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Persistent Pollutants

US drinking water to be tested for 29 PFAS

EPA will use data to determine public health risks

by Cheryl Hogue
December 22, 2021


US utilities will have to monitor the drinking water they supply for the presence of 29 per- and polyfluoroalkyl substances (PFAS) from 2023 through 2025, under a regulation the US Environmental Protection Agency issued Dec. 20.

The EPA will use the monitoring data to determine whether these environmentally persistent synthetic compounds need regulation in drinking water to protect public health.

Chemical structure of perfluorooctanesulfonic acid

“We are advancing the science and the monitoring that are necessary to protect all communities from PFAS,” EPA Administrator Michael S. Regan says in a statement.

All 29 PFAS selected for monitoring contain reactive sites. The chemicals include sulfonic acids and carboxylic acids of perfluoroalkyls and fluorethers.

Chemical structure of perfluorooctanoic acid

Two of the chemicals, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are widespread water contaminants even though they are no longer manufactured in the US. Exposure to PFOA or to PFOS is associated with cancer, immune system dysfunction, and endocrine disruption. The EPA plans to propose legally enforceable limits on these chemicals in drinking water in 2022.

Chemical structure of 4,8-dioxa-3H-perfluorononanoic acid
ADONA is the ammonium salt of 4,8-dioxa-3H-perfluorononanoic acid.

Two other chemicals on the monitoring list are related to substances developed by chemical companies to replace PFOA as manufacturing aids to produce fluoropolymers. One is 4,8-dioxa-3H-perfluorononanoic acid, the parent acid of 3M’s ADONA ammonium salt. The other is hexafluoropropylene oxide dimer acid (HFPO-DA), the chemical that forms when Chemours’s GenX hydrolyzes into in the presence of water.

Two chemicals that are environmental transformation products of certain commercial PFAS, including the pesticide sulfluramid, are also on the list. The compounds, which include N-ethyl perfluorooctane sulfonamido acetic acid (N-EtFOSAA), eventually break down into PFOS.

In addition, the EPA selected two chlorinated polyfluorinated ether sulfonic acids for monitoring in drinking water. The two are components of a mixture known by the trade name F-53B that was developed in China and is used as a replacement for PFOS in the electroplating industry.

Along with the 29 PFAS, the EPA is requiring utilities to monitor for the presence of lithium in drinking water. The element, which occurs naturally in some groundwater, is found at levels that could pose a risk to human health in 45% of US public-supply water wells, according to a study released in February.


This article was updated on Dec. 29, 2021, to correct the name 4,8-dioxa-3H-perfluorononanoic acid. The original omitted the 4. The N-EtFOSAA structure label was also amended on Dec. 23, 2021, to add the second A.



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