Occurrence of cyanobacteria producing toxins in irrigation freshwaters: Which impacts on crop quality and public health?

Cyanobacteria are a group of unicellular and multicellular photosynthetic prokaryotes that occur worldwide in water bodies. blooms of cyanobacteria can be potentiated by a combination of several environmental factors,such as nutrient availability,water temperature and light intensity. cyanobacterial blooms represent an emerging human and environmental concern because of some species producing toxins (cyanotoxins) that can affect a large number of chain food organisms,such as human,fish,birds and plants irrigated with contaminated water. microcystins (a group of cyanotoxins) are the most common and most concerned in case of human health. cyanobacteria blooms occurred in a wide range of freshwaters habitats and then the possibility of exposure to microcystins exists via skin contact or by ingestion of contaminated food and/or water. in terrestrial irrigated plants,it seems that the effects caused by microcystins vary from inhibition of seed germination to seedling development,by the reduction of protein phosphatases 1 and 2a activities,the oxidative stress,the decrease of photosynthetic activity and even cell apoptosis,as well as the bioaccumulation of toxins in plant tissues. the microcystins bioaccumulation in plant tissue occurs at concentrations higher than their respective recommended tolerable daily intake,recommended by who. thus,the irrigation of crop plants by microcystins contaminated water,is not only a socio-economical problem but becomes a public biohazard health risk because of the possible chain food contamination. this route of exposure requires careful monitoring by the responsible authorities,since there are gaps remaining concerning information on the provisional guidelines for the tolerable concentration of microcystins in irrigation water.