An international collaborative study critically reviewed the derivation methods for Water Quality Guidelines (WQG) protective of aquatic ecology that are currently endorsed and adopted in the following five countries: Australia, Belgium, Canada, the Netherlands and the United States of America (USA).
The study identified that each country adopted different WQG derivation methods encompassing various combinations of species sensitivity distributions (SSD), the Assessment Factor (AF) method, geometric mean calculations, dietary exposure modelling, biotic ligand models and soil-water equilibrium partitioning methods. The approaches for incorporating bioaccumulation (indirect ecotoxicity), background concentrations and toxicity modifying factors (e.g. temperature, salinity and pH) also differed between countries. Our in-depth review highlighted the role of policy in setting WQG and the importance of understanding the sources of data and the science used to underpin the WQG rather than blindly applying values during management of water quality.
So which country got it right? Perhaps it isn’t that simple to award first prize. Many factors will influence which derivation method can (or should) be adopted including data availability and each chemical’s toxicity mode of action. Furthermore, country-specific methods for interpretation of ecotoxicity data and availability of funding (and therefore frequency of WQG revisions) will influence which derivation method is adopted.
The information generated from this study will allow an informed and transparent selection of international WQG by those jurisdictions (including Australia) that do not have endorsed WQG, and will help to ensure scientifically robust and appropriate values are adopted for water quality management.