ABSTRACT
Microcystins (MCs) are hepatotoxic secondary metabolites produced by several genera of cyanobacteria. Human exposure routes include drinking contaminated water and consuming contaminated fish, vegetables, crops, and even food supplements that contain cyanotoxin. This study investigated the presence of MCs in a stream with a long history of use as a source of water for irrigation farming. To establish the risk of a lack of monitoring programs, we studied MCs contamination of irrigated vegetables. Toxin levels in the water were generally <0.05 µg L-1 in all the investigated stations. Total microcystin concentrations in spinach (0.306 µg Kg-1 upstream and 0.217 µg Kg-1 downstream), lettuce (0.085 µg Kg-1 upstream and 0.462 µg Kg-1 downstream), carrot (0.050 µg Kg-1 downstream and 0.116 µg Kg-1 downstream), cabbage (0.014 µg Kg-1 upstream and 0.031 µg Kg-1 downstream), tomatoes (0.233 µg Kg-1 upstream), and bitter leaf (0.460 µg Kg-1 upstream and 0.050 µg Kg-1 downstream) collected in March were higher than the levels detected in samples of the same vegetables collected in April. These results highlight Nigeria's severe public health problem, especially in regions with long dry season spells. The level of MCs contamination of irrigated vegetables implies a potential for chronic exposure and associated health challenges.
