Bioaccumulation of deltamethrin, tebuconazole and chlormequat chloride in T. molitor larvae and risks associated with their human consumption

Edible insects are generally reared on agricultural product-based diets. These feeding substrates may contain pesticides or toxins that are derived from field practices for plant growth and defence and that may represent a health risk to insect consumers. The present study investigated Tenebrio molitor capability to uptake from contaminated substrates three chemical compounds that are employed in agricultural practices: the insecticide deltamethrin (DELTA), the fungicide tebuconazole (TEB) and the plant growth regulator chlormequat chloride (CCC), all with different properties of lipophilicity and potentially harmful for human and animal health. Newly optimised and validated LC-MS/MS methods have been used for the quantification of pesticide residues in larvae samples. Analysis showed that DELTA and TEB are retained by larvae, even after 24 h of fasting, due to their lipophilicity. Larvae fasting period allowed the elimination of 47% of DELTA residues and 78% of TEB ones. Diversely, CCC, the most hydrophilic chemical compound, was completely eliminated after the fasting. The toxicity of pesticides to larvae has been also investigated. The highest mortality of T. molitor larvae (close to 50%) was recorded for the insecticide DELTA, at the dose of 20 mg/kg and for CCC (15%) at the concentration of 4 mg/kg. The safety of insects as food and feed represents an important section in the field of the control of food of animal origin and animal health. Nevertheless, to date, this aspect is not yet completely determined due to the lack of scientific data in this area. By assessing the accumulation rate of some chemicals in reared insects and by evaluating the toxic effects that chemicals may have on larvae, this study could contribute to filling this gap.