Toxic Chemicals

The 2012 Great Lakes Water Quality Agreement states that “the Waters of the Great Lakes should be free from pollutants in quantities or concentrations that could be harmful to human health, wildlife, or aquatic organisms through direct exposure or indirect exposure through the food chain.”

Status: Fair
Trend: Unchanging to Improving

Assessment highlights

The Toxic Chemicals indicator shows that concentrations of most toxic chemicals in the Great Lakes have decreased over the long term in water, air, sediment, fish and Herring Gull eggs. Overall, the status of Toxic Chemicals is Fair and the trend is Unchanging to Improving.

Many chemicals, including mercury and PCBs, have decreased significantly since the 1970s. Even with these long-term reductions, there are some instances of chemicals of mutual concern (CMCs), including polychlorinated biphenyls (PCBs), perfluorooctane sulfonate (PFOS), and polybrominated diphenyl ethers (PBDEs) exceeding ecosystem-based objectives in water, sediment, fish and Herring Gull eggs. Concentrations of other chemicals, including polycyclic aromatic hydrocarbons (PAHs), are higher in the waters of lakes Erie and Ontario than in the other lakes.

The 10-year trend for most of the Toxic Chemical sub-indicators show Unchanging or Improving conditions. However, atmospheric deposition remains a significant pathway for mercury, PCBs, PBDEs, and other contaminants into the Great Lakes. In addition, localized areas of highly contaminated sediment in or adjacent to urban areas and in Areas of Concern (AOCs) continue to act as sources of contaminants to the lakes.

Bar chart of total air vapor concentrations of PCBs (pg/m3) from 1992 to 2018 at Sturgeon Point, Lake Erie. Overall concentrations have declined.

Air vapor concentrations of PCBs at Sturgeon Point in eastern Lake Erie have declined by about 50% every decade since the early 1990s

Scatter plot of total PCB concentrations (ug/g wet weight) in whole Lake Trout in Lake Huron based on data from Environment and Climate Change Canada (orange points and trend curve) and the U.S. Environmental Protection Agency (blue points and trend curve) from 1977 to 2018. Overall concentrations have declined.

 

PCBs in whole Lake Trout have decreased

 

Sub-indicator supporting the Toxic Chemicals assessment

Sub-Indicator

Lake Superior

Lake Michigan

Lake Huron

Lake Erie

Lake Ontario

Good and Unchanging

Fair and Unchanging

Good and Unchanging

Fair and Improving

Fair and Improving

Fair and Improving

Fair and Undetermined

Good and Unchanging

Fair and Unchanging

Fair and Unchanging

Fair and Unchanging

Fair and Unchanging

Fair and Unchanging

Fair and Unchanging

Fair and Unchanging

Good and Improving

Good and Improving

Good and Improving

Good and Unchanging

Good and Improving

Fair and Improving (No lake-by-lake assessments were determined)

Status

Green indicator (good status). Most or all ecosystem components are in acceptable condition.
Good
Yellow indicator (fair status). Some ecosystem components are in acceptable condition.
Fair
Red indicator (poor status). Very few or no ecosystem components are in acceptable condition.
Poor
Grey indicator (status indeterminate). Data are not available or are insufficient to assess condition of the ecosystem components.
Undetermined