Studies that illustrate the harmful effects of secondary smoke will help convince the public to demand laws restricting smoking where it can affect non-smokers' health. Defined as the unavoidable inhalation of tobacco smoke by nonsmokers, ETS is primarily comprised of sidestream smoke, which is derived from smoldering tobacco found in a burning cigarette between puffs. ETS is also made up of the smoke caused by the burning cigarette paper and the burning cone during inhalation, as well as the portion of mainstream smoke exhaled by the smoker. Interestingly, the smoker has a slight advantage over the involuntary smoker, for he or she inhales through a filtered cigarette that somewhat reduces the concentration of harmful materials. The involuntary smoker has no mechanism for filtering out harmful products and, consequently, is fully exposed to dangerous smoke.
Scientists report that sidestream smoke is actually more toxic than mainstream smoke.
It has been associated with an increased atherosclerotic progression and also contributes toward ischaemic heart disease. While increasing myocardial oxygen demand, ETS simultaneously reduces oxygen supply. Both smokers and nonsmokers experience an increased heart rate and blood pressure. However, a combined analysis of 18 ETS studies involving more than half a million people hypothesizes that secondhand smoke increases a nonsmoker's risk of heart disease by 25 percent. The cardiovascular impact, however, is much greater.