Poisoned Legacy

Ten Years Later, Chemical Safety and Justice for DuPont’s Teflon Victims Remain Elusive

May 1, 2015

Poisoned Legacy: Appendix

Understanding PFCs

Per- and polyfluorinated chemicals (PFCs), more precisely defined as per- and polyfluoroalkyl substances (PFASs), are a family of chemicals used to make Teflon, Scotchgard, Gore-Tex as well as many other non-stick, stain-resistant or waterproof coatings. These chemicals share two characteristics: they take a long time to break down in the environment, and they can accumulate in the blood and organs of animals and people exposed to them. (EPA 2015) Further, the chemicals that have been studied in detail raise many similar health concerns, from cancer to liver or kidney toxicity and reproductive effects. (Scheringer 2014)

Life on earth is carbon-based. Carbon atoms form the fundamental building blocks of our bodies and those of other living organisms. Chemical compounds are built on carbon atoms bonded to atoms of such elements as hydrogen, oxygen, nitrogen, fluorine and sulfur. The carbon-fluorine bond is particularly strong, and bonding more fluorine to carbon increases the strength of all the bonds. (Kirsch 2006) The strength and stability of the bonds produces chemicals that are the slippery, repel water and dirt, resist breakdown, resist electrical current and persist in the environment for decades.

In 1938, Dr. Roy J. Plunkett, a chemist at DuPont’s laboratory in Deepwater, N.J., was trying to produce a refrigerator coolant when he accidentally synthesized PTFE. The compound was patented in 1941. (USPTO US2230654) PTFE is a synthetic plastic, or polymer, constructed from a long chain of carbon atoms with two fluorine atoms attached to each carbon atom. This two-to-one pairing produces a molecule of fluorinated ethylene. The goal in polymer production is to maximize the chain length or the number of ethylene repeats.


Chemical structure of PTFE


PTFE or Teflon

In 1945, DuPont trademarked PTFE as Teflon for use in industrial applications. (USPTO 1945) Subsequent trademark filings for Teflon and related chemicals chronicle its expansive usage in textiles, non-stick coatings on pans, snow shovels, bags, briefcases and umbrellas. (USPTO 1954, 1965, 1969, 2014)

PTFE has a tendency to become lumpy or bubble up. To smooth it for use as Teflon, perfluorooctanoic acid (PFOA) was added. The PFOA stabilizes the production of the polymer, and in principle should not be a component of the finished plastic. However, production and disposal result in large quantities of PFOA waste, which DuPont and other manufacturers dumped as wastewater effluent in landfills and into the air through factory smokestacks.

Chemical structure of PFOA


Perfluorooctanoic acid (PFOA)

Perfluorooctanesulfonic acid (PFOS) is a closely related perfluorinated chemical that also has a carbon backbone of eight atoms. Like PFOA, its discovery was an accident: In 1952, 3M chemists Patsy Sherman and Sam Smith spilled an experimental fluorochemical on tennis shoes. (Schwarcz 2004) Smith and Sherman had created the first pair of non-stick, stain-resistant shoes, and within years clothing and other textiles were widely treated with PFOS-based Scotchgard. PFOS was also used widely as a coating on food wrappers for everything from carry-out containers to microwave popcorn.

Chemical structure of PFOS


Perfluorooctanesulfonic acid (PFOS)

For replacements, the chemical companies have shifted toward shorter-chain perfluorinated compounds. The shorter-chain molecules are generally less bioaccumulative but often have decreased performance, so the U.S. market has been slow to shift to the alternatives. (Scheringer 2014) Concern has been raised that the alternatives may require higher concentrations in products to achieve the same performance, reducing the environmental or health benefits. (Scheringer 2014)

In replacing PFOA, DuPont has shifted to a shorter-chain length fluorinated chemical, known as a six-two fluorotelomer alcohol, indicating that the fluorinated carbon length is six atoms long. Keeping the fluorinated section of the molecule less than eight carbon atoms long assures that the chemical will not break down to PFOA or PFOS in the environment. (DuPont 2015A)

Chemical structure of Dupont replacement for PFOA


DuPont replacement for PFOA

3M developed an alternative to PFOA, abbreviated as ADONA, by breaking up the fluorinated carbon backbone with oxygen atoms. (Gordon 2010) This approach limits the maximum length of a breakdown product to three carbon atoms or less.

Chemical structure for 3M replacement for PFOA


3M replacement for PFOA

Since 2000, EPA has received and reviewed pre-manufacture notices for more than 150 different chemicals to replace the longer-chain PFCs. (Krasnic 2014) Neither the chemical companies nor EPA have provided information on how the safety of these replacement chemicals has been verified or how many of these chemicals have already found their way onto the market.

The PFOS replacements include chemicals that incorporate PBSA, a four-carbon chain sulfonamide. It has been reported that the salts of the 6:2 fluorotelomer sulfonic acids are also being used as replacements. (Chu 2014, Wang 2013 B) The main reported in-vitro metabolite of ScotchGard post-2002 is PBSA. (Chu 2014)

Chemical structure of PBSA