The American Cancer Society put figures of non-smokers who develop lung cancer as 10 to 15 percent.
Researchers announced results of a study that offer support to these estimates, in the form of similar figures.
Publishing their findings in the Journal of Oncology, Dr. Heather Wakelee of Stanford University in California and epidemiologist Ellen Chang said that around 20 percent of lung cancer patients are women who have never smoked. Non -smoking men who go on to get the disease are recorded as 8 percent.
This appears conclusive proof of the drawbacks of second-hand smoke or passive smoking.
This also gives fodder for thought on why women are more prone to the effects of passive smoking, than men.
The researchers said conclusions were reached after an extensive study of a million lung cancer subjects in Sweden and the U.S aged between 40 and 79.
Smoking is by far the leading cause of lung cancer though radon, asbestos, chromium and arsenic are also associated with lung cancer.
The American Cancer Society predicts that lung cancer will be diagnosed in 213,000 Americans in 2007 and kill 160,000 of them.
Says Chang," We know that secondhand smoke does increase the risk of lung cancer so it's likely that a lot of these cases we observe are attributable to that."