Hing Man Chan

Impacts of Mercury on Freshwater Fish-Eating Wildlife and Humans

This paper reviews the current state of knowledge of the toxic effects of mercury on fish-eating birds, mammals, and humans associated with freshwater ecosystems, including new information on the relative risk of elevated methyl Hg exposure for fish-eating birds inhabiting aquatic ecosystems impacted by mining/smelting activities and areas characterized by high geological sources of Hg. The influence of various environmental conditions such as lake pH, DOC, and chemical speciation of Hg, on fish-Hg concentrations and Hg exposure in fish-eating wildlife, are discussed. Although a continuing global effort to decrease the release of this nonessential metal into the environment is warranted, Hg methylation and biomagnification may be limited in some environments due to chemical speciation of mercury in soils and sediments (e.g., HgS) and water quality conditions (e.g., high alkalinity and pH) that do not facilitate high methylation rates. We have shown such limitations for a lake where historic Hg mining greatly increased sediment-Hg loadings, yet Hg increases in small fish of various species are currently lower than expected, and top predators (bald eagles), despite having elevated concentrations of Hg in their blood compared with individuals from nearby lakes, exhibit no Hg-related reproductive impairment or other signs of MeHg intoxication. Recent epidemiological studies have shown that fish-eating human populations may be exposed to Hg sufficient to cause significant developmental effects. However, for humans, we conclude that the current USEPA reference dose for MeHg may be too restrictive, particularly for the less sensitive adult. The health status of indigenous peoples relying on the subsistence harvest of wild foods may be negatively affected by such restrictions.

Mercury in the traditional diet of indigenous peoples in Canada

Traditional food of indigenous people in Canada, particularly fish and marine mammal meat, has mercury (Hg) concentrations exceeding the Canadian consumption guideline level of 0.5 microg/g. Health effects of Hg in traditional food are, therefore, a concern. We conducted contaminant exposure assessments in 28 indigenous communities in Canada. Hg exposure was greatest among communities with high use of marine mammals as food. Exposure among other communities was variable. Recent adoption of a lower intake guideline for women of reproductive age and by Health Canada may decrease the use of traditional food, and could result in other health problems, such as increased risk of diabetes and cardiovascular disease.

Healthy living in Nunavut: an on-line nutrition course for inuit communities in the Canadian arctic

Objectives. It is recognized that empowerment of Indigenous Peoples through training and education is a priority. The objective was to design a course that would provide an innovative training approach to targeted workers in remote communities and enhance learning related to the Nunavut Food Guide, traditional food and nutrition, and diabetes prevention. Study Design. A steering committee was established at the outset of the project with representation from McGill University and the Government of Nunavut (including nutritionists, community nurses and community health representatives (CHRs), as well as with members of the target audience. Course content and implementation, as well as recruitment of the target audience, were carried out with guidance from the steering committee. Methods. An 8-week long course was developed for delivery in January - March, 2004. Learning activities included presentation of the course content through stories, online self-assessment quizzes, time-independent online discussions and telephone-based discussions. Invitations were extended to all prenatal nutrition program workers, CHRs, CHR students, home-care workers, Aboriginal Diabetes Initiative workers and public health nurses in Nunavut. Results. Ninety-six health-care workers registered for Healthy Living in Nunavut, with 44 actively participating, 23 with less active participation and 29 who did not participate. Conclusions. Despite having to overcome numerous technological, linguistic and cultural barriers, approximately 40% of registrants actively participated in the online nutrition course. The internet may be a useful medium for delivery of information to target audiences in the North. (Int J Circumpolar Health 2004; 63(3):243–250)