There is compelling evidence that secondhand smoke can trigger heart attacks, according to a new report from the Institute of Medicine (IOM), and people with heart conditions are urged to avoid exposure to tobacco smoke, the Associated Press reported Oct. 15.

The report, requested by the U.S. Centers for Disease Control and Prevention (CDC), said there is no safe level of exposure to secondhand smoke, and that people with cardiovascular disease could risk heart attack with less than an hour's exposure to environmental tobacco smoke, which restricts blood vessels and increases clotting.

"If you have heart disease, you really need to stay away from secondhand smoke. It's an immediate threat to your life," said researcher Neal Benowitz of the University of California at San Francisco.

Benowitz added that everyone, in fact, should avoid secondhand smoke, since many people who have heart disease are not aware of the problem if they have never had a heart attack. "Even if you think you're perfectly healthy, secondhand smoke could be a potential threat to you," he said.

"The evidence is clear," said CDC head Thomas Frieden. "Smoke-free laws don't hurt business ... but they prevent heart attacks in nonsmokers."

Researchers found "clear and consistent" evidence that smoking bans cut the rate of heart attacks, according to statistician Stephen Feinberg of Carnegie Mellon University, a member of the IOM committee that compiled the report.