The Conference of the Parties (COP) to the Stockholm Convention on Persistent Organic Pollutants reached a landmark agreement in May 2025 when it voted to add long-chain perfluorocarboxylic acids (LC-PFCAs)—covering carbon chain lengths from C9 to C21—to Annex A of the Convention. This listing triggers a global obligation for all Parties to eliminate the production, use, import, and export of these substances, with the ban taking effect in December 2026.
What Are Long-Chain PFCAs?
Long-chain perfluorocarboxylic acids are a large subclass of PFAS comprising more than 200 individual compounds. They include perfluorononanoic acid (PFNA, C9), perfluorodecanoic acid (PFDA, C10), perfluoroundecanoic acid (PFUnDA, C11), and longer chain homologs up to C21. These compounds share PFAS’s characteristic extreme environmental persistence, bioaccumulation in food chains, and toxicity to liver, immune system, thyroid, and reproductive function. They have been used historically in industrial surfactants, fluoropolymer production as processing aids, and as components of aqueous film-forming foam (AFFF) formulations.
Why This Listing Matters Globally
The Stockholm Convention has 186 parties, covering the vast majority of the world’s nations. The addition of LC-PFCAs to Annex A creates a legally binding obligation for all Parties to phase out production and use by December 2026, though specific implementation timelines at the national level are subject to domestic law and available exemptions. Critically, the listing applies even to countries that have not yet developed national PFAS regulations—including many in Asia, Africa, and Latin America—potentially transforming the global supply landscape for fluorochemicals.
The United States, which signed but has not ratified the Stockholm Convention, is not legally bound by this listing at the federal level, though U.S. TSCA regulations independently restrict several LC-PFCAs. The EU is required to update its Persistent Organic Pollutants (POPs) Regulation to incorporate the Stockholm Convention listing, and the European Commission began that process in 2025, with LC-PFCAs expected to be added to Annex I of the EU POPs Regulation during 2026.
Exemptions and Uncertainties
The Stockholm Convention listing includes specific use exemptions that allow Parties to continue using LC-PFCAs for critical applications where no alternatives exist, for a defined transition period. Environmental groups have criticized the scope of some exemptions—particularly for fluoropolymer manufacturing uses, where LC-PFCAs may be present as trace processing aids—arguing that broad industrial exemptions undermine the intent of the global ban. The exemption framework will be reviewed at the next COP, and the strength of monitoring and enforcement at the national level will determine the real-world impact of the listing.
Connection to C9 PFNA and OEM Filter Certification
Perfluorononanoic acid (PFNA, C9) is among the shortest-chain LC-PFCAs covered by the Stockholm Convention listing and is simultaneously one of the six PFAS compounds for which the U.S. EPA originally established a drinking water MCL of 10 ppt in its 2024 NPDWR. EPA’s proposed rescission of the PFNA MCL in its 2025 rule revision creates a regulatory gap between the global production ban under the Stockholm Convention and the U.S. drinking water protection framework. States with their own PFNA standards—including Minnesota, Massachusetts, and Vermont—will continue to drive filter performance requirements for this compound regardless of federal MCL rescission.
Implications for Filter Media and Water Treatment
The global production ban on LC-PFCAs beginning December 2026 will accelerate the detection of these compounds in environmental monitoring programs as legacy contamination becomes the primary source rather than ongoing industrial discharge. Surface water and groundwater monitoring campaigns in countries that adopt the Convention listing will reveal the geographic extent of historical LC-PFCA contamination—particularly from fluorochemical manufacturing sites, AFFF storage and use areas, and industrial parks where these compounds were used as surfactants. Each new contamination discovery is a potential driver of demand for water treatment and filtration solutions. OEM filter media manufacturers with performance data for long-chain PFAS removal beyond PFOA and PFOS—specifically PFNA, PFDA, and PFUnDA—should begin developing compound-specific validation datasets to support market entry in newly regulated markets.