Lung cancer is a leading cause of death in the United States, and is one of the most common types of cancer in the world. Tobacco smoke is the primary risk factor. Due to declining numbers of smokers, we have seen an expected decline in lung cancer cases. However, lung cancer in nonsmokers has been increasing.
Nonsmokers believe that they are unlikely to get lung cancer. Although it is true that the odds of getting lung cancer are in their favor, many nonsmokers are diagnosed each year. According to the American Cancer Society (ACS), in 2018, roughly 20% of people in the US who died of lung cancer never smoked.
Many nonsmokers are people who don’t currently smoke, but may have smoked in the past. Nonsmokers who never smoked at all appear to develop cancers resulting from genetic mutations or abnormalities that can be detected in the tumor. These cancers may be treated differently than the cancers commonly found in smokers.
Besides smoking, risk factors also include a family history of lung cancer and environmental causes.
There are different types of lung cancer. Primary lung cancer starts in the lungs and may be non-small cell lung cancer or small cell lung cancer. The almost quarter of a million cases diagnosed each year in the US are of these two types.
More than half of cancers diagnosed in smokers tend to be a type of non-small cell lung cancer called squamous cell carcinoma. Most nonsmokers are diagnosed with a different form of non-small cell lung cancer, called adenocarcinoma. Lung cancer in nonsmokers tends to grow more slowly and is less likely to spread.
The causes of cancer in nonsmokers are many, but numerous studies have shown that genetic mutations or abnormalities play a major role in the development of lung cancer in nonsmokers. The ACS also lists the following possible causes of lung cancer in nonsmokers:
Radon gas accounts for about 21,000 lung cancer deaths per year. It is invisible and occurs outdoors naturally, but can also be found in the home, sometimes in high concentrations. Radon gas tests are available to monitor dangerous levels.
Second-hand smoke is linked to an estimated 7,000 lung cancer deaths per year in the US.
Carcinogens found at work or in the environment, such as asbestos, heavy metals and diesel exhaust are dangerous for people who have prolonged exposure.
Air pollution may be a factor, but in the US the risk is low, in comparison to other countries where air quality is not regulated.
According to the CDC, about 10-20% of lung cancers, or 20,000-40,000 lung cancer cases per year, happen in people who never smoked or smoked fewer than 100 cigarettes during their lifetimes.
The risk of getting lung cancer can be lowered by avoiding secondhand smoke, diesel exhaust and other types of air pollution. Tests for radon in your home are available online and easy to use, and instructions for lowering high radon levels are available.
