Smoking leaves an archaeological record in the body: contrary to beliefs that once a person stops smoking he is free, a new study has shown the effects of smoking in the body is permanent.
The study as reported by the BBC shows that smoking causes a myriad of DNA mutations in the Lungs which remain permanent and continuous even when a person stops smoking.
According to scientists, a person who smoked 20 sticks of cigarette would have an average of 150 DNA mutation in every lung cell, the BBC reports.
The study further showed that with every mutation comes the risk of developing cancer of the lungs.
Pamela Pugh, 69, was diagnosed with lung cancer in 2013. She started smoking aged 17 and quit in her early 50s.
But she said: “Even though I gave up many years ago, the effects of smoking caught up with me.
“Had I known as a teenager that smoking caused mutations which would stay with me for life then I would never had started”.
The study, in the journal Science, was carried out by an international group, including the Wellcome Trust Sanger Institute in Cambridgeshire and the Los Alamos National Laboratory in New Mexico.
The analysis shows a direct link between the number of cigarettes smoked in a lifetime and the number of mutations in tumour DNA.
The authors found that, on average, smoking a packet of cigarettes a day led to:
- 150 mutations in each lung cell every year
- 97 in the larynx or voice box
- 23 in the mouth
- 18 in the bladder
- six in the liver
Joint lead author Prof Sir Mike Stratton, from the Wellcome Trust Sanger Institute, said: “The more mutations there are, the higher the chance that these will occur in the key genes that we call cancer genes, which convert a normal cell into a cancer cell.”
The researchers said that in tissues such as the lung, which are directly exposed to smoke, they could find the mutational signature of the chemicals in tobacco smoke, of which at least 60 are carcinogens.
However, they could not find this same pattern in tissues such as the bladder, which are not directly exposed.
Prof Stratton said in these organs smoking seemed to be accelerating a natural mutational process, but how it did this was “mysterious and complex”.
He said the same investigative approach could be used with other cancers where the underlying causes were less well understood.
“By looking in the genomes of the cancers, we will find the archaeological traces of past exposures which have been responsible for generating the cancers and that may potentially lead to prevention,” he said.