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. Results are provided in parts per trillion. A part per trillion (ppt) is the equivalent of 1 drop of water in 20 Olympic-size swimming pools
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.