Prenatal exposure to mixtures of heavy metals and neurodevelopment in infants at 6 months

HDL cholesterol: A potential mediator of the association between serum levels of a mixture of metals and the risk of aortic dissection in a Chinese population

Aortic dissection (AD) is a severe cardiovascular disease with a high mortality rate. However, the associations between the serum levels of metals and the risk of AD remain unclear. One hundred twenty-seven patients with AD (type A and B) identified from 2017 to 2019 at the Second Affiliated Hospital of Nanjing Medical University were included; 183 controls that were also included. A logistic regression analysis was performed to determine the associations between serum levels of metals and the risk of AD. Weighted Quantile Sum (WQS) regression and Bayesian Kernel Machine Regression (BKMR) analyses were performed to explore the effects of mixtures of metals on the risk of AD. A linear regression analysis was performed to evaluate the relationships between the serum levels of metals and the white blood cells (WBCs) count and serum lipid levels and blood glucose. We conducted a mediation analysis to explore the contribution rates of WBC counts or serum lipid levels and blood glucose to the association between metal levels and the risk of AD. Exposure to serum levels of Cu (coefficient = 6.33; 95 % CI = 2.52, 10.14; p trend < 0.001) were significantly and positively associated with the risk of AD. In the WQS analysis, Cu (50.3 %), Ni (32.7 %) and Mo (17.1 %) contributed to the AD risk. In the BKMR analysis, Cu and Mo were shown to play important roles in the association with the AD risk. Moreover, serum concentrations of Cu were significantly and inversely associated with HDL-cholesterol levels. HDL-cholesterol levels mediated 7.42 % of the association between serum Cu levels and the prevalence of AD. Our study provided the first evidence that serum levels of mixtures of metals are associated with the AD risk in a Chinese population. Increased concentrations of metals, particularly Cu, may increase the risk of AD by reducing HDL-cholesterol levels.

Trimester-specific associations of maternal exposure to disinfection by-products, oxidative stress, and neonatal neurobehavioral development

BACKGROUND

Toxicological studies suggest that maternal exposure to disinfection by-products (DBPs) can impair fetal neurodevelopment. However, evidence from epidemiological studies is scarce and the underlying mechanisms remain unclear.

OBJECTIVE

To explore the trimester-specific associations between maternal blood trihalomethane (THM) and urinary haloacetic acid (HAA) concentrations and neonatal neurobehavioral development, and the potential mediating role of oxidative stress (OS).

METHODS

We included 438 pregnant Chinese women from the Xiaogan Disinfection By-Products (XGDBP) birth cohort. Biospecimens were repeatedly collected across trimesters and measured for blood THMs, urinary HAAs, and urinary OS biomarker concentrations. On the third day after birth, the Neonatal Behavioral Neurological Assessment (NBNA) test was administered to newborns. Associations of trimester-specific DBP measurements and OS biomarkers with neonatal NBNA scores were assessed using linear regression models with generalized estimating equations. The potential mediating role of maternal OS biomarkers was also investigated using mediation analyses.

RESULTS

After adjusting for potential confounders, blood bromodichloromethane (BDCM) concentrations in the first trimester were inversely associated with NBNA scores [percent change comparing the extreme BDCM tertiles = -28.1% (95% CI: -55.2%, -0.88%); p for trend = 0.043]. Besides, third-trimester urinary trichloroacetic acid (TCAA) concentrations were inversely associated with NBNA scores [percent change comparing the extreme TCAA tertiles = -32.9% (95% CI: -64.7%, -1.0%); p for trend = 0.046]. These inverse associations differed across pregnancy trimesters (Type 3p-value = 0.066 and 0.053, respectively) and were stronger in male infants and mothers aged ≥25 years. There was no evidence of mediating effect by 8-hydroxy-2-deoxyguanosine (8-OHdG), 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA), or 8-iso-prostaglandin F_2α (8-isoPGF_2α).

CONCLUSIONS

Higher prenatal BDCM and TCAA concentrations during specific pregnancy trimesters were associated with lower NBNA scores. However, additional research is required to investigate underlying mechanisms.

Association of prenatal exposure to cadmium with neurodevelopment in children at 2 years of age: The Japan Environment and Children's Study

BACKGROUND

Prenatal cadmium exposure has been associated with adverse neurodevelopmental outcomes. However, previous findings are contradictory, and little is known about the potential modifiers of the cadmium-related neurodevelopmental risk. We investigated the associations between prenatal cadmium exposure and neurodevelopment in 2-year-old children and examined the influence of mother/child characteristics.

METHODS

We recruited 3545 mother-child pairs from the Japan Environment and Children's Study. We collected maternal blood during mid/late pregnancy and cord blood at delivery, and measured cadmium concentrations using inductively coupled plasma mass spectrometry. Neurodevelopment was assessed using the Kyoto Scale of Psychological Development (KSPD), which includes cognitive-adaptive (C-A), language-social (L-S), postural-motor (P-M) and developmental quotient (DQ) domains. Associations between cadmium and KSPD scores were tested using multivariable models after controlling for confounders.

RESULTS

Median levels (interquartile ranges) of cadmium in maternal and cord blood were 0.70 (0.52-0.95) and 0.04 (0.03-0.06) μg/L, respectively. Maternal blood cadmium concentrations were inversely associated with P-M scores in boys (β = -1.4, 95% confidence interval (CI): -2.7, -0.038), DQ in children of mothers who smoked during pregnancy (β = -2.9, 95% CI: -5.7, -0.12), P-M (β = -5.4, 95% CI: -10, -0.67), C-A (β = -6.1, 95% CI: -11, -1.8), L-S (β = -9.0, 95% CI: -13, -4.8) and DQ scores (β = -6.4, 95% CI: -9.6, -3.1) in children born to mothers with gestational diabetes. Cord blood cadmium concentrations were negatively associated with L-S scores (β = -6.0., 95% CI: -11, -0.91) in children born to mothers with gestational diabetes.

CONCLUSIONS

Prenatal cadmium exposure was negatively associated with neurodevelopment in boys, in children whose mothers smoked, and in children born to mothers with gestational diabetes. Further studies in other populations are needed to confirm our findings.

Exploring the relationship between metal exposure, BDNF, and behavior in adolescent males

BACKGROUND

Brain-derived neurotrophic factor (BDNF) plays an important role in brain development by regulating multiple pathways within the central nervous system. In the Human Biomonitoring for Europe Project (HBM4EU), this neurotrophin is being implemented as a novel effect biomarker to evaluate the potential threats of environmental chemicals on neurodevelopment.

OBJECTIVES

To explore the relationships among exposure to environmental metals, BDNF biomarkers at two levels of biological complexity, and behavioral function in adolescent males.

METHODS

Data were gathered from 125 adolescents on: spot urine sample total concentrations of the neurotoxic metal(oid)s arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb); serum BDNF protein concentrations; and concurrent behavioral functioning according to the Child Behavior Check List (CBCL/6-18). In 113 of the participants, information was also collected on blood BDNF DNA methylation at six CpGs. Associations were evaluated by multivariate linear regression analysis adjusted for confounders.

RESULTS

As, Cd, Hg, and Pb were detected in 100%, 98.5%, 97.0%, and 89.5% of urine samples, respectively. Median serum BDNF concentration was 32.6 ng/mL, and total percentage of BDNF gene methylation was 3.8%. In the adjusted models, urinary As was non-linearly associated with more internalizing problems and Cd with more externalizing behaviors. The percentage BDNF DNA methylation at CPGs #5 and the mean percentage CpG methylation increased across As tertiles (p-trend = 0.04 and 0.03, respectively), while 2nd tertile and 3rd tertile of Cd concentrations were associated with lower serum BDNF and higher CpG3 methylation percentage. Additionally, when BDNF was categorized in tertiles, serum BDNF at the 3rd tertile was associated with fewer behavioral problems, particularly withdrawn (p-trend = 0.04), social problems (p-trend = 0.12), and thought problems (p-trend = 0.04).

CONCLUSION

Exposure to As and Cd was associated with BDNF gene DNA methylation BDNF gene and serum BDNF, respectively. Associations with DNA methylation may be attributable to a higher variability over time in circulating BDNF concentrations than in the methylation status of this gene. Caution should be taken when interpreting the results relating postnatal Pb and Hg to behavioral functioning. Further studies are needed to verify these findings.

Associations between urinary phthalate metabolite concentrations and markers of liver injury in the US adult population

BACKGROUND

Phthalates have been largely used for years in varieties of products worldwide. However, research on the joint toxic effect of various phthalates exposure on the liver is lacking.

OBJECTIVES

We aimed to assess exposure to phthalates on liver function tests (LFTs).

METHODS

This analysis included data on 6046 adults (≥20 years old) who participated in a National Health and Nutrition Examination Survey (NHANES) in 2007-2016. We employed linear regression and Bayesian kernel machine regression (BKMR), to explore the associations of urinary phthalate metabolites with 8 indicators of LFTs.

RESULTS

Di(2-ethylhexyl) phthalate (ΣDEHP) was found to be positively associated with serum alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT) and alkaline phosphatase (ALP) (all P _FDR < 0.05). We found significant positive associations of ∑DEHP, mono-ethyl phthalate (MEP) and mono-(carboxyisononyl) phthalate (MCNP) with total bilirubin (TBIL) (all P _FDR < 0.05). ΣDEHP, mono-n-butyl phthalate (MBP), mono-(3-carboxypropyl) phthalate (MCPP) and mono-benzyl phthalate (MBzP) were negatively associated with serum ALB (all P _FDR < 0.05). The BKMR analyses showed a significantly positive overall effect on ALT, AST, ALP and TBIL levels with high concentrations of phthalate metabolites and a significantly negative overall effect on ALB and TP, when all the chemicals at low concentrations.

CONCLUSIONS

Our results add novel evidence that exposures to phthalates might be adversely associated with the indicators of LTFs, indicating the potential toxic effect of phthalate exposures on the human liver.

Risk assessment of heavy metals in milk from cows reared around industrial areas in India

This study assessed the health risk associated with exposure to heavy metals through consumption of milk from cows reared around industrial areas in India. Heavy metals, namely Cu, Zn, Cr, Pb, and Cd, were determined in water and forage from four locations as well as in milk produced by dairy cattle raised in these locations, using inductively coupled plasma-mass spectrometry. A quantitative risk assessment using probabilistic approaches was performed to assess the exposure of adults and children to the heavy metals via milk consumption. In milk samples, the highest levels of Cd and Pb were 0.18 mg L^-1 and 0.37 mg L^-1, respectively, which were above the international permissible levels. Possible sources of Pb in the milk could be the industrial by-products and wastes or automobiles exhaust gas. Significant (P < 0.05) positive relationships were found between the concentration of Cu, Cr, Pb, and Cd in milk and in the environmental samples (water or forage). Exposure assessment showed that milk consumers were mostly exposed to Zn, Cd, and Pb, with 63.7%, 51.2%, and 41.2% of children exposed to a dose greater than the references dose for these metals, respectively. Our results suggest that industrial activities lead to possible transfer of heavy metals to cows from their rearing environment (water, plant), which can be accumulated and cause potential health risks to milk consumers. The outcome of this study can be used by policy makers to manage the potential health risk.

Metal mixtures and neurodevelopment: recent findings and emerging principles

Children are constantly exposed to a wide range of environmental factors including essential and non-essential metals. In recent years, the mixtures paradigm has emerged to foster the examination of combined effects that emerge from exposures to multiple elements. In this review, we summarized recent literature studying the relationship between prenatal and childhood metal mixtures with neurodevelopmental outcomes. Our review highlights two basic principles to emerge from this approach. First, recent findings emphasize that the effect of a given exposure is contextual and may be dependent on past or concurrent metal exposures. Second, the timing of exposures is equally critical to the mixture composition in determining neurodevelopmental effects. Our discussion emphasizes how these principles may apply to future exposure-related neurodevelopmental studies.

Prenatal Environmental Metal Exposure and Preterm Birth: A Scoping Review

Preterm birth (PTB) and its complications are the leading causes of under-five year old child deaths, accounting worldwide for an estimated one million deaths annually. The etiology of PTB is complex and multifactorial. Exposures to environmental metals or metalloids are pervasive and prenatal exposures to them are considered important in the etiology of PTB. We conducted a scoping review to determine the extent of prenatal exposures to four metals/metalloids (lead, mercury, cadmium and arsenic) and their association with PTB. We reviewed original research studies published in PubMed, Embase, the Cochrane Library, Scopus, POPLINE and the WHO regional indexes from 2000 to 2019; 36 articles were retained for full text review. We documented a higher incidence of PTB with lead and cadmium exposures. The findings for mercury and arsenic exposures were inconclusive. Metal-induced oxidative stress in the placenta, epigenetic modification, inflammation, and endocrine disruptions are the most common pathways through which heavy metals and metalloids affect placental functions leading to PTB. Most of the studies were from the high-income countries, reflecting the need for additional data from low-middle-income countries, where PTB rates are higher and prenatal exposure to metals are likely to be just as high, if not higher.

Cadmium and lead in geophagic clay consumed in Southern Nigeria: health risk from such traditional nutraceutical

Geophagy is a cultural behavior, based on the recurrent intentional eating of clay soil, that is raising increasing concern as it implies multidimensional (space, time) potential risk of serious adverse health effects. This study investigated the level of toxic metals (Cd and Pb) in 20 Nigerian geophagic clays intended for both local consumption and distribution to the West Africa market. After sampling in 4 open markets in southern Nigeria (Akwa Ibom, Abia, Rivers, Imo), samples were subjected to digestion, ashing and analysis. The Pb levels in all samples exceeded the WHO/FAO maximum permissible limit of 0.1 mg kg^-1 whereas 16% exceeded the Cd limit of 0.3 mg kg^-1. The estimated daily intake of Pb for all samples ranged from 0.0032-0.0286 mg kg_bw^-1 day^-1 to 0.0024-0.0215 mg kg_bw^-1 day^-1 for children and adults, respectively. The estimated daily intakes for Cd ranged from bdl (below detection limit)-0.0010 mg kg_bw^-1 day^-1 to bdl-0.0028 mg kg_bw^-1 day^-1 for children and adults, respectively. In both cases, the WHO/FAO provisional Tolerable Weekly Intake is exceeded through the ingestion of these soils. Our results confirm health risks related to the geophagic practices, its role in exceeding health guidelines when considering aggregate exposure in the Nigerian scenario and body burden in developing organisms, young women, women at fertile age, and pregnant women. We discuss how geophagists consider clays as traditional nutraceuticals and how clarifying the nutraceutical role of geophagy could facilitate risk communication. Geophagic products are implicitly or explicitly marketed as dietary supplements, and as such they should be regulated (1) by labeling, and prohibition of scientifically unfounded health claims and (2) by safety standards before marketing. This is particularly critical when clays originate from countries living rapid, unplanned and uncontrolled development and dumped, like Nigeria.

Early exposure to food contaminants reshapes maturation of the human brain-gut-microbiota axis

Early childhood growth and development is conditioned by the consecutive events belonging to perinatal programming. This critical window of life will be very sensitive to any event altering programming of the main body functions. Programming of gut function, which is starting right after conception, relates to a very well-established series of cellular and molecular events associating all types of cells present in this organ, including neurons, endocrine and immune cells. At birth, this machinery continues to settle with the establishment of extra connection between enteric and other systemic systems and is partially under the control of gut microbiota activity, itself being under the densification and the diversification of microorganisms' population. As thus, any environmental factor interfering on this pre-established program may have a strong incidence on body functions. For all these reasons, pregnant women, fetuses and infants will be particularly susceptible to environmental factors and especially food contaminants. In this review, we will summarize the actual understanding of the consequences of repeated low-level exposure to major food contaminants on gut homeostasis settlement and on brain/gut axis communication considering the pivotal role played by the gut microbiota during the fetal and postnatal stages and the presumed consequences of these food toxicants on the individuals especially in relation with the risks of developing later in life non-communicable chronic diseases.