WHO: 30-50 percent of cancer cases preventable
The World Heath Organization estimates between 30-50 percent of all cancer cases are preventable. Prevention offers the most cost-effective long-term strategy for the control of cancer. WHO research concludes that policies and programs should be implemented to raise awareness, to reduce exposure to cancer risk factors, and to ensure that people are provided with the information and support they need to adopt healthy lifestyles.
To wit, worldwide, tobacco use is the single greatest avoidable risk factor for cancer mortality. Tobacco-related cancer and diseases kill approximately 6 million people each year. Tobacco smoke has more than 4,000 chemicals — and at least 250 are known to be harmful and more than 50 are known to cause cancer.
Tobacco smoking causes many types of cancer, including cancers of the lung, esophagus, larynx, mouth, throat, kidney, bladder, pancreas, stomach and cervix. Second-hand smoke, also known as environmental tobacco smoke, has been proven to cause lung cancer in non-smoking adults. Smokeless tobacco (chewing tobacco or snuff) causes oral, oesophageal and pancreatic cancer. Nearly 80 percent of the 1 billion smokers in the world live in low- and middle-income countries. 
- Tobacco smoking: causes cancers of the lung, esophagus, larynx (voice box), mouth, throat, kidney, bladder, pancreas, stomach and cervix;
- Second-hand smoke (also known as environmental tobacco smoke): causes lung cancer in non-smoking adults; and
- Smokeless tobacco (also called oral tobacco, chewing tobacco or snuff): causes oral, oesophageal and pancreatic cancer.
The tobacco epidemic kills around 6 million people a year — more than 5 million of those deaths are the result of direct tobacco. More than 600,000 are the result of non-smokers being exposed to second-hand smoke.
Second-hand smoke is the smoke that fills restaurants, offices or other enclosed spaces when people burn tobacco products such as cigarettes, bidis, and water pipes. There are more than 4,000 chemicals in tobacco smoke, of which at least 250 are known to be harmful and more than 50 are known to cause cancer.
- Almost half of children regularly breathe air polluted by tobacco smoke in public places.
- Second-hand smoke causes more than 600 000 premature deaths per year.
- In 2004, children accounted for 28 percent of the deaths attributable to second-hand smoke.
There is no safe level of exposure to second-hand tobacco smoke.
In adults, second-hand smoke causes serious cardiovascular and respiratory diseases, including coronary heart disease and lung cancer. In infants, it causes sudden death. In pregnant women, it causes low birth weight. 
- World Health Organization. Cancer prevention. http://www.who.int/cancer/prevention/en/
- World Health Organization. Tobacco. http://www.who.int/mediacentre/factsheets/fs339/en/