For many smokers, it's difficult to take the dangers of smoking seriously because many years often pass before painful symptoms such as a cough and shortness of breath start to show up. However, a new study shows that smoking a pack of cigarettes each day for just one year can lead to an extra 150 mutations in the lungs, and many more mutations in other important organs throughout the body — even if a smoker still feels fine.

Researchers say they're shown a direct link between the number of cigarettes smoked in a lifetime and the number of mutations in a smoker's DNA. The team of scientists identified several different mechanisms by which tobacco smoke causes mutations, and counted an average of 150 extra mutations in every single lung cell after only a year of smoking a pack of cigarettes a day. In addition, smoking a pack-a-day for a year produced an average 97 mutations in each cell in the larynx (voice box), 39 mutations in the pharynx (top part of the throat), 23 in the mouth, 18 in the bladder and six in the liver, according to a recent statement from the Wellcome Trust Sanger Institute.

“This study offers fresh insights into how tobacco smoke causes cancer,” study co-author Ludmil Alexandrov of the Los Alamos National Laboratory, told The Independent. “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.”

For their research, the team analyzed over 5,000 tumors, and compared cancers from smokers with cancers from people who had never smoked. In doing so, they were able to see specific signs of DNA damage only in the DNA of smokers. They then counted how any of these mutations occurred in different types of tumors. Although the most damage was seen in organs that came into direct contact with tobacco, such as the lungs, other areas of the body also suffered indirect damage due to smoking. According to lead study author Sir Mike Stratton, of the Wellcome Trust Sanger Institute in the statement, these findings suggest that tobacco smoking cause cancers in ways more complex than we previously believed.

“This study of smoking tells us that looking in the DNA of cancers can provide provocative new clues to how cancers develop and thus, potentially, how they can be prevented,” added Stratton.

Source: Alexandrov LB, Ju YS, Van Loo P, et al. Mutational signatures associated with tobacco smoking in human cancer. Science . 2016

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