Tobacco companies have made cigarettes deadlier than ever
Compared to cigarettes in Australia and Canada, tobacco blends used in U.S. cigarettes have higher levels of tobacco-specific nitrosamines (TSNAs), chemicals known to cause cancer. TSNA levels have increased since 1964.
Cigarette companies also introduced ventilation holes in cigarette filters so that cigarettes would look healthier on paper. The ventilation holes cause machines to report lower levels of tar and nicotine when testing cigarettes. However, it's been documented that these ventilation holes actually change how people smoke cigarettes. Smokers inhale more frequently and more deeply, drawing cancer-causing chemicals farther into the lungs. The ill effects of these design changes are compacted by efforts to make cigarettes more attractive and more addictive.
Tobacco companies have introduced flavorings to make the taste of cigarettes more appealing, while also introducing chemicals that reduce discomfort and irritation in the lungs. Higher levels of nicotine, ammonia, and sugars have increased the addictiveness of cigarettes over time.
The smoking rate in the United States has hit an historic low but tobacco use remains the greatest source of preventable death in the United States. According to the Surgeon General, smoking kills 480,000 Americans each year. It's estimated that half of today's smokers will die prematurely, losing, on average, ten years of life. It takes a toll on the nation's economy, too: $289 billion is spent on health care and other financial losses associated with cigarettes annually.
http://www.vox.com/2014/6/23/5835158/tobacco-companies-have-made-cigarettes-deadlier-than-ever