SETAC Globe
10 Jul 2025

Advances in Bioaccumulation Science and Assessment

Leslie Saunders, Concawe; Maike Habekost, BASF; Marco Franco, Swiss Federal Institute of Aquatic Science and Technology (Eawag); and Jane Caley, European Chemicals Agency (ECHA)

The session “Advances in Bioaccumulation Science and Assessment” at the SETAC Europe 35th Annual Meeting in Vienna, Austria, highlighted timely and important progress in the field of bioaccumulation. A key theme of the session revolved around the advancement of New Approach Methods (NAMs) for bioaccumulation assessment, including the use of fish cell lines and the testing of bioconcentration in aquatic invertebrates (Hyalella azteca and Gammarus pulex). The session was complemented by stimulating presentations on regulatory bioaccumulation assessment (such as the use of benchmarking or the OECD IATA), superhydrophobic chemicals, toxicokinetics and measurement of bioaccumulation in terrestrial species.

Below is a summary of the ten platform presentations on topics ranging from in vitro- to ecosystem-level investigations in bioaccumulation science.

Supporting Chemical Bioaccumulation and Biotransformation Assessments With NAMs

  • Use of fish cell lines in bioaccumulation assessment: Paloma de Oro-Carretero, Complutense University of Madrid, developed an approach using zebrafish liver cell lines on glass plates. The 72-hour in vitro assay used two moderately hydrophobic organic chemicals with well-known biotransformation product profiles. Concentrations both in the test medium and inside the cells were determined. The results were used in mass balance and kinetic approaches coupled with in vitro to in vivo extrapolation (IVIVE) models to predict bioconcentration factors (BCF). The use of fish cell lines is a promising development since it would completely remove the need for live fish, while allowing the assays to be conducted for a longer period.
  • Support of IVIVE for bioaccumulation assessment: Aurelia Lapczynski, Research Institute for Fragrances Materials, presented a case study with a fragrance compound, showcasing how in vitrobiotransformation assays can accurately predict fish BCFs. Using rainbow trout liver S9 fractions (OECD TG 319B), the studies showed 90% depletion of the parent compound and IVIVE modelling predicted a BCF of 309 L/kg. This extrapolated BCF showed excellent agreement with the BCF measured an in vivoOECD TG 305 study for the same chemical in bluegill sunfish (412 L/kg).
  • Bioaccumulation NAMs for birds: Matthew Schultz, University of Saskatchewan, presented a novel approach for assessing biotransformation and bioaccumulation in birds using in vitro clearance assays with avian liver S9 fractions. The study underlined the ecological importance of birds and the need to develop alternative approaches to assess bioaccumulation in air-breathing species. Initial assays with mallard duck liver S9 fractions showed consistent intrinsic clearance rates for two test chemicals across different replicates. Future work is planned with other test chemicals and to further develop the assay for other bird species. This approach lays the groundwork to support the integration of NAMs into wildlife risk assessment frameworks.

Mechanistic Insights

  • Irreversible binding: Clarissa von Au, Eawag, tested bioconcentration of four polar insecticides on G. pulex and H. azteca. Their study demonstrated the influence of receptor binding in bioaccumulation, which caused a fraction of the chemical to bind to the membrane proteins in the body long after the aqueous concentrations fell below the detection limit.
  • PFAS toxicokinetics: Kaue de Oliveira Chinaglia, Eawag, exposed H. azteca to per-and poly-fluoroalkyl substances (PFAS). They developed and applied a delicate technique to collect the haemolymph (blood) and measured the PFAS concentrations in it. This information was used to generate toxicokinetic data, revealing extremely slow elimination half-lives for long-chain PFAS in invertebrates.

From Lab to Landscape

  • Hydrocarbon bioaccumulation: Danielle Philibert, Huntsman Marine Science Center, investigated the bioaccumulation of polycyclic aromatic compounds (PACs) in blue mussels exposed to different crude oils. As an important food source and biomonitoring species, it is important to determine when blue mussels are safe for human consumption. The team applied a flow-through passive dosing technique to investigate the bioaccumulation behaviour of water-soluble PACs. Significant accumulation occurred within three hours, reflecting real-world exposure following small-scale oil spills in maritime harbours. Additional studies on different aquatic invertebrate species are planned for future research.
  • Microplastics: Frank Wania, University of Toronto, presented a fugacity-based investigation assessing whether the presence of microplastic (MP) in food accelerates the biomagnification of organic contaminants in polar bears. Using equilibrium sampling techniques, Wania and their team evaluated how the presence of MPs changes the fugacities of polychlorinated biphenyls (PCBs) and polymer additives in paired food and faeces samples collected from a zoo-housed individuals. The fugacity ratios of the PCBs in diet and faeces were below one, whereas the fugacity ratios for the polymer additives were 200–300. These observations suggest that that MPs have the potential to reduce the uptake of PCBs from the gastro-intestinal tract whereas MPs leached polymer additives into dietary and faecal matter and could lead to increased uptake of these compounds.
  • Food-web biomagnification: Ioanna Gkika, University of Amsterdam, performed a large-scale field study by sampling and analysing terrestrial and aquatic organisms living in a pond and its surroundings contaminated with PFAS. Their study reported trophic magnification factors (TMFs) above one for some PFAS indicating that they biomagnified in that food web. Variations in the levels and profiles of PFAS among species were noted to influence resulting TMFs, depending on species considered in the assessment.

Regulatory Bioaccumulation Assessments

  • Bioaccumulation thresholds for invertebrates: Leslie Saunders, Concawe, compared measured BCFs in fish and H. azteca (OECD TG 321) for 26 neutral organic chemicals. For moderately biotransformed chemicals, BCFs in H. azteca were typically much higher than fish BCFs, likely due to amphipods’ lower metabolic capacity. The AQUAWEB model was adapted to evaluate how bioaccumulation in an amphipod near the base of the food chain compared to higher trophic level fish. Modeling showed amphipod BCFs for biotransformed chemicals may be more conservative than modeled BCFs and biomagnification factors (BMF) in fish and more conservative than TMFs derived for the food chain. Invertebrate BCF tests are being considered as alternative methods for bioaccumulation assessment, though outcomes may differ from fish data.
  • Chemical benchmarking in bioaccumulation assessment: Shoko Furuno, ECHA, shared a data collection effort for benchmark cases to support regulatory assessment of fish dietary bioaccumulation tests (OECD TG 305). They analysed 21 fish dietary studies which have published conclusions on their bioaccumulation potential and found that many had missing study details to allow a proper comparison with other studies. There was a large variation between the key parameters relevant for benchmarking, such a depuration constant, assimilation efficiency and BMF. The work will be expanded by including new case studies and adding ionisable substances and aqueous exposure tests.

Poster Highlights

The bioaccumulation session also included twenty poster presentations. Some key take aways were:

  • Superhydrophobics: A systematic and model-based evaluation of superhydrophobic chemicals indicates the need to revise current bioaccumulation testing guidelines. Traditional fish BCF tests may underestimate bioaccumulation behaviour of these substances due to experimental limitations, such as sorption to organic carbon and prolonged equilibration times.
  • Invertebrates: Several posters showcased studies covering bioaccumulation testing in invertebrates. One group demonstrated that the H. azteca BCF test guideline can be successfully applied to the European amphipod Gammarus fossarum. Another highlighted a semi-automated culturing and sorting technique to systematically select test organisms in H. azteca BCF tests.
  • Evaluation of bioaccumulation NAMs: Two bioaccumulation NAMs (in vitro biotransformation assays and the H. azteca BCF test) were critically compared based on several evaluation criteria to assess their suitability for bioaccumulation assessments. The poster highlighted the greater throughput and mechanistic insight offered by in vitro biotransformation methods and the wider chemical space currently covered using such approaches.
  • Integrated testing and assessment: An Integrated Approach to Testing and Assessment (IATA) has been developed to critically evaluate and integrate multiple types of data (e.g. in silico models, in vitro methods) for evaluating chemical bioaccumulation. Case studies with fragrance ingredients and surfactants showcased the value of such a framework to support clear and transparent decision-making in regulatory bioaccumulation assessments.
  • Mammalian bioaccumulation assessments: “Intelligent sampling” during standard mammalian (i.e., rodent) in vivo toxicity studies can be used to collect kinetic data without increasing animal use, presenting an alternative approach for assessing bioaccumulation in mammals.

Key Messages and the Way Forward

The session highlighted a shared interest in moving away from vertebrate testing (i.e., fish) towards in vitro methods and aquatic invertebrates and showcased new methods for bioaccumulation assessment using bird-derived liver S9 fractions and fish cell lines. The session also indicated the need for further research on testing superhydrophobic chemicals and to further explore invertebrate BCF and toxicokinetics data for bioaccumulation assessment.

Final Remarks

The co-chairs thank all speakers and poster contributors for their inspiring science and lively discussion. For those interested in staying connected with the bioaccumulation community, please join the Bioaccumulation Science Interest Group.

Contact: [email protected]

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