Per- and Polyfluoroalkyl Substances (PFAS)


Monthly monitoring of our treated water has been initiated for the 2021 calendar year.  This will help determine our compliance with the recently adopted drinking water standard of 20 parts per trillion (ppt), for water systems in Massachusetts.  Previous monitoring in 2020 has improved our knowledge of how PFAS is impacting our water system and we continue to work with State regulators, consultants, and others to address PFAS in Sudbury’s drinking water.

On September 24, 2020, the Massachusetts Department of Environmental Protection (MassDEP) announced the final regulations for PFAS in drinking water and continue to clarify how laboratory results should be calculated and reported.  The MassDEP Press release can be found here: MassDEP Press Release


According to the United States Environmental Protection Agency, PFAS are a group of man-made chemicals that includes PFOA, PFOS, GenX, and many other chemicals. PFAS have been manufactured and used in a variety of industries around the globe, including in the United States since the 1940s. PFOA and PFOS have been the most extensively produced and studied of these chemicals. Both chemicals are very persistent in the environment and in the human body – meaning they don’t break down and they can accumulate over time. There is evidence that exposure to PFAS can lead to adverse human health effects.

PFAS can be found in:

  • Food packaged in PFAS-containing materials, processed with equipment that used PFAS, or grown in PFAS-contaminated soil or water.
  • Commercial household products, including stain- and water-repellent fabrics, nonstick products (e.g., Teflon), polishes, waxes, paints, cleaning products, and fire-fighting foams (a major source of groundwater contamination at airports and military bases where firefighting training occurs).
  • Workplace, including production facilities or industries (e.g., chrome plating, electronics manufacturing, or oil recovery) that use PFAS.
  • Drinking water, typically localized and associated with a specific facility (e.g., manufacturer, landfill, wastewater treatment plant, firefighter training facility).
  • Living organisms, including fish, animals, and humans, where PFAS have the ability to build up and persist over time.

Certain PFAS chemicals are no longer manufactured in the United States as a result of phase-outs including the PFOA Stewardship Program in which eight major chemical manufacturers agreed to eliminate the use of PFOA and PFOA-related chemicals in their products and as emissions from their facilities. 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, rubber, and plastics.


In order to understand what a chemical measurement means, one needs to have a basic understanding of the type of measuring units used, and what they mean. As mentioned above, most of our contaminants are measured using concentration units such as ppm and ppb.  But what is a ppm, ppb, or ppt for that matterin plain English?

As an example, let’s use an example of liquid chlorine added to our water in the treatment process at 1.0 ppm. This value refers to one part of chemical (in this case liquid chlorine) found in one million parts of our water. To realize how small a value this actually is, read the analogies listed below:

  • One part per million (ppm) = 1 inch in 16 miles
  • One part per billion (ppb) = 1 inch in 16,000 miles
  • One part per trillion (ppt) = 1 inch in 16 million miles (600+ times around the earth)


If you do not typically receive a water bill from Sudbury Water District and wish to receive future updates regarding PFAS, please visit this website periodically or send an email to with “Updates” in the subject line.  Please include your name, address, and email to be informed of new information and future developments related to PFAS.


Many people have tried to determine where the water serving them is from.  Our water system is a dynamic system that includes eight wells, two treatment plants, four water storage tanks, and over 135 miles of water main.  Because the water all pumps into the system, and system hydraulics (how the water moves around in the pipes) can change based on time of day, season, water demand, and how we are operating the various systems, it is difficult to pinpoint this information.


For customers wishing to reduce exposure from PFAS in drinking water by filtration in the home should follow the guidance of MassDEP featured below.  The Sudbury Water District does not make recommendations on filters.  If you currently own a filter, it is best to contact the manufacturer directly to determine if it is effective at reducing or removing PFAS. If a current filter is not effective, the manufacturer may be able to advise you on an alternate filter that can be installed using existing equipment.

From MassDEP:

Home Water Filters

There are also home water treatment filters capable of removing PFAS from drinking water for the countertop or under the sink. Filters certified by NSF have been demonstrated to be effective in removing two of these compounds, PFOS and PFOA, to below the USEPA Health Advisory of 70 parts per trillion (ppt).  Many of these filters will likely be able to reduce PFAS levels to well below 70 ppt, however, MassDEP has no independently verifiable monitoring results demonstrating this performance.  If you chose to install a filter, you should check to see if the manufacturer has monitoring results demonstrating that the device can reduce PFAS to below your level of concern. For example, MassDEP recently proposed a drinking water limit, or Maximum Contaminant Level, of 20 ppt for the sum of the levels of six PFAS compounds.


USEPA PFAS Resources 

MassDEP PFAS Resources for Public Water Supplies

MassDEP PFAS Regulatory Process

MassDEP Bottled Water PFAS Results

MassDEP Certified Labs

Environmental Toxicology Program

Green Acton

Agency for Toxic Substances and Disease Registry (ATSDR) Guide for Clinicians

American Water Works Association PFAS Cycle

Safe Water Massachusetts