PFAS in the buzz: Seasonal biomonitoring with honey bees (Apis mellifera) and bee-collected pollen

Per- and polyfluoroalkyl substances (PFAS) are emerging environmental contaminants with known persistence, bioaccumulation potential, and ecotoxicological relevance. This study investigates the occurrence, distribution, and potential exposure pathways of PFAS in honey bee-related matrices (pollen, forager bees, hive bees). Samples were collected from six sites over a full season representing diverse land uses (urban, semi-urban, rural, and agricultural). A total of nine different PFAS were detected across 90 samples, with short-chain compounds such as 4:2 FTS, PFPS, and PFBS predominating. Hive bees exhibited the highest average sum of target PFAS concentration (5.29 ng g^ꟷ1), followed by forager bees (1.93 ng g^ꟷ1), and pollen (1.10 ng g^ꟷ1). Differences in PFAS occurrence among sample types, especially PFPS between forager and hive bees, suggested various exposure routes, including pollen ingestion, atmospheric deposition, and contact with contaminated surfaces. Temporal and spatial differences were notable. Site-specific PFAS patterns highlighted potential contamination sources, such as fluorinated pesticide use, while seasonal variation suggested influence from plant phenology and rainfall. Principal component analysis (PCA) confirmed the dominance of shared PFAS profiles, with some outlier samples exhibiting unique signatures. PFPS and PFBS were positively correlated with total fluorine (TF) concentrations, while 4:2 FTS showed a strong site-specific association. Extractable organic fluorine (EOF) remained below detection limits (800 ng F g^ꟷ1), but TF was present in all samples above LOD (500 ng F g^ꟷ1) confirming the presence of additional unidentified fluorinated compounds. Although EOF and PFAS concentrations varied, we showed that forager bees can introduce PFAS in the hive, either on their bodies, or through contaminated resources such as nectar or pollen. These findings demonstrate the suitability of honey bees as bioindicators for PFAS contamination but emphasise the need for harmonized sampling to fully assess PFAS exposure dynamics.