Microcystin levels in irrigation water and field-vegetable plants, and food safety risk assessment: A case study from Egypt.

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 (1.3-93.7 μg L) 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 fresh weight, FW) followed by spinach (180 μg kg FW), onion (170 μg g FW), Swiss chard (160 μg kg FW) and fava bean (46 μg kg FW). These MC concentrations in vegetables led to estimated daily intake (EDI) values (0.08-1.13 μg kg bw d for adults and 0.11-1.5 μg kg bw d for children), through food consumption, exceeding the WHO recommended TDI (0.04 μg kg bw d) 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.