Formulation Matters: Differential Genotoxic and Cytotoxic Effects of Lambda-Cyhalothrin Pesticide Formulations on Human Hepatocellular Cells

Pesticide formulations may influence toxicological outcomes beyond the intrinsic properties of active ingredients; however, these differences are often overlooked in regulatory risk assessment. Using human liver HepG2 cells, this study compared the cytotoxic and genotoxic effects of two commercial lambda-cyhalothrin formulations that differ in formulation type and in composition: an emulsifiable concentrate (Lambda-Cyhalothrin 5% EC) and a suspension concentrate co-formulated with thiamethoxam (Duer SC). Cytotoxicity was assessed using propidium iodide exclusion, while genotoxicity was evaluated using the cytokinesis-block micronucleus (CBMN) and alkaline comet assays. Lambda-Cyhalothrin 5% EC showed significant cytotoxicity from 500 μM onward, whereas Duer SC induced cytotoxic effects even at lower concentrations beginning at 200 μM, indicating greater cytotoxic potency of the combined formulation. Lambda-Cyhalothrin 5% EC induced a concentration-dependent increase in the number of binucleated cells containing micronuclei, with a significant effect at 50 μM. Duer SC also increased micronucleus frequency but did not differ significantly from the negative control. Proliferation indices remained comparable to controls for both formulations. The comet assay showed that Lambda-Cyhalothrin 5% EC produced significant DNA damage from 10 μM onward, while Duer SC exhibited minimal genotoxic effects. These findings demonstrate that formulation type modifies the toxicological profile of lambda-cyhalothrin.