The Guardian: DNA study lays bare devastating damage caused by smoking. “Major investigation into root causes of cancer reveals how tobacco smoke mutates DNA and gives rise to more than a dozen types of tumour.”

“The devastating impact of cigarette smoke on the body’s DNA has been laid bare by the first comprehensive study into the damage tobacco inflicts on human cells.

People who smoke a pack of cigarettes each day for a year develop on average 150 extra mutations in every lung cell, and nearly 100 more mutations than usual in each cell of the voice box, researchers found. More still build up in the mouth, bladder, liver and other organs.
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“There is a message here for people who are occasional or social smokers who think it doesn’t do anything,“ said Alexandrov. “If you smoke four to five packs of cigarettes in your lifetime it doesn’t sound that much, but you still get several mutations in every cell in your lungs and these are permanent, they do not go away. There are a lot of things that do revert back when you stop smoking, and this shouldn’t discourage people from giving up, but the specific mutations in the lung cells are like scars. If you stop smoking, they’ll still be there.“ “