If you’re out swimming this summer, stay away from foam. That’s the message from the Michigan Department of Health and Human Services, which has reissued its yearly reminder.

The department’s Andrea Keatley tells us for a variety of reasons, you’re better off just avoiding foam floating in the water.

“It’s getting warmer outside and more people are going to be excited about getting into the lakes and rivers and water bodies in Michigan,” Keatley said. “We want to make sure that we remind them to avoid foam, especially on our surface waters, because it helps them reduce their exposures to harmful substances that might be in that foam.”

This isn’t just for areas known to have contamination issues.

“Foam can have chemicals in it and have bacteria in it. It’s just a statewide messaging for water bodies where foam may develop.”

Chemicals that could be in foam include PAS, exposure to which can lead to a variety of health problems. Keatley says foam could also just be the result of plant matter breaking down, but it’s a safer bet to avoid it.

You can learn more about foam in Michigan waterways right here.