Abstract:
Background: Within the last decades, there has been increasing research on the occurrence of chemicals of emerg-ing concern (CECs) in aquatic ecosystems due to their potential adverse effects on freshwater organisms and risk to
human health. However, information on CECs in freshwater environments in sub-Saharan countries is very limited.
Here, we investigated the occurrence of CECs in snails and sediments collected from 48 sites within the Lake Victoria
South Basin, Kenya, which have been previously investigated for water contamination. Samples were analyzed by
liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) with a target list of 429 compounds.
Results: In total, 30 compounds have been detected in snails and 78 in sediment samples, compared to 79 previ-
ously identified compounds in water. By extending the monitoring of CECs to snails and sediments, we found 68
compounds that were not previously detected in water. These compounds include the anti-cancer drug anastrozole,
detected for the first time in the Kenyan environment. Individual compound concentrations were detected up to
480 ng/g wet weight (N-ethyl-o-toluenesulfonamide) in snails and 110 ng/g organic carbon (pirimiphos-methyl) in
sediments. Higher contaminant concentrations were found in agricultural sites than in areas not impacted by anthro-pogenic activities. Crustaceans were the organisms at greatest toxic risk from sediment contamination [toxic unit
(TU) up to 0.99] with diazinon and pirimiphos-methyl driving this risk. Acute and chronic risks to algae were driven by
diuron (TU up to 0.24), whereas fish were found to be at low-to-no acute risk (TU up to 0.007).
Conclusions: The compound classes present at the highest frequencies in all matrices were pesticides and biocides.
This study shows substantial contamination of surface water in rural western Kenya. By filling data gaps on contami-
nation of sediments and aquatic biota, our study reveals that CECs pose a substantial risk to environmental health in
Kenya demanding for monitoring and mitigation.