Dissipation pattern and dietary risk assessment of chlorfenapyr and methomyl in corn under Egyptian field conditions

Abstract

Corn is the second most widely farmed grain for human consumption. Low corn productivity due to damage caused by pests has led to using pesticides to control pest infestations. However, the uncontrolled application of pesticides on corn harms both environmental and human health. Accordingly, field experiments followed good agricultural practices to investigate the dissipation pattern and terminal residues of chlorfenapyr and methomyl in corn and compare the values with established safety limits. Gas chromatography-tandem mass spectrometer coupled with the quick, easy, cheap, effective, rugged, and safe technique was used to analyze residues of chlorfenapyr and methomyl in corn. The average recoveries varied from 94% to 105%, with relative standard deviations (RSDs) of 8%-13% for chlorfenapyr and from 99% to 111%, with RSDs of 10-16% for methomyl. Chlorfenapyr and methomyl residues degraded in corn following a first-order kinetic model, with an estimated half-life (t_1/2) of 3.9 and 2.8 days, respectively, and significant degradation (91.4%-98.1.5%, respectively) after 14 days. Although the maximum residue limits of chlorfenapyr and methomyl for corn are yet to be formulated in Egypt, the long-term dietary risk for those pesticides was acceptable, with arisk quotient < 100%, according to the national assessments. These findings are required to guide the correct and safe application of these insecticides in Egypt.