By Barbara A. Brehm, Ed.D.

Many scientific studies have linked secondhand smoke to negative health effects in both children and adults. These studies have prompted many states, businesses and other organizations to tighten smoking regulations. Workers have expressed concern about the air quality in their work environments, and work places have responded by eliminating smoking or limiting it to certain areas. Many nonsmokers have breathed a sigh of relief to hear the experts agree that clean air is a greater fundamental right than the privilege to smoke.

Is secondhand smoke really that badfor you?

Tobacco smoke, whether from cigarettes, pipes or cigars, is a complex mixture of more than 4,000 chemicals. At least 40 of these cause cancer in people or animals. Others are irritants. Some are chemicals known as free radicals, which interact in a destructive fashion with cellular components. You absorb all of these substances through your lungs and into your bloodstream when you breathe second-hand smoke.

Secondhand smoke was made up of both mainstream smoke, which has been exhaled by a smoker, and side-stream smoke, which comes directly from the burning tobacco. Mainstream smoke is less hazardous because the smoker has partially filtered it for you. Side-stream smoke contains a higher concentration of toxic and carcinogenic compounds and comprises about 80 percent of secondhand smoke.

Does secondhand smoke have an impacton health?

Chronic exposure to secondhand smoke increases lung cancer risk. The U.S. Environmental Protection Agency (EPA) has classified secondhand smoke as a known cause of lung cancer in humans. The EPA has estimated that secondhand smoke causes about 3,000 lung cancer deaths in nonsmokers each year.

Less dramatic, but more common, is the irritation caused by secondhand smoke. Smoke irritates the eyes, nose and throat. It can also irritate the lungs, and lead to coughing, excess mucus production and, over time, reduced lung function.

Secondhand smoke can have especially deleterious effects on people with certain health problems. It can cause chest pain in people with heart problems. Nonsmokers with allergies experience more allergy symptoms, such as headaches, cough, sore throat and nausea after exposure to secondhand smoke. Secondhand smoke can also trigger asthmatic attacks in people with asthma.

How much is harmful?

No one knows exactly how much exposure to secondhand smoke is harmful. We do know that many of the negative health effects, such as lung cancer, are related to secondhand smoke in a dose-response fashion: The higher your dose, both in terms of time and concentration, the greater your risk of these negative health effects. If you are in good health, with no asthma or allergies, and occasionally choose to have lunch in a coffee shop that is somewhat smoky, your risk of developing a health condition associated with secondhand smoke is probably minimal. The greatest risks occur in people who work in a smoke-filled environment year after year, or who spend their lives in smoky homes.

Aren't children especially sensitive to secondhand smoke?

The EPA has estimated that 150,000 to 300,000 children under the age of 18 months develop bronchitis and pneumonia each year as a result of exposure to secondhand smoke. Thousands of these children require hospitalization. Infants of parents who smoke have a greater risk of dying from sudden infant death syndrome (SIDS). Young children exposed to secondhand smoke have higher levels of fluid in the middle ear, which is associated with infection. Secondhand smoke increases risk for the development of asthma in children and exacerbates the condition in children who already have asthma.

What if some of my best friends are smokers?

If a little secondhand smoke does not bother you, then you needn't make an issue of it if most of your time at home and at work is spent in a smoke-free environment. You have the most control at home. You might consider asking smokers to smoke outside, especially if you have children. Some households have become smoke-free even if some members are smokers. Outside of the home, you can avoid the smokiest of restaurants and public places and still go out with your smoking friends. And best of all, you can lovingly support them in their efforts to quit smoking.