Assessment of fish consumption beneficial use impairment at the Great Lakes Thunder Bay and St. Marys River Areas of Concern, Canada

Abstract

The North American Great Lakes were designated with 43 locally degraded Areas of Concern (AOCs) in the 1980s. Remediation activities geared towards restoring beneficial use impairments (BUIs) at the AOCs have been conducted by both the American and Canadian governments. Here we examine if the fish consumption BUI has been restored at the Thunder Bay Harbour and St. Marys River AOCs within the Canadian waters by applying a three-tier assessment framework using the fish contaminant data collected by the Government of Ontario, Canada. Fish consumption advisories published by the government as well as simulated advisories based on the post-2005 data were examined in Tiers 1 and 2. The results highlighted that the restrictions advised on eating fish from the AOCs are mild and are typically similar to other non-AOC areas of lakes Superior and Huron. Temporal trend analyses of three contaminants of concern, mercury, PCB and dioxins/furans, generally showed substantial improvements over the last 30+ years and mostly continued declining trends in the recent years. These findings support a re-designation of the fish consumption BUI to “not impaired” at the two AOCs. As a follow up, it is recommended to confirm improvements in the dioxin/furan/dioxin-like PCB levels in fish at the Thunder Bay AOC. It is also advisable to conduct a survey to properly define “beneficial use” of fish consumption for the AOCs (i.e., which fish and in what quantity do people eat), and thereby validate the critical assumption of 8+ meals/month as a non-restrictive advice used in this assessment.