More than 126 million nonsmoking Americans are regularly exposed to someone else's tobacco smoke. The surgeon general in 2006 cited "overwhelming scientific evidence" that tens of thousands die each year as a result, from heart disease, lung cancer and a list of other illnesses.
Yet smoking bans have remained a hard sell in Ohio and elsewhere, as lawmakers and business owners debate whether such prohibitions are worth the anger of smoking customers or employees.
Thursday's hard-hitting report from the Institute of Medicine promises to influence that debate here and abroad.
"The evidence is clear," said Dr. Thomas Frieden, head of the federal Centers for Disease Control and Prevention, which requested the study. "Smoke-free laws don't hurt business ... but they prevent heart attacks in nonsmokers."
Among the IOM report's conclusions: While heavier exposure to secondhand smoke is worse, there's no safe level. And it cited "compelling" if circumstantial evidence that even less than an hour's exposure might be enough to push someone already at risk of a heart attack over the edge as the smoke's pollution-like small particles and other substances can quickly affect blood vessels.
"There is no question that smoking bans have a positive health effect," said Dr. Lynn Goldman, an environmental health specialist at Johns Hopkins University who chaired the IOM committee.
Since New York led the way in 2003, 21 states plus the District of Columbia now have what the CDC calls comprehensive statewide laws banning smoking in both public and private workplaces, restaurants and bars with no exception for ventilated smoking areas. Some other states have less restrictive laws.
That means 41 percent of Americans are as protected in public from secondhand smoke as possible, Frieden said. The IOM report found just 5 percent of the world's population was covered by comprehensive smoke-free laws.
In Ohio, a workplace smoking ban approved by voters took effect in May 2007 and has faced several legal challenges since.
While the public mostly connects smoking with lung cancer, heart disease is a more immediate consequence. About a third of all heart attacks in the U.S. are related to smoking, Frieden said. Both actively smoking and breathing others' smoke can damage blood vessels and increase heart attack-causing blood clots.
How much do bans help? That depends on how existing bans were studied and how much secondhand smoke exposure different populations have. Some heavily exposed nonsmokers have the same risk of heart damage as people who smoke up to nine cigarettes a day, Goldman said.
Her committee reviewed 11 key studies of smoking bans in parts of the U.S., Canada, Italy and Scotland, and found drops in the number of heart attacks that ranged from 6 percent to 47 percent.
The impact can be quick: Helena, Mont., for example, recorded 16 percent fewer heart attack hospitalizations in the six months after its ban went into effect than in the same months during previous years, while nearby areas that had no smoking ban saw heart attacks rise. More dramatically, heart attack hospitalizations dropped 41 percent in the three years after Pueblo, Col., banned workplace smoking.
The Institute of Medicine is part of the National Academies, an independent organization chartered by Congress to advise the government on scientific matters.