PFAS (Per-and Polyfluoroalkyl Substances)

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What is PFAS?

PFAS stands for per- and polyfluoroalkyl substances, which are a group of synthetic chemicals. They have been widely used in various industrial and commercial applications since the 1940s due to their unique properties, including heat resistance, water repellency, and oil repellency. PFAS compounds are exceptionally persistent in the environment, earning them the nickname “forever chemicals” as they do not easily break down.

There are thousands of PFAS compounds, but two of the most well-known ones are perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). These have been extensively studied, and their health effects are of particular concern.

Regulatory agencies and public health organizations worldwide have become increasingly concerned about the potential risks posed by PFAS. As a result, several measures are being taken to reduce exposure, including increased monitoring of drinking water, tighter regulations on PFAS usage, and research into safe alternatives.

Is My Water Safe?

It is the mission of the Jamestown Water Department (JWD) to continue to provide safe clean drinking water to all our customers. JWD is currently in the process of sampling for PFAS compounds as required by both the State of Rhode Island and the EPA. The Rhode Island PFAS in Drinking Water, Groundwater, and Surface Waters Act requires public water systems in Rhode Island to sample for per and polyfluorinated substances (PFAS). The law also set an interim standard for PFAS in drinking water of 20 parts per trillion (ppt) for a total of six PFAS chemicals.

Additionally, the EPA is proposing a National Primary Drinking Water Regulation (NPDWR) to establish legally enforceable levels, called Maximum Contaminant Levels (MCLs), for six PFAS in drinking water, see Table 1. PFOA and PFOS as individual contaminants, and PFHxS, PFNA, PFBS, and HFPO-DA (commonly referred to as GenX Chemicals) as a PFAS mixture. EPA is also proposing health-based, non-enforceable Maximum Contaminant Level Goals (MCLGs) for these six PFAS.

JWD tested for 29 PFAS compounds in 2023. The results of this analysis shows that JWD water is below the State and Federal limits for all 29 compounds. Of the 29 PFAS compounds targeted, only four were detected in our system, PFOS, PFOA, PFHxS and PFBA.  PFOS was detected in two samples at a level of 1.62 and 1.57 parts per trillion; PFOA was detected in three samples at a level of 1.46, 1.49 and 1.29 parts per trillion; PFHxS was detected in two samples at a level of 1.77 and 1.49; and, PFBA was detected in one sample at a level of 12 parts per trillion. These results are below both the Rhode Island Regulated Sum of Six PFAS compounds and the EPA’s proposed MCL (maximum contaminant level). The data for PFAS sampling can be found below.

Table 1. Proposed EPA National Primary Drinking Water Regulation1


Proposed MCLG

Proposed MCL (enforceable levels)



4.0 parts per trillion (also expressed as ng/L)



4.0 ppt


1.0 (unitless)

Hazard Index2

1.0 (unitless)

Hazard Index 2




(commonly referred to as GenX Chemicals)


2 What is a Hazard Index? The Hazard Index is a long-established tool that EPA regularly uses, for example, in the Superfund program, to understand health risks from chemical mixtures. EPA is proposing a Hazard Index MCL to limit any mixture containing one or more of PFNA, PFHxS, PFBS, and/or GenX Chemicals. The Hazard Index considers the different toxicities of PFNA, GenX Chemicals, PFHxS, and PFBS. For these PFAS, water systems would use a hazard index calculation to determine if the combined levels of these PFAS in the drinking water at that system pose a potential risk and require action.

More Information

EPA’s PFAS Information Website:

EPA’s Question and Answers: Drinking Water Health Advisories for PFOA, PFOS, GenX Chemicals, and PFBS:

Rhode Island Department of Health PFAS Website:

Rhode Island Department of Health Frequently Asked Questions about PFAS Contamination of Water:

American Water Works (AWWA) Per – and Polyflouroalkyl Substances:


JWD PFAS Sampling Results