I remember driving through the L.A. Basin last year. Coming down from Cajon Summit on I-15, it was like driving into a brown wall.
I really hate to disapoint you but.. that was not the LA basin you drove into over the Cajon Pass, that was the Inlans Empire,and it's always been Smogy from Trains and Semi that load and unload. La is now where near as smoggy as it was even 30yrs ago.