Why are there so many chemicals in cigarettes?

The main thing that smokers are addicted to is nicotine, which is a drug that your brain starts to crave after you've been exposed to it. There's more than 4000 chemicals in cigarettes, and they come from a variety of sources. Some of them are in the tobacco plant itself, absorbed from the air by the plants including chemicals such as polonium. Some chemicals are produced when the tobacco is processed, some are added in when cigarettes are made. The most dangerous chemicals in tobacco are actually created when you burn a cigarette; the chemicals of burning are produced by the act of lighting a cigarette and inhaling something that is burning.There are a few extra chemicals added during the process of making a cigarette, and so smoking straight tobacco would lack these, but the important chemicals are created by the simple act of burning the tobacco.A lot more information is available from Cancer Research UK's smoke is poison campaign, www.smokeispoison.com.