Non-targeted screening of emerging contaminants in South African surface and wastewater

Targeted analysis of contaminants in water are often focused on a narrow range of chemicals, falling short of the true pollution status of water bodies. Non targeted screening presents several advantages in identifying less prioritized pollutants, entirely unknown compounds and transformation products. In this study we employed a non-targeted screening workflow established on a high-resolution quadrupole time-of-flight mass spectrometer coupled to an ultrahigh performance liquid chromatograph (UHPLC-QTOF-MS) to identify known and unknown pollutants in South African waste and surface waters. Level two confidence identification of 315 compounds was achieved based on mass accuracy, isotope patterns and MS/MS spectra match. Pharmaceuticals, drugs, and metabolites made up 40% of the detected compounds, biological compounds and industrial chemicals along with their metabolites constituted 24 and 18% respectively, while personal care products, pesticides and food additives made up approximately 5, 4 and 4% respectively. Several antiretroviral drugs were confirmed with level one confidence using isotope labelled standards. A wide range of “new” pharmaceuticals, pesticides and metabolites were documented in South African waters for the first time. Seventeen (17) pharmaceuticals were reported for the first time in South African waters, of which four are reported for the first time ever in surface water.

The result of this exploratory study highlights the presence of several contaminants of public health concern that have hitherto received little to no attention in previous wastewater-based epidemiological studies. We provide a detailed list of priority contaminants for future studies on targeted-analysis.