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

•
PFAS was detected in bees and pollen at a quantifiable level.
•
Seasonal variation, including bloom timing and rainfall, influences PFAS uptake.
•
Bees and pollen allow the monitoring of acute and seasonal changes in contaminants.

Abstract
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 gꟷ1), followed by forager bees (1.93 ng gꟷ1), and pollen (1.10 ng gꟷ1). 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 gꟷ1), but TF was present in all samples above LOD (500 ng F gꟷ1) 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.

Graphical abstract
Download: Download high-res image (297KB)
Download: Download full-size image


Introduction
Per - and polyfluoroalkyl substances (PFAS) are of growing concern to the environment due to their strong chemical and thermal stability originating from the strong C-F bonds. This enables PFAS bioaccumulation, which is observed not only in long chain (C > 8), but also short chain (C < 8) and ultrashort chain (C < 3) PFAS as well. The use of sentinel animals, including humans, is an effective way to monitor PFAS contaminants in the environment (Aristizabal-Henao et al., 2021; Andrews et al., 2023; Rock et al., 2023; Khalid et al., 2024; Libenson et al., 2024).
Bees usually forage around a two to three km radius of the hive (Garbuzov et al., 2015, 2020; Danner et al., 2017), thus making them an excellent sentinel animal for local contaminations (Bargańska et al., 2016; Cunningham et al., 2022; Farias et al., 2023; Glinski et al., 2024) of pesticides (Murcia-Morales et al., 2020a, 2020b; Catalano et al., 2024 Donley et al., 2024), microplastics (Edo et al., 2021), heavy metals (Zarić et al., 2022; Bora et al., 2023), polycyclic aromatic hydrocarbons (PAHs) (Lambert et al., 2012; Murcia-Morales et al., 2024; Catalano et al., 2024), dioxins and dioxin-like compounds (Catalano et al., 2024), fine particles (Meza-Figueroa et al., 2024), particulate matter (Marcoccia et al., 2024), explosives (Filipi et al., 2022), but also antimicrobial resistance (Resci et al., 2024). The most studied matrix is honey as it is not only a possible storage for the pollutants but is also a human food (e.g. Bora et al., 2023; Nowak & Nowak, 2021; Smith et al., 2019). Also, live or dead bees are commonly sampled (Zarić et al., 2022). During the active foraging season, honey bee workers live only a few weeks, which increases the time increments that can be analysed. Furthermore, honey bees show an interesting division of labour: Whereas young bees stay in the hive to consume bee bread (stored pollen) and feed larvae, older bees fly out foraging on plants for nectar, honeydew or pollen (Seeley, 2009).
Although there are limited investigations of PFAS in honey bees and bee products, it was shown that honey originating from an industrial region contained 20 % higher concentrations of perfluorocarboxylic acids (PFCAs) than those from a non-industrial origin (Surma et al., 2016), and that bee colonies exposed to perfluorooctansulfonic acid (PFOS) show an adverse effect on the colony activity, hive maintenance and defence, amongst others (Sonter et al., 2021). All of these highlight the importance of investigating PFAS in bees and hive products. However, there are many things to be considered during sampling, as plants tend to accumulate PFAS at different rates based on the environmental conditions (e.g. water/rain). The use of fluorinated pesticides could also influence PFAS concentrations and uptake as these pesticides break down over time to trifluooracetic acid (TFA) (Joerss et al., 2024).
The above-mentioned publications showed the presence of PFAS in bee products and possible adverse effects of PFAS on colonies, however, they do not give a picture of the PFAS contamination of the bees, which eventually are in contact with the environment. Therefore, the aim of this study was to investigate PFAS in different colonies with a multi-platform approach using liquid chromatography coupled to electrospray tandem mass spectrometer (LC-ESI-MS/MS) for targeted analysis, and combustion ion chromatography (CIC) for assessing the total fluorine content and extractable organofluorine (EOF) content in bees and pollen. We also utilised a mass balance approach to give a better overview about the PFAS burden in the environment using bees and bee products as biomonitoring tools.