The research, published on Thursday in the journal Science, analyses and compares tumours, providing the first accurate measure of the devastating genetic damage smoking inflicts not only in lungs but also in other organs not directly exposed to smoke. Ludmil Alexandrov of Los Alamos National Laboratory in the United States, one of those who carried out the research, explained that in particular, it had until now been difficult to explain how smoking increases the risk of cancer in parts of the body that don't come into direct contact with smoke. "Before now, we had a large body of epidemiological evidence linking smoking with cancer, but now we can actually observe and quantify the molecular changes in the DNA due to cigarette smoking," Alexandrov said. "With this study, we have found that people who smoke a pack a day develop an average of 150 extra mutations in their lungs every year, which explains why smokers have such a higher risk of developing lung cancer," Alexandrov said. In addition to the mutations, the analysis found a range of "molecular signatures" -- patterns that are significantly different from other sequences in the DNA -- based on changes to DNA that were linked to people smoking. The results also showed that a smoking a pack of cigarettes a day led to an average 97 mutations in each cell in the larynx, 39 mutations for the pharynx, 23 for the mouth, 18 for the bladder, and six mutations in every cell of the liver each year.
A research team at Los Alamos National Laboratory quantifies the molecular damage inflicted on DNA and discloses that every 50 cigarettes smoked generates an average of one DNA mutation in each lung cell.