GenX in the Cape Fear River, A Short Compendium: Part 2, The Research
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.
Standardizing Aqueous PFC Sample Determination
Research into the detrimental effects of PFCs both environmental and biological go back as far as at least the 1980’s when it was found that, particularly, PFOA and PFOS were biologically toxic. As the years rolled on, studies into PFCs continued to increase worldwide attention as more evidence mounted that these compounds were both ecologically and biologically detrimental, particularly based on animal models. This prompted a voluntary phase-out of two compounds of greatest concern (PFOA and PFOS) in both Europe and North America.3, 6, 8 Several studies of note, out of Japan, suggested a correlation between PFC blood levels in humans and water concentration. One US study suggested a correlation between PFC blood levels and home grown food and ground water in heavily contaminated areas.3
Despite the mounting ecological concern, surprisingly, it wasn’t until about 2007 that an attempt was made to develop a rigorous standardized method for the determination of aqueous PFC samples. Before, there was a disconcerting lack of detail concerning how the handful of studies developed their methodology in aqueous PFC analysis.3 Dr. Nakayama et al published a pilot-scale evaluation of PFCs in the Cape Fear River Basin in order to demonstrate the effectiveness of a rigorous method that, it was hoped, would become more standardized in such analysis.3
At 80 different sites along the Cape Fear River Basin, 100 samples were collected in order to analyze 10 different PFCs, among these, PFOA and PFOS. A field blank along with a spiked sample was also transported to and from the sample site along with the samples themselves. The analysis was performed on a High Pressure Liquid Chromatography/Tandem Mass Spectrometer setup. Calibration curves for each batch were produced using standards for each of the 10 target compounds and therefore the results can be considered quantitative. Nakayama et al worked closely with the US EPA and the National Exposure Research Laboratory in the development of this method and was, in part, partially funded through those federal agencies.3
In 2008. the EPA would publish Method 537 for the select determination of Perfluorinated Alkyl Acids in Drinking Water using Solid Phase Extraction with Liquid Chromatography/Tandem Mass Spectrometry. It is unknown to me if Nakayama et al’s work influenced that method but it would be the basis for certain regulatory results to follow under the Unregulated Contaminates Monitoring Rule III. However Nakayama et al’s work would be the basis for two important studies that have, and will affect the course of actions of the North Carolina Department of Environmental Quality and ultimately the NC Legislature and possibly federal regulation.
NC DEQ states that:
“GenX is a trade name for a man‐made and unregulated chemical used in manufacturing nonstick coatings and for other purposes. Chemours’ facility in Fayetteville began producing GenX commercially in 2009 as a replacement for PFOA. The same chemical is also produced as a byproduct during other manufacturing processes and it may have been present in the environment for many years before being produced commercially as GenX.”1
This statement however is partially misleading. GenX more accurately refers to the GenX technology developed by Chemours to replace PFOA. The compound colloquially termed GenX is actually perfluoro-2-propoxypropanoic acid but that isn’t the active component in the process it is to replace. The active compound is used to control the polymerization to make fluropolymers like Teflon is a propanoate. This active compound is formed by mixing the propanoic acid compound with ammonium hydroxide solution which simply deprotonates the hydroxyl group and replaces it with an ammonium cation on the, now, anionic oxygen.11 It is also worth mentioning that during the manufacturing of these resins, the propanoate compound is transformed into a water-insoluable hydride. The hydride and propanoic acid are emitted into the air during processing and GenX and it’s precursor (the propanoic acid) are emitted into the water.11
Following the work of Nakyama, Dr. Knappe extended the work to include newer, short-chain PFCs like GenX. Dr. Knappe’s team stated three objectives for the study.2 1) Identify and Quantify presence of 7 legacy PFCs and 3 newer PFCs 2) Assess Removal by Conventional and Advanced WT Processes 3) Evaluate Adsorbability of PFASs on PAC. As previously stated, the methodology here was based upon Nakayama et al’s work but extended to include newer short chain PFCs like GenX. While analytical standards exist for many of the legacy PFCs, they do not exist for the short chain PFCs like GenX and the results of the study can only be considered semi-quantitative and, until such time as standards are developed the results for those compounds can only be considered insensitive and may not reflect actual concentrations, as they detail explicitly in the study.
Dr. Knappe collaborated with three treatment facilities along the Cape Fear River Basin, including the Sweeny Plant in Wilmington. The study was released in 2016 and it was this study that prompted the backlash from the public after it was revealed that GenX was found in the Cape Fear River. The levels of GenX in the Sweeny samples prompted swift action from both the state and the facility itself. In regards to the treatment plant removal, removal of short-chain PFCs by conventional processes are negligible at best and the affinity for PFCs on PAC decreases by shortening the alkyl chain. In effect this means that removal of the type of compounds like GenX requires more specialized treatment processes. It is worth mentioning that at the time of this writing CFPUA has been and is exploring treatment options. The specifics will be relegated to the final part of this series, but the results are positive.
The details of the events from the regulatory and media reactions to the GenX presence will be left for the last part of this series but one result was HB56 passed in 2017. This is currently funding a UNCW study by the MACRL group in the Chemistry Department. The stated goal of this study is two fold. First, to extend the work of Nakayama et al for PFAS. Second, once confidence in the method is established, begin a sampling campaign of raw and finished drinking water to quantify known PFAS in those samples and identify unknowns, if possible.17 Periodic updates on the ongoing research are provided to the public via Cape Fear Public Utilities Authority.
So far, what has been observed are fluctuating levels of GenX in the river, all below the DHHS Health Goal of 140 ppt. However, there are a number of times where the raw water source shows lower or non-detectable levels of PFCs but the finished water shows low, but detectable levels of PFCs. This may indicate that PFCs may be trapped in the treatment process and are being desorbed during the treatment process into the finished water. One confirmed source of desorption of PFCs are the GAC/BAC. This was also observed in a Pender County WTP.15, 16
In the final part of this series, the regulatory and media response to the GenX phenomenon will be explored. This will not only include the response to water, but air quality and not only the response from the NC DEQ, but the legislature, and any federal actions into both GenX but legacy PFCs as well.