New European PFAS Thresholds Put Focus on Analysis of ‘Unknown’ Chemicals

The relevance of a per- or polyfluoroalkyl substance (PFAS) can be assessed by combining its occurrence, or concentration, and its severance, or harmful effect, according to Bjorn Berendsen, a senior researcher and manager of the Statutory Tasks Food Safety—Policy program at Wageningen University & Research in The Netherlands. Berendsen presented research conducted with Stefan P. J. van Leeuwen during a session on emerging and environmental food contaminants at the 2023 North American Chemical Research Workshop (NACRW) in Fort Lauderdale, Florida, USA (1).

What is dangerous PFAS - Perfluoroalkyl and Polyfluoroalkyl Substances - and where is it found? | Image Credit: © Francesco Scatena - stock.adobe.com

PFAS are persistent in the environment and can accumulate in the human body over time. Studies have linked exposure to PFAS with adverse health effects, including increased risk of certain cancers, liver damage, immune system disruption, and developmental issues in children. The potential dangers of PFAS in food products underscore the need for stricter regulations, monitoring, and risk assessment to safeguard public health and reduce exposure to these harmful substances.

Berendsen and van Leeuwen’s presentation, “PFAS Analysis in Food Products—Challenges, Methods, and Results,” stems from the European Food Safety Authority (EFSA)’s recently published opinion that lowered the tolerable weekly intake (TWI) for PFAS with particular attention to four substances: perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS). To illustrate the new EFSA standards, Berendsen said the level of quantification (LOQ) of PFOA in milk, in terms of pg/g, is now lower than it had previously been by a factor of 100 (1).

The problem with this, as Berendsen explained in email correspondence with LCGC prior to his NACRW presentation, is not necessarily with the revised EFSA limits, but with the sheer amount of unknown information about PFAS at large. He said there are thought to be more than 6,000 such substances and the relevancy of each has not been determined, although the consensus has been that the immunotoxicity effects of PFAS, even those currently “unknown,” need to be determined most urgently.

“Only a few of them have been studied in more detail; most we do not know much about,” Berendsen said. “EFSA wrote an elaborate opinion on PFAS, and a main conclusion is that there is insufficient data available.”

Though focusing mostly on outcomes, Berendsen did address separation methods both in his presentation and in speaking directly with LCGC. Among the roadblocks of these processes is that, as he opines, analysis of short- and long-chain PFAS “cannot be combined in a single method without compromising the quality of the method and the detection limits.” He emphasized the necessity of deploying multiple approaches to paint a complete picture, saying for instance that only in cases where an isotopically labeled standard is available can solvent calibrations be applied to PFAS—otherwise, quantitation will be compromised.

Solid-phase extraction (SPE), he said, is still the preferred method for food analysis, citing severe matrix effects elsewhere and proposing an organic extraction combined with anion exchange. But even that isn’t a big enough umbrella.

“Considering the diversity of PFAS in polarity but also in ionization (anionic, neutral, cationic) it is clear that not all will fit in a single method,” Berendsen said. “Even with the chromatography only, we see that specific groups need special conditions. As such, we always need to choose the method based on the substance scope.”

Whether that means nontargeted screening, total organofluorine (TOF) analysis, or total oxidizable precursor assay (TOPA), or something else entirely, may depend on even further future changes to TWI limits and how much that is currently “unknown” about PFAS becomes known as these minimum or maximum concentrations evolve.

For more coverage of NACRW 2023, click here.

Reference

(1) Berendsen, B.J.A.; van Leeuwen, S.P.J. PFAS analysis in food products – challenges, methods and results. Presented at the 59th North American Chemical Residue Workshop, Fort Lauderdale, Florida, July 25, 2023.