What is PFAS?

Per- and poly-fluoroalkyl substances, also referred to as PFAS, are man-made chemicals that are found in many commonly used products. There are thousands of different variations of PFAS, but the most common are Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS).

PFAS chemicals are commonly 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.

Because PFAS is so prevalent and chemically stable in the environment, these types of chemicals can be found in water, air, animals, 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 and in the environment. There are some drinking water sources that have been found to have PFAS. Because of this, many PFAS-containing products are being banned from use. For example, beginning in January 2022, California banned PFAS-containing firefighting foam.

Is PFAS in the drinking water in Windsor?

The Town is not currently required to measure PFAS in its drinking water. However, Windsor participated in a sampling study in 2014, required by the EPA Unregulated Monitoring Contaminant Rule (UCMR). As part of this study, the water system was sampled for PFAS, PFOS, PFOA, PFNA, and PFHxS, among many other constituents. All sample results in 2014 were non-detect. 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. Sonoma Water has been testing for PFOS/PFOA and its variants annually for several years, all with non-detect results.

Windsor recently began monitoring PFAS in source water prior to EPA requirements to be proactive and inform the community. Sampling conducted in April 2023 showed that although most levels of PFAS constituents remain non-detect in our source water, two components (PFBS and PFHxS) were detected at very low levels. PFBS was detected at 1.4 nanograms per liter (ng/L) and PFHxS was detected at 0.93 ng/L. PFBS (perfluorobutanesulfonic acid) was a replacement product for a more toxic stain-guard compound. PFHxS (perfluorohexanesulfonic acid) is used in aqueous firefighting foams, textile coating, and metal plating and is one of the most commonly detected forms of PFAS. Both compounds were detected at very low levels (below the instrument calibration range) and are well below currently proposed health advisory levels. Despite the low amounts, the Town of Windsor staff takes this issue very seriously and will continue to monitor and notify residents if the amounts approach action levels.  

The EPA has recently issued another round of required sampling under the UCMR and Windsor will be sampling for 29 PFAS compounds. The Town will be following the EPA-issued sampling schedule and will be publishing any detected constituents in the Annual Water Quality Report following that sampling event. Current and previous 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 biosolids handling facility, including a pyrolysis treatment phase. As of December 2022, the Town had completed 30% of design drawings in coordination with its project consultants. Town staff are currently working on securing project funding and support

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

More information on biosolids and pyrolysis can be found at the following sites:

Basic Information about Biosolids | US EPA

EPA Pyrolysis Research

Bioforcetech Corporation - Biomass Management Systems