Arsenic methylation capacity and skin cancer.

Chronic ingestion of arsenic from drinking water is associated with the occurrence of skin cancer. To clarify the role of arsenic methylation capacity in the development of arsenic-associated skin lesions, an epidemiological case-control study was conducted in the southwestern region of Taiwan, in which 26 skin disorder patients were matched with control subjects. The objective of this study was to determine whether arsenic methylation capacity of patients with skin disorders differed from that of matched controls. Both cases and controls had been exposed to similar high concentrations of arsenic in drinking water. Results indicated that skin lesion cases had higher percents of inorganic arsenic (InAs, 13.1+/-3.7%), methylarsonic acid (MMA, 16.4+/-3.2%), lower percent of dimethylarsinic acid (DMA, 70.5+/-5.8%), and higher ratio of MMA to DMA (MMA/DMA, 0.24+/-0.06) than matched controls (InAs: 11.43+/-2.1%; MMA: 14.6+/-2.6%; DMA: 73.9+/-3.3%; MMA/ DMA: 0.20+/-0.04). Individuals with a higher percentage of MMA (>15.5%) had an odds ratio of developing skin disorder 5.5 times (95% confidence interval, 1.22-24.81) higher than those having a lower percentage of MMA. This association was not confounded by hepatitis B surface antigen, cigarette smoking, or alcohol and tea consumption. It is concluded that arsenic biotransformation including methylation capacity may have a role in the development of arsenic-induced skin disorders.