Aviation and PFAS – What’s the Connection?
If you have been following the news, you have probably heard about PFAS contamination at both civilian and military aviation facilities. Do you know how the two are connected? It comes down to the firefighting foam.
September 7, 2018
There has been no shortage of news stories this year about PFAS (per- and polyfluorinated alkyl substances) issues at aviation facilities, both civilian (see VPR and WWMT) and military (see MLive and AirForceTimes). So what’s the connection? If you’ve been following any of those stories, you probably already know it has something to do with firefighting foam, which is correct. However, there’s more to the story. In this article, we’ll discuss potential sources of PFAS at aviation facilities, present some facts and try to dispel misconceptions.
Most of the news stories you read about PFAS and aviation facilities mention foam, but what exactly are they referring to? Aqueous film-forming foam, or AFFF, is a material used for firefighting. It is very good at extinguishing petroleum fires. AFFF’s chemical properties make it particularly good at forming a dense “foam blanket” that prevents oxygen from reaching the fire, basically smothering it. AFFF also releases liquid that creates an aqueous film around the fuel, sealing it from the atmosphere and preventing fuel vapors from escaping. AFFF has been around since the mid-1960s and has been commonly used at civilian and military aviation facilities since the 1970s.
The close association between AFFF and PFAS is the result of the long history of AFFF product use at aviation facilities as well as the products currently certified for use at U.S. airports containing PFAS compounds. An obvious question is, “If we know PFAS causes environmental impacts, why are products with PFAS being used at aviation facilities?” PFAS-based AFFF products are demonstrably superior for extinguishing petroleum fires than previously used protein foams. In addition, the Federal Aviation Administration (FAA) requires that AFFF used at airports be certified to meet strict performance specifications, including the U.S. Department of Defense Military Specification (MIL-SPEC) MIL-F-24385F.
Aqueous film-forming foam (AFFF) is a material used for firefighting. AFFF’s chemical properties allow it to form a dense “foam blanket” that prevents oxygen from reaching the fire, making it highly effective at putting out petroleum fires.
The only AFFF products currently available in North America that meet the MIL-SPEC contain PFAS. As environmental concerns associated with two particular PFAS compounds (perfluorooctane sulfonic acid [PFOS] and perfluorooctanoic acid [PFOA]) were identified and U.S. EPA issued new regulations regarding use of these compounds, manufacturers have transitioned away from PFOS and PFOA and are using other PFAS compounds instead. The state of the science for understanding the potential effects and behavior of these other PFAS compounds in the environment is evolving and they are now also receiving increased regulatory attention.
Aircraft Hydraulic Fluid
Another possible, although not proven, source of PFAS at aviation facilities is aircraft hydraulic fluid. Although much less publicized than AFFF as a source of PFAS, some aviation hydraulic fluids have been reported to contain PFOS or PFOS precursors (such as potassium perfluorooctane sulfonate) as an additive to reduce erosion of aircraft parts, at concentrations less than 1%. It is important to note that aircraft hydraulic fluids are used in enclosed mechanical systems under controlled conditions, significantly reducing the risk of release to the environment. However, the possibility of hydraulic fluid release to the environment during aircraft maintenance activities, accidents involving damage to an aircraft, or incidents at material storage areas cannot be ruled out completely as potential sources of PFAS to the environment. That being said, a recent internal review of the technical literature on PFAS impacts at aviation facilities by LimnoTech did not reveal any case studies where PFAS impacts to the environment were attributed to hydraulic fluids.
Although several sources of PFAS at aviation facilities have been floated, AFFF is the only PFAS source that has been confirmed as impacting the environment with actual case studies.
Aircraft Deicing Fluids
There have been recent assertions that aircraft deicing and anti-icing fluids (ADAF) may contain PFAS, making it another possible source at aviation facilities. Although ADAF typically contains surfactants, there isn’t any evidence that ADAF contains PFAS. In 2012, the U.S. EPA (1) identified surfactants used in ADAF as alcohol ethoxylates, alkylbenzene sulfonates, alkylphenol ethoxylates, diamines, polyethylene oxide monomer and polymer, and nonionic detergents (polyoxyethylene monoleate, peg-20 sorbitan oleate). None of these compounds are fluorinated, whereas all PFAS compounds are fluorinated.
In 2010, the Airport Cooperative Research Program (ACRP), a program of the Transportation Research Board (TRB) within the National Academies, published research findings to better understand the current and prospective future components of aircraft deicing and anti-icing and pavement deicing materials. The results were published as ACRP Web-Only Documents #3 and #8. These studies included a components analysis on commercial aircraft and pavement deicing materials, which also found no fluorinated compounds.
We’ve also reviewed a wide array of technical literature on potential sources and uses of PFAS, published both in the U.S. and elsewhere. Recent reports on potential sources of PFAS by the National Groundwater Association (NGWA) and the Interstate Technology and Regulatory Council (ITRC) do not mention PFAS in aircraft deicing or anti-icing fluids as a potential source of PFAS. Similarly, studies in Europe by the Swedish Chemical Agency (KEMI) and Environment Agency Austria do not discuss PFAS in aircraft deicing or anti-icing fluids. These studies present very thorough evaluations of other sources, including AFFF and aircraft hydraulic fluid. To date, we haven’t found any reference to aircraft deicing or anti-icing fluids as a potential source of PFAS in current peer-reviewed publications.
A recent internal review of the technical literature on PFAS impacts at aviation facilities by LimnoTech did not reveal any case studies where PFAS impacts to the environment were attributed to aircraft hydraulic fluids. We also haven’t found any reference to aircraft deicing or anti-icing fluids as a potential source of PFAS in current peer-reviewed publications.
Summary & Conclusion
The connection between AFFF and PFAS at aviation facilities is well-established, but not all AFFF contains PFOS or PFOA, the two most commonly regulated PFAS compounds. The presence and extent of potential environmental impacts depend on the nature and history of past AFFF use at each facility. Although some hydraulic fluids used in aircraft may contain PFAS, the nature and quantities used indicate that hydraulic fluid releases are likely a minor potential source compared to AFFF. To date, there isn’t any evidence that ADAF contains PFAS.
This article is the fourth in a series of articles authored by LimnoTech staff on PFAS-related issues. Follow us on LinkedIn or Twitter (@LimnoTech) and check the News and Media page on our website for more information and updates. Links to the other PFAS articles in this series are provided below:
Scott Bell, PE, BCEE, is a senior environmental engineer and Vice President at LimnoTech. Scott has extensive experience in water resources engineering analysis and has been with LimnoTech since 1992. In addition to managing staff, projects, and clients, Scott has technical expertise in environmental remediation and restoration, hydrologic and hydraulic engineering, wastewater discharge impact analysis and mitigation, and stormwater management. He is currently supporting industrial and civilian aviation clients in Michigan with their PFAS-related problems.
Chris Cieciek is a senior project scientist at LimnoTech. He is a specialist in the areas of airport stormwater discharge compliance, deicing operations and controls, and evaluating impacts of deicing runoff on the environment. He has managed multi-disciplinary teams providing environmental consulting for airport stormwater management and environmental on-call issues. His technical skills include installation and operation of deicing controls; water quality monitoring and assessment; NPDES permit compliance evaluation and negotiation; investigation of per- and polyfluoroalkyl substances (PFAS); implementation of innovative stormwater management programs; and quality assurance/quality control programs for field and laboratory data collection.