Triggered by Recent Sampling: Illinois EPA Notifies Village of Dupo and Connected Water Systems of Right-to-Know Requirements

DUPO — The Illinois Environmental Protection Agency (Illinois EPA) has detected perfluorooctanesulfonic acid (PFOS), a type of PFAS chemical, in the Dupo Community Water System’s (CWS) most recent water sample, officials have announced.

The Illinois EPS said the most recent water sample showed PFOS at 4.5 parts per trillion (ppt), exceeding the federal Maximum Contaminant Level (MCL) and Illinois Class I groundwater quality standard of 4 ppt.

The Illinois EPA is notifying the owners and operators of the Dupo CWS, as well as those of the Columbia CWS and Prairie du Pont Public Water District, which can receive water from Dupo through an emergency connection. Under the Illinois Environmental Protection Act, water system operators must notify customers within five business days when groundwater contamination surpasses state quality standards and poses a public exposure risk.

“Right-to-Know laws were developed to ensure the public is informed when contamination poses a threat of exposure,” said Illinois EPA Acting Director James Jennings. “While this notice applies to specific locations, Illinois EPA encourages all residents to take steps to reduce exposure to PFAS compounds.”

PFAS, or per- and polyfluoroalkyl substances, are a large group of human-made chemicals used since the 1940s for their oil- and water-resistant properties in consumer products, industrial processes, and firefighting foams. These chemicals persist in the environment and do not readily break down, leading to widespread contamination of air, water, and soil.

Illinois has taken a proactive stance on PFAS regulation, establishing health advisories and groundwater quality standards for six PFAS compounds, including PFOS, as of 2025. The U.S. Environmental Protection Agency recently set federal MCLs for certain PFAS, with compliance required by April 2029.

Exposure to PFAS primarily occurs through ingestion of contaminated food and water, contact with treated products, and incidental ingestion of household dust. The Illinois EPA advises residents to reduce exposure by using water filters certified to remove PFAS, avoiding products containing PFAS, and selecting cookware and personal care items without PFAS-related chemicals.

The Illinois Department of Public Health (IDPH) also recommends that private well owners near the affected water systems test their water for PFAS and consider treatment options such as activated carbon filters. “When elevated levels of contaminants are found in drinking water supplies, it is important for nearby private well owners to take appropriate precautions,” said IDPH Director Dr. Sameer Vohra.

Private well owners seeking assistance can contact IDPH at (217) 782-5830.

The public health notices and additional information about PFAS, including health effects and exposure reduction strategies, are available on the Illinois EPA website. Further resources can be found through the Agency for Toxic Substances and Disease Registry and the Illinois Department of Public Health.

The notice provided to CWS will be posted on the Illinois EPA website at: https://epa.illinois.gov/topics/drinking-water/public-water-users/notices.html. More information regarding PFAS, including health effects and additional ways to reduce exposure, is available on the Illinois EPA PFAS webpage at https://epa.illinois.gov/topics/water-quality/pfas.html.

Additional information can be found on the Agency for Toxic Substances and Disease Registry website at: https://www.atsdr.cdc.gov/pfas/. The IDPH provides additional information on PFAS in drinking water at: https://dph.illinois.gov/topics-services/environmental-health-protection/private-water/fact-sheets/pfas-drinking-water.html.

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