03/18/2010 05:12 am ET Updated May 25, 2011

Deadly Traffic: Tests Link Freeway Smog To Brain Cancer

In as little as three months, the brains of laboratory rats begin to change after being exposed to the air around congested Southern California freeways.

"The evidence we are clearly seeing is the molecular cascade that can lead to the development of cancer," said Dr. Keith L. Black, chairman of the department of neurosurgery at Cedars-Sinai Medical Center in Los Angeles.

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