Risk of Pesticides Mixtures in Rice to Birds and Humans in Iran

Rice is a staple in the diet of nearly half of the world’s population. As with most crops, pesticides are used as a tool to increase crop yield in rice farming. This study investigated the residues of 14 organophosphate insecticides and 2 herbicides in rice cultivated at five locations in the southwest of Iran. The pesticide residues were then used to estimate the risk that they may pose to the health of bird and human consumers. The rice samples from the five locations contained residues from 10 to 13 pesticides. Of the 16 pesticides measured, the mean concentration of 12 pesticides exceeded the maximum residue limit set by the Iranian National Standards Organization at two or more of the sampling sites. The greatest total exceedance (sum of all pesticides detected in rice) of the species sensitivity distributions constructed for birds was 0.74% and the level of concern set for the assessment was an exceedance ≥ 5%, which suggests a relatively low risk to birds. For human consumers, no single pesticide measured in rice samples posed a considerable risk. However, when considering the mixture of pesticides present in rice samples, the cumulative risk exceeded the level of concern in all samples from all sites. The margin of safety for the mixture of pesticides present in rice samples ranged from 5.8 to 29.1, with 1 being the level of concern. The results of this study indicate that efforts need to be made to mitigate the exposure of human consumers to pesticides present in rice cultivated in Iran. This study also highlights the need to collect data on pesticides residues in other crop cultivated in Iran.