Abstracts: ISEE 21st Annual Conference, Dublin, Ireland, August 25-29, 2009: Oral Presentations
Background and Objective:
Subsistence riverside dwellers (ribeirinhos) of the Amazon Basin depend on fish for their principal source of protein, but fish availability changes with seasonal high and low waters. We report monthly changes in fish consumption and attendant methyl-mercury (meHg) concentrations and hair-Hg of a traditional village population of the Rio Madeira in Brazilian Amazonia.
A total of 120 villagers in 18 households were followed for six months (August to February) for weighed portions of fish consumed. Mean daily per capita fish-consumption was high (406 g/day) with a household eating a fish meal 4 to 14 times a week; the integrated yearly consumption was estimated at 148.2 kg/person. Carnivorous fish are the major source of meHg, but six of the more consumed fish species contributed the most to Hg exposure: curimatã (Prochilodus spp.), pacú (Mylossoma spp.), tucunaré (Cichla monoclus), cará (Astronotus spp.), chora (Potamorhina spp.), and jaraquí (Semaprochilodus ocellaris) comprised more than 50% of the fish caught and consumed.
In these species (as consumed) median total-Hg concentrations ranged from 0.011 to 0.409 ppm. The villagers mean hair-Hg concentration was high (17.4 μg.g−1), 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. However, hair-Hg concentrations were well correlated within families; maternal hair-Hg was significantly correlated with respective children's hair-Hg (Spearman r = 0.5390; P < 0.0001). Due to high levels of consumption these villagers exceeded recommended Hg exposure in 40 of 45 species regularly consumed, regardless of trophic position in the food web.
Although predatory species carry the highest concentrations of Hg, the high daily fish intake of these villagers is predominantly of species with much lower Hg concentrations. Therefore, fish advisories aiming at predatory species may not be effective in lowering hair-Hg of subsistence villagers.