Hydrophobicity-dependent QSARs to predict the toxicity of perfluorinated carboxylic acids and their mixtures

Perfluorinated carboxylic acids (PFCAs) have wide industrial applications because of their unique physicochemical characteristics. However, data on the toxicity of much of this chemical class is lacking, particularly with regard to mixture toxicity. In this study, the toxicity of individual PFCAs and their mixtures to Photobacterium phosphoreum were observed. There was a tendency of increasing toxicity from C3 to C14 PFCA and a tendency of decreasing toxicity from C14 to C18 PFCA because of “the maximum tolerance of the cell membrane”. Using the equivalent log KOW (octanol–water partition coefficient) and log KSD (C18-Empore™ disks/water partition coefficient), two linear quantitative structure–activity relationship (QSAR) models were formulated. This indicated both KSD and KOW can describe the hydrophobicity of a single chemical. However, for the PFCA mixtures, KMD is the more reasonable parameter than Kowmix to describe the hydrophobicity because only the equivalent log KMD could be used to predict the mixture toxicity.

► Equivalent KOW and KSD can be used to predict the single toxicity of the PFCAs.
► The mixture effect of the PFCAs is simple addition.
► Equivalent KMD can be used to predict the mixture toxicity equivalent Kowmix cannot.
► KMD is the more reasonable parameter to describe the hydrophobicity of the mixture.