Smoking is the single biggest cause of cancer in the world, and accounts for one in four cancer deaths in the States. Smoking is known to cause around eighty percent of lung cancer around the world. The 1996 National Household Survey on Drug Abuse has shown that about 62 million people in the United States above 12 years or below 29 percent of the population are current cigarette smokers. So, this makes nicotine, the addictive component of tobacco, one of the most heavily used addictive drugs in the United States. Within the United States, tobacco use was responsible for nearly 1 in 5 deaths or an estimated 438,000 premature deaths per year from 1997 to 2001 & thus, smoking kills five times more people than road accidents, overdoses, murder, suicides and HIV all put together.

Nicotine: Many people believe that nicotine causes cancer but the fact is that it only leads to addiction. Whenever a person inhales cigarette smoke, the nicotine present in the smoke is rapidly absorbed into the blood and its affect on the brain is shown within 7 seconds. In the brain, nicotine activates the same reward system as do other drug abuse such as cocaine or amphetamine, but to a lesser extent. Nicotine acts on this reward system and is believed to be responsible for drug-induced feelings of pleasure and, over time, nicotine addiction. It also increases alertness and enhances mental performance. Studies indicate that nicotine by itself may not be harmful. But, when it is combined with other harmful substances such as areca nut, cancer causing catechu substitutes like gambier & magnesium carbonate, it may show damaging effects.

Apart from nicotine, cigarette smoke contains around 4,000 different compounds, many of which may cause cancer. In fact tobacco smoke contains about 70 different carcinogens or cancer-causing substances. When you inhale smoke, these chemicals enter your lungs and spread around the rest of your body. Scientists have shown that these chemicals are mutagenic & can damage DNA and change expression of various genes which may lead to cancer by making your cells proliferate and multiply uncontrollably. No wonder, smoking is the major cause of lung cancer and is also associated with the increased risk for cancer of the mouth, nasal cavities (nose), larynx (voice box), pharynx (throat), esophagus (swallowing tube), stomach, liver, pancreas, kidney, bladder, uterine cervix, and acute myeloid leukemia.

Oral tobacco products contain 28 known cancer-causing agents (carcinogens). Chewing tobacco is a known cause of oral cancer & according to Women's Health in South East Asia (WHOSEA), almost one-half of all cancer cases in men and one-quarter of all cancer cases in women in India are believed to be tobacco-related.

Not all smokers get cancer: Years of research has proven that smoking causes cancer but this doesn't mean that all smokers will definitely get cancer or that all non-smokers won't. It means that smoking greatly increases the risk of cancer & Smokers are, on average, much more likely to get cancer than non-smokers.