EARTH Thailand

Mercury pollution in the Tapajos River basin, Amazon Mercury level of head hair and health effects

Authors: Masazumi Haradaa, Junko Nakanishib, Eiichi Yasodab, Maria da Conceicao N. Pinheiroc, Teiichi Oikawac, Geraldo de Assis Guimaraesc, Bernardo da silva Cardosoc, Takako Kizakid, Hideki Ohnod. Published by Environment International, 2001

aDepartment of Social Welfare Studies, Kumamoto Gakuen University, Japan
bInstitute of Environmental Science and Technology, Yokohama National University, Japan
cNucleo de Medicina Tropical, Universidade Federal do Para, Brazil
dDepartment of Molecular Predictive Medicine and Sport Science, School of Medicine, Kyorin University, Japan


There is increasing concern about the potential neurotoxic effects of exposure to methylmercury for the 6 million people living in the Amazon, even in regions situated far away from the gold mines (garimpos), considered to be the major source of mercury pollution. In November 1998, a spot investigation on mercury contamination was conducted in three fishing villages on the Tapajos River, an effluent on the Amazon, situated several hundred kilometers downstream from the gold-mining areas. A total of 132 fishermen and their families volunteered for the current study.  As was anticipated, the total mercury levels in the head hair collected from the fishing villages were relatively high and the number of subjects with a high total mercury level over 10 ppm (the least upper bound of a normal value) was 103 (78.0%) in total, along with various symptoms, thereby suggesting wife mercury contamination in the Tapajos River basin. Moreover, in view of the absence of other diseases (e.g., alcoholism or malaria), a high intake of fish containing a methylmercury level, and high hair mercury levels in addition to the various symptoms such as sensory disturbance (especially glove-and-stocking type, which is characteristic of Minamata disease), tremor, failure in two-point discrimination, and slight balancing failure, several subjects examined were diagnosed with mild Minamata disease. The findings obtained suggest, thus, that the mercury pollution in the Amazon should be crucially observed for head hair mercury level and health in a much broader region.

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