PFAS
What is PFAS?
Per- and poly-fluoroalkyl substances, also referred to as PFAS, are a group of man-made chemicals that are found in many commonly used products. PFAS are sometimes referred to as “forever chemicals” because they do not readily nor naturally break down into more inert compounds in the environment. Many commonly used products contain PFAS such as food packaging, non-stick cookware, stain and water-repellent products like carpets, clothing, and other fabrics, and in some personal care products such as shampoo, dental floss, and cosmetics. For more information and a list of PFAS-free products, go to: PFAS-Free Products - PFAS Central.
Research suggests exposure to certain PFAS could result in harmful health outcomes, including cancer, increased cholesterol levels, and immune system effects, particularly to those in occupations that are known to be exposed more than the general U.S. population such as chemical manufacturing and firefighting.
Because PFAS are so prevalent and chemically stable in the environment, these types of chemicals can be found in water, air, and soil. Many PFAS are found in the blood of people and animals, including fish, all over the world and are present at low levels in a variety of food products. Because of this, many PFAS-containing products are being banned from use. For example, beginning in January 2022, California banned PFAS-containing firefighting foam.
What are the EPA limits for PFAS?
There are thousands of different variations of PFAS, but the most extensively produced and studied of these chemicals are Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS). On April 17, 2024, the EPA designated PFOA and PFOS as hazardous substances. Although PFOA and PFOS are no longer manufactured in the United States, they are still produced internationally and can be imported into the United States in consumer goods such as carpet, leather and apparel, textiles, paper and packaging, coatings, and rubber and plastics.
On April 10, 2024, EPA announced the final National Primary Drinking Water Regulation, establishing legally enforceable levels, called Maximum Contaminant Levels (MCLs) for six PFAS compounds (see Table 1). EPA also finalized health-based, non-enforceable Maximum Contaminant Level Goals (MCLGs) for these PFAS. Note that in May 2025, the US EPA announced its intent to rescind the regulations and reconsider the regulatory determinations for PFHxS, PFNA, HFPO-DA (commonly known as GenX), and the Hazard Index mixture of these three plus PFBS to ensure that the determinations and any resulting drinking water regulation follow the legal process laid out in the Safe Drinking Water Act. Final regulations are expected in 2026.
The Maximum Contaminant Level for PFOA and PFOS is 4.0 parts per trillion (ppt). For perspective, one ppt is equivalent to a single drop in 20 Olympic-sized swimming pools, or one second in over 31,000 years.
Is PFAS in the drinking water in Windsor?
Windsor's drinking water remains safe and protected from elevated contaminant levels, including PFAS. The Town also purchases a portion of its water from Sonoma Water, and their water source off the Russian River is very near the Town's river wells. Both the Town and Sonoma Water have been monitoring for PFAS quarterly and have not found concentrations above the maximum contaminant levels set by the EPA on April 10, 2024.
Recent sampling shows that while most levels of PFAS remain undetected in our source water, trace levels of some PFAS were detected at or below the 2.0 ppt reporting limit (Table 2). Despite detections below current health advisory levels, the Town of Windsor staff takes this issue very seriously and will continue to monitor and notify residents if the amounts approach action levels.
Additionally, in 2025, the Town participated in the USEPA’s Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) and Windsor’s Russian River Well sample resulted in non-detect for 29 PFAS compounds measured. The Town publishes any detected constituents from required sampling in our Annual Water Quality Report (also known as Consumer Confidence Report (CCR)). Current and previous Water Quality reports can be found here.
Is the Town doing anything related to PFAS?
Biosolids are one of the known pathways where PFAS can be found. Biosolids are a product of the wastewater treatment process. During wastewater treatment, the liquids are separated from the solids. Typically, in the Town of Windsor, we produce what is known as “Class B biosolids”. Biosolids are mechanically dried by a contractor, trucked offsite, and land applied on agricultural fields that are used to grow hay or other fodder crop. This current process does not treat PFAS. In fact, there are very few technologies that are currently available to remove PFAS from biosolids. Promising research has been done recently to identify technologies that can destroy PFAS in solid waste streams. Pyrolysis is one of the technologies that has emerged as a reasonable and effective method for removing PFAS from biosolids.
The Town has initiated the process of designing a Class A EQ biosolids handling facility, including a pyrolysis treatment phase. As of November 2025, the Town had completed 50% of design drawings and completed on-site sludge dewatering pilot testing to help finalize equipment selection in coordination with its project consultants. The Town has been approved for a low interest loan from the State of California to fund a significant part of this project and is currently working with the Environmental Protection Agency’s Water Infrastructure and Innovation Act (WIFIA) to secure the remainder of needed funds.
More information on PFAS, health risks, and how you can protect yourself can be found on the following sites:
Per- and Polyfluoroalkyl Substances (PFAS) | US EPA
Centers for Disease Control and Prevention PFAS Fact Sheets
PFAS Drinking Water | California State Water Resources Control Board
If you want to test your well water, a list of labs accredited for this method can be found here: