LANSING, Mich. The Michigan Department of Health and Human Services (MDHHS) is warning Michigan residents to avoid foam on Michigan lakes and rivers that have per- and polyfluoroalkyl substances (PFAS) in the water. An example of PFAS foam buildup along the edge of a body of water in Michigan. (EGLE)Officials say that PFAS could pose a health risk, especially if the foam is swallowed. PFAS do not move easily through the skin, but MDHHS officials say repeated, prolonged whole-body contact with PFAS foam could create a health risk. Click here for tips from the state to help you identify if the foam is naturally-occurring or PFAS foam.