LANSING – Foam from Muskegon Lake contained over 4,000 parts per trillion of a synthetic chemical known to harm human and environmental health, researchers said.

That’s unusually high, but its cause and the implications of the event are still unclear.

The foam, sampled in mid-August, contained large concentrations of PFOS (perfluorooctane sulfonate), one of almost 15,000 chemicals in the PFAS family.

But the amount of PFOS in the foam may not reflect the water quality of the lake, said Alan Steinman, a research professor at Grand Valley State University’s Annis Water Resources Institute which monitors the lake for water quality, including PFAS, which are known as “forever chemicals.”

“This was really an unusual event,” he said. “It was almost an aberration.” The sample wasn’t collected as part of a study, he said.

“We saw the foam, we grabbed the foam,” he said. “We weren’t sure how long it would last.”

Not all foam found on water surfaces is toxic. Some foam on lakes and rivers occurs naturally as biological matter breaks down.

PFAS foam tends to accumulate in large piles and may be whiter than other foam. The state has warned residents not to ingest or touch any foam they find.

Scientists are still studying what causes PFAS foam to form on water body surfaces. Factors include wind direction, treated wastewater discharge and oxygen levels in the water.

“We’re racking our brains trying to figure out what the source was” for Muskegon Lake’s foam, Steinman said. He declined to speculate on the source

“At this point, it’s better to say we don’t know than to give wrong answers,” he said.

There are several potential sources of the chemical near the lake, according to a statement from the Department of Environment, Great Lakes and Energy and the Michigan PFAS Action Response Team (MPART):

“The Michigan PFAS Action Response Team is aware of the recent PFAS foam reports on Muskegon Lake and continues to investigate these sporadic foam events.

It is part of MPART’s ongoing statewide effort to track the sources of the contamination which is often associated with the past use of class-B firefighting foam.

It is important to note that Muskegon gets its drinking water from Lake Michigan, and the city’s water has consistently complied with state regulations that place strict limits PFAS in drinking water.

MPART has received complaints about foam in Muskegon Lake in 2020 and 2022. Like the recent reports, the team said it hasn’t yet been able to identify the source because a number of former industries along the shoreline could have used PFAS foam for fire protection or in their industrial processes.

Although recreation in water containing PFAS is not considered harmful because the amount of PFAS is typically low, MPART and the Department of Health and Human Services, recommend avoiding direct physical contact with foam on lakes and rivers and rinsing themselves and pets off after contact with foam, it said

The department asks the public to report foam they find on a water body that could contain PFAS. Verified reports inform where the state collects water samples for testing, according to MPART’s website.

Steinman said the foam on Muskegon Lake is one example of many PFAS contamination situations across the state, making it difficult for regulators to address them all.

He reiterated the state’s warnings to residents.

“If you see this massive foam that’s accumulating, washing up somewhere on the lakeshore, stay away from it,” Steinman said. “You don’t want to touch it. We can’t say for sure that it’s PFAS, but why take the risk?”

Elinor Epperson has an environmental reporting internship under the MSU Knight Center for Environmental Journalism’s diversity reporting partnership with the Mott News Collaborative and CNS. This story was produced for Michigan Public.