Two novel indices for quantitatively characterizing the toxicity interaction between ionic liquid and carbamate pesticides

Compound contamination and toxicity interaction demand the development of models that have an insight into the combined toxicity of chemicals. Two novel mixture toxicity indices, concentration addition index (CAI) and effect addition index (EAI), were developed to quantitatively characterize the toxicity interaction within four binary mixture systems containing carbamate pesticides and 1-benzyl-3-methylimidazolium tetrafluoroborate (IL). To examine the applicability of CAI and EAI, we compared the indices with the other indices such as the sum of toxic unit (STU), model deviation ratio (MDR), and effect residual ratio (ERR) and isobologram approach. The results showed that CAI and EAI could more clearly and effectively characterize the toxicity interaction within IL–pesticide mixtures than the other four methods. According to CAI and EAI, IL–aldicarb, IL–baygon and IL–methomyl mixture systems displayed clear antagonism at relatively low effect regions, while IL–pirimicarb mixture systems basically exhibited additive action. The most interesting observation is that all five indices (CAI, EAI, MDR, ERR, and STU) are well correlated with the concentration ratio of IL in the mixtures.