Prioritisation of emerging chemical pollutants in South African water resources

Abstract

Emerging chemical pollutants (ECPs) are defined as new chemicals which do not have a regulatory status, but which may have an adverse effect on human health and the environment. Sources and environmental pathways of these ECPs have been increasingly associated with waste and wastewaters arising from industrial, agricultural and municipal activities. The ECPs of current concern include a wide range of compounds including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), brominated flame retardants (BFRs), antivirals, antiretrovirals, pesticides, phthalates, disinfectants, psycho-stimulants, diuretics, cosmetics, contrast media, neuroactive compounds, blood lipid lowering agents, beta-blockers, antibiotics and, analgesics and anti-inflammatory drugs. There is currently a lack of information regarding the nature, concentration, variability, transport and fate of these compounds in water, which is of global concern. A recent South African survey on emerging contaminants in drinking water in South Africa detected a total of 34 pharmaceuticals or pesticides, which indicates the need for more research in this area. In this study a prioritisation methodology for emerging chemical pollutants in water was developed and used. A group of 168 ECPs were prioritised based on various factors including toxicity (acute toxicity in rats), environmental persistence (half-life in water), relevant physicochemical data (partition coefficient) and global prevalence. The ECPs were then ranked by assigning weightings to these factors. The ranks each substance obtained were then summed across all the factors in order to obtain a final weighting for each substance. Each substance was then ranked in accordance with its final summed total which resulted in a ranked list of priority ECPs. After the prioritisation process, it became apparent that pesticides were a class of compounds that warranted further studies as they accounted for many of the highest ranked ECPs. The full list of ranked ECPs generated can prove to be an invaluable starting point for further research into ECPs in South African water bodies and to compare various ECPs with each other in term of their persistence, bioaccumulation and toxicity and thus the hazard they pose to the environment. Additionally, relevant surface water sampling sites in the Gauteng Province of South Africa were identified utilising a geographic information system (GIS) to generate maps. The sites were identified by identifying potential sources of ECPs, including hospitals and clinics, sewage treatment plants, and areas with high population densities or areas that were vulnerable from an environmental point of view. Buffers were drawn around these areas to identify the water sources which have the highest probability of containing the relevant ECPs. The wards that are located along the identified at-risk river areas were also identified in an attempt to aid decision and policy makers within both the private sector and government in making informed decisions regarding ECPs.