Michigan establishes new water quality values for two PFAS chemicals

Oct. 24, 2023

The Michigan Department of Environment, Great Lakes, and Energy has set human health water quality parameters, which measure the maximum substance concentrations before adverse health effects, of 210 ppt for PFHxS and 30 ppt for PFNA.

The Michigan Department of Environment, Great Lakes, and Energy (EGLE) announced that it has established new water quality values (WQVs) for the PFAS compounds Perfluorohexanesulfonic Acid (PFHxS) and Perfluorononanoic Acid (PFNA). PFHxS and PFNA are members of the larger group of per- and polyfluoroalkyl substances (PFAS).

EGLE's Water Resources Division determined water quality values for both PFHxS and PFNA. For surface water, the division determined a PFHxS concentration of 210 parts per trillion and PFNA concentration of 30 ppt. Concentrations of 59 ppt for PFHxS and 19 ppt for PFNA were established for surface water specifically protected as a drinking water source. Aquatic life values for PFHxS and PFNA are currently under development.

The new WQVs are the latest to be added to the state’s existing list of three PFAS compounds for which values have been established, bringing the total to five. WQVs are designed to protect the designated uses of Michigan’s surface waters, including protections for aquatic life and public health.

The agency’s Water Resources Division (WRD) determined that sufficient data was available to generate human health WQVs for both PFHxS and PFNA. Following the risk assessment method provided in Rule 323.1057 (Rule 57), a PFHxS concentration of 210 parts per trillion (ppt; or nanograms per liter) and a PFNA concentration of 30 ppt was set for surface water. Concentrations of 59 ppt for PFHxS and 19 ppt for PFNA were established for surface water specifically protected as a drinking water source.

Aquatic life values for PFHxS and PFNA are currently under development. For PFAS, human health WQVs are significantly lower when compared to aquatic life values and provide a more conservative endpoint with the overall goal of protecting public health. Therefore, the decision was made to move forward with publication of the human health WQVs for PFHxS and PFNA while the aquatic life values are still being prepared.

The Rule 57 Water Quality Values for Select PFAS (listed in nanograms per liter which is equivalent to parts per trillion) are as follows:

Water quality values define the maximum concentration of a chemical that can be in Michigan’s surface waters (lakes, rivers, streams, etc.) without adversely impacting aquatic life, recreational activities, fish consumption, and other beneficial uses. They are also used to help determine limits for discharging pollutants from water treatment plants, industrial and commercial facilities, and other regulated entities.

The human health WQVs are not the same as the PFAS Maximum Contaminant Levels (MCLs) which apply to drinking water systems. The Michigan PFAS MCLs are intended to apply to public water systems, protect people from excessive exposure to PFAS substances from the ingestion of finished drinking water, and were derived using methodologies equivalent to the Safe Drinking Water Act.