Testing Bacillus thuringiensis biopesticides for invertebrate toxicity, mutagenicity and non-target chemical analysis

Bacillus thuringiensis (Bt) biopesticides are widely used for their claimed specificity and safety, yet their effects on non-target aquatic species are poorly understood. This study assessed the acute toxicity of three commercial Bt products (Acta, HizoBio and Dipel) on two aquatic model organisms. Tests were conducted using whole products and their respective supernatants. Non-target chemical screening and mutagenicity assays were performed to complement the evaluation as coadjuvants were not disclosed on labels. Daphnia were the most sensitive test organism. Dipel was the most toxic (EC50 = 0.001%) followed by Hizo (EC50 = 0.013%) and Acta (EC50 = 6.87%). Different undisclosed substances were identified in the chemical formulation using non-target analysis, including fungicides. Only Dipel was mutagenic, an effect that seems to be related to undisclosed coadjuvants present in the supernatant. Hizo and Dipel may pose risk to the environment based on the recommended application dose. Further studies are needed to confirm the chemicals responsible for the toxicity, and product components should be disclosed to inform consumers and allow risk evaluation.