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Maximum Contaminant Levels (MCLs)

Maximum Contaminant Levels (MCLs)

In August 2020, the Michigan Department of Environment, Great Lakes, and Energy (EGLE) promulgated rules establishing maximum contaminant levels (MCLs) for seven PFAS compounds under the authority of the Safe Drinking Water Act. These levels were based on health based values provided by the MPART Science Advisory Workgroup in its 2019 report, Health-Based Drinking Water Value Recommendations for PFAS in Michigan.

Maximum contaminant levels apply to approximately 2,700 public drinking water supplies in Michigan. These 2,700 public water supplies include:

  • Community water supplies, including large regional and municipal (city, village, township, etc.) supplies, apartments, condos, nursing homes, and mobile home parks
  • Noncommunity water supplies (nontransient), including schools, daycares, factories, offices, and other places of employment.

Drinking water MCLs in Michigan

Specific PFAS

Drinking water MCL (ppt)

PFNA

6 ppt

PFOA

8 ppt

PFHxA

400,000 ppt

PFOS

16 ppt

PFHxS

51 ppt

PFBS

420 ppt

HFPO-DA (GenX)

370 ppt

ppt = parts per trillion

What is a maximum contaminant level?

A maximum contaminant level (MCL) is the maximum amount of a contaminant allowed in a public drinking water supply.

Compliance with Michigan’s MCLs for PFAS is determined based on a calculated running annual average of sample results for a public water supply. When the running annual average of a contaminant in drinking water is higher than the MCL, the water supply must take action as outlined in the Safe Drinking Water Act or its accompanying administrative rules. 

Such actions may include:

  • Public notice
  • Treatment to reduce the level of PFAS contaminants
  • Additional testing
  • Other actions

Drinking water rules in Michigan were amended to include the above PFAS MCLs, establishing sampling requirements for these seven PFAS compounds in public water supplies covered under the Michigan Safe Drinking Water Act.

  • A preview of the MPART Geographic Information System showing the whole state and dots all over

    Statewide PFAS survey of public water supplies

    In April 2018, EGLE started a statewide survey to test Michigan's public water supplies for PFAS. Browse over 5,000 results from municipal water supplies, schools, parks, offices, daycares, and more

What’s happening at the federal level?

In April 2024, US EPA issued new national drinking water standards for PFAS. They set enforceable limits (Maximum Contaminant Levels (MCLs)) for six PFAS. Five of them (PFOA, PFOS, PFHxS, PFNA, and HFPO‑DA) have individual limits. EPA also created a Hazard Index limit for mixtures that include two or more of PFHxS, PFNA, HFPO‑DA, and PFBS. EPA also set non‑enforceable health goals (MCLGs) for these PFAS.

In May 2025, EPA announced it planned to change the rule by removing all the 2024 PFAS limits except for PFOA and PFOS. They also proposed giving water systems more time to comply. EPA published these proposed changes for public comment in May 2026.

These proposed rules do not change the initial monitoring requirements from the 2024 rule. Public water supplies must complete their first round of PFAS testing by June 2027 and continue regular monitoring and reporting after that.

Starting in June 2029, public water supplies with PFAS levels above any EPA MCL must take steps to reduce PFAS and notify the public. The proposed rules would allow eligible water systems to request extra time to meet the PFOA and PFOS limits, with extensions lasting until April 2031.

For up to date information from EPA, visit EPA.gov/PFAS