Abstract
Background: Mercury is present in the Amazonian aquatic environments from both natural andanthropogenic sources. As a consequence, many riverside populations are exposed tomethylmercury, a highly toxic organic form of mercury, because of their intense fish consumption.Many studies have analysed this exposure from different approaches since the early nineties. This review aims to systematize the information in spatial distribution, comparing hair mercury levels bystudied population and Amazonian river basin, looking for exposure trends. Methods: The reviewed papers were selected from scientific databases and online libraries. Weincluded studies with a direct measure of hair mercury concentrations in a sample size larger than10 people, without considering the objectives, approach of the study or mercury speciation. Theresults are presented in tables and maps by river basin, displaying hair mercury levels and specifyingthe studied population and health impact, if any.Results : The majority of the studies have been carried out in communities from the centralAmazonian regions, particularly on the Tapajós River basin. The results seem quite variable; hairmercury means range from 1.1 to 34.2 μg/g. Most studies did not show any significant difference inhair mercury levels by gender or age. Overall, authors emphasized fish consumption frequency asthe main risk factor of exposure. The most studied adverse health effect is by far the neurologicalperformance, especially motricity. However, it is not possible to conclude on the relation betweenhair mercury levels and health impact in the Amazonian situation because of the relatively smallnumber of studies.Conclusions : Hair mercury levels in the Amazonian regions seem to be very heterogenic,depending on several factors. There is no obvious spatial trend and there are many areas that havenever been studied. Taking into account the low mercury levels currently handled as acceptable,the majority of the Amazonian populations can be considered exposed to methylmercurycontamination. The situation for many of these traditional communities is very complex because oftheir high dependence on fish nutrients. It remains difficult to conclude on the Public Healthimplication of mercury exposure in this context.