Mercury is an important environmental pollutant for the world and, specially, for the Amazon. Presently, there are some evidences about chronic exposure to relatively low concentrations of mercury initiating genotoxic processes (DNA damage) in humans. However, to date, few epidemiological studies were carried out with Amazonian populations exposed to mercury, but no study included a population as a control to compare. The aim of this study was to identify the technique more adequate for analyzing mercury genotoxicity in Amazonian populations and to establish control values of genotoxicity in an Amazonian riverside population. To carry out in vitro tests, two traditional methods to detect genotoxicity (micronuclei and chromosomal aberrations) were applied and compared. Primary cultures of blood lymphocytes of volunteers from Belém, were exposed to relatively low concentrations of methylmercury (1-500μg/l or 0,004-2 μM). Mitotic index (proportion of cells in metaphase) originated with the method of detection of chromosomal aberrations was the parameter more sensitive to mercury genotoxicity. After identification of the method and the parameter more sensitive to mercury genotoxicity, this method was applied to study an Amazonian riverside population as a control for studies about mercury genotoxicity. Panacauera was selected as control population and mitotic index for this population was 0.077 ± 0.045. Detected values of mitotic index showed variability, not related to age or sex. When these values were compared to the values of Brasilia Legal (community exposed to methylmercury) registered in literature, mitotic index of Brasilia Legal for some groups was below mitotic index of Panacauera, pointing to an inhibition of the cell-cycle progression and/or loss of proliferative capacity due to mercury intoxication. These results support the idea that mitotic index may serve as an essential parameter for the early diagnosis of the damage provoked by mercury exposure, and they contribute to the epidemiological knowledge about the consequences of the chronic exposure with mercury in Amazonian populations.
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