Over the past few decades, concern for the environment and the mitigation of human impact has increasingly become a topic of global interest. As concern for the environment moves to the forefront of social and political discussions, many governments, both national and regional, are proposing and enacting legislation to regulate the use and release of harmful chemicals such as Per- and polyfluoroalkyl substances (PFAS).
By Foster Voelker II, Director of Engineering – Williams Valve
The United States House of Representatives passed HR2467 PFAS Action Act in July of 2021. According to the United States EPA, “Harmful per- and poly-fluoroalkyl substances (PFAS) are an urgent public health and environmental issue facing communities across the United States. PFAS have been manufactured and used in a variety of industries in the United States and around the globe since the 1940s, and they are still being used today. Because of the duration and breadth of use, PFAS can be found in surface water, groundwater, soil, and air—from remote rural areas to densely populated urban centers. A growing body of scientific evidence shows that exposure at certain levels to specific PFAS can adversely impact human health and other living things. Despite these concerns, PFAS are still used in a wide range of consumer products and industrial applications. Every level of government—federal, Tribal, state, and local—needs to exercise increased and sustained leadership to accelerate progress to clean up PFAS contamination, prevent new contamination, and make game-changing breakthroughs in the scientific understanding of PFAS.”1
Similar concerns can be found on the other side of the pond, in the European Union. A proposal unveiled by the European Chemical Agency (ECHA) suggests a comprehensive ban on the usage of PFAS in all industrial sectors of the European Union (EU). For certain applications that are extremely challenging to replace, restrictions would be gradually implemented over a period of up to 12 years. Obviously, the implications of this growing body of proposed PFAS regulations could have a widespread impact on the valve industry.
What are PFAS?
What are PFAS? Although it may seem like a simple question, the scope of materials included in the term PFAS necessitates precisely defined classifications, as the way these substances are categorized from a regulatory standpoint could have far-reaching consequences across numerous industries. The term PFAS is recently utilized nomenclature, having gained traction within the past 15 years.2 The term per-fluorinated chemicals (PFC) was used in older references, but it has been largely phased out due to the potential for confusion with perfluorocarbons, which are entirely made up of carbon and fluorine and have different properties than PFASs.3
PFASs are chemicals that contain one or more perfluoroalkyl moieties. According to a 2021 article published in the Environmental Science and Technology Journal, “In 2011, to harmonize communication, Buck et al.2 published a milestone paper, providing the first clear structural definition of PFASs and recommendations on the names and acronyms for over 200 individual PFASs. Since then, research and regulation has expanded from PFOA and PFOS to a much wider range of substances.”
“In 2018, the so-called ‘Global PFC Group’ led by the Organization for Economic Co-operation and Development (OECD) and the United Nations Environment Program (UNEP) published a list of over 4700 PFASs that contain a −CnF2n− (n ≥ 3) or −CnF2nOCmF2m− (n and m ≥ 1) moiety and that were known or likely to have been on the global market. The list included substances that contain fully fluorinated carbon moieties, but do not meet the PFAS definition in Buck et al.2 due to a lack of a −CF3 group in the molecule. Additionally, recent advancement of nontargeted analytical techniques enabled identification of many unknown PFASs in environmental and product samples. These developments provided motivation to reconcile the terminology of the PFAS universe, including a renewed look at the PFAS definition.”4 Examples of implications of this definition change can be found in Figure 1.4
Additionally, many PFASs can be divided into two sub-groups: non-polymeric and polymeric PFASs.
Non-polymeric PFASs can be classified into four categories. The most historically significant is perfuoroalkyl acids (PFAAs) including perfluoroalkyl carboxylic (PFCAs) and perfluoroalkane sulfonic (PFSAs) acids. Certain ‘long chain PFASs’, such as PFOS and PFOA, which have long been under regulatory scrutiny fall in this category. The other categories include chemicals derived from perfluoroalkane sulfonyl fluoride (PASF) compounds, fluorotelomer (FT)-based compounds, and per- and polyfluoroalkyl ether (PFPE)-based compounds.
Polymeric PFASs can be categorized into three types: fluoropolymers, side-chain fluorinated polymers, and perfluoropolyethers. General classifications are outlined in Figure 2.3
This concise overview of PFAS classifications reveals the need for a basic technical comprehension of chemical composition and properties in order to delineate the materials encompassed by this term. The term does not necessarily imply toxicity and comprises both safe and unsafe chemicals.
This subject can rapidly become intricate, underscoring the imperative for any governmental organization seeking to regulate these products to establish precise legislation that addresses discrete classifications. Broad legislation, in the absence of precise classifications, could have unintended repercussions considering the significant use of these materials in industry.
Concerns regarding the classification of safe materials are already being voiced by industry organizations such as the Fluid Sealing Association (FSA), whose Government Affairs Committee is “turning its attention towards the intensifying scrutiny by various organizations over the use of a class of chemicals called PFAS (per- and polyfluoroalkyl substances) which are man-made chemicals that do not occur in nature that have been found to accumulate in humans and wildlife. The PFAS category covers a wide range of materials of which fluoropolymers are just one class. Fluoropolymer materials are ubiquitous in our day-to-day lives. Fluoropolymers are used by most if not all sealing device manufacturers due to their unique and extremely useful properties. Fluoropolymers are very stable materials (physically, chemically & bio- logically) that do not break down into other PFAS materials, and fluoropolymers do not have viable alternatives with the same properties.”5
Impacts on the Valve Industry
The largest concern for the valve industry would be the inclusion of fluoropolymers, especially PTFE. PTFE can be found in numerous applications within the valve industry. It is utilized for resilient (soft) seated valve designs providing excellent chemical resistance and closure performance. PTFE lined valves can be found in highly corrosive applications, PTFE gaskets are found in chemical plants, PTFE coated bolts are used for harsh atmospheric conditions, and PTFE lubricants are utilized in the nuclear industry, along with countless other uses.
However, from an environmental perspective, the largest impact would be on the recent implementation of Certified Low Leak Technology (CLLT). CLLT packing refers to a valve stem seal (packing) design that will not exceed a 100 ppm fugitive emission threshold for a minimum of five years as defined in various EPA consent decrees. The implementation of CLLT packing by the EPA was a result of years of data estimating that 60% of all fugitive emissions could be attributed to valve stem seals or packing.
The CLLT requirements forced packing manufactures to develop new configurations to meet these stringent requirements which almost universally included the addition of PTFE as a blocking agent and lubricant. Thus, any legislation prohibiting the use of PTFE would negate the significant progress made in reducing fugitive emissions from various sources. Alternatives that would provide the same level of performance are not readily available.
Another area of concern with regard to stem seals is control valves. Control valves used for fine-tuned process control often employ PTFE packing due to the low coefficient of friction. Transitioning these components to an alternative stem seal such as graphite, would often require a larger actuator to deal with the increased friction. Thus, existing control valve packages would likely need to be resized to accommodate the change.
Conclusion
The real-world consequences of this pending legislation can already be seen. In December of 2022, the company 3M, which produces a significant portion of the global PTFE supply and other fluoropolymers, announced it will exit PFAS manufacturing to discontinue the use of PFAS across its entire product portfolio by the end of 2025.6
Moving forward, if significant industry impacts are to be avoided, governments should not enact legislation that broadly classifies and regulates all PFAS as a singular group, includes provisions that mandate hazardous designations for all PFAS, and/or prohibits the design and development of new nonharmful PFAS. Instead, regulatory efforts should be anchored on standardized test methods with defined acceptance criteria, continued mitigation measures, and the utilization of classifications to differentiate hazardous chemicals from non-hazardous ones.
References:
- https://www.epa.gov/system/fi les/documents/2021-10/ pfas-roadmapfinal-508.pdf
- Buck RC, Franklin J, Berger U, Conder JM, Cousins IT, de Voogt P, Jensen AA, Kannan K, Mabury SA, van Leeuwen SP. Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins. Integr Environ Assess Manag. 2011 Oct;7(4):513-41. doi: 10.1002/ieam.258. PMID: 21793199; PMCID: PMC3214619. https:// pubmed.ncbi.nlm.nih.gov/21793199/
- OECD(2013), OECD/UNEP Global PFC Group, Synthesis paper on per- and polyfluorinated chemicals (PFCs), Environment, Health and Safety, Environment Directorate, OECD. https://www.oecd.org/ chemicalsafety/risk-management/synthesis-paper-on-per-and-polyfluorinated-chemicals.htm
- Zhanyun Wang, Andreas M. Buser, Ian T. Cousins, Silvia Demattio, Wiebke Drost, Olof Johansson, Koichi Ohno, Grace Patlewicz, Ann M. Richard, Glen W. Walker, Graham S. White, and Eeva Leinala. A New OECD Definition for Per- and Polyfluoroalkyl Substances, Environmental Science & Technology 2021 55 (23), 15575-15578 DOI: https://pubs.acs.org/ doi/10.1021/acs.est.1c06896
- https://www.fluidsealing.com/pfas-and-fluoropolymers/ 6. https://news.3m.com/2022-12-20-3M-to-Exit-PFAS- Manufacturing-by-the-End-of-2025
