Assessment of contaminant levels in fish from the Toronto waterfront area

The Toronto waterfront area of Lake Ontario is part of the Toronto and Region Area of Concern (AOC), partly due to elevated contaminant levels in fish and the resulting restrictive fish consumption advisories. Data collected by the Province of Ontario were used to investigate long-term (1975-2011) temporal trends of mercury, polychlorinated biphenyls (PCBs), mirex, and toxaphene levels in multiple fish species collected from the Toronto waterfront area. Recent (2000-2012) mercury and total PCB levels in fish from the Toronto waterfront area were compared to those for other regions, including other AOCs, of the Canadian waters of the Great Lakes. A similar comparison of fish PCB levels was also conducted for the Canadian AOCs for a historical scenario. Mercury and PCB levels in fish from the Toronto waterfront area demonstrated significant decreasing trends over time in multiple species, and recent mercury levels are well below the current consumption advisory benchmarks. In some cases, PCB levels remain above the current consumption advisory benchmarks and above the levels observed in fish from other AOC and non-AOC regions of the Canadian Great Lakes. Half-life calculations for these species indicate that it may take 8-26 years for total PCB concentrations in certain fish species to decrease below the current consumption advisory benchmarks. Sustained monitoring of PCBs in fish from the Toronto waterfront area is recommended to aid in ensuring that recovery continues.