Coffin nails

15 cigarettes: all it takes to harm genes that headline you might be forgiven for thinking that after your first fifteen ciggies you have created one genetic mutation and for every fifteen cigarettes you smoke thereafter another mutation occurs. This, of course, is bollocks. There is no way that a calculation like this could be made. The figure was arrived at by dividing the total number of cigarettes smoked by a cancer victim and dividing it by the number of mutations, 23,000 in this case. It's just an averaging out of a lifetime's smoking and the mutations it causes. There are no details of the age of the cancer sufferer nor how long he had been smoking but I'm guessing he smoked an average of 20 - 25 cigarettes a day for between 35 and 40 years.

We know that giving up smoking, even after many years of the habit, eventually reduces the risk of lung cancer to almost the same level as a lifelong non-smoker. It also seems, looking at the Nature article from which this story is extracted, that some repair seems to take place over time. We also need more studies on more smokers who show no sign of lung cancer to see if they have fewer mutations and to discover why.

It is obvious that smoking causes cancer, although it seems that some people seem to able to smoke as much as they like without suffering from any ill-effects, probably because of protective genetic factors, and it is obvious that the more you smoke and the longer you smoke the greater the risk. But that is a long way from saying that all it takes to harm genes is fifteen cigarettes. Very sloppy.