A careful reading of the article will show, I believe, that about 80% of the particulate smog comes from the crude oil (that barely can be called diesel) fuel used the very large number of ships in the harbor.

Under current "international agreements" there's virtually NOTHING that can be done about this source, so instead new rules are proposed for automobiles and trucks.

The current administration has flatly refused to permit California to impose local regulations even on auto and truck greenhouse emissions, on the pretext that "national standards" are required by the auto industry "to avoid serious market impact." (So California is choking, but isn't allowed to do anything about it, because "it's not our problem" for the rest of the country, and the lobbiests for the automakers don't live there.)

For current auto and diesel powered vehicles, including Interstate trucking, there are existing US emissions inspection and inforcement rules, although they may not be as "tight" as some would prefer.

Congressional legislation to bar admission of uninspected Mexican trucks under Nafta are being ignored by the Administration on grounds that it barred any appropriation "to permit" uninspectable trucks, and the administration says "it's already been done." The assurance that Herr Bush "believes they're safe" is rather hollow when NTHS inspectors are BANNED FROM INSPECTING THEM due to their "foreign registration," even with respect to highway load limits, operable mechanical condition, or driver hour/distance regulations. In other words, they can burn unrefined crude, just like the ships, and California - or any other state - can't do a thing about it. (More likely they can just rip off the emissions controls that were on the truck when they stole it in LA to get an extra 0.2 mpg, with the same exemption from inspection.)

Too many irrational political things in all this to even scratch the surface.

John