Smog: And Now, the Hard Part

News that much of Mexico City’s infamous smog--long blamed on cars and factories--is produced by millions of leaking household fuel tanks should be both sobering and heartening to those in Mexico and here who are engaged in the continuing effort to clean the air.

Mexico City’s smog has increased dramatically in recent decades and now mirrors the levels suffered in the Los Angeles Basin during the 1960s and ‘70s. Like Los Angeles, Mexico has concentrated on reducing emissions from automobiles and industry. But scientists at UC Irvine recently found that liquefied petroleum gas, Mexico’s predominant fuel for cooking and heating, is a “large, previously unrecognized source” of the city’s smog-causing fumes.

The news is no doubt discouraging to Mexican air pollution control officials, for one’s stove is at least as cherished as one’s car. But as they now discuss policy options, the new finding offers them the opportunity to realize some progress against smog. The same could said here. For decades, scientists believed that the sources of Los Angeles’ smog were generated in roughly equal measure by automobiles and so-called fixed sources: factories, refineries and other businesses. A growing body of research now identifies auto and truck emissions as responsible for as much as 75% of the problem.

New knowledge presents challenges to policy-makers, sometimes wedded to outdated regulatory schemes, and to a public resistant to new pollution controls. The easy victories in the war against smog may have been won. Now comes the hard part.