High Concentrations of Pharmaceuticals in a Nigeria River Catchment

Pharmaceutical contamination of the environment is recognized as a global problem although most work has focused on Europe and North America to date and there remains a dearth of information for developing countries, including those in Africa. To address this data gap the occurrence of thirty‐seven pharmaceuticals belonging to nineteen therapeutic classes was monitored in surface water and effluents in Lagos State, Southwest Nigeria. Samples were collected quarterly between April 2017 and March 2018 from 22 sites, and 26 compounds were detected at least once, many in the microgram per litre range. Maximum concentrations for those compounds detected ranged from 75 to 129 µg L‐1 and even mean concentrations for thirteen compounds were in the order of µg L‐1. These values are amongst the highest ever measured globally. Sewage effluent was more important than drug manufacturing waste in polluting rivers although there are likely to be numerous unregulated sources of effluent being discharged to rivers which require further study, including urban waste collection areas and vacuum trucks which collect effluent. Seasonal trends in the data were complex with some compounds being found at higher concentrations in the dry season and, conversely, others being greater during the wet period, this variation potentially relating to the variety of pollution sources in the catchment. Pharmaceuticals are indispensable to human health although their usage and discharge into the aquatic environment may lead to ecological problems and antibiotic resistance. The data presented in this paper indicate that pharmaceutical pollution of freshwaters is a serious issue in Nigeria and management efforts are needed to improve this problem.