Profile of urinary arsenic metabolites during pregnancy.

Abstract

Chronic exposure to inorganic arsenic (In-As) from drinking water is associated with different health effects, including skin, lung, bladder, and kidney cancer as well as vascular and possibly reproductive effects. In-As is metabolized through the process of methylation, resulting in the production and excretion of methylated species, mainly monomethylarsenate (MMA) and dimethylarsenate (DMA). Because a large percentage of the dose is excreted in urine, the distribution of urinary In-As, MMA, and DMA is considered a useful indicator of methylation patterns in human populations. Several factors affect these patterns, including sex and exposure level. In this study, we investigated the profile of urinary In-As, MMA, and DMA of pregnant women. Periodic urine samples were collected from early to late pregnancy among 29 pregnant women living in Antofagasta, Chile, who drank tap water containing 40 micro g/L In-As. The total urinary arsenic across four sampling periods increased with increasing weeks of gestation, from an initial mean value of 36.1 to a final value of 54.3 micro g/L. This increase was mainly due to an increase in DMA, resulting in lower percentages of In-As and MMA and a higher percentage of DMA. Our findings indicate that among women exposed to moderate arsenic from drinking water during pregnancy, changes occur in the pattern of urinary arsenic excretion and metabolite distribution. The toxicologic significance of this is not clear, given recent evidence suggesting that intermediate methylated species may be highly toxic. Nevertheless, this study suggests that arsenic metabolism changes throughout the course of pregnancy, which in turn may have toxicologic effects on the developing fetus. Key words: arsenic, arsenic metabolism, arsenic methylation, Chile, pregnancy, urinary arsenic.

Scientific Opinion on Arsenic in Food

“…Similar results have been reported from experimental studies on mice, with most of the arsenic in foetal tissues being dimethylarsinate (Devesa et al, 2006). The metabolic methylation of arsenic via one-carbon metabolism increases in women during pregnancy (Concha et al, 1998;Hopenhayn et al, 2003a). For that reason, the human foetal is likely to be exposed to more inorganic arsenic and methylarsonate in early gestation.…”

Rice consumption contributes to arsenic exposure in US women

“…Total arsenic concentrations were unrelated to gestational week (r s = −0.03, P = 0.66). Although other studies found that arsenic methylation increased with gestational week (27,28), methylation efficiency measured as the ratios of MMA to iAS, and DMA to MMA, was not associated with gestational week in our sample (r s = −0.002, P = 0.98 and r s = 0.01, P = 0.86, respectively), possibly due to the narrow gestational window under observation (IQR 23.9-28.0 wk). Among the 180 subjects who reported using their tap water for drinking or cooking, home water arsenic concentration was associated with total urinary arsenic concentration (r s = 0.43, P < 0.0001).…”

Associations between prenatal arsenic exposure with adverse pregnancy outcome and child mortality

“…The underreporting and misclassification of spontaneous abortion outcomes in this study could have led to an underestimation of the association between prenatal arsenic exposure and early pregnancy loss. Second, previous studies have shown that arsenic metabolism efficiency among pregnant women varies across trimesters, with evidence to suggest that metabolism efficiency increases in the first trimester (Gardner et al 2011; Hopenhayn et al 2003). However, it was not possible to evaluate the effect of trimester-specific arsenic exposure in this study.…”