Have we been kidding ourselves about car exhaust?

Scientists at Carnegie Mellon University warn that we may underestimate the bad effects of exhaust from internal combustion engines.

It's not just gases in the exhaust; particulates may be even worse air pollutants. Research at Carnegie Mellon shows that the particulates are chemically changed once freed into the air. They spread farther and have more negative effects than past estimates indicated. The scientists suggest that government regulators need new ways to measure and control particulates.

Not only are these tiny solid bits contributing to the greenhouse effect, they're a serious health threat to human hearts and lungs.