Title

Focusing on Human Contaminants Exposure Pathways and Contaminant Levels in Food Sources

Fiscal Year

2008-2009

Community/Region

Wabaseemoong First Nation and Asubpeeschoseewagong First Nation (Kenora), Ontario

Principal Investigator

Dr. Leanne Simpson

Community Project Lead

Judy DaSilva

Project Members

Chief Simon Fobister, Betty Riffel, Roberta Keesic, Anthony Henry and Dr. Patricia Sellers

Project Summary

In the 1960s, a major spill from a chlor-alkali plant resulted in the discharge of approximately 10 000 kg of mercury into the Wabigoon River. This incident caused many residents of Wabauskang, Grassy Narrows, and Whitedog to get sick from eating fish caught from the Wabigoon-English river system. Since members of these First Nations communities continue to harvest fish from these waters, exposure to mercury is an ongoing concern.

The objective of this study was to assess mercury levels in samples of sediment and crayfish muscle tissue collected from several sites near Whitedog and one site near Quibel, Ontario.

According to the study results, two out of four sites near Whitedog had mercury concentrations in surface sediment that were three to five times higher than what were considered to be background for the region. Mercury concentrations in the surface sediment at Shallow Lake, a small lake adjacent to the Wabigoon River and upstream of Quibel, was about 70 times higher than what was considered as background. Sediment cores that were collected and analyzed from the confluence of the English and Winnipeg Rivers also showed slightly elevated levels of mercury. Moreover, there were higher mercury levels in newly accumulated sediment compared to sediment that was 12 or 35 years old. One possible explanation is that old, mercury-rich sediments from upstream locations closer to Dryden, Ontario, where the chlor-alkali plant existed, became resuspended in the water column during flood events and then transported to downstream sites where they became freshly deposited. However, the concentration of mercury in crayfish at an upstream site was not elevated, which suggested that total mercury in sediments did not necessarily reflect food-web mercury dynamics. Concentrations of mercury in crayfish at a downstream site were inconclusive and warrant further investigation.

The study authors recommended that First Nation communities continue to monitor mercury levels in the Wabigoon and Winnipeg River Systems using crayfish as a bioindicator of mercury. In addition, sections of the river system that could not be evaluated in this study should be surveyed in future studies.