Cyanobacteria and microcystins contamination in drinking water sources: a review of occurrence, exposure, and mitigation measures

This review provides a comprehensive literature search on the occurrence of cyanobacteria blooms and microcystins contamination in drinking water sources, potential human exposure, mitigation, and the associated challenges. A total of 49 relevant studies indicate that cyanobacterial blooms are commonly reported on six continents, including Asia, Africa, North America, South America, Europe, and Australia. Overall, cyanobacterial biomass reported in these reviewed studies falls within the classification of Alert Level 2, which is indicated by chlorophyll-a concentrations exceeded 12 μg/L. Moreover, the published data also revealed that 59% of the reported microcystins concentrations exceeded the WHO guideline value for safe lifetime consumption of 1 μg/L. These potential human exposures to cyanobacteria and microcystins are based on the concentrations reported in raw drinking water sources, as a lack of studies have emphasized the detection of microcystins in the treated drinking water or at the last stage of the water treatment process. Nevertheless, it is important to acknowledge the potential health risk associated with the exposure to microcystins contamination in drinking water, as this metabolite is potent and chemically stable. Mitigation measures, including management approaches, physical, chemical, and biological techniques, can be applied to control cyanobacterial blooms and microcystins contamination in drinking water sources.