Studies on secondhand smoke have varied in their judgment of just how harmful it may be. Though it's probably not as damaging as smoking the cigarette yourself, smoke is still a polutant, and should be avoided.
Most lung cancer is caused by cigarette smoking.
Scientists have found that nonsmokers who live or work with smokers have a higher lung cancer risk than nonsmokers who do not have this type of exposure. The immediate effects of breathing second-hand smoke include an increase in heart rate and blood pressure, and dangerous levels of carbon monoxide in the blood. The smoke from the burning end of a cigarette is filled with hundreds of dangerous chemicals and contains more tar and nicotine than the smoke that's directly inhaled by the smoker. While adults can try to avoid being in smokey areas, children and infants are especially vulnerable. Studies show that babies whose parents smoke are hospitalized twice as often for conditions such as bronchitis and pneumonia.