Effectiveness and limitations of environmental risk assessments to identify antibiotics of greatest concern in Australia

Environmental Risk Assessments (ERAs) are a helpful tool to identify medicines that pose the greatest risk to the environment. While these are integrated into regulatory frameworks overseas, they are not yet required for medicines in Australia. As a result, there is limited local data on the volumes of pharmaceuticals entering the environment and their downstream impacts. This study uses local data to calculate predicted environmental concentration and risk quotient values for antibiotics used in the community in Australia. The results from this analysis demonstrate that the environmental risks posed by antibiotics in Australia may be significant with amoxicillin, cefalexin, clindamycin, azithromycin and phenoxymethylpenicillin predicted to exceed environmental risk thresholds. However, a sensitivity analysis revealed limitations in the accuracy of this model and demonstrated that risk quotients can vary greatly based on assumptions made by the assessor. This has implications for the applicability of current environmental risk assessment models both in Australia and overseas. Despite these limitations, this model presents several advantages as a simple method to screen for high-risk antibiotics and is still more effective than the current Australian approach of having no ERA requirements for medicines.