People who does not smoke, but who lives in an area that has higher pollution levels are approximately  20 percent more expected to die from lung cancer than people who got exposed to cleaner air, researchers conclude in a new study.

Professor at the Harvard School of Public Health, Francine Laden says it is another dispute for why the narrow levels (for air pollutants) be as low as possible.

Nevertheless, smoking considered to be the number one causes of lung cancer, an estimated one in 10 people who develop lung cancer never tried smoking in his lifetime.

Lead author of the study and a graduate student at the University of Ottawa, Michelle Turner says lung cancer for those who never smokes is an important cancer. It is considered as the sixth leading cause of cancer in United States.

Earlier estimates of how many non-smokers get lung cancer range from 14 to 21 out of every 100,000 women and five to 14 out of every 100,000 men.

The subtle particles in air pollution, irritating the lungs and cause inflammation considered to be a risk factor for lung cancer. However, researchers had not clearly teased apart their influence from that of smoking.

In this study, Turner and her colleagues monitored over 180,000 non-smokers for 26 years. During the study period, 1,100 people died from lung cancer.

People who participated in the study came from all 50 states and in Puerto Rico, and based on their zip codes, the researchers estimated how much air pollution they got exposed to — measured in units of micrograms of particles per cubic meter of air.

Pollution levels in another location ranged from a low of around six units to a high of 38. The levels fell down over time, however, from an average of 21 units in 1979 – 1983, to 14 units in 1999 – 2000, which produces an overall average pollution level of 17 units across the study period.

After the team had considered the other cancer risk factors, which involves second-hand smoke and radon exposure, they discovered that, for every 10 extra units of air pollution exposure, a person’s risk of lung cancer rose by 15 to 27 percent.

The escalated risk for lung cancer connected with pollution is small in contrast to the 20 times increased risk from smoking.

The study team never did say that the pollution caused the cancer cases, but “there are lots of proof that exposure to fine particles raises cardiopulmonary mortality.