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Occasional smokers at risk of lung cancer

Occasional smoking also found to be harmful Even low level exposure to cigarette smoke harmful

Occasional smokers tend to dismiss the negative health effects of a cigarette here and there, but new research has found that even low levels of cigarette smoke may put people at risk of lung cancer and chronic obstructive pulmonary disease.

"Even at the lowest detectable levels of exposure, we found direct effects on the functioning of genes within the cells lining the airways," said lead author Dr Ronald Crystal of NewYork-Presbyterian/Weill Cornell Medical Center.

Genes which are commonly activated in the cells of heavy smokers were found to be activated in those with very low-level exposure to cigarette smoke.

"The genetic effect is much lower than those who are regular smokers, but this does not mean that there are no health consequences," said Dr Crystal.

"Certain genes within the cells lining the airways are very sensitive to tobacco smoke, and changes in the function of these genes are the first evidence of 'biological disease' in the lungs or individuals," he added.

Epidemiological studies have long shown that secondhand smoke is dangerous, but until now there have never been conclusive biological tests demonstrating what it does to the body at a gene function level.

The study tested 121 people, including nonsmokers, active smokers and low exposure smokers, scanning each person's entire genome to determine which genes were either activated or deactivated in cells lining the airways. They found that there was no level of nicotine or cotinine that did not also correlate with genetic abnormalities.

"This means that no level of smoking, or exposure to secondhand smoke, is safe," Dr Crystal said.

The authors said this is further evidence supporting the public smoking ban, as any exposure to smoke creates the risk of future lung disease.

The study is published today in the American Journal of Respiratory and Critical Care Medicine.

This article was published on Fri 20 August 2010



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