The negative effects of tobacco smoke are well known and as revealed by recent research, it is the leading cause of avoidable cancer cases in the UK. But what about the potential positive effects of kicking the habit? Is there any way back for a smoker's body? As part of a report released by the World Health Organization for World No Tobacco Day shows, the potentially devastating effects of smoking are actually far from a one way street. After just 20 minutes, the first health improvements begin, with a drop in heart rate and blood pressure. Within 12 hours carbon monoxide levels return to normal and after a few weeks lung function increases and circulation improves. Even the heightened risk of stroke or coronary heart disease is gone within 15 years. Lung cancer also becomes a much less significant threat after about ten years.