While cigarette smoking is the main cause of lung cancer, it's possible to get the disease without ever lighting up.

"Anyone with lungs can get lung cancer," said Dr. Missak Haigentz Jr., chief of Thoracic and Head and Neck Medical Oncology at Rutgers Cancer Institute of New Jersey in New Brunswick.

In fact, a new U.S. National Cancer Institute study estimates 10% of men and 20% of women who develop lung cancer have never used tobacco products. There are three types of lung cancer in nonsmokers, according to the study.

"What we know already is that lung cancers, despite appearing similar under the microscope, may develop differently in never-smokers, and this information on molecular differences has already had a tremendous impact in the way we treat the disease with targeted cancer therapies," Haigentz said in a Rutgers news release.

Lung cancer in nonsmokers results from other known exposures, including radon gas or secondhand smoke. Asbestos exposure carries a risk for mesothelioma, a rare type of cancer affecting the thin tissue that covers the majority of a person's internal organs.

"Anything that we inhale can potentially expose our airways and our lungs to damaging agents that may give rise to cancer -- we have not yet identified all of these," Haigentz said.

In smokers, it's often caused by years of exposure to cancer-causing substances in tobacco smoke. These substances cause multiple genetic changes in cells that line the lungs.

Haigentz said this new research helps scientists understand how smokers and never-smokers can benefit from treatments such as targeted cancer therapeutics.

Based on the molecular features of lung cancers, scientists have recently developed several effective treatment options targeting its biology, Haigentz said. More advances are anticipated.

Nonsmokers who are worried about lung cancer can take a number of steps, according to Haigentz.

Most important, never start smoking. Experts now recommend lung cancer screening with yearly low-dose CT scans for those who have had significant exposure to smoking, including former smokers. And test your home for radon gas.

"Most importantly, we need to remove the stigma of lung cancer; understand that there are people who have smoked their whole life and never develop cancer, and there are people who have never smoked at all who develop lung cancer," Haigentz said.