weight. Our findings suggest a role of interacting essential and contaminant elements on birth weight that may be mediated by changes in the growth and function of the placenta.

Placental Expression of Imprinted Genes, Overall and in Sex-Specific Patterns, Associated with Placental Cadmium Concentrations and Birth Size

BACKGROUND

Prenatal cadmium (Cd) exposure has been recognized to restrict growth, and male and female fetuses may have differential susceptibility to the developmental toxicity of Cd. Imprinted genes, which exhibit monoallelic expression based on parent of origin, are highly expressed in placental tissues. The function of these genes is particularly critical to fetal growth and development, and some are expressed in sex-specific patterns.

OBJECTIVES

We aimed to examine whether prenatal Cd associates with the expression of imprinted placental genes, overall or in fetal sex-specific patterns, across two independent epidemiologic studies.

METHODS

We tested for Cd–sex interactions in association with gene expression, then regressed the placental expression levels of 74 putative imprinted genes on placental log-Cd concentrations while adjusting for maternal age, sex, smoking history, and educational attainment. These models were performed within study- and sex-specific strata in the New Hampshire Birth Cohort Study (NHBCS; [Formula: see text]) and the Rhode Island Child Health Study (RICHS; [Formula: see text]). We then used fixed-effects models to estimate the sex-specific and overall associations across strata and then examine heterogeneity in the associations by fetal sex.

RESULTS

We observed that higher Cd concentrations were associated with higher expression of distal-less homeobox 5 (DLX5) ([Formula: see text]), and lower expression of h19 imprinted maternally expressed transcript (H19) ([Formula: see text]) and necdin, MAGE family member (NDN) ([Formula: see text]) across study and sex-specific strata, while three other genes [carboxypeptidase A4 (CPA4), growth factor receptor bound protein 10 (GRB10), and integrin-linked kinase (ILK)] were significantly associated with Cd concentrations, but only among female placenta ([Formula: see text]). Additionally, the expression of DLX5, H19, and NDN, the most statistically significant Cd-associated genes, were also associated with standardized birth weight z-scores.

DISCUSSION

The differential regulation of a set of imprinted genes, particularly DLX5, H19, and NDN, in association with prenatal Cd exposure may be involved in overall developmental toxicity, and some imprinted genes may respond to Cd exposure in a manner that is specific to infant gender. https://doi.org/10.1289/EHP4264.

Cadmium: Toxic effects on placental and embryonic development

Cadmium is a non-essential trace metal that has strong teratogenic and mutagenic effects in living organisms. The content is more highly enriched in women than in men and can enter the embryo through the placenta and destroy the placenta's morphological structure, resulting in fetal growth restriction. In this report, we review published data linking pregnancy exposure to cadmium to placenta and fetal growth and development toxicity and summarize the related mechanisms. An understanding of how cadmium exposure contributes to placental and fetal development is necessary for the development of prevention and control strategies for fetal development defects caused by cadmium exposure during pregnancy.

Analysis of spatial distribution of trace metals, PCB, and PAH and their potential impact on human health in Virginian Counties and independent cities, USA

Increasing anthropogenic alteration has resulted in increased exposure to both point and nonpoint source pollution. These exposures are increasingly studied for their role in human diseases, including diseases with known genetic or lifestyle risk factors. This study analyzed associations between a variety of human diseases and trace metals, PCBs, and PAHs in soil, groundwater, sediment, and fish. Contaminant spatial data at the county level from Virginia were used in ArcGIS to identify these associations among socially vulnerable populations. The neurologic and psychiatric disorders and cognitive markers were associated with numerous metals in groundwater/soil and/or aquatic system contaminants. Cancer death rates, fetal deaths, and infant deaths were also related to multiple environmental exposures from both categories of exposure. In contrast, many of the chronic diseases which are primarily attributed to lifestyle showed little association with these exposures with the exception of COPD which did appear to be associated with multiple metal exposures. Asthma showed similar associations compared to COPD. Our data suggest that within the context of socially vulnerable populations, where disease burden is often highest, exposures to metals, PAHs, and PCBs may play a role in the development or exacerbation of several highly prevalent categories of disease. These environmental exposures likely act through a variety of pathways all generally leading to increased oxidative stress, inflammation, or interference with biological systems and a subsequent role in disease development.

Prenatal cadmium exposure is associated with shorter leukocyte telomere length in Chinese newborns

BACKGROUND

Newborn telomere length (TL) is considered a potential marker for future disease and lifelong health, but few epidemiological studies have examined the determinants of TL in early life. The study aim was to investigate whether there is an association between prenatal cadmium exposure and relative cord blood TL in Chinese newborns.

METHODS

Participants were 410 mother-newborn pairs drawn from a prospective birth cohort study conducted in Wuhan, China, between November 2013 and March 2015. Urine samples were collected from pregnant women during their period of institutional delivery. Urinary cadmium concentrations were measured by inductively coupled plasma mass spectrometry. The real-time quantitative polymerase chain reaction detection was used to measure relative TL using genomic DNA isolated from umbilical cord blood leukocytes. Multivariate linear regression models were used to estimate the effect of prenatal urinary cadmium concentration on relative cord blood TL.

RESULTS

The geometric mean of maternal urinary cadmium concentration was 0.68 μg/g creatinine. In the multivariate-adjusted linear regression model, per doubling of maternal urinary cadmium concentration was associated with 6.83% (95% CI - 11.44%, - 1.97%; P = 0.006) shorter relative cord blood TL. Stratified analyses indicated that the inverse association between prenatal urinary cadmium and newborn relative TL was more pronounced among female infants and mothers < 29 years, while there were no significant effect modification according to infant sex (P for interaction = 0.907) and maternal age (P for interaction = 0.797).

CONCLUSIONS

The findings indicated that increased maternal urinary cadmium was associated with shortened relative cord blood TL. The results provide more evidence of the negative effects of environmental cadmium exposure and suggest that accelerated aging or cadmium-related diseases may begin in early life.

Associations of Prenatal Exposure to Cadmium With Child Growth, Obesity, and Cardiometabolic Traits

Prenatal cadmium exposure has been associated with impaired fetal growth; much less is known about the impact during later childhood on growth and cardiometabolic traits. To elucidate the associations of prenatal cadmium exposure with child growth, adiposity, and cardiometabolic traits in 515 mother-child pairs in the Rhea Mother-Child Study cohort (Heraklion, Greece, 2007-2012), we measured urinary cadmium concentrations during early pregnancy and assessed their associations with repeated weight and height measurements (taken from birth through childhood), waist circumference, skinfold thickness, blood pressure, and serum lipid, leptin, and C-reactive protein levels at age 4 years. Adjusted linear, Poisson, and mixed-effects regression models were used, with interaction terms for child sex and maternal smoking added. Elevated prenatal cadmium levels (third tertile of urinary cadmium concentration (0.571-2.658 μg/L) vs. first (0.058-0.314 μg/L) and second (0.315-0.570 μg/L) tertiles combined) were significantly associated with a slower weight trajectory (per standard deviation score) in all children (β = -0.17, 95% confidence interval (CI): -0.32, -0.02) and a slower height trajectory in girls (β = -0.30, 95% CI: -0.52,-0.09; P for interaction = 0.025) and in children born to mothers who smoked during pregnancy (β = -0.48, 95% CI: -0.83, -1.13; P for interaction = 0.027). We concluded that prenatal cadmium exposure was associated with delayed growth in early childhood. Further research is needed to understand cadmium-related sex differences and the role of coexposure to maternal smoking during early pregnancy.

Urinary metabolomics reveals novel interactions between metal exposure and amino acid metabolic stress during pregnancy

Pregnant women are a unique group undergoing profound structural modifications in uterus, breast, adipose tissue and extracellular fluids. Amino acid metabolic stress is a unique physical process that occurs during pregnancy. Metals constitute a fundamental part of the maternal body and have a universal effect on amino acid metabolism. However, the exact interaction between metals and amino acid metabolism during pregnancy is unknown. The aim of the present study was to determine the correlations of metals with amino acid metabolic intermediates in the urine of 232 healthy pregnant women in their first, second and third trimesters during normal pregnancy. Sixteen metals in the urine of 232 healthy pregnant women in their first, second and third trimesters were quantified using inductively coupled plasma mass spectrometry (ICP-MS). An ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometer (UPLC-QTOFMS)-based metabolomics approach was conducted to detect intermediate products involved in amino acid metabolism during the entire pregnancy period. A panel regression model was established to investigate the relationship between urine metals and amino acid metabolism. Seven metals-cadmium, cobalt, copper, cesium, manganese, thallium and vanadium-showed significant association with amino acid metabolic intermediates, including 2-oxoarginine, 3-indoleacetonitrile, indole, indole-5,6-quinone, N2-succinyl-l-glutamic acid 5-semialdehyde, N-methyltryptamine and N-succinyl-l,l-2,6-diaminopimelate, in the healthy pregnant women. These findings indicated that exposure to cadmium, cobalt, copper, cesium, manganese, thallium and vanadium significantly affected the metabolic status of tryptophan, arginine, proline, tyrosine and lysine metabolism in the maternal body during normal pregnancy.

Prenatal co-exposure to neurotoxic metals and neurodevelopment in preschool children: The Environment and Childhood (INMA) Project

We sought to determine whether prenatal co-exposure to As, Cd, Hg, Mn, and Pb was associated with impaired neurodevelopment in preschool children from the Spanish Environment and Childhood (INMA) Project, using the placenta as exposure matrix. We measured metal levels in placenta tissue samples randomly selected from five of the seven population-based birth cohorts participating in the INMA Project, collected between 2000 and 2008. Neuropsychological assessment of cognitive and motor function was carried through the use of the McCarthy Scales of Children's Abilities (MSCA) at the age of 4-5years. Data on placental metal levels, MSCA scores, and relevant covariates was available for 302 children. Mn was detected in all placental samples, Cd in nearly all placentas (99%) and As, Hg, and Pb in 22%, 58%, and 17% of the placentas, respectively. After adjusting for potential confounders, detectable As levels were associated with decrements in global and verbal executive functions and quantitative abilities; detectable Hg was associated with lower scores on the verbal function of posterior cortex in a dose-response manner, and non-linearly related to poorer motor function and gross motor skills; and Mn levels were associated with decrement in perceptual-performance skills in a dose-response manner but with better memory span and quantitative skills. A synergistic interactive effect was found between As and Pb with respect to the general cognitive score, whereas an antagonistic interaction was found between Mn and Hg. Prenatal exposure to As and Hg may be a risk factor for cognitive and motor impairment in children, while the effects of Cd and Mn on neurodevelopment are less clear. Future studies should examine combined and interactive effects of exposure to multiple metals during vulnerable periods of brain development prospectively.

Household environmental exposures during gestation and birth outcomes: A cross-sectional study in Shanghai, China

Several studies have reported that certain aspects of the household environments are associated with adverse birth outcomes, but associations have been inconsistent. Few of these studies have been conducted in China. During 2011-2012, we conducted a retrospective cross-sectional study and collected 13,335 parents-reported questionnaires for 4-6-year-olds children in Shanghai, China. We investigated associations of household environmental factors (environmental tobacco smoke (ETS), cooking fuel, dampness, pet-keeping, and home renovation) during gestation with preterm birth (PTB, gestational age<37weeks), low birth weight (LBW, birth weight<2500g), term low birth weight (T-LBW, LBW when the gestational age was ≥37weeks), and small for gestational age (SGA, birth weight<10th percentile of birth weight for gestational age). A total of 4.1% children were premature; 2.9% had LBW and 1.6% had T-LBW; 8.1% were SGA. In the multiple logistic regression analyses, home renovation during gestation was associated with PTB (adjusted odds ratio (OR), 95% confidence intervals (CI): 1.68, 1.11-2.54) and LBW (1.64, 0.99-2.72). Paternal smoking was associated with PTB (1.18, 0.98-1.43). No significant associations were found for SGA. Neither household dampness nor cooking fuel were significantly associated with birth outcomes. For boys, paternal smoking was associated with PTB (1.31, 1.02-1.69); home renovation during gestation was associated with PTB (2.14, 1.27-3.61) and LBW (2.19, 1.09-4.43). Among children whose mothers were ≥34-year-olds during gestation, paternal smoking (1.73, 1.04-2.76) and home renovation during gestation (1.80, 1.18-2.76) was associated with PTB. Our findings demonstrate that home renovation and ETS during gestation may be risk factors for adverse birth outcomes. Associations of these factors with adverse birth outcomes appear to be stronger in boys and among mothers older than 34years during gestation. Home renovation and ETS exposure should be avoided during gestation, especially for pregnancies with male fetuses and older pregnant women.

Maternal occupational cadmium exposure and nonsyndromic orofacial clefts

BACKGROUND

Cigarette smoking is a well-studied risk factor for orofacial clefts (OFCs). Little is known about which constituents in cigarette smoke contribute to this teratogenicity in humans. One constituent, cadmium, has been associated with OFCs in animal studies; in humans, the role of maternal cadmium exposure on OFCs, independent of cigarette smoke, is unclear. In particular, the relation between maternal occupational cadmium exposure and OFCs is largely unexplored.

METHODS

Using data from a large, population-based case-control study, we compared expert rater assessed maternal occupational cadmium exposure from self-reported occupational histories during the period 1 month before through 3 months after conception between OFC cases (n = 1,185) and unaffected controls (n = 2,832). Multivariable logistic regression analyses were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals for any (yes/no) and cumulative (no, low, high exposure) occupational cadmium exposures and all OFCs, cleft lip ± cleft palate (CL/P) and cleft palate (CP).

RESULTS

Overall, 45 mothers (cases = 13, controls = 32) were rated as having occupational cadmium exposure. Comparing all OFCs to controls, we observed inverse, nonsignificant aORs for any or low exposure, and positive, nonsignificant aORs for high exposure. Where data were available, aORs for CL/P and CP tended to parallel those for all OFCs.

CONCLUSION

To our knowledge, this is the first study to specifically examine maternal occupational cadmium exposure and OFCs, using expert rater exposure assessment. The small numbers of exposed mothers observed, however, led to imprecise estimates. Continued research using more detailed occupational exposure assessment and increased sample sizes is recommended.

Critical Windows of Prenatal Exposure to Cadmium and Size at Birth

Prenatal cadmium (Cd) exposure has been associated with adverse birth outcomes, but the findings of previous studies are inconsistent. We measured Cd concentrations in urine samples at or near 13, 24, and 35 gestational weeks from 282 women in Wuhan, China. We used generalized estimating equation models to assess the associations between maternal creatinine adjusted urinary Cd concentrations at each trimester and birth size. A significant inverse association was observed between higher maternal Cd levels measured during the 1st trimester and birth size in girls. For each log unit increase in Cd (µg/g creatinine) levels from the 1st trimester, there was a decrease in birth weight by 116.99 g (95% confidence interval (CI): -208.87, -25.11 g). The Cd levels from the 1st and 2nd trimesters were also borderline significantly associated with ponderal index in girls. Joint estimation of trimester-specific effects suggested that associations with Cd levels for ponderal index (pint = 0.02) were significantly different across trimesters, and differences for effects across trimesters for birth weight were marginally significant (pint = 0.08) in girls. No significant associations were observed between Cd levels from any trimester and birth size in boys. Maternal Cd exposure during earlier periods of pregnancy may have a larger impact on delayed fetal growth.