The study, by researchers at Brigham Young University, New York University's School of Medicine and the University of Ottawa, examined data from people living in metropolitan locations versus those living in rural areas.
The study found those people in metro areas exposed long-term to emissions from factories, coal-fired power plants and diesel trucks had a 12% higher death rate from lung cancer than those living in rural areas. The study added that such long-term exposure to air pollution is comparable to the cumulative effects of inhaling second-hand cigarette smoke.
Some scientists dispute those findings, however, saying that the data does not account for several variables, including a person's job and eating habits.