Tobacco smoking—including cigarette, cigar and pipe smoking—is the most important risk factor for lung cancer. Most lung cancer occurs in people who smoke or smoked in the past. Tobacco smoke damages cells in the lungs, causing the cells to grow abnormally. The risk that smoking will lead to cancer is higher for people who smoke heavily and/or for a long time.
Being exposed to secondhand tobacco smoke is also a risk factor for lung cancer. Secondhand smoke is the smoke that comes from a burning cigarette or other tobacco product, or that is exhaled by smokers. People who inhale secondhand smoke are exposed to the same cancer-causing agents as smokers, although in smaller amounts.
Environmental Risk Factors
- Radon This is an inivisible, odorless gas naturally released by some soil and rocks. Exposure to radon has been associated with an increased risk of some cancers, including lung cancer. Most hardware stores have kits that test home radon levels, and basements can be ventilated to reduce radon exposure.
- Asbestos These hair-like crystals are found in many types of rock and are often used as fireproof insulation in buildings. When asbestos fibers are inhaled, they can irritate the lung. Many studies show that the combination of smoking and asbestos exposure is particularly hazardous. People who work with asbestos in jobs, such as shipbuilding, asbestos mining, insulation or automotive brake repair, and smoke have a higher risk of developing lung cancer. Using protective breathing equipment reduces this risk.
- Air pollution Some studies have shown a link between air pollution and an increased risk of lung cancer.
- Other environmental factors There are other environmental risk factors for lung cancer. These include: arsenic, chromium, nickel, and tar and soot. These substances can cause lung cancer in people who are exposed to them in the workplace and have never smoked, but the risk is higher in people who are exposed and also smoke. Being exposed to these substances is much less likely to cause lung cancer than cigarette smoking is.
Some studies have shown that drinking large amounts of alcohol is linked to an increased risk of lung cancer.
Beta Carotene Supplements (in Heavy Smokers)
Taking beta carotene supplements (pills) can increase the risk of lung cancer in smokers who smoke one or more packs a day. The risk is higher in smokers who also drink one or more alcoholic drinks every day.