By using the rat hepatoma cell line FaO, Bjork et al. (2021) concluded that binary mixtures of PFOS, PFOA, PFHxS, PFBA and PFBS have antagonistic effects in upregulating the PPARα target gene Ehhadh. Thus, taken together, the different studies on PPARα activation and on PPARα target gene expression available so far do not give a consistent picture whether PFAS mixtures have an additive, a synergistic or an antagonistic effect on PPARα activation. The gene discussed is PPARA; the disease is hepatocellular carcinoma.