Bioaccumulation

In addition to toxicity, the potential of test chemicals to bioaccumulate is often assessed using fish. However, there are opportunities to reduce and replace the use of fish while advancing the goal of environmental protection.

OECD IATA framework

The OECD case study on the use of Integrated Approaches for Testing and Assessment (IATA) for bioaccumulation provides a weight-of-evidence framework for bioaccumulation. Multiple lines of evidence (LoE) can be used to quantify, measure, and qualify the common metrics; namely the bioconcentration factor (BCF), bioaccumulation factor (BAF), biomagnification factor (BMF) and trophic magnification factor (TMF). These LoE can comprise in silico predictions, combinations of in vitro and in silico data, e.g. in vitro–in vivo extrapolation (IVIVE), and measured laboratory or field data.

In Vitro Methods to Predict Hepatic Clearance and Bioconcentration Factors

In 2018, two Organisation for Economic Co-operation and Development (OECD) Test Guidelines (TG) to determine in vitro hepatic clearance using rainbow trout hepatocytes and S9, and an associated guidance document (GD) were adopted by the OECD (OECD TGs 319A and 319B, OECD GD 280). In combination with in silico models, hepatic clearance can be used to predict bioconcentration factors for bioaccumulation assessment, e.g. in the context of the bioaccumulation IATA discussed above.

Reducing the Number of Fish Used in Bioaccumulation Testing

In July 2020, the US Environmental Protection Agency (EPA) released new guidance clarifying the number of treatment concentrations required for fish bioconcentration factor (BCF) studies for pesticide registration. The policy change brings the EPA into alignment with international regulations and will prevent as many as 240 fish from being used in BCF studies each year while safeguarding human health and the environment.

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