Burning tobacco creates high levels of harmful chemicals
Decades of scientific research show that the primary cause of smoking-related diseases is the high levels of Harmful and Potentially Harmful Constituents (HPHCs) in smoke formed during the burning process. When a cigarette is lit, the tobacco inside it combusts (burns), producing ash, heat, light (energy), and smoke, which contains thousands of chemicals. Once it has started, combustion is a self-sustaining process that will continue as long as there is enough tobacco (fuel) and oxygen available.
When burning takes place, the temperature in a cigarette can rise above 800 °C at the tip. These high temperatures trigger the generation of more than 6000 different chemicals, many of which are harmful or potentially harmful. For reference: