@cicerone imposter,
I've never been to Los Angeles, but I've seen pictures of what it was like back in the eighties. Probably a lot like Beijing is now. A lot of local pollution, mostly from cars and industry. The haze in the air is some combination of nitric acid, sulfuric acid, unburned hydrocarbons and particulates. The actual carbon in the form of carbon dioxide is invisible and in low concentrations is not toxic. The problem with it is that it reflects (or is opaque to) infrared radiation. It acts like an insulating layer, trapping heat near the surface.