Potential for contamination of crops by microbial human pathogens introduced into the soil by irrigation with treated effluent

In arid and semiarid regions throughout the world, shortage of water necessitates utilization of marginal water for agricultural irrigation. Because of its availability and relatively low cost, treated wastewater is commonly considered as an alternative water source for agricultural needs. Application of treated wastewater for agricultural irrigation may result in exposure of soil to pathogens, creating potential public health problems. Raw sewage water is known to contain a variety of human pathogens. Although their concentrations decrease during the wastewater reclamation process, the secondary treated effluents most commonly used for irrigation today still contain bacterial human pathogens. Therefore, irrigation with treated effluents introduces bacterial human pathogens to the soil. Although not in their natural host, human pathogenic bacteria are capable of surviving long periods of time in soil and water and thereby have the potential to contaminate crops in the field. Therefore, there is a risk of direct contamination of crops by human pathogens from the treated effluents used for irrigation, as well as a risk of indirect contamination of the crops from contaminated soil at the agricultural site. Bacterial human pathogens were recently demonstrated to have the ability to enter plants through their roots and translocate and survive in aerial plant tissues. The practical implications of these findings for food safety no doubt depend on the ability of bacterial pathogenic microorganisms to survive and multiply in the irrigated soil, in the water, and in the crop.