England's department of health has launched a new, very graphic anti-smoking TV ad (see the [BBC STORY][1]). Aside from the graphic imagery it makes the specific claim that a smoker will suffer one mutation fo every 15 cigarettes smoked. Is this claim credible? And, perhaps more importantly, is it *significant* given the background level of mutagenic chemicals and radiation we are exposed to? [1]: http://www.bbc.co.uk/news/health-20805059