REPORT / INTERNATIONAL NEWS

The survey by Clean Air Watch volunteers is the first comprehensive snapshot of smog in the United States in 2009. It found that the national health standard for smog, technically ozone, was breached more than 2,600 times through August 31 at monitoring stations in 37 states and the District of Columbia.

During the same period last year, there were more than 5,000 such events, known in the jargon of the bureaucracy as "exceedences."

There were several key factors in the smog drop, according to Frank O'Donnell, president of Clean Air Watch: cooler, wetter weather, less use of coal-burning electric power plants to run air conditioners, the general decline in the economy, and the continuing turnover of cars and trucks to new models that meet tougher clean-air requirements.