Individuals who carry a particular genetic variant are at much higher risk of developing lung cancer from exposure to second-hand smoke than others, even if they rarely come into contact with it, according to a new study.

Researchers at the University of Cincinnati say that for family members who carry this genetic variant, the risk of lung cancer is similar for both light and heavy smokers, adding that even non-smokers who are exposed to second-hand cigarette smoke and have a family history of lung cancer should be monitored for early detection.

The study was conducted by the Genetic Epidemiology of Lung Cancer Consortium (GELCC),

"The study shows a strong gene-environment interaction between a region of chromosome 6q and smoking. People with this susceptibility locus can develop lung cancer even with a very little bit of smoking," said Marshall Anderson, a professor in UC's cancer and cell biology department, is principal investigator of the GELCC

To study the chromosome region's effect on lung cancer risk, the researchers identified a haplotype (a portion of a chromosome containing genes that tend to be inherited together) that was associated with lung cancer.

Collecting data from several recruitment sites including UC, they then divided smoking exposures into never smokers, light smokers (fewer than 20 pack years, with a pack year being the equivalent of a pack a day for 20 years), moderate smokers (20-40 pack years) and heavy smokers (40 or more pack years).

For family members without this genetic lung cancer risk, the risk of developing the disease tracked closely with the level of smoking-in other words, heavy smokers had a significantly greater risk of developing lung cancer than moderate smokers, who had a significantly greater risk than light smokers.

But in family members with the genetic risk haplotype, even light smoking resulted in a greatly increased risk for developing lung cancer. From there, increasing smoking behaviours in this group of family members carried only weakly increasing risk for developing lung cancer.

Susan Pinney, a co-author of the study, said: "If you carried the inherited risk and then you smoked, it didn't matter if you were a light smoker or a heavy smoker-you were significantly more likely to develop lung cancer."

The study has been published online March 9, 2010, ahead of print by Cancer Research. (ANI)