Residents urge immediate sampling after white foam observed on Au Sable River; agencies outline limitations

Connie reported extensive white foam on the Au Sable River downstream of the Mio Dam and urged the agency to sample it immediately. "There is an awful lot of white foam going down the Au Sable River downstream of the Mio Dam... I would just beg respectfully that somebody grab a sample of that white foam and let's test it," Connie said.

Agency staff responded that the state accepts foam reports and that sampling is done where it will address the highest number of complaints, but acknowledged sampling foam is technically difficult because foam can disappear within minutes. Staff explained that in prior foam sampling, PFAS concentrations can be elevated in foam, and that dams and high flows agitate water and concentrate foam. "Wherever foam is being agitated, you're concentrating in that foam," one staff member said.

Dan added that foam can look different — some foams resemble 'shaving-cream' and have been found to contain higher PFAS, while other foams are organic and more common during high runoff. He and others urged caution for anglers and recreational users near dams during high flows because foam can aerosolize PFAS and lead to contact exposure.

Michelle from the Michigan Department of Health and Human Services said MDHHS will distribute spring press materials on foam and fish consumption guidance. Staff noted that fish-consumption advisories are based on lifetime exposure, so a short-term foaming event may change contact recommendations but does not automatically change long-term consumption guidance.

Agency staff committed to reviewing foam complaints for the Mio/Grayling area and to coordinate whether targeted foam or surface-water sampling is warranted; they also encouraged the public to submit foam reports so staff can prioritize sampling work.