Per- and polyfluoroalkyl substances (PFAS) are a large, complex group of synthetic chemicals that have been used in consumer products around the world since about the 1950’s. They are ingredients used in various everyday products. These products have applications in many industries, including the aerospace, semiconductor, medical, automotive, construction, electronics, and aviation industries, as well as in consumer products.
Some consumer product examples include: PFAS used to keep food from sticking to packaging (microwave popcorn bags, burger wrappers) or in non-stick cookware. Making clothes and carpets resistant to stains, cosmetics, and create firefighting foam that is more effective.
PFAS molecules have a long-chain of linked carbon and fluorine atoms.
Because the carbon-fluorine bond is one of the strongest, these chemicals do not degrade easily in the environment, thus given the term “Forever Chemicals”
All PFAS contain a chain of carbon atoms bonded to fluorine atoms. Some also have a functional
group at the end of the chain. These structures are the basis for different chemical properties and their different chemical names. We’ll look at the more common ones below.
The number of PFAS and their uses have expanded over the years. It has been estimated that the PFAS family may include more than 12,000 chemical substances, not all of which can be detected with current tests; the USGS study tested for the presence of 32 types.
A recent inventory of PFAS identified more than 4,700 PFAS with Chemical Abstracts Service (CAS) Registry Numbers that could have been, or may be, on the global market.
The following graphic shows the PFAS Emergence Timeline, including development, manufacturing, phase-out, reductions/alternatives, health concerns, and detection.
Types of Forever Chemicals
PFOA (Perfluorooctanoic Acid) and PFOS (Perfluorooctanesulfonic acid) are the most common types in the PFAS family.
PFAS (PFOA, PFOS, PFHxS and PFNA) levels have been reduced greatly over the past 20 years, mainly due to large manufacturers move to other chemical derivatives.
PFOA (Perfluorooactanoic acid) is a highly fluorinated compound with low surface tension, making it an effective chemical to help make products non-stick (pots and pans) and water resistant and stain resistant carpets as an example.
PFOS (Perfluorooctanesulfonic acid)
PFOS (Perfluorooctanesulfonic acid) is a close relative to PFOA, and is omnipresent in the environment. Its main use has been as a stain repellant and fabric protector; it is the main ingredient in the popular brand of rain repellant Scotchguard® and is also an ingredient in toxic firefighting foam.
PFHxS (Perfluorohexane sulfonic acid)
PFHxS (Perfluorohexane sulfonic acid) is also ever-present in the environment. One study has shown PFHxS were detected in most people who were tested for PFASs.
PFNA (Perfluorononanoic acid) and PFDoA (Perfluorododecanoic acid)
PFNA (Perfluorononanoic acid) and PFDoA (Perfluorododecanoic acid) are synthetic perfluorinated chemicals that have been found in both humans and various wildlife species worldwide. Recent PFNA studies indicate it may lead to developmental and reproductive toxicity to males.
PFOA & PFOS substitutes
Perfluorohexanoic acid (PFHxA) and Perfluoroheptanoic acid (PFHpA) are shorter chain PFASs that have been detected in drinking water sources such as municipal water providers and wells on private properties.
The following map shows well water samples contaminated in the U.S.
Perfluorobutane sulfonic acid (PFBS) was first developed in 2003 as a PFOS replacement. PFBS has been found in drinking water and samples of whole fish including both freshwater and ocean species.
Perfluorooctane sulfonamide (PFOSA) has been found to damage the health of cells in various fish populations. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6943835/
Short-chain and long-chain PFCAs and PFSAs Chart:
| Number of Carbons | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| PFCAs | Short-chain PFCAs | Long-chain PFCAs | |||||||
| PFBA | PFPeA | PFHxA | PFHpA | PFOA | PFNA | PFDA | PFUnA | PFDoA | |
| PFSAs | PFBS | PFPeS | PFHxS | PFHpS | PFOS | PFNS | PFDS | PFUnS | PFDoS |
| Short-chain PFSAs | Long-chain PFSAs | ||||||||
Sources:
https://awsedap.epa.gov/public/extensions/PFAS_Tools/PFAS_Tools.html
Page: Most Common Types of PFAS updated on October 26, 2023.