Prenatal Co-Exposure to Methylmercury and Inorganic Arsenic

Abstract

Background/Aim: In the human body, arsenite is transported into cells through membrane channel proteins (i.e., aquaporins), while mercury decreases the permeability of aquaporins by binding to thiol groups. Thus exposure to mercury (through fish ingestion) may affect the metabolism of arsenite. This pilot study is focused on pregnant mothers, because the fetal period is considered the most vulnerable exposure window for methylmercury and arsenic.Methods: In 2019, 45 healthy pregnant mothers (<21 weeks gestation) were enrolled at a hospital in Eugene, Oregon. After providing written informed consent, biomarkers were collected (blood, urine and hair samples). Blood methylmercury concentrations were determined, while arsenic species were analyzed in urine [inorganic arsenic, dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA)]. A tap water sample was brought from home for analysis of arsenic. We investigated unadjusted associations between blood methylmercury and urine arsenic species [%MMA (of total arsenic) and %DMA (of total arsenic)].Preliminary Results: All tap water arsenic concentrations were below the detection level (<2 ppb); however the sum of urine arsenic species (= inorganic As + DMA + MMA) averaged 3.0 ppb (median: 2.5 ppb, range: 0.31-11 ppb, unadjusted for specific gravity). These values were comparable to other cohorts of pregnant mothers in the U.S. and Europe, where drinking water arsenic levels were low. Urine %MMA (of total arsenic) was inversely correlated with log10 blood methylmercury (Pearson's r: -0.25, p=0.12), while urine %DMA (of total arsenic) was positively correlated with log10 blood methylmercury (Pearson's r: 0.15, p=0.35).Conclusions: Although trends were non-significant, associations between urine arsenic species and blood methylmercury were suggestive. Analyses of specific aquaporins are ongoing, which may provide insight into these preliminary findings.