PFAS Forever Chemicals in Great Lakes Drinking Water: Contamination Data and Safety Guidelines

Per- and polyfluoroalkyl substances, the class of synthetic chemicals commonly known as PFAS or “forever chemicals,” have been detected in drinking water sources across the Great Lakes basin. As Health Canada and the U.S. Environmental Protection Agency tighten regulatory limits on these persistent compounds, Great Lakes communities face growing costs for water treatment upgrades and contamination remediation.

What Are PFAS and Why Do They Matter

PFAS are a family of over 14,000 synthetic fluorinated compounds that have been manufactured since the 1940s for use in non-stick coatings, waterproof fabrics, food packaging, and firefighting foams. Their carbon-fluorine molecular bonds are among the strongest in organic chemistry, which makes them extremely resistant to natural degradation. This persistence has earned them the “forever chemicals” designation.

Health concerns associated with PFAS exposure have been documented in extensive epidemiological research. A 2024 review published in The Lancet Planetary Health examined over 200 studies and found consistent associations between elevated PFAS blood levels and increased risk of kidney and testicular cancer, thyroid disease, immune system suppression, and adverse reproductive outcomes. Health Canada’s risk assessment, updated in 2024, identifies PFAS as substances of concern requiring active management in drinking water supplies.

PFAS Contamination in the Great Lakes

Multiple research programs have documented PFAS contamination throughout the Great Lakes system. A binational study coordinated by the International Joint Commission and published in 2024 analyzed surface water samples from 85 locations across all five Great Lakes. The study detected PFAS in 100 percent of samples, with total PFAS concentrations ranging from 2 nanograms per litre in open Lake Superior waters to over 40 nanograms per litre near urban discharge points in Lake Ontario and Lake Michigan.

Point sources of PFAS contamination in the Great Lakes basin include military bases and airports where aqueous film-forming foam (AFFF) was used for fire training, industrial facilities that manufactured or used PFAS compounds, municipal wastewater treatment plants that receive PFAS-containing consumer products, and landfills that accept PFAS-containing waste.

In Ontario, the Ministry of the Environment, Conservation, and Parks identified 23 sites with confirmed PFAS groundwater contamination as of its 2025 provincial inventory. Notable contamination sites include the former CFB Borden near Lake Simcoe, the Smithville area in Niagara Region, and several locations in the Kitchener-Waterloo region where industrial PFAS use has impacted municipal well fields.

Regulatory Framework

Canada and the United States are taking increasingly stringent approaches to PFAS regulation, though the two countries’ standards differ in their specifics.

Health Canada published updated Maximum Acceptable Concentrations (MACs) for PFAS in drinking water in 2024, setting a limit of 30 nanograms per litre for the sum of 24 specified PFAS compounds. This standard is legally binding for federally regulated water systems and serves as a guideline for provincial and territorial regulators.

The U.S. EPA finalized its National Primary Drinking Water Regulation for PFAS in April 2024, setting individual maximum contaminant levels (MCLs) of 4 nanograms per litre for PFOA and PFOS, the two most widely studied PFAS compounds. The EPA’s standard is substantially more stringent than Canada’s current limit, creating a disparity that has prompted calls from Canadian health advocates for tighter domestic regulation.

Water Treatment Challenges

Conventional water treatment processes, including coagulation, sedimentation, and chlorination, are ineffective at removing PFAS from drinking water. Effective treatment technologies include granular activated carbon (GAC) filtration, ion exchange resins, and high-pressure membrane systems including nanofiltration and reverse osmosis.

Upgrading existing water treatment plants to remove PFAS requires significant capital investment. A 2024 analysis by the Canadian Water and Wastewater Association estimated that the total cost of PFAS treatment upgrades for affected Great Lakes municipal water systems could reach 2.8 billion dollars over the next decade. Smaller communities face disproportionately higher per-capita costs due to the economies of scale inherent in advanced treatment technologies.

What Residents Should Know

Residents concerned about PFAS in their drinking water can access water quality reports from their municipal water provider, which typically include PFAS testing results where monitoring is conducted. Private well owners in areas near known contamination sites should consider having their water tested by an accredited laboratory.

Point-of-use water filters certified to NSF/ANSI Standard 53 for PFAS removal can reduce PFAS concentrations in tap water. These are typically activated carbon filters designed for installation at individual faucets or under the sink. Not all household water filters are effective against PFAS, so consumers should verify the specific certifications of any filter before purchase.

Environment Canada maintains a PFAS information portal with current monitoring data and health guidance. The Ontario Drinking Water Surveillance Program publishes water quality results for participating municipal systems at ontario.ca/drinkingwater.