ABSTRACT
Microcystin (MC), a hepatotoxin that is harmful to human health, has frequently increased in freshwaters worldwide due to the increase in toxic cyanobacterial blooms. Despite many studies reported the human exposure to MC through drinking water, the potential transfer of this toxin to human via consumption of vegetables grown on farmlands that are naturally irrigated with contaminated water has not been largely investigated. Therefore, this study investigates the presence of MC in irrigation water and its potential accumulation in commonly consumed vegetables from Egyptian farmlands. The results of toxin analysis revealed that all irrigation water sites contained high MC concentrations (1.3-93.7µg L-1) along the study period, in association with the abundance of dominant cyanobacteria in these sites. Meanwhile, MCs were detected in most vegetable plants surveyed, with highest levels in potato tubers (1100 µg kg-1 fresh weight, FW) followed by spinach (180 µg kg-1 FW), onion (170µg g-1 FW), Swiss chard (160µg kg-1 FW) and fava bean (46µg kg-1 FW). These MC concentrations in vegetables led to estimated daily intake (EDI) values (0.08 to 1.13µg kg bw-1 d-1 for adults and 0.11to 1.5µg kg bw-1 d-1 for children), through food consumption, exceeding the WHO recommended TDI (0.04µg kg bw-1 d-1) for this toxin. As eutrophic water is widely used for irrigation in many parts of the world, our study suggests that cyanotoxins in irrigation waters and agricultural plants should be regularly monitored to safeguard the general public from inadvertent exposure to harmful toxins via food consumption.
