Determinants of arsenic metabolism: blood arsenic metabolites, plasma folate, cobalamin, and homocysteine concentrations in maternal-newborn pairs

Abstract

Background: In Bangladesh, tens of millions of people have been consuming waterborne arsenic for decades. The extent to which As is transported to the fetus during pregnancy has not been well characterized.

Objectives: We therefore conducted a study of 101 pregnant women who gave birth in Matlab, Bangladesh.

Methods: Maternal and cord blood pairs were collected and concentrations of total As were analyzed for 101 pairs, and As metabolites for 30 pairs. Maternal urinary As metabolites and plasma folate, cobalamin, and homocysteine levels in maternal cord pairs were also measured. Household tube well-water As concentrations exceeded the World Health Organization guideline of 10 microg/L in 38% of the cases.

Results: We observed strong associations between maternal and cord blood concentrations of total As (r = 0.93, p < 0.0001). Maternal and cord blood arsenic metabolites (n = 30) were also strongly correlated: in dimethylarsinate (DMA) (r = 0.94, p < 0.0001), monomethylarsonate (r = 0.80, p < 0.0001), arsenite (As(+3)) (r = 0.80, p < 0.0001), and arsenate (As(+5)) (r = 0.89, p < 0.0001). Maternal homocysteine was a strong predictor of %DMA in maternal urine, maternal blood, and cord blood (beta = -6.2, p < 0.02; beta = -10.9, p < 0.04; and beta = -13.7, p < 0.04, respectively). Maternal folate was inversely associated with maternal blood As(5+) (beta = 0.56, p < 0.05), and maternal cobalamin was inversely associated with cord blood As(5+) (beta = -1.2, p < 0.01).

Conclusions: We conclude that exposure to all metabolites of inorganic As occurs in the prenatal period.

Keywords: B12; DMA; MMA; arsenic; blood arsenic metabolites; folate; homocysteine; maternal; newborn.

Figure 1

Associations between cord and maternal blood arsenic for (A) total blood arsenic (n = 30, r = 0.97, β = 0.90, blue line; n = 101, r = 0.93, β = 0.94, black line) and (B) the adjusted sum of blood arsenic metabolites (DMA + MMA + As⁺³ + As⁺⁵) (n = 30, r = 0.99, β = 1.16).

Figure 2

Spearman correlation coefficients (r) and regression coefficients (β) for pairwise comparisons of cord blood arsenic metabolites and maternal blood arsenic metabolites: As⁺³ (r = 0.80, β = 0.77) (A), As⁺⁵ (r = 0.89, β = 0.97) (B), MMA (r = 0.81, β = 0.97) (C), DMA (r = 0.94, β = 1.06) (D) (n = 30).