Methylmercury in hair samples from different riverine groups, Amazon, Brazil

The present study was aimed to evaluate comparatively the levels of methylmercury (MeHg) in human hair, collected from different groups of Amazonian populations exposed to contamined fish. The study was undertaken in fishing villages and gold mining areas, mainly in the Tapajós and Madeira river basins, two of the main tributaries of Amazon river. The study population included 125 hair samples, chosen from a collection of over one thousand samples collected in different periods. Hair analyses were conducted with a new efficient extraction technique and measured with ECD-gas chromatographer. This analytical method presented good accuracy and precision when compared with standard hair samples from IAEA. A highly significant correlation was found at the interlaboratory exercise between National Institute for Minamata Disease and our laboratory at Federal University of Rio de Janeiro. The results of the present study showed, through hair analysis, a relationship between environmental contamination by mercury and methylmercury and dietary habits of the Amazon population. The highest levels of MeHg in hair samples were found in riverine population from upper Tapajós river and in riverine population from some tributaries of Madeira river, followed by population of fishing villages from Madeira river. Majority of the women of child-bearing age presented high MeHg concentration in hair samples (10 mg.kg-1). On the other hand, Yanomami Indians presented MeHg concentration below the limit tolerable of 6 mg.kg-1.