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 Tapaj?s
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 Tapaj?s River, an area heavily influenced by
gold mining activity, we studied the communities of S?o Luiz do Tapaj?s (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 S?o Luiz do Tapaj?s 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 S?o Luiz do Tapaj?s (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.
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