Community-directed risk assessment of mercury exposure: gold mining, fish, and unsuspected ethylmercury.

The interesting paper by Peplow and Augustine (1) addressed an issue important to Amazonian populations: self-diagnosis of environmental and public health problems. The case of the Kwakoegron community of Maroons is particularly interesting because of their awareness of research needs, health priorities, and need for risk assessment programs regarding mercury (Hg) contamination. Based on the research results (and understanding the hair Hg numbers), the villagers “proposed an intervention plan contemplating: (1) routine analysis of Hg exposure to monitor trends and track the effects of exposure-reduction efforts; (2) routine health assessments to determine the effects of Hg exposure, particularly in children less than 5 years of age; and (3) fish advisories based on fish biology and trophic level....” I fully agree with the paper’s conclusions in the specific confine of their objectives, but I would like to share a broader perspective of issues related to Hg exposure, fish consumption, and alluvial gold mining. For subsistence, fish is a central dietary item of Amazonian villagers (which might be the case with the Kwakoegrons) and, regardless of gold mining activities, they bioconcentrate methylmercury as a secondary constituent (2). The Kwakoegrons’ mean hair Hg concentration (4.41 μg·g–1) denotes regular fish consumption that is much lower than the mean reported for neighboring Rio Negro riverines (3), who are without neurological problems and eat fish from waters with no history of gold mining activity. Although Peplow and Augustine’s paper clearly discussed how Hg gets in fish, there is evidence that Hg released from gold amalgamation is only a tiny fraction of the natural Hg in Amazon soil (4). Furthermore, there are no significant differences in mean fish Hg concentration in rivers with and without gold mining activities (5). Actually, the Hg methylation activity (necessary for Hg to gain access to the aquatic food web) explained by Peplow and Augustine is disrupted during river bank dismounting or bottomsediment scarification (by dredges) commonly applied in alluvial gold extraction in Amazon rivers. I do not dispute the research findings of neurobehavioral tests in Amazonian fish eaters (the one reporting significant alterations and those showing no effect of fish Hg and not referred to in the paper), but it is important to note that neuropathies associated with food and nutrition in the last two decades have not implicated fish-eating habits (6). La Revista Panamericana de Salud Pública/Pan American Journal of Public Health se complace en publicar cartas de los lectores dirigidas a estimular el diálogo sobre los diversos aspectos de la salud pública en las Américas, así como a esclarecer, discutir o comentar de manera constructiva las ideas expuestas en la revista. Las cartas deben estar firmadas por el autor y especificar su afiliación profesional y dirección postal. Cuando se trate de comentarios sobre un artículo que requieran contestación del autor, se procurará conseguir esa respuesta con el fin de publicar ambas cartas. La Redacción se reserva el derecho de editar las cartas recibidas y resumirlas para mayor claridad.