When a smoker lights a cigarette, the temperature at the tip (end) rises to between 700 and 900 degrees centigrade and releases more than 7,000 chemical compounds. At least 70 of these are known to cause cancer. Half of all people who smoke will die prematurely from smoking-related diseases. 

Many people - including many health professionals - believe that it is the nicotine in cigarettes which causes cancer. This is wrong. It is the toxins in cigarettes, released when tobacco is burned which cause cancer. 

In comparison, the evidence shows that safer nicotine products which do not burn tobacco, like e-cigarettes / vaping devices, heated tobacco products, snus / smokeless (as well as nicotine replacement therapies) are all substantially safer than smoking.