Illinois EPA Issues Health Advisory for Perfluorooctanesulfonic Acid (PFOS) and an Updated Health Advisory for Perfluorobutanesulfonic Acid (PFBS)

Illinois Environmental Protection Agency Director John J. Kim today announced the issuance of a health advisory for Perfluorooctanesulfonic Acid (PFOS) in accordance with Illinois groundwater regulations. Illinois EPA also issued an updated health advisory for Perfluorobutanesulfonic Acid (PFBS), which was initially issued in January. Health advisories are issued when there is detection of a chemical substance(s) harmful to human health for which no numeric groundwater standard(s) exists, and resampling confirms the presence in a community water supply well (35 Ill. Adm. Code 620.605). On January 28, 2021, Illinois EPA issued health advisories for four chemicals. Similar to those health advisories, PFOS is a compound included in the family of per- and polyfluoroalkyl substances (PFAS), often referred to as “forever chemicals” because of their persistence over time in surface water and groundwater. On April 8, 2021, U.S. EPA updated its Provisional Peer-Reviewed Toxicity Value for PFBS, resulting in Illinois EPA’s issuance of an updated PFBS health advisory guidance level. The health advisories contain a general description of the chemicals, information on carcinogenicity and potential adverse health effects, and a guidance level. The below chart provides the heath advisory guidance levels for the chemicals identified.

Chemical Abstract Services Registry Number (CASRN) Substance Name Substance Acronym HA Guidance Level in milligrams per liter (mg/L) HA Guidance Level in nanograms per liter (ng/L)
1763-23-1 Perfluorooctanesulfonic Acid PFOS 0.000014 14
375-73-5 Perfluorobutanesulfonic Acid PFBS *0.0021 *2,100

*Updated health advisory guidance level

The health advisories will be published in the Environmental Register, a publication of the Illinois Pollution Control Board, and placed on the website: The health advisories are also available on the Illinois EPA website at:

The guidance level contained in each of the health advisories is not an enforceable groundwater or drinking water standard. However, the Illinois EPA will use the health advisory guidance levels and data gathered from the statewide drinking water investigation in the development of enforceable drinking water standards for PFAS known as Maximum Contaminant Levels. The statewide PFAS investigation, which began in September 2020, is expected to be completed in the fall of 2021. The Illinois EPA is sampling drinking water at every community water supply in Illinois. If PFAS chemicals are confirmed at concentrations above laboratory minimum reporting levels, the Illinois EPA works directly with those community water supplies to ensure residents are informed and to determine next steps for reducing exposure. To date, Illinois EPA has collected samples from 858 community water supplies in Illinois. An additional 588 systems will be sampled as the investigation continues. A complete listing of sample results to date is available on the interactive map established by Illinois EPA at: additional information, please visit the Statewide PFAS Investigation Network webpage at:





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