UNDERSTANDING PFAS: ANALYSIS AND IMPLICATIONS 36 Air Monitoring
Per- and polyfl uoroalkyl substances (PFAS) are a large group of man-made chemicals that have been used in a wide range of industrial applications and consumer products since the 1940s [1,2]. Known for their persistence in the environment and human body - hence their nickname ‘forever chemicals’ - PFAS pose signifi cant concerns for public health and environmental safety [1-3]. PFAS comprise a diverse class of thousands of chemicals characterised by the fully (per) or partly (poly) fl uorinated carbon chain connected to diff erent functional groups. The carbon-fl uorine bond is one of the strongest in organic chemistry, contributing to this class of chemical’s remarkable stability. This stability is advantageous for applications requiring resistance to heat, water, and oil [1-2]. Consequently, PFAS such as the synthetic fl uoropolymer of tetrafl uoroethylene - polytetrafl uoroethylene (PTFE) have been used in products such as non-stick cookware and other industrial applications. Dupont created the Tefl onTM
brand
name of PTFE, meanwhile it has become synonymous and it is worth noting that it’s use is strictly regulated and requires licensing. Moreover, other PFAS compounds and industrial uses includes and is not limited to: water-repellent clothing, stain-resistant fabrics, food packaging, and fi refi ghting foams [1-2].
PFAS contamination is widespread and persistent [2], accumulating in the environment and in living organisms [2-6]. The chemicals can be found in soil, air, water, and in the blood of humans and wildlife globally [2-8]. Health studies have linked PFAS exposure to various adverse outcomes, including thyroid disease, elevated cholesterol levels, weakened immune response, and an increased risk of some cancers [7-9]. Given their persistence, once PFAS enter the environment, they are diffi cult to remove. It is thus important that these chemicals can be monitored and appropriate remediation applied to contaminated environments [10]. PFAS have become a focal point for regulatory agencies worldwide due to their persistence, bioaccumulation, and potential adverse health effects. The regulatory landscape for PFAS is complex, involving multiple challenges and considerations. This article examines the key regulatory issues associated with PFAS and looks at the analytical challenges that face the chromatographer in analysing these compounds.
One of the primary regulatory challenges is the lack of uniform standards for PFAS across different jurisdictions. While some countries and regions have established regulations, the standards often vary signifi cantly. For instance:
• In the United States, the Environmental Protection Agency (EPA) has issued legally enforceable levels for six PFAS, including PFOA and PFOS at maximum contaminant levels of 4.0 parts per trillion (ppt), but does not have enforceable federal limits for other PFAS in drinking water [11].
• The European Union has set limits for PFAS in drinking water, with the Drinking Water Directive establishing a sum limit of 0.5 µg/L for all PFAS, set on 12 January 2021 [12].
• Different U.S. states have their own regulations, with OEHHA California publishing a public health goal of 0.007 ppt for PFOA and 1 ppt for PFOS in April, 2024, limits much lower than the federal advisories [13].
This disparity complicates compliance for industries operating in multiple regions and creates confusion regarding safe levels of exposure [14]. The legislation is continually evolving in response to scientifi c fi ndings, that has led manufacturers and researchers to continuously improve their analytical workfl ows with regards to the limits of sensitivity and resolution. Furthermore, to identify, minimise and/or avoid PFAS interferences to the sample analysis where possible, e.g., not being able to use mobile phase modifi ers that can be classifi ed as PFAS such as trifl uoroacetic acid (TFA) – typically used for ion pairing attributes [15].
As new PFAS are continually developed, as is our greater understanding of the dangers associated with them, regulators face the challenge of keeping pace with substances whose health and environmental impacts are not yet fully understood [10, 14]. This piecemeal approach can lead to the substitution of regulated PFAS with unregulated alternatives that may pose similar risks. Regulating PFAS is further complicated by scientifi c uncertainties. The health effects of many PFAS are not well characterised, and there is ongoing research to determine safe exposure levels. Risk assessment methodologies vary, and long-term epidemiological studies are needed to fully understand the implications of chronic low-level exposure.
1. PFBS 2. PFHxA 3. 13
C2 C3 PFHxA
4. HFPO-DA 5. 13
6. PFHpA 7. PFHxS
-HFPO-DA
8. ADONA 9. PFOA 10. 13
C2 C4
11. PFOS 12. 13
13. PFNA 14. 9Cl-PF3ONS
15. PFDA 16. 13
C2 -PFOA -PFOS -PFDA
17. NMeFOSAA 18. d3
19. PFUnA 20. NEtFOSAA 21. d5
-NMeFOSAA -NEtFOSAA
Calibration standard with PFAS standards, IS and surrogates standards at 500 ng/L (in sample concentration of 2 ng/L, after 250x sample pre-concentration during sample preparation specifi ed in EPA 537.1).
The separation and detection were performed using an Avantor® with the mobile phase A: 5 mM ammonium acetate in H2
ACE® Excel® 3 C18, 100 x 2.1 mm, O and B: methanol (MeOH).
The fl ow rate was set to 0.4 mL/min, and the column thermostat set at 40 °C. Table 2 details the gradient conditions employed. A PFAS delay column (Avantor® mm) was employed, and installed prior to the injector loop. [19]
ACE® PFAS Delay Column, 50 x 2.1
22. 11Cl-PF3OUdS 23. PFDoA 24. PFTrDA 25. PFTA
PFAS contamination is widespread, affecting water supplies, soil, and air. Identifying and managing contaminated sites is a signifi cant regulatory challenge. The cost of remediation is high, and there is often uncertainty about the most effective methods for removing PFAS from the environment. Liability for contamination is another contentious issue [3]. Determining responsibility for cleanup costs can lead to extensive legal battles, especially in cases involving historical contamination by manufacturers and users of PFAS. Effective regulation requires robust monitoring and enforcement mechanisms. Monitoring PFAS in the environment is technically challenging due to their low concentrations and the need for sophisticated analytical methods [10]. Ensuring compliance with regulations requires signifi cant resources, and enforcement actions can be hindered by limitations in detection and measurement capabilities.
There have been various policy and legislative initiatives aimed at addressing PFAS contamination:
• In the U.S., the PFAS Action Act aims to designate PFAS as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as the Superfund law. This would facilitate the cleanup of contaminated sites and hold polluters accountable. [16]
• The European Chemicals Agency (ECHA) is working towards restricting the manufacture, use, and sale of PFAS under the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulation [17].
These initiatives refl ect growing recognition of the need for comprehensive regulatory frameworks but also highlight the challenges of implementing and enforcing such measures. Regulating PFAS has signifi cant implications for industries that manufacture or use these chemicals. Compliance with stricter regulations can entail substantial costs for monitoring, reporting, and implementing alternative substances or technologies. The economic impact on industries, particularly in sectors like manufacturing, textiles, and fi refi ghting, needs careful consideration to balance environmental protection with economic sustainability. The use of PFAS in so many areas has resulted in a relatively high level of background contamination, since so many materials contain it, from tissues to lab-coats. This makes the analysis of PFAS incredibly challenging as it requires the separation of background PFAS from sample PFAS.
With all of the interest in PFAS, it is evident that methods are required for the analysis of these potentially carcinogenic compounds. Using regulatory guidance, EPA 537.1 [18] and similar methods, the following 18 compounds were highlighted for separation and detection along with suitable isotopically labelled internal standards.
Table 1. List of test compounds and internal standards utilised
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