Effects of arsenic methylation and metabolism on the changes of arsenic-related skin lesions.

Little was known about the arsenic metabolism and arsenic methylation associated with the changes of skin lesions after reducing the arsenic in drinking water (WAs). Therefore, urinary concentrations and proportions of arsenic species were determined for recovery (RC), improvement (IC), persistent (PE), aggravation (AC), new incidence (NC), and no sign (HC) groups based on the changes of skin lesions between before (in 2004) and after (in 2017) WAs reduction. The results indicate that the urinary concentrations of inorganic arsenic (iAs), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and total arsenic (TAs) were much higher for RC and IC groups than for the other groups in 2004, while these values varied slightly among the groups in 2017. The urinary %iAs of all the groups was significantly decreased after WAs reduction. In contrast, the urinary %DMA of RC, IC, AC, and NC groups was increased. From 2004 to 2017, the PE and HC groups had lower decrease rate of %iAs and %MMA, and increase rate of %DMA, primary methylation index (PMI), and secondary methylation index (SMI) after WAs reduction. The adjusted odd ratios (ORs) showed that the RC, IC, AC, and NC groups were positively related with %iAs and %MMA and were negatively correlated with %DMA, PMI, and SMI before WAs reduction. It can be concluded that higher urinary %iAs and %MMA before WAs reduction increased the probability of skin lesions recovery and improvement, and the risks of skin lesions aggravation and incidence. Higher increase rate of urinary %DMA was positively associated with of skin lesions recovery and improvement. Moreover, higher urinary %iAs and %MMA or lower increase rate of urinary %DMA might increase the risk of skin lesions aggravation.