Genetic polymorphism in the biotransformation of inorganic arsenic and itsrole in toxicity

Arsenic is a recognized human carcinogen, but experimental cancer studies a re negative. There is a variation in susceptibility among individuals, whic h probably is related to variation in metabolism. Inorganic arsenic is meth ylated to methylarsonic acid (MMA) and dimethylarsinic acid (DMA), which ar e less toxic and more readily excreted in urine than the inorganic arsenic. The rate of methylation of arsenic varies considerably between species. Mo st population groups studied so far have on average 10-30% inorganic, 10-20 % MMA, and 60-70% DMA in urine, but there is a considerable inter-individua l variation. Also, recent studies have identified groups with unusually low or high urinary excretion of MMA. Thus, there seems to be a genetic polymo rphism in the biomethylation of arsenic. However, the methyltransferases in volved in arsenic methylation have not been characterized. (C) 2000 Publish ed by Elsevier Science Inland Ltd. All rights reserved.