Temporal Evolution of Exposure to Mercury in Riverside Communities in the Tapajós Basin, from 1994 to 2010

Abstract

Our objective was to evaluate the temporal evolution of mercury exposure in two riverside communities, Barreiras and São Luiz do Tapajós, downstream of gold mining areas in the Tapajós basin, Brazilian Amazon. The quantification of mercury in hair sample was made by atomic absorption spectrophotometry in the period between 1994 and 2010. In São Luiz do Tapajós the mercury exposure varied, in log units, from the peak of 1.21 ± 0.03 μg/g in 1996 to 1.16 ± 0.07 μg/g in 2007. Mercury exposure in Barreiras varied, in log units, from 1.25 ± 0.04 μg/g in 1994 to 1 ± 0.03 μg/g in 2010, peaking in 1995 at 1.25 ± 0.06 μg/g. Total mercury concentration found in both communities had no statistical differences across the years (p > 0.05) and they were higher than non-mercury exposed communities in Brazil and in South America. We concluded that the mercury exposure in the Tapajós basin is more than regulatory levels or higher than the general population.

Teores de mercúrio em cabelo e consumo de pescado de comunidades ribeirinhas na Amazônia brasileira, região do Tapajós

“…Com todos esses casos mencionados, houve a crescente conscientização das consequências que o mercúrio pode causar no ecossistema e na saú-de pública 4 . Estudos na Amazônia, acerca dos níveis de exposição ao Hg, datam desde os anos 90, perí-odo o qual altas concentrações foram identificadas, sendo objeto de preocupação em virtude dos riscos a saúde que este metal poderia provocar a populações expostas [5][6][7][8][9][10][11][12][13][14][15] . Na região do Tapajós, os índices em amostras de cabelos configuram uma exposição permanente, sendo o pescado da região a fonte desta exposição 10,11,16 .…”

“…Estudos na Amazônia, acerca dos níveis de exposição ao Hg, datam desde os anos 90, perí-odo o qual altas concentrações foram identificadas, sendo objeto de preocupação em virtude dos riscos a saúde que este metal poderia provocar a populações expostas [5][6][7][8][9][10][11][12][13][14][15] . Na região do Tapajós, os índices em amostras de cabelos configuram uma exposição permanente, sendo o pescado da região a fonte desta exposição 10,11,16 . A poluição ambiental neste local foi resultante tanto do despejo de mercúrio metáli-co decorrente da garimpagem de ouro, como de outras fontes que contaminaram os ecossistemas aquáticos, chegando à população humana através da dieta, em sua forma de metilmercúrio 17 .…”

Manifestações emocionais e motoras de ribeirinhos expostos ao mercúrio na Amazônia

“…The Hg levels in hair samples is considered the best bioindicator of exposure to Hg from ingestion of contaminated food 17 and is commonly used by several authors 5,[7][8][9][10][11]23,29 to measure long-term exposure. Through the different hydrographic locations it is possible to identify Hg exposure variations in each region.…”

“…In these studies, the Hg levels in Itaituba were significantly higher (p < 0.0001) than those in Acará. The riverside-dwelling communities in the Tapajós region have a history of long-term exposure, for approximately two decades, and are known for uncontrolled mineral exploration [5][6][7][8]26 . Riverside dwellers in Acará had low HgT levels, which can be explained by the location, which is far from mineral prospecting, and by fish consumption with low HgT levels.…”

“…The case provided an important body of information on the clinical symptoms and epidemiological characteristics of mercury poisoning, serving as a milestone for the mobilization of organized segments of civil society in different parts of the world, including Brazil 2 . In the Amazon region, several studies monitor the levels of mercury exposure in the population [3][4][5][6][7][8][9][10][11] and the fish [12][13][14] , as the region presents a consequent contamination resulting from mineral prospecting, forest fires, the presence of large natural reservoirs and the implantation of hydroelectric plants that cause flooding, transferring mercury from the soil to the water column 15 . Mercury (Hg) as a fish contaminant is a form of non-occupational exposure; its concentration occurs in the organic form of methylmercury (MeHg).…”