Total mercury concentration in Amazonian riverside communities of two different areas with similar life style and differente influence of gold mining activity - a comparative study

Abstract

The inhabitants of several riverside communities in the Amazonian region, mainly located in areas under heavy influence of gold mining activity, have been evaluated for mercury exposure due to their rich fish diet associated with the occurrence of contaminated fish. This has been performed by measuring the TotalHg concentration in hair samples. Studies performed in villages afilie Tapajós river basin have shown TotalHg concentrations higher than 500 ppb in some fish species, high TotalHg in hair samples of riverside inhabitants, high prevalence of human exposure to mercury, and occurrence of some mild cases of mercury intoxication. We evaluated TotalHg concentration and mercury exposure prevalence among adults of four riversides communities located in two areas with different influence of gold mining activity. In the Tapajós River, an area heavily influenced by gold mining activity, we studied the communities of São Luiz do Tapajós (32 adults) and Barreiras (37 adults). In the Tocantins River, an area with low influence ofgold mining activity, we Studied the communities of Panacauera (23 adults) and Pindobal Grande (43 adults and 88 children). Hair sample TotalHg concentration was determined by atomic absorption spectrometry. In Panacauera it was 8.13:1: 5.89 um/g, range of 1.46 -25.58 ug/g, and mercury exposure prevalence of 34.7%. In Barreiras it was 15.38:1: 9.31 ug/g, range of 3.32 -35.68 ug/g, and mercury exposure prevalenceof 73.02%. In São Luiz do Tapajós it was 14.72 :I: 7.27 ug/g, range of 1.92 -29.96 ug/g, and prevalence of 68.70%. Panacauera showed TotalHg concentration and mercury exposure prevalence index smaller than Barre:iras and São Luiz do Tapajós (p < 0.05). Pindobal Grande had a very low TotalHg concentration, similar in adults and children (p > 0.05), and very low mercury exposure in adults and children. The present results support the view that inhabitants of Amazonian riversides communities bearing similar life style but different influence of gold mining activity exhibit different levels of TotalHg in hair samples. The TotalHg concentration found in the community of Pindobal Grande may be acceptable as the reference standard for Amazonian populations free from the influence of gold mining activity.