Estimation of risk to soil and human health during irrigation using ZnO nanoparticles-containing water

This work estimated ecological and human health risks for the exposure pathway of spinach irrigation with metal oxide nanoparticles-contaminated river water. Using literature studies, log-logistic plant uptake models were developed to predict metal uptake in plant parts. Reported or expected values of ZnO nanoparticles (NPs) in surface water were collected from published literature for realistic scenarios and used to estimate the risk to human health in terms of hazard quotient (HQ). Monte Carlo simulation and uncertainty analysis were conducted to assess the variability in the obtained results. The Hazard Quotient (HQ) values obtained at environmental concentrations of ZnO nanoparticles were all below 1 for all age groups. Although the 99th percentile value of HQ was found to be the highest (3.57 x10- 3) for the age group (1-6) years, the probability of HQ value being greater than unity was found to be null for all age groups. The 99th percentile values of contamination factor, potential ecological risk factor, and geo-accumulation index, computed as part of ecological risk assessment, were found to be 0.098, 0.098, and -0.62, respectively, well within their respective contamination limits. Bio-concentration and translocation factors were also computed to quantify the internal uptake of the plant. The results implied that at the current levels of zinc oxide nanoparticles in surface water, no health risk would be exerted on humans upon spinach consumption under the assumptions used. Also, negligible chances of soil contamination were observed due to zinc accumulation after irrigation. The approach proposed in this work can be used to determine potential health and ecological risks when reusing metal oxide NP-contaminated water for irrigating edible crops. This especially gains significance in a future perspective due to a likely increase in nanoparticles' concentration in the environmental media.