A study of long-term toxicity of multiple mixtures with hormetic effects by the characteristic parameter σ²_(k∙ECx)...

A previous study found that the characteristic parameter σ²_(k∙ECx) (the concentration EC_x and slope k of the concentrationresponse curve (CRC) at the effect x %) can predict the acute combined toxicity of multiple mixtures with S-shaped CRCs. In this paper, the competence of σ²_(k∙ECx) to predict the long-term toxicity of multiple mixtures with J-shaped CRCs was explored using the Aliivibrio fischeri as the test organism. The combined toxicity was evaluated by the independent action (IA) model and the effect ratio (ER_x) model. The stepwise method was used to divide J-shaped CRC into ML and MR (SL and SR). The results showed that the σ²_(k∙ECx) and ER_x of each segment was in good agreement with the exponential function. A new type of mixture was added to the original type A and type B, whose rules of interaction were opposite to those of type B (named opposite B, OB). This paper improves the understanding and analysis of the J-shaped CRCs in environmental risk assessment.