Moreover, PM2.5 significantly increased the expression of core genes associated with the biosynthesis (Cyp7a1, Cyp27a1, Baat, and Bacs) and regulation (Shp, Fgfr4) of primary bile acids, suggesting that cholestasis is an important cause of PM2.5 hepatotoxicity. Here, FGFR4 is linked to cholestasis.