Quantification of pharmaceutical residues in wastewater impacted surface waters and sewage sludge from Lagos, Nigeria

Information on the occurrence of pharmaceuticals in the environment of Nigeria is limited, only a single publication previously on pharmaceutical occurrence in the environment of Nigeria, which measured general estrogen levels in Enugu, South-East Nigeria. In order to establish a first overview, surface water samples from six locations as well as ten sewage sludge samples from waste water treatment plants were analysed for a range of different pharmaceuticals, including antibiotics, estrogens, and lipid-lowering drugs. The results of this monitoring campaign were evaluated in comparison to published measured environmental concentrations in Africa and worldwide. In surface water samples, 12 of 37 pharmaceutical substances were detected at concentrations ranging from Limits of Detection (LOD) up to 8.84 µg/l. Four of these pharmaceuticals were found at concentrations exceeding ecotoxicological predicted no-effect concentrations (PNEC). In industrial, domestic, and hospital sewage sludge, nine different pharmaceutical substances were detected with the NSAID diclofenac present in all samples at concentrations of up to 1100 µg/kg dry weight, exceeding the highest measured concentration of 560 µg/ kg reported in sludge samples worldwide. This study proves the presence of several pharmaceuticals at relevant concentrations in the environmental matrices studied. Further, more comprehensive monitoring campaigns, especially in locations with high population density and low dilution of treated or untreated waste water in receiving streams are recommended.   Key words: Nigeria, pharmaceuticals, liquid chromatography-tandem mass spectrometry (LC-MS/MS), water, sludge.