Tobacco smoke contains over 4,000 chemical compounds. More than 60 of these compouds are known or suspected to cause cancer.

Second-hand smoker is a term we used for identifying people who doesn't actually smoke, but they inhale the smoke from a smoker.
Second-hand smoker is also known as environmental tobacco smoke (ETS) or passive smoke. The passive smoker is actually inhaled 2 kind of smoke.
The first is the sidestream smoke (smoke that comes from the end of a lighted cigarette, pipe, or cigar) and the second one is the mainstream smoke (smoke that is exhaled by a smoker). Second-hand smoker has already been acknowledged by government and research.

Secondhand smoke is classified as a "known human carcinogen" (cancer-causing agent) by the U.S. Environmental Protection Agency (EPA), the U.S. National Toxicology Program, and the International Agency for Research on Cancer (IARC), a branch of the World Health Organization.

Being exposed to cigarette smoke for four or more hours a day can make your RealAge as much as 6.9 years older.

 http://www.smith.edu/health/smokefree/images/chemicals.jpg

Other diseases caused by Second-hand smoke, In the United States alone it is responsible for:

• an estimated 46,000 deaths from heart disease in non-smokers who live with smokers

• Thirty minutes of secondhand smoke can impair the normal flow of blood to the heart in non-smokers

• about 3,400 lung cancer deaths in non-smoking adults

• Just thirty minutes of exposure to secondhand smoke can cause heart damage similar to that of habitual smokers. Nonsmokers' heart arteries showed a reduced ability to dilate, diminishing the ability of the heart to get life-giving blood. In addition, the same half hour of secondhand smoke exposure activates blood platelets, which can initiate the process of atherosclerosis (blockage of the heart's arteries) that leads to heart attacks. These effects explain other research showing that nonsmokers regularly exposed to SHS suffer death or morbidity rates 30% higher than those of unexposed nonsmokers.

• Long-term exposure to secondhand smoke increases the risk of developing breast cancer in younger, primarily premenopausal, women.

• other breathing problems in non-smokers, including coughing, mucus, chest discomfort, and reduced lung function

• There is a link between secondhand smoke to an increased risk of stroke. Regular exposure to secondhand smoke, such as in restaurants, heightens one's chance of stroke by 50 percent.

• 150,000 to 300,000 lung infections (such as pneumonia and bronchitis) in children younger than 18 months of age, which result in 7,500 to 15,000 hospitalizations annually

• increases in the number and severity of asthma attacks in about 200,000 to 1 million children who have asthma

• more than 750,000 middle ear infections in children

• Pregnant women exposed to secondhand smoke are also at increased risk of having low birth- weight babies.

Based on The 2006 Surgeon General's Report on The Health Consequences of Involuntary Exposure to Tobacco Smoke the only proven way to prevent exposure is to have a smokefree environments.
There is also a proven study of restaurants and bars located in smokefree city have 82% less indoor air pollution than other restaurants and bars that doesn't have smokefree protection.

In 2007 MRI technology has helped the research of damage detection on nonsmokers who are exposed by second-hand smoke.  You can read the study abstract of Courtesy of RSNA and Chengbo, Wang, PhD. or you can watch a video made by CNN here.


Some Answered Myth for Second-hand Smoker

Planning to dodge the risks of secondhand smoke by sitting outside at a wine bar tonight? Surprise: If people are smoking on the patio or sidewalk, the air there is just as bad as it is in the smoking section indoors.

Huh?

Yes, secondhand smoke is as bad outside as it is inside, unless you're sitting in such a wind tunnel that your napkin must be tied down and you need a seat belt. Otherwise, a nearby outdoor smoker pollutes your lungs as much as an indoor one.

Next question: Which is worse? Spending a few hours in a car, windows cracked, with a smoker -- or sitting through a couple of jazz sets in a smoky bar. Answer: The car. Even with the windows open a bit, it's worse than the smoke-filled bar. So the next time anyone asks, don't think twice about saying, "No, PLEASE don't smoke while I'm around."