Methylmercury and the health of indigenous peoples: a risk management challenge for physical and social sciences and for public health policy

Methylmercury in aquatic ecosystems and bio-accumulated in aquatic biota, e specially fish, is a major public health concern internationally. Precautio nary efforts are currently underway internationally to reduce the anthropog enic release of mercury, which in turn, over time, will reduce human exposu re. However, at the present time, it is important to address the issue of m anagement of the risks of exposure as they exist now. Of particular concern are the impacts of methylmercury on indigenous populations which depend on fish as a subsistence food source, both in remote areas of developed count ries, such as Canada, and in developing countries such as Brazil. Research into these impacts over the past two or three decades has shown that, other than in very severe pollution situations such as occurred in Minamata, Jap an, the direct impacts on human health are difficult to prove. On the other hand, the indirect negative effects of methylmercury on health, mediated t hrough the disruption of lifestyle and eating patterns and the associated s ocio-cultural and socio-economic consequences among the affected native pop ulations, have, in many cases, been significant. These social factors have raised serious challenges in determining practical public health policies o n the issue. Policy development relating to environmental contaminants has been presented, with the problem of assessing the role of the various facto rs which contribute to the impact on health as a result of socio-cultural d isruption. These factors include changes in diet and lifestyle due to methy lmercury in the environment and its real or perceived risk. The standard ph ysical sciences risk assessment process, based on the lowest observed adver se effects level (LOAEL) or no observed adverse effects level (NOAEL) used in defining health policies may be seen as over-simplistic theoretical extr apolations when viewed in the context of the concerns of the social science s. Both approaches, however, have relevance to health policies that address the risks posed by environmental methylmercury. Therefore, the standard ph ysical sciences approach of the past three decades now needs to be linked w ith the social sciences approach, with its focus on the indirect impacts of exposure to methylmercury, to provide a comprehensive approach to public h ealth policy development. With this objective in mind, this paper reviews m ethylmercury-related data from both physical and social sciences. It attemp ts to draw on the findings in both disciplines to provide suggestions for a n integrated approach in policy development relating to human health and hu man exposure to methylmercury, especially among indigenous peoples in remot e areas and in developing countries. An integrated approach such as this ma y help to limit adverse health effects in the indigenous communities affect ed. (C) 2000 Elsevier Science B.V. All rights reserved.