Up in Smoke

I don't smoke cigarettes and have always been cautious about breathing secondhand smoke, but I never worried too much if I inhaled a little of the stuff in a bar, a restaurant or a building entranceway in cities like New York where indoor-smoking bans have driven smokers onto the sidewalks. So I was surprised when I heard that the Centers for Disease Control and Prevention (CDC) had issued a warning advising anyone at risk of heart disease entirely to avoid indoor public spaces where smoking is allowed. According to the CDC, exposure to secondhand smoke for as little as 30 minutes can significantly increase your risk of heart attack.

The health risks posed by secondhand smoke are well documented, but what triggered the warning, which was published in the British Medical Journal and is sure to fire up the tobacco lobby, was a small study out of Helena, Mont. When the city passed an ordinance banning indoor smoking in 2002, Helena's only heart hospital recorded a 40% drop in the number of heart attacks (from an average of 40 per six months to just 24 in that city of 26,000). What's more, when a court order lifted the ban half a year later, the heart-attack rate bounced right back. Dr. Robert Shepard, who wrote the Helena study, offers this explanation: "There is laboratory evidence that secondhand smoke makes platelets stickier, causing clots and sending arteries into spasm both of which can lead to heart attacks." The chemical reaction and the resulting damage occur quickly.

Those findings could be significant. The CDC estimates that in the U.S., secondhand smoke causes 35,000 deaths a year from heart disease a figure some experts believe will have to be revised upward, since 60% of Americans, smokers and nonsmokers, show biological effects of tobacco-smoke exposure. Shepard did offer some reassurance for city dwellers who have to pass through nicotine clouds every time they enter and leave an office building. Exposure for a few seconds probably doesn't do much harm, he says, because the toxins in cigarette smoke are quickly diluted in outside air.

Sanjay Gupta is a neurosurgeon and CNN medical correspondent