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. This evidence concerns the gene SLC27A5 and cholestasis.