Species-specific PFAS profiles in companion dogs and cats: paired serum–food evidence for dietary long-chain PFCA exposure in Japanese cats

Per- and polyfluoroalkyl substances (PFAS) are hazardous persistent contaminants, but source attribution in domestic exposure systems remains poorly resolved. Companion animals may serve as One Health sentinels because they share household environments and food-related exposure pathways with humans. This study analyzed serum from privately owned dogs (n = 23) and cats (n = 30) from Hokkaido, Osaka, and Ehime, Japan, together with paired dry pet foods consumed by animals in the Ehime cohort (dog food, n = 10; cat food, n = 12). Thirty-eight PFAS, including branched isomers and emerging compounds, were targeted by LC–MS/MS. Eighteen PFAS were detected in serum, indicating widespread exposure in both species. Serum profiles differed clearly between dogs and cats. Cats showed marked enrichment of long-chain perfluoroalkyl carboxylic acids, including PFNA, PFDA, PFUnDA, PFDoDA, and PFTrDA, whereas dogs showed a profile more influenced by PFOS and PFHxS. Paired serum–food analysis supported pet food as one contributor: cat foods contained higher concentrations of PFOS, PFDA, PFUnDA, PFTrDA, and total PFAS than dog foods, and serum–food relationships were stronger in cats for PFOS, PFUnDA, PFTrDA, and total PFAS. In dogs, significant relationships were limited to PFOS and total PFAS, suggesting more heterogeneous exposure sources. 9Cl-PF3ONS was detected in serum, indicating exposure to regionally distinctive emerging PFAS. These findings move beyond occurrence monitoring by showing that consumed pet food may contribute to feline long-chain PFCA burdens under real-world household conditions and that dogs and cats record different aspects of domestic PFAS exposure.