Persistent Pollutants

A guide to the PFAS found in our environment

Chemical structures and origins of per- and polyfluoroalkyl substances that are polluting our world

A class of synthetic chemicals that contain fluorine atoms is grabbing headlines as emerging contaminants. More and more communities around the world are finding their drinking water supplies tainted with per- and polyfluoroalkyl substances (PFAS).

Chemical companies have manufactured PFAS for decades for use as manufacturing aids and in consumer products. These compounds offer characteristics such as heat, stain, and water resistance that are desired by industry and consumers alike. According to the US government, at least 4,000 PFAS are or have been on the market.

PFAS owe their properties to the carbon-fluorine bond, which is one of the shortest and strongest known. This property also makes these chemicals—or the parts of them composed of C–F bonds—highly resistant to breakdown in the environment, earning them the nickname “forever chemicals.”

Some types of PFAS, while not broken down easily, are considered chemically inert because the molecules lack chemically active groups. Others, including most listed in this library, have reactive sites, including sulfonic and carboxylic acid groups.

Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), perhaps the two best-known PFAS, aren’t made intentionally in the US anymore. But they are the most widespread pollutants of concern from this chemical class, at least so far.

Companies have developed substitutes for these two compounds. Many of these alternatives are seen as new persistent pollutants, some of which appear to be less bioaccumulative than PFOS and PFOA. They join manufacturing by-products and environmental breakdown products in ecosystems.

This library of PFAS chemicals will expand as more of these chemicals and their breakdown products are found in the environment and come to the attention of the public and regulators. If you have suggestions for additions or changes, please comment below or email cenprojects@acs.org.

Sources: CAS (a division of the American Chemical Society, which publishes C&EN), Chemours, DuPont, Interstate Technology & Regulatory Council, US Environmental Protection Agency, Minnesota Department of Health, North Carolina Department of Environmental Quality, West Virginia Department of Environmental Protection, Dutch National Institute for Public Health and the Environment, and others identified in related C&EN coverage.

Note: Some PFAS are or were intentionally manufactured as commercial chemicals and are also breakdown products of other PFAS.

Credits

Research: Cheryl Hogue

Editing: Sabrina Ashwell, Jyllian Kemsley, Marsha-Ann Watson, and Amanda Yarnell

Structures: Bethany Halford, Samantha Jones, Yang Ku, William Ludwig, and Tien Nguyen

Presentation: Tchad Blair and Nader Heidari