Regular exposure to secondhand smoke increases the risk of heart disease… (Lawrence K. Ho / Los Angeles…)
California legislators want to ban smoking at state beaches and parks, and they've sent a bill to the governor that would do just that. It remains to be seen whether he'll sign the measure, designed to reduce the public's exposure to secondhand smoke, not to mention cut back on cigarette butt litter.
But just what are the health effects of inhaling the smoke of somebody else's cigarette? And does it matter if exposure is fleeting — and outdoors? Researchers have answers about the health effects (and yes, they're negative), but their conclusions are based on smoke-filled indoor environments; the relevance for outdoor settings is less clear.
In recent years, the U.S. surgeon general, the Institute of Medicine and the California Environmental Protection Agency have reviewed evidence and found that regular exposure to secondhand smoke can increase the risk of heart attack and heart disease, respiratory infection, lung cancer and sudden infant death syndrome. In addition, a growing body of research has found that smoking bans in workplaces, public buildings and restaurants have a positive effect on public health.
People might not think they're inhaling much smoke, at least not enough to be dangerous, when they're around smokers. But, says Stanton Glantz, who directs the Center for Tobacco Control Research and Education at UC San Francisco, "a cigarette is like a little toxic waste dump on fire. If you're upwind of it, you don't have much effect. But if you happen to be in the plume — or you're congregating around a doorway — you can get quite high levels of exposure."
Cigarette smoke contains hundreds of chemicals, including benzene, carbon monoxide and nicotine, many of them known carcinogens. Fine particulate matter within smoke can carry those chemicals deep into the lungs, Glantz says.
Here's a closer look at the health effects of secondhand smoke.
Cigarette smoke in the air affects the first organs it comes in contact with — the lungs. In susceptible people, even short exposure can trigger asthma attacks, shortness of breath and wheezing. In children, chronic exposure can increase the risk of respiratory tract and ear infections.
But even in normal, healthy adults, such as a nonsmoker married to a smoker or people who work alongside smokers, secondhand smoke increases the risk of developing lung cancer by 20% to 30%. It causes an estimated 3,400 lung cancer deaths in nonsmoking Americans each year, according to the national Centers for Disease Control and Prevention. Secondhand smoke also increases the risk of breast cancer, but the surgeon general does not say the relationship is causal, as is the case with lung cancer.
In addition, regular exposure to secondhand smoke increases the risk of heart disease by 25% to 30% and accounts for 46,000 deaths from heart disease in the U.S. each year, the CDC says. Again, the data were collected in home and workplace environments, where people spend a significant chunk of their day, almost every day.
However, short-term effects do occur. In nonsmoking healthy adults, 30 minutes of exposure to the amount of smoke you might find in a bar causes changes to blood vessels and blood components, says Glantz, who reviewed the scientific literature on how tobacco smoke affects the cardiovascular system for the journal Circulation in 2005.
Secondhand smoke damages the lining of the blood vessels, which makes them less elastic, and it makes circulating platelets stickier and more likely to clot. "That's very important in terms of heart disease because those processes are all tied up in the process of having a heart attack," Glantz says. Further, these effects, triggered with a half-hour exposure to the amount of smoke you might find in a bar, persist for at least a day.
The timing is important because it means that cigarette smoke in environments where people might spend only a couple of hours, such as restaurants or clubs, can have negative cardiovascular effects. Whether those effects in turn can trigger a heart attack is not proved, although the Institute of Medicine report says the circumstantial evidence is compelling.
What's most surprising about the myriad effects that secondhand smoke has on the blood and blood vessels is that they're comparable to those seen in smokers, says Katherine Hammond, a professor of environmental health sciences at UC Berkeley. Secondhand smoke, which is much less concentrated than the smoke a smoker gets from a cigarette, might be expected to cause less harm, she says — and yet that's not the case.
Researchers found a similar proportion of platelets affected and 60% of the platelet clumping in subjects breathing in a smoky environment, as compared with those actually smoking a cigarette.