Scientific Overview of PFAS and Drinking Water | AAAS EPI Center
Figure 1 - Chemical Structure of PFOS (Example Structure of a PFAS Chemical)
The carbon chain can be designated as “long-chain” or “short-chain” PFAS 4 . Long-chain PFAS are the PFAS most commonly found in the environment and are sometimes referred to as “legacy” PFAS, as they have been in use for their stable, water-repellent properties since the 1940s. While some U.S. manufacturers phased some of these legacy PFAS out of certain products and processes in the early 2000s, their persistence means that they continue to be present in the environment 5 . Long-chain PFAS include those that have a sulfonic acid functional group (made up of a sulfur atom, oxygen, and hydrogen atoms — SO 3 H) and contain six or more carbons, or those that have a carboxylic acid functional group (made up of carbon, oxygen, and hydrogen atoms — COOH) and contain eight or more carbons. Long-chain PFAS include PFOA and PFOS, which are the most commonly recognized PFAS. Short-chain PFAS that have been utilized as replacements to long-chain PFAS are also persistent, and some may bioaccumulate and induce adverse human health effects. These PFAS are mobile and are even more difficult to remove from water 6 . Short-chain PFAS are those with a sulfonic acid functional group and five or fewer carbons, or those with a carboxylic acid functional group and seven or fewer carbons. Short-chain PFAS are just as difficult to break down, are just as persistent in the environment, and are widely used in industries 6 . Another unique aspect to PFAS is the strength of carbon-fluorine bonds , which makes PFAS resistant to breakdown through conventional water treatment processes 3 . Due to their high thermal and chemical stability, PFAS are often referred to as “forever chemicals.” Lastly, functional groups also can increase or decrease the likelihood of a particular PFAS to persist and accumulate. Thousands of PFAS Have Been Produced The EPA estimates that thousands of PFAS have been developed and used in industrial and consumer applications since the 1940s, but only about 600 PFAS are currently approved for commercial use in the U.S. 7 . PFAS are used in applications such as firefighting foam, furniture chemical coatings, food product containers (e.g., pizza boxes, wrappers), and water-repellent materials used in clothing (e.g., raincoats). Despite numerous industry uses, detecting each PFAS in the environment may not be possible due to
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