A common tactic for people trying to give up smoking is to quantify exactly how much damage — financial or physical — each cigarette or pack of cigarette does. How much does smoking cost you per month, for example, or how much shorter is your life going to be for each drag you take? Well, a new study into the dangers of smoking now lets us measure this damage right down to the number of mutations in your DNA.
A research team led by scientists from Los Alamos National Laboratory compared tissue samples from 1,063 non-smokers and 2,490 smokers, examining each individual's DNA to look for mutations. They found that for every 50 cigarettes smoked, there is one extra DNA mutation for each cell in the lungs. Over the course of a year, this means that someone who smokes a pack a day (20 cigarettes) has 150 extra mutations per cell in the lung, 97 per larynx cell, 23 per mouth cell, 18 per bladder cell, and six per liver cell.
These changes to the cells aren’t dangerous in themselves, but each one has the potential to turn into a cancerous growth. "Smoking is like playing Russian roulette: the more you play, the higher the chance the mutations will hit the right genes and you will develop cancer," Ludmil Alexandrov, the co-lead author of the study, told the New Scientist. "However, there will always be people who smoke a lot but the mutations do not hit the right genes."
The reason for all these extra mutations is found in tobacco smoke — a substance that contains some 7,000 different chemicals, over 70 of which are known to cause cancer. How exactly different types of cell mutations lead to cancer is less clear, and the team from Los Alamos are hoping next to drill down further into this line of research and find out the probabilities that any individual DNA mutation will turn into cancer.
The good news for smokers, though, is that it’s never too late to quit. Although smoking causes regular DNA mutations, as soon as people give up cigarettes, the mutations stop too. One UK study from 2004 found that those who quit smoking at age 30 nearly eliminate the risk of dying prematurely, while those who quit at 50 halve it. For people trying to give up, those are certainly some more comforting odds.