PFAS are turning up in the Great Lakes, putting fish and water supplies at risk – here’s how they get there

No matter where you live in the United States, you have likely seen headlines about PFAS being detected in everything from to to to .

PFAS, or per- and polyfluoroalkyl substances, are a group of . They have been used for decades to make products waterproof and stain- and heat-resistant – picture food wrappers, stain-resistant carpet, rain jackets and firefighting foam.

These chemicals are a growing concern because some PFAS are and associated with health risks like . And some of the most common PFAS , which is why they are often referred to as “forever chemicals.”

Now, PFAS are posing a threat to the Great Lakes, one of America’s most vital water resources.

The five Great Lakes are massive, with over (16,000 kilometers) across two countries and containing . They provide drinking water to and are home to a robust commercial and recreational .

study how chemicals like PFAS are affecting water systems. Here’s what we’re learning about how PFAS are getting into the Great Lakes, the risks they’re posing and how to reduce those risks in the future.

PFAS’ many pathways into the Great Lakes

Hundreds of rivers flow into the lakes, and each can be contaminated with PFAS from sources such as in their watersheds. Some , which can wash off farm fields and into creeks, rivers and lakes.

The concentration of PFAS in rivers can vary widely depending on these upstream impacts. For example, we found concentrations of in Great Lakes tributaries in Wisconsin near where firefighting foam has regularly been used. That’s more than 400 times higher than for PFOS and PFOA, both 4 parts-per-trillion.

However, concentration alone does not tell the whole story. We also found that with relatively low amounts of PFAS can put more of these chemicals into the lakes each day compared with smaller rivers with high amounts of PFAS. This means that any effort to limit the amount of PFAS in the Great Lakes should consider both high-concentration hot spots and large rivers.

Groundwater is another key route carrying PFAS into the Great Lakes. Groundwater is a drinking water source for in the U.S., and it when PFAS in firefighting foam and other PFAS sources seep into soil.

When these contaminated plumes enter the Great Lakes, they carry PFAS with them. We detected PFAS concentrations of over 260 parts-per-trillion in the bay of Green Bay in Lake Michigan. The chemicals we found were associated with firefighting foam, and we were able to trace them back to a .

PFAS can also enter the Great Lakes in unexpected ways, such as . PFAS can get into the atmosphere from industrial processes and waste incineration. The chemicals have been detected in rain , including in .

Although PFAS concentrations in precipitation are typically lower than in rivers or groundwater, this is still an important contamination source. Scientists estimate that of PFAS to Lake Superior, which receives about through precipitation.

Where PFAS end up determines the risk

Much of the PFAS that enter Lake Superior will eventually make their way to the downstream lakes of Michigan, Huron, Erie and Ontario.

These chemicals’ ability to travel with water is one reason why PFAS are such a concern for drinking water systems. Many communities get their drinking water from the Great Lakes.

PFAS can also contaminate other parts of the environment.

The chemicals have been detected in of all the Great Lakes. Contaminated sediment into the overlying water, where fish and aquatic birds can ingest it. So, future remediation efforts to remove PFAS from the lakes are about more than just the water – they involve the sediment as well.

PFAS can also accumulate in foams that form on lake shorelines during turbulent conditions. Concentrations of PFAS can be up to compared with the water because PFAS are surfactants and build up where air and water meet, like bubbles in foam. As a result, recommend washing skin that comes in contact with foam and preventing pets from playing in foam.

Some PFAS bioaccumulate, or build up, within fish and wildlife. Elevated levels of PFAS have been detected in , raising .

High PFAS concentrations in fish in coastal areas and inland waters have led to how .

Looking ahead

Water cycles through the Great Lakes, but the process can take many years, from .

This means that PFAS that enter the lakes will be there for a very long time.

Since it is not possible to clean up the over in the Great Lakes after they have been contaminated, preventing further contamination is key to protecting the lakes for the future.

That starts with identifying contaminated groundwater and rivers that are adding PFAS to the lakes. The and the , including the that I direct, have been supporting research to map these sources, as well as helping translate that knowledge into actions that policymakers and resource managers can take.

PFAS contamination is an issue beyond the Great Lakes and is something everyone can work to address.

• Drinking water. If you are one of the millions of people who drink water from the Great Lakes, find out the PFAS concentrations in your drinking water. This data is increasingly available from .
• Fish. Eating fish can provide great health benefits, but be aware of about fish caught in the Great Lakes and in so you can balance the risks. Other chemicals, such as mercury and PCBs, can also lead to fish advisories.
• Personal choice. Scientists have proposed that when they have vital functions and there are no alternatives. Consumer demand for PFAS-free products is . Several states have also introduced legislation to in some applications.

Decreasing use of PFAS will ultimately prevent downstream contamination in the Great Lakes and around the U.S.