Health Risk Assessment of pharmaceuticals in drinking water from de facto water reuse in South Africa - And an investigation of the public’s perception of de facto water reuse

Abstract

In the last decades pharmaceuticals originating from wastewater have been detected in drinking water around the world. Consequently, a concern regarding human health risks due to long term exposure of pharmaceuticals in drinking water have been raised among water suppliers and consumers. In South Africa, in periods of drought, rivers that are used as raw water in drinking water treatment plants (DWTPs) have showed to contain up to 99% of treated wastewater, which is called de facto (unintendedly) water reuse. The occurrence of de facto water reuse might increase the concentration of pharmaceuticals in drinking water. The aim of this study was to develop a model for Quantitative Chemical Risk Assessment (QCRA) of human health risks due to long-term exposure of carbamazepine, diclofenac, and sulfamethoxazole in drinking water in two DWTPs along Berg River, South Africa. A sensitivity analysis with different scenarios (conventional treatment and chlorination, no treatment, and conventional treatment and Granular activated carbon (GAC) filters) was performed in the QCRA-model for the population groups: infants, children, and adults. As a second part the public’s perception of water reuse and the level of trust in safe water quality was investigated through an interview study. Results showed that there is no human health risk for any of the population groups exposed to the pharmaceuticals studied via drinking water. Even with no treatment in the DWTPs no risk will occur with exposure of the pharmaceuticals studied. The result that was closest to a risk was exposure of diclofenac for infants that are formula fed. As a future scenario, if the concentrations of pharmaceuticals may increase, a suggestion would be to implement GAC filters, since the results shows a reduction of the risk, especially for diclofenac and carbamazepine. The results from the interview study showed that the overall perception of water reuse is that most people seem to accept it as a water source, but the majority have doubts that it is safe to drink. To overcome this great barrier, higher public involvement and knowledge sharing actions are needed to increase the trust in that reused water is safe to drink.