Context: Approximately 100 million people throughout the world consume water contaminated
with arsenic at levels above carcinogenic thresholds, including 40 million in Bangladesh
alone, with up to one-fourth of deaths attributed to arsenic exposure in the worst-affected
regions. There are no proven therapies for treating chronic arsenic toxicity or for
preventing arsenical cancers. Selenium has been known to counter arsenic toxicity in a
variety of animal models. The investigators have recently shown in animals and humans that
this effect is mediated by the formation of [(GS)2AsSe]- , the seleno-bis(S-glutathionyl)
arsinium ion, which is then rapidly excreted via the hepatobiliary system. Concurrently, two
Phase II studies in China and Bangladesh have suggested clinical benefit to selenium
supplementation in arsenicosis patients.
Objective: To assess whether daily selenium supplementation counters arsenic toxicity in
patients exposed to drinking water arsenic. If proven effective, selenium supplementation
might be safely and cost-effectively implemented in the worst-affected localities.