The American Lung Association released its annual report card on smog, giving 60 percent of American counties and cities a grade of "F." In each year's report the ALA flunks over half of the places it examines, despite the fact that smog levels in America have been declining steadily for decades. EPA statistics indicate that ozone, the primary constituent of smog, has declined by about 30 percent since the 1970s, a trend that is expected to continue. While some areas sometimes exceed the federal standard for ozone, the number of such spikes is declining. Los Angeles, for example, now has a quarter of the smog alert days it had ten years ago. Moreover, the ALA based its failing grades on just a few worst-case readings that exceeded an even more stringent federal air-quality standard that is not yet in force. In many cases, readings from instruments used to measure pollution could not be replicated by other instruments at the same site.

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