Per- and polyfluoroalkyl substances (PFASs) are man-made chemicals with high persistence, that are utilized in numerous consumer and industrial applications. The most well-known substances of this group are perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). They are used in various products such as non-stick cookware, textiles, paint, firefighting foams, surfactants, food packaging, and personal care items. Due to their extensive usage, they are frequently detected in water sources globally, with PFOS’s reported concentrations reaching 187 and PFOA’s 1371 ng L^-1. PFOS and PFOA have also been reported in all levels of aquatic life. Indicatively, PFOS has been found in Crassostrea virginica in concentrations up to 1225 ng g^-1 (dw) and PFOA in Sebastes mentella at 5.3 ng g^-1 (dw). As PFASs are widely detected in the environment, they may induce toxic effects on a variety of aquatic organisms, and thus their investigation is crucial.

The present study aimed at investigating the potential toxic effects of PFOS and PFOA (individually), as well as those of their their mixture, on a saltwater microalga and a bacterium. The tested organisms were exposed to different concentrations of the studied compounds, and the growth inhibition percentages, alongside the IC₅₀ values, were calculated. The microalga and the bacterium presented different sensitivities to the target compounds. The mixture of PFOS and PFOA presented more adverse effects in comparison to the individual compounds in the bacterium. Dissimilarly, the highest effect on the microalga was observed when the organism was exposed to PFOA.