By 1956, the Surgeon General established its first scientific study group to analyze the health effects of smoking, and in 1962 established an advisory panel to completely assess data and make formal recommendations. To many, the subsequent Surgeon General's Report of 1964 was a turning point in the medical community's and public's perception of smoking. If cigarette warning labels listed all of the compounds in cigarette smoke the way food labels list ingredients, the packaging would read like a chemistry mid-term. Reported for the first time in 1964, and confirmed and expanded upon in following Surgeon General Reports, cigarettes consist of ingredients, that when heated, create a smoking material comprised of more than 4,000 compounds. Many of these gaseous compounds alter as the temperature of the burning cigarette rises and falls with inhalation.
Evidence also indicates that such damage diminishes when one quits smoking.
The two most commonly cited culprits in cigarette smoke are nicotine and carbon monoxide. Nicotine, best known as the addictive agent in cigarettes, is readily absorbed through tiny air sacs in the lungs and is metabolized primarily in the liver. Atherosclerosis, or the build-up of fatty substances or plaque in the inner lining of the artery, is promoted and accelerated by nicotine through several mechanisms. Nicotine damages the endothelium, or cells lining the blood vessels. Nicotine in the bloodstream also lowers one's threshold for ventricular fibrillation, the most serious cardiac rhythm disturbance.