Oil refiners are sending greater amounts of an especially dirty crude oil product called “tar sands” to their Southern California refineries.
Now environmental groups want regulators to take a closer look
Tar sands hold a kind of semi-solid petroleum. To refine it enough for California standards takes more processing. Oil companies – including Valero, Tesoro and Conoco Phillips – say they’re bringing in more of this raw material because liquid petroleum in California is drying up.