Determination of mercury and selenium in hair samples of Brazilian Indian populations living in the Amazonic region by NAA

Biomonitoring of mercury contamination of Brazilian Indian population group s living in the Xingu Park, a reservation situated in the Amazonic region, has revealed very high levels of mercury in hair samples as compared to con trols. Total mercury was determined by INAA in most of the tribes living in the Park and methylmercury was determined by CVAAS in samples with total m ercury above 10 mg/kg. Due to the fact that selenium seems to protect anima ls against the toxic effects of methylmercury, it was considered also of in terest to determine its concentrations in the hair samples with very high m ercury levels. Selenium was determined by INAA via the short-lived radionuc lide Se-77m (T-1/2 = 17.45 s). The correlations between selenium and mercur y concentrations in Brazilian controls and in the Indian population groups are discussed.