Although the finding comes as no surprise to most experts, it may nevertheless plug a troublesome hole in the conventional analysis of the ozone problem.

"You end up with this ozone problem throughout much of the Eastern United States."

"The aim was to alleviate our ozone problem, but it had the second and unpredicted effect of lowering carbon-monoxide levels as well," she said.

Diesel trucks and buses emit different chemicals, and experts say they do not add to the ozone problem.

Research into the biology and chemistry of the ozone problem is intensifying.

But experts agree that the key to the ozone problem lies in the kinds of cars Americans drive and how much they use them.

Regulations set in California, which has the nation's most severe ozone problem by far, appear to be setting a national pattern.

If it turns out that only global cooperation is needed to solve ozone problems, then nation-against-nation competition must quickly become obsolete.

It's a cinch we can't solve the ozone problem if our wheels come off.

All those weeks in bed I had tried to think about the ozone problem; it was like staring down an empty test tube.