While scientists have known that breathing bad air is harmful, they have never pinpointed what it is in fine particles that causes conditions usually associated with smoking such as lung disease.

Now a piece of the pollution puzzle has snapped into place with new findings from Louisiana State University.

Led by chemist H. Barry Dellinger, LSU researchers have discovered that free radicals, similar to those in cigarettes, exist in polluted air. Furthermore, they found that free radicals often persist for days or even indefinitely.

Kent Pinkerton, director of the University of California, Davis, Center for Health and the Environment, said the LSU study is significant in changing scientific perceptions of free radicals as being short-lived.

"If certain forms of free radicals are actually persistent, that increases chances they may interact with biological cells to create damage," Pinkerton said.

Even a day of air that meets federal standards set by the Environmental Protection Agency exposes people to as many harmful free radicals as smoking one cigarette, the researchers learned. But breathing heavily polluted air could expose a person to 100 cigarettes' worth of free radicals in one day, researchers said.

Read the full story at sacbee.com.