Comparative study of mercury speciation in commercial fishes of the Brazilian Amazon

Mercury is responsible for serious episodes of en- vironmental pollution throughout the world, especially in the Amazon. This toxicity has led regulatory agencies to focus on fish as the target organism for protecting the health of humans and other sensitive organisms. Unfortunately, in the Amazon area, different sampling strategies and the wide variety of sampling areas and fish species make it extremely difficult to determine relationships across geographic regions or over time to ascertain historical trends. Thus, the aim of this work was to achieve three main objectives: a comparative study of mercury contamination in fish of Itaituba (Tapajos, located downstreamofthelargestgold-miningregioninAmazon)and Belem (an area non-exposed to mercury pollution of anthro- pogenic origin), perform an analysis of inorganic mercury (IHg) versus monomethylmercury (MeHg) contents, and, fi- nally, compare mercury contamination in Tapajos over time. Five piscivorous species were obtained in Itaituba and Belem. Also, four non-piscivorous species were collected in Itaituba. For the first time, mercury speciation showed that (1) current MeHg levels in piscivorous species in Tapajos are higher than those of the non-exposed area, (2) piscivorous species from Itaituba (dourada, filhote, and sarda) contained mercury levels above the World Health Organization safety limit (~17 %) and/or above the US Environmental Protection Agency tissue residue criterion (40 %), (3) increased MeHg is usually ac- companied by increased IHg, and (4) the mean total mercury concentrations for piscivorous species in Itaituba were within the same range and, associated uncertainties as those previ- ously reported, although a remarkable decreasing trend over time was observed for mean total Hg concentrations in non- piscivorous species from Itaituba. The present study supports the importance of continuous monitoring of both populations in the Amazon Rivers. Our results will better assist the devel- opment of preventive strategies and governmental actions to confront the problem of mercury contamination in the Amazon.