Alan Eastman, in his letter "Utah should require cleaner cars, as California does" (Forum, Jan. 10), mistakenly attributes improvement in air quality in the Los Angeles Basin to "very efficient pollution controls on all automobiles sold in the state." With very minor exceptions, all vehicles sold in the U.S. are 50-state legal.
The primary reason for the improvement in L.A.'s air quality is due to reformulation of gasoline. Fifty years ago, it took about two hours for tailpipe emissions to turn into photochemical smog, which was trapped in the L.A. basin. Now, it takes about 10 hours for tailpipe emissions to turn into photochemical smog.
The result: Tailpipe emissions have enough time to blow east from L.A. to San Bernardino and Riverside counties. So, L.A.'s air is better, and the air in mid-size cities of San Bernardino, Rialto, Highland, Riverside and Ontario is dramatically worse.