Evaluation of the acute toxicity of perfluorinated carboxylic acids using eukaryotic cell lines, bacteria and enzymatic assays.

The acute biological activity of a homologous series of perfluorinated carboxylic acids - perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) - was studied. To analyze the potential risk of the perfluorinated acids to humans and the environment, different in vitro toxicity test systems were employed. The cytotoxicity of the chemicals towards two different types of mammalian cell lines and one marine bacteria was investigated. The viability of cells from the promyelocytic leukemia rat cell line (IPC-81) and the rat glioma cell line (C6) was assayed calorimetrically with WST-1 reagent. The evaluation was combined with the Vibrio fischeri acute bioluminescence inhibition assay. The biological activity of the compounds was also determined at the molecular level with acetylcholinesterase and glutathione reductase inhibition assays. This is the first report of the effects of perfluorinated acids on the activity of purified enzymes. The results show these compounds have a very low acute biological activity. The observed effective concentrations lie in the millimole range, which is well above probable intracellular concentrations. A relationship was found between the toxicity of the perfluorinated carboxylic acids and the perfluorocarbon chain length: in every test system applied, the longer the perfluorocarbon chain, the more toxic was the acid. The lowest effective concentrations were thus recorded for perfluorononanoic and perfluorodecanoic acids.