One reason why dual use of ecigs and cigs is worse than using either product alone Stanton Glantz blog Guide to What Are The 4000 Chemicals In Cigarettes Unlike cigarettes, smoke free alternatives such as e cigarettes and heated tobacco products don't burn tobacco and that makes a big difference. Burning tobacco creates high levels of harmful chemicals. Heated tobacco products, How are Non Combusted Cigarettes, Sometimes Called Heat Not Burn Products, Different from E Cigarettes and Cigarettes? FDA