Reducing the number of fish in bioconcentration studies with general chemicals by reducing the number of test concentrations

- We assessed differences in general chemical BCF values determined at two exposure concentrations.
- Generally there is no difference in the BCF value generated by low or high exposure concentrations.
- Therefore a one concentration approach is suitable for the BCF testing of general chemicals.
- We recommend the single exposure concentration should be set as the high value.
- This approach will significantly reduce the number of vertebrates used in bioaccumulation assessment.

Fish bioconcentration test guidelines generally require that bioconcentration factors (BCFs) are determined at two exposure concentrations. However, recent revisions to the OECD test guideline for bioconcentration testing (TG 305) provide the option to use only one exposure concentration, when justification is provided, although two concentrations may still be required for some regulatory purposes. Recently, this justification has been demonstrated for plant protection product active ingredients. To determine whether this justification has a broader validity for general chemicals, an analysis of 236 BCF studies on general chemicals was conducted. The results presented here again demonstrate that BCF values do not significantly differ between concentrations when more than one concentration is used. This relationship is particularly strong for BCFs ⩾1000 L/kg, which is beneficial, since only chemicals with BCFs >2000 L/kg may require regulatory action. This analysis therefore provides a data-driven rationale for using the one test concentration approach for general chemical substances and thus could contribute to a substantial reduction in the use of fish in bioconcentration tests.