Ronaldo Almeida

Mercury-selenium relationships in liver of Guiana dolphin: the possible role of Kupffer cells in the detoxification process by tiemannite formation.

Top marine predators present high mercury concentrations in their tissues as consequence of biomagnification of the most toxic form of this metal, methylmercury (MeHg). The present study concerns mercury accumulation by Guiana dolphins (Sotalia guianensis), highlighting the selenium-mediated methylmercury detoxification process. Liver samples from 19 dolphins incidentally captured within Guanabara Bay (Rio de Janeiro State, Brazil) from 1994 to 2006 were analyzed for total mercury (THg), methylmercury (MeHg), total organic mercury (TOrgHg) and selenium (Se). X-ray microanalyses were also performed. The specimens, including from fetuses to 30-year-old dolphins, comprising 8 females and 11 males, presented high THg (0.53–132 µg/g wet wt.) and Se concentrations (0.17–74.8 µg/g wet wt.). Correlations between THg, MeHg, TOrgHg and Se were verified with age (p<0.05), as well as a high and positive correlation was observed between molar concentrations of Hg and Se (p<0.05). Negative correlations were observed between THg and the percentage of MeHg contribution to THg (p<0.05), which represents a consequence of the selenium-mediated methylmercury detoxification process. Accumulation of Se-Hg amorphous crystals in Kupffer Cells was demonstrated through ultra-structural analysis, which shows that Guiana dolphin is capable of carrying out the demethylation process via mercury selenide formation.

Mercury and DDT exposure risk to fish-eating human populations in Amazon

In order to investigate the potential risk of mercury and DDTs exposure to fish-eating human populations in Samuel Reservoir, not affected directly by gold-mining activities, the axial muscle of Cichla monoculus was analyzed. Twenty-nine and thirty adults individuals were collected respectively on February (rainy season) and August (dry season) 2007. The specimens were sacrificed by spinal section before sex identification, body weight and total length determination. For total mercury, DDT and DDE quantifications and cholinesterase activity samples of the axial muscle were frozen at -20°C, and for histopathological studies gill and liver were fixed in ALFAC solution for 16 h. A value of 48.2% and 33% of the individuals, respectively from rainy and dry seasons, presented mercury concentrations higher than the maximum established for safe human consumption (0.5 μg g⁻¹) by World Health Organization. A positive correlation between body weight and Hg concentration was observed only in individuals from the rainy season, but no correlation was observed to DDT and DDE from both seasons. Differently from that observed to mercury, DDT levels presented a significant difference between both studied seasons, but no correlation was observed for both mercury and DDTs and sex. The levels of DDTs in muscle of C. monoculus are under the maximum established by FAO-Alimentarius CODEX and Swedish Food Regulation for human consumption. The histopathological and neurotoxic findings showed that the wild population of fish is affected by chronic exposure to mercury, meaning risk also to fish-eating populations. Finally, the results showed that C. monoculus is an important vehicle for human exposure to mercury and DDTs in Samuel Reservoir and that it is necessary a continuous biomonitoring of the levels of both pollutants in order to manage the risk of exposure to human populations.

Fish consumption by traditional subsistence villagers of the Rio Madeira (Amazon): Impact on hair mercury

Abstract Background: Subsistence ribeirinhos of the Amazon Basin depend on fish for their principal source of protein, but fish availability changes with seasonal high and low waters. Aim: To assess taxa and quantity of fish consumed and estimate attendant exposure to methyl-Hg in a traditional subsistence high fish-eating community of the Amazon Basin. Subjects and methods: 120 villagers in 18 households were followed for 6 months (August to February) for weighed portions of fish consumed. Results: Mean daily per capita fish consumption was high (406 g/day) with fish meals ranging from 4 to 14 times/week and an integrated yearly consumption of 148.2 kg/person. Median total-Hg concentrations in fish ranged from 0.011 to 0.409 ppm; six of the more consumed fish species comprised more than 50% of the fish consumed. The villagers mean hair-Hg concentration was high (17.4 ± 11.5 μg/g), with both inter- and intra-household variation despite similar high fish consumption; only 7% showed hair-Hg concentrations < 5 μg/g, but 75% had hair-Hg levels above 10 μg/g. Maternal hair-Hg was significantly correlated with respective childrens hair-Hg (Spearman r = 0.5390; p < 0.0001). The high daily fish intake of these villagers is predominantly of species with much lower Hg concentrations. Conclusion: In Amazonian lifestyle of ribeirinho communities traditional fish consumption is high and depends on available species; fish is also the principal via of meHg exposure and attendant hair-Hg concentrations.

A description of mercury in fishes from the Madeira River Basin, Amazon, Brazil

Over the last 20 years several projects carried on the Madeira River basin in the Amazon produced a great amount data on total Hg concentration in different fish species. In this paper we discuss temporal trends in Hg contamination and its relation to body weight in some of those fishes, showing that even within similar groups, such as carnivorous and non-migratory fish, the interspecies variability in Hg accumulation is considerable.

Contaminação de aqüífero por hidrocarbonetos: estudo de caso na Vila Tupi, Porto Velho - Rondônia

Underground storage tanks (UST) are widely used in the Porto Velho area. A large number of these USTs are in bad condition due to corrosion processes causing groundwater contamination. A large number of these leaking underground fuel tanks (LUFT) are in urban areas but due to the lack of water quality monitoring, they are only detected when there is a high contamination level. This study identified petroleum hydrocarbons, derived from a LUFT, by a silica gel/petroleum ether partitioning gravimetric method and by gas chromatographic analysis of samples collected in wells dug in a gas station and in houses in the aforementioned neighborhood.