A person living with a smoker has twice the risk of lung cancer. Air pollution from motor vehicles, factories, and other sources may increase your risk, but the degree of increase has not been established accurately. Asbestos exposure increases the risk of lung cancer by 9 times. A combination of asbestos exposure and cigarette smoking compounds the risk up to 50-fold. Radon exposure poses another risk.
Radon is a by-product of naturally occurring radium, which is a product of uranium.
Radon is present in indoor and outdoor air. Your risk increases with significant long-term exposure, although no one knows the exact risk. A person with COPD has 4-6 times greater risk of lung cancer once the effect of cigarette smoking is excluded. In these cases doctors identify an incidental abnormality on a chest x-ray. In other words, the chest x-ray was not done specifically to look for lung cancer but as part of other medical testing.