Maternal Blood Levels of Toxic and Essential Elements and Birth Outcomes in Argentina: The EMASAR Study

Concentrations and influencing factors of 17 elements in placenta, cord blood, and maternal blood of women from an e-waste recycling area

BACKGROUND

The effects of prenatal element exposure on mothers and fetuses have generated concern. Profiles of trace and toxic elements in biological material are urgently desired, especially for women who reside near e-waste recycling facilities. The aim of this study was to investigate elements concentrations in placenta, cord blood, and maternal blood of women and to evaluate the influencing factors.

METHODS

A group of 48 women from an e-waste recycling site and a group of 31 women from a non-e-waste recycling site were recruited. Basic characteristics were collected by questionnaire and the concentrations of 17 elements in placenta, cord blood, and maternal blood samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Finally, the generalized linear model regression analysis (GLM) was used to test the association between element concentrations and possible factors.

RESULTS

Compared to the control group, the exposed group had significantly elevated cadmium (Cd), zinc (Zn), nickel (Ni), and antimony (Sb) in placenta, and higher lead (Pb) in maternal blood and cord blood (P<0.05). Sb concentration in maternal blood was significantly lower than in the control group (P<0.05). GLM analysis showed that element concentrations were mainly associated with maternal age [chromium (Cr), iron (Fe), selenium (Se), cobalt (Co), mercury (Hg) in placenta, copper (Cu) in maternal blood], education (Se, Sb in placenta), family income (Cu in maternal blood and Ni in placenta), passive smoking [Cu and Zn in placenta, Pb in maternal blood], and e-waste contact history (Hg in cord blood, Cu, Zn, and Cd in maternal blood).

CONCLUSIONS

Women in the e-waste recycling area had higher toxic element levels in the placenta and blood samples. More preventive measures were needed to reduce the risk of element exposure for mothers and fetuses in these areas.

Update of the risk assessment of inorganic arsenic in food

The European Commission asked EFSA to update its 2009 risk assessment on arsenic in food carrying out a hazard assessment of inorganic arsenic (iAs) and using the revised exposure assessment issued by EFSA in 2021. Epidemiological studies show that the chronic intake of iAs via diet and/or drinking water is associated with increased risk of several adverse outcomes including cancers of the skin, bladder and lung. The CONTAM Panel used the benchmark dose lower confidence limit based on a benchmark response (BMR) of 5% (relative increase of the background incidence after adjustment for confounders, BMDL05) of 0.06 μg iAs/kg bw per day obtained from a study on skin cancer as a Reference Point (RP). Inorganic As is a genotoxic carcinogen with additional epigenetic effects and the CONTAM Panel applied a margin of exposure (MOE) approach for the risk characterisation. In adults, the MOEs are low (range between 2 and 0.4 for mean consumers and between 0.9 and 0.2 at the 95th percentile exposure, respectively) and as such raise a health concern despite the uncertainties.

Fetoplacental Disposition and Toxicity of Cadmium in Mice Lacking the Bcrp Transporter

The environmental toxicant cadmium (Cd) impairs the growth of rodents and humans in utero which in turn heightens susceptibility to diseases later in life. We previously demonstrated that the maternal-facing efflux transporter, breast cancer resistance protein (human BCRP/ABCG2, mouse Bcrp/Abcg2) confers resistance against Cd toxicity in human trophoblasts. In the current study, we sought to determine whether the absence of Bcrp alters the fetoplacental disposition and toxicity of Cd in mice. Pregnant female wild-type (WT) and Bcrp-null mice (n = 9-10/group) were administered a single injection of saline (5 ml/kg) or CdCl2 (5 mg/kg) on gestational day (GD) 9. Following Cd treatment, Bcrp-null offspring were shorter and accumulated more Cd in their placentas on GD 17 compared to WT mice. Because Cd can adversely impact placentation and transplacental nutrient delivery in mice, multiple pathways were assessed using morphometrics and immunohistochemistry including placenta zonation, vasculature development, and nutrient transporter expression. Most notably, the placentas of Bcrp-null mice had reduced immunostaining of the cell adhesion marker, β-catenin, and the trophoblast marker, cytokeratin, as well as decreased expression of divalent metal nutrient transporters (Dmt1, Zip14, and ZnT1) following Cd treatment. In summary, the absence of Bcrp expression increased placental concentrations of Cd which was associated with shorter fetal size that may be related to differential changes in molecular patterns of placental development and nutrition.

Cadmium reduces growth of male fetuses by impairing development of the placental vasculature and reducing expression of nutrient transporters

In utero exposure to the toxic metal cadmium (Cd) alters fetoplacental growth in rodents and has been inversely associated with birth weight and infant size in some birth cohorts. Moreover, studies suggest that Cd may have differential effects on growth and development according to offspring sex. The purpose of the current study was to evaluate changes in male and female fetoplacental development following a single injection of saline (5 ml/kg ip) or cadmium chloride (CdCl2, 2.5, 5 mg/kg, ip) on gestational day (GD) 9. By GD18, no changes in fetal or placental weights were observed after treatment with 2.5 mg/kg CdCl2. By comparison, the weight and length of male fetuses and their placentas were reduced following treatment with 5 mg/kg CdCl2 whereas no change was observed in females. In addition, the area of maternal and fetal blood vessels as well as the expression of the glucose transporters, Glut1 and Glut3, and the endothelial marker, CD34, were reduced in the placentas of CdCl2-treated male offspring compared to females. Interestingly, the placentas of females accumulated 80% more Cd than males after CdCl2 (5 mg/kg) administration. Female placentas also had higher concentrations of zinc and the zinc transporter Znt1 compared to males which may explain the limited changes in fetal growth observed following CdCl2 treatment. Taken together, disruption of vasculature development and reduced expression of glucose transporters in the placenta provide potential mechanisms underlying reduced fetal growth in male offspring despite the greater accumulation of Cd in female placentas.

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.

Nutritional, pharmacological, and environmental programming of NAFLD in early life

Nonalcoholic fatty liver disease (NAFLD) is the main liver disease worldwide, and its prevalence in children and adolescents has been increasing in the past years. It has been demonstrated that parental exposure to different conditions, both preconceptionally and during pregnancy, can lead to fetal programming of several metabolic diseases, including NAFLD. In this article, we review some of the maternal and paternal conditions that may be involved in early-life programing of adult NAFLD. First, we describe the maternal nutritional factors that have been suggested to increase the risk of NAFLD in the offspring, such as an obesogenic diet, overweight/obesity, and altered lipogenesis. Second, we review the association of certain vitamin supplementation and the use of some drugs during pregnancy, for instance, glucocorticoids, with a higher risk of NAFLD. Furthermore, we discuss the evidence showing that maternal-fetal pathologies, including gestational diabetes mellitus (GDM), insulin resistance (IR), and intrauterine growth restriction (IUGR), as well as the exposure to environmental contaminants, and the impact of microbiome changes, are important factors in early-life programming of NAFLD. Finally, we review how paternal preconceptional conditions, such as exercise and diet (particularly obesogenic diets), may impact fetal growth and liver function. Altogether, the presented evidence supports the hypothesis that both in utero exposure and parental conditions may influence fetal outcomes, including the development of NAFLD in early life and adulthood. The study of these conditions is crucial to better understand the diverse mechanisms involved in NAFLD, as well as for defining new preventive strategies for this disease.