Our Waters, Our Fish, Our People – Mercury Contamination in Fish Resources of Two Treaty #3 Communities

Members of the Grassy Narrows and Wabaseemoong First Nation communities, located along the English-Wabigoon River watershed in northwestern Ontario, have been severely impacted by mercury contamination since the 1970s. Currently, significant concern continues to exist about the potential health risks associated with fish consumption, which has been a principal component of their traditional diet, and which provide nutritional, social and cultural benefits to the community.

The objective of this research was to quantify the levels of mercury in local fish and assess the body burden of mercury among residents of these two communities. Samples of the four most commonly consumed species of fish, walleye, northern pike, large-mouth bass, and whitefish, were collected from lakes near the communities and analyzed for their mercury content. Residents of Grassy Narrows and Wabaseemoong also participated in dietary interviews and samples of their hair were collected for mercury analysis.

The highest mercury concentrations were found in northern pike and the lowest in whitefish. The concentrations of mercury in fish species from Clay Lake were consistently higher than those from other lakes. Therefore, it was recommended that consumption of fish from Clay Lake should be avoided. Two participants from Grassy Narrows (3.5%) and 4 participants from Wabaseemoong (11.1%) had hair mercury concentrations that exceeded the no risk level of 6 mg/kg established by Health Canada. There was a significant correlation between hair mercury concentrations and the amount of fish intake. It was concluded that there should be minimal concern about mercury contamination in these two communities. Given the substantial nutritional benefits of eating fish and the generally low mercury body burden among members of the Grassy Narrows and Wabaseemoong communities, they were encouraged to continue using local fish resources. However, the study authors recommended that frequent fish consumers reduce their mercury intake by eating smaller fish and more whitefish.