Frederica Freyberg:
You know, the foam you sometimes see on the shores of lakes and rivers. Be forewarned. A new study shows the foam can contain very high levels of forever chemicals or PFAS, even if the water below may not. The University of Wisconsin Aquatic Sciences Center analyzed foams and water of 43 lakes and rivers in Wisconsin. Its director, Christy Remucal, is here with more on this finding. And thanks a lot for being here.

Christy Remucal:
Thanks for having me.

Frederica Freyberg:
Really important information. What does this foam look like?

Christy Remucal:
So this looks like soap that you might see in a bathtub. It’s a white, foamy material. Sometimes you see it on a lake or a river, like on a windy day or downstream of a dam, places like that.

Frederica Freyberg:
How high were the levels you found?

Christy Remucal:
So we measured PFAS concentrations in this foam and also in water. And what we found were the PFAS concentrations were 50 to 7000 times higher in the foam compared to in the water.

Frederica Freyberg:
On what body of water did you find these highest readings?

Christy Remucal:
The place where we found the highest concentrations were in Lake Monona here in Madison.

Frederica Freyberg:
So how dangerous is it to ingest?

Christy Remucal:
So PFAS, the main way we’re exposed to it is through ingestion. So we mainly think about exposure through drinking water or food or things like that. So the concentrations we’re concerned about are very low. The ones that can cause adverse health outcomes. People probably aren’t eating a lot of foam, but we still think it’s good to avoid coming in contact with it.

Frederica Freyberg:
What kind of warning would you give to folks who see it on bodies of water?

Christy Remucal:
I think our research really echoes what our state Department of Natural Resources has already said that people should avoid coming into contact with foams. They should keep their pets, their dogs out. They’ll get into the foam. They shouldn’t have their kids play in the foam. And if you do come into contact with it, you should wash your hands before eating or drinking.

Frederica Freyberg:
Your study found the high levels of PFAS in the foams didn’t necessarily translate, though, to the water below.

Christy Remucal:
Well, the ratios were relatively similar. So if we — if there was a lake that had higher concentrations of PFAS, we also had higher concentrations of PFAS in the foam. So Lake Monona, for example, it had among the higher concentrations in water in the state as well as in the foam. So they were correlated. But I think the thing that was really surprising was because the concentration effect was so high in the foam, even a lake like Lake Mendota, which has lower concentrations in the water, you still found amounts in the foam that might be of concern.

Frederica Freyberg:
So 43 site samples for this research, could we extrapolate and say, if you see this foam across the state, it’s likely the same?

Christy Remucal:
I think that’s probably true. We really try in this study to sample different water bodies. Some lakes we know have higher concentrations of PFAS. We also made sure to sample places where the concentrations are lower. So we could look at how things varied depending on the site.

Frederica Freyberg:
How does this discovery help scientists understand how these forever chemicals move in groundwater and what is the implication of that?

Christy Remucal:
So PFAS are surfactants which means they like to accumulate at the air-water interface, so the very top of the water. And so that’s why they’re in the foam where there’s lots of little bubbles. Underground, this partitioning behavior is really important for how PFAS move. So in the subsurface there’s little — lots of these little interfaces so PFAS can kind of get trapped there and that slows down how they move. And this process is really well known underneath the ground. But this was one of the first times we saw it in lakes and rivers.

Frederica Freyberg:
How does this research inform paths to PFAS cleanup?

Christy Remucal:
Yeah. So people are actually trying to generate foam on purpose as a way to concentrate PFAS and remove it from the water. So that’s something that’s under research development right now. So taking advantage of this natural ability of PFAS to accumulate in these types of environments, they’re trying to use that as a remediation approach.

Frederica Freyberg:
What’s been the reaction from the scientific community to this?

Christy Remucal:
I think — that’s a good question. And I mean, the paper just came out, so it’s a little hard to know. I think the thing that will probably be the most surprising is the concentrations of PFAS we found in foams in lakes and rivers that had lower concentrations in the water. I think that will be the biggest surprise.

Frederica Freyberg:
All right. We leave it there. Thank you very much for the information, Christy Remucal.

Christy Remucal:
Thank you.