GenX in the Cape Fear River, A Short Compendium: Part 1, What are PFCs
In the summer of 2017, the story broke that a compound colloquially known as “GenX”. The catalyst for the news story, the resulting response from the Department of Environmental Quality, the NC Legislature and a research project from the University of North Carolina Wilmington was another study out of NC State to measure these compounds in the Cape Fear River released a year earlier. In trying to understand more about GenX while I was a student at UNCW, I was motivated to write a short compendium on GenX. This series will not address health concerns in any serious way. This series of articles is an attempt to highlight not only GenX itself, but a bit of the history of it’s class of compounds, associated research and legislative responses which does include health advisory goals. Unlike standard articles, I have given the greatest effort to include references to the associated literature for all facts, these are included as a separate link at the bottom associated by the superscript numeral.
What are PFCs?
The name of the compound that most people are familiar with is GenX1 but is known to chemists as perfluoro-2-propoxypropanoic acid. It belongs to a class of compounds known as perfluoronated compounds, or more chemically accurate as organoflourine compounds. These compounds resemble a standard alkane chain with a functional group attached to one of the terminal carbons with one major difference, the saturation of the carbons are almost entirely made up of fluorine.7 It is this C-F bond that gives this class of compounds it’s extraordinary stability. While some reactions do occur, they’re almost entirely on the hydrophilic group attached to the terminal carbon.7
These properties are why these compounds have found uses in products like Gore-Tex and Teflon4 but also oil and water repellents, food packing materials, electronics, surfactants, cosmetics and others.10 However these same properties make them heavily resistant to degradation and contributes to its environmental and biological accumulation that has been the focus of a great deal of research for the last 40 or so years. They persist indefinitely in the environment because of the strength of the C-F bond. Depending on the PFC, some are highly water soluble and therefore extremely mobile in the environment.12
One such compound, perfluorooctanoate (PFOA), has been a topic of research since at least the 1980s and found to be toxic then.9 Manufacture of such compounds goes back as far as World War II.4 Some PFCs have been phased out in both Europe and the US. These include most long-chain PFCs such as PFOA and others such as perfluorooctanic sulfonate (PFOS). It is important to note that this phase out did not really occur before about 2000.6, 8 The EPA states that long chain PFCs are in the process of being phased out and specifically, PFOS, was not reported as being imported or manufactured in the US as of 2012 but existing stocks may have limited uses.6 The phase out of long chain PFCs has been occurring for roughly 6-10 years longer in Europe but Asia remains considerably more deregulated.8
Two main processes are known to produce PFCs. PFOS and some other PFCs are commercially produced using a process known as electro-chemical fluorination. This process uses an electrical current to fully fluorinate an organic feedstock that is dispersed in hydrogen fluoride. This process however is not exclusive to the target compound. Other perfluoroalkyl homologues are known to form at the same time. Reaction by-products are usually branched-chain isomers. The other major process used to produce PFCs is telomerization which uses perfluoroalkyl iodies to form the target compound but doesn’t produce branched-chain isomers as seen in ECF.7
The newer PFCs are generally referred to as short chain PFCs. Usually, this means a PFC with a carbon chain less than six or seven6 and these are set to replace their longer-chain predecessors. It was the accumulating evidence since the 80s about it’s ecological persistence and human health effects upon exposure to these long chain PFCs that prompted both the voluntary phase out and increased regulatory response in both Europe, US and Canada. It also prompted manufacturers to move production to Asia where it is more deregulated.6 Short chain PFCs like GenX are, as of yet, relatively unknown and are not yet classified as an emerging contaminate under the EPA. The only known published occurrence data before 2016 was from Europe and China.6, 14 This leaves the current GenX phenomenon very early in the stages of emerging contaminates research and regulation., even to the extent that laboratory determination methods are still being developed for PFCs and the GenX-type subclass referred to as perfluoroalkyl ether carboxylic acids (PFECAs).
As we move through this series exploring the research into PFCs and the proliferation of the GenX phenomenon and the legislative response, it is important to understand a fundamental fact about our chemical universe. There are roughly 80-130 million chemicals in existence and about 85,000 are used in commerce. Of those, less than 10,000 have ever been tested for toxicity. Under the Clean Water Act, 126 have been flagged as priority pollutants, 65 are flagged as toxic pollutants and only 9 have ever been banned by the EPA outright.13 The Clean Water Act is the vehicle for which the EPA and States regulate pollution discharge, but there is a catch. The Clean Water Act regulates pollution discharge by regulated listed compounds, it basically states what you can’t discharge. It does not prevent emerging contaminates from being discharged nor anything entirely unlisted. It is only after evidence is found of harm that these compounds move up the EPA regulatory framework.
In the next part, we will dive into more specifics of what GenX is as well as the methodologies of measuring GenX and PFCs and the elements of the most important studies surrounding PFCs in the Cape Fear River.