Public water supplies may be large, like the Great Lakes Water Authority, which serves 3.7 million residents, or they may be smaller, such as a supply serving a manufactured housing community.  Some public water supplies get water from groundwater, some from surface waters (lakes or rivers) and some blend groundwater and surface water sources together. To ensure the drinking water for the largest portion of Michigan residents was tested for PFAS, beginning in April 2018, the Michigan Department of Environment, Great Lakes, and Energy (EGLE) implemented a statewide survey to test Michigan's public water supplies across several phases of sampling.

Prior to the beginning of this statewide survey, the United States Environmental Protection Agency (USEPA) set a Lifetime Health Advisory (LHA) level for two PFAS in drinking water: perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). The LHA level is 70 parts per trillion (ppt, equal to 70 ng/L) for PFOA and PFOS combined, or individually if only levels for other PFAS chemicals. In the absence of a promulgated drinking water PFAS standard(s) at the time, the State of Michigan used 70 ppt for decision making purposes during the statewide survey. 

What did the statewide testing initiative involve?

• Phase I of the statewide PFAS survey initially included community water supplies (including subdivisions, apartment complexes, and mobile home parks) with their own source, as well as schools on their own well. This list was expanded to also include childcare providers and Michigan Head Start programs on their own well.
• Phase II of the statewide PFAS survey expanded the sampling list to include additional noncommunity public water supplies serving sensitive populations.

Approximately 80 public water supplies tested during Phase I and Phase II of the statewide survey have returned results greater than 10 ppt total tested PFAS. EGLE placed these supplies onto a quarterly sampling schedule from 2019 - 2020, to help determine if PFAS levels in these supplies changed over time and to help prioritize and direct recommendations and further actions.

Approximately 70 public water supplies sampled in Phase I use surface water as a source. These supplies were sampled monthly in 2019, and every other month in 2021, to assess whether PFAS levels change over time in Michigan’s surface water sources. Additional sampling was planned for 2022.