October 5, 2020 by Adam Peters

Adam and Graham have been working with colleagues in Arche Consulting, NiPERA, IZA and ECI to evaluate the reliability of the simplified metal bioavailability tool bio-met for copper, nickel, and zinc. We have evaluated the consistency of the outputs of bio-met against the available laboratory toxicity test data. This could not be done directly because bio-met only provides the local EQS for a given water chemistry. The EQS for each metal is set as the hazardous concentration for 5% of species in the ecosystem, and is calculated from a species sensitivity distribution that includes many different species. The evaluation process therefore had to follow an indirect approach based on three stages and involved the Biotic Ligand Models that provide the basis for the bio-met predictions to facilitate the comparisons between species-specific data and thresholds that have been set for the whole aquatic community. In the first stage ecotoxicity data for specific species from laboratory tests in natural waters are compared against predictions by the individual species BLMs included in the full BLMs. Secondly, the site-specific HC5 values predicted by bio-met for the natural waters used for ecotoxicity testing are compared against those provided by the full BLMs. Thirdly, using a larger set of European natural waters additionally demonstrates the reliability of bio-met over a broad range of water chemistry conditions.

This work has recently been accepted for publication in Environmental Toxicology and Chemistry and demonstrates that bio-met is an appropriate tool for performing compliance assessments against EQS values in Europe, due to the demonstrated consistency with the toxicity test data. The pre-publication version of the paper can be found here.