A new study revealed that smoking a pack of cigarettes a day could cause several mutations in our body's tissue, including 150 mutations in the lungs, increasing the risk of cancer.

The study, published in the journal Science, demonstrated that smoking causes cancer by promoting somatic mutations that both directly damage DNA and increase the speed of an endogenous molecular clock.

"Our analysis demonstrates that tobacco smoking causes mutations that lead to cancer by multiple distinct mechanisms," explained Dr. Ludmil Alexandrov, Oppenheimer Fellow at Los Alamos National Laboratory and co-lead author of the study, in a statement. "Tobacco smoking damages DNA in organs directly exposed to smoke as well as speeds up a mutational cellular clock in organs that are both directly and indirectly exposed to smoke."

For the study, the researchers compared the cancers of 2,490 smokers and 1,063 non-smokers. By comparing the cancers of smokers and non-smokers, the researchers were able to identify the mutation signatures and methylation changes in 5,243 genome sequences of smoking-related cancers.

The researchers found that DNA in the lungs of people smoking at least one pack a day per year acquired about 150 new mutations. Furthermore, tobacco smoking also caused several mutations in other respiratory organs, including 97 new mutations in the larynx, 39 in the pharynx and 23 in the oral cavity,

Smoking a pack every day could also promote mutations in organs not directly exposed to the tobacco smoke. The researchers observed about 18 new mutations in the bladder and six new mutations in the liver.

Tobacco smoking was also linked to more than 20 mutational signatures across the 17 cancer types. However, only five of those mutations were elevated in cancers of smokers. The researchers noted that some cancer types may only present a single mutational signature in smokers, while other type may present multiple mutational signatures.

According to the report from Los Angeles Times, cigarette smoking is responsible for at least 167,133 cancer deaths every year in the United States.