Development of a prioritisation framework for emerging organic contaminants in South African drinking water

There is a growing concern regarding the possible presence of emerging organic contaminants (EOCs) in South African drinking water arising from anthropogenic activities like agricultural, chemical, manufacturing, and mining processes. The introduction of these EOCs into water sources leads to a deterioration of water quality, whilst their presence in drinking water may pose significant health risks. This necessitates regular proactive monitoring of EOCs in drinking water, although the South African drinking water standard may not include these compounds. Due to limited resources in Africa, there is a pressing need to prioritise EOCs to assess which are most relevant to the region and which pose the greatest risk, and therefore which should be monitored. This will in turn inform updating of regulations to ensure safe drinking water. We therefore present a novel prioritisation approach which was developed to identify high-risk EOCs in South African drinking water. To achieve this, a database of 509 EOCs was compiled, which were then scored based on occurrence, solubility, volatility, carcinogenicity, reproductive toxicity, and the availability of regulatory standards. The compounds were then ranked into high-, medium-, and low-priority categories for probability, physicochemical properties and toxicity, respectively, with the most compounds ranking in the high-score category for physicochemical properties (239 compounds) followed by probability of occurrence (197 compounds). The final overall high-priority list contained 165 contaminants, which were dominated by 78 pesticides and 48 pharmaceuticals and personal care products. The results of this study provide guidance to local drinking water monitoring programmes, policy development, and improved resource allocation for safer drinking water in South Africa.