What Causes Lung Cancer?

A risk factor is anything that increases a person's chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking, can be controlled. Others, like a person's age or family history, can't be changed. But having a risk factor, or even several, doesn't mean that a person will get the disease. Smoking is by far the leading risk factor for lung cancer.

Tobacco smoking: Tobacco smoking is thought to be responsible for 8 out of 10 cases of lung cancer. The longer a person has been smoking and the more packs per day smoked, the greater the risk. If a person stops smoking before lung cancer develops, the lung tissue slowly returns to normal. Stopping smoking at any age lowers the risk of lung cancer. Cigar and pipe smoking are almost as likely to cause lung cancer as cigarette smoking. There is no evidence that smoking low tar cigarettes reduces the risk of lung cancer.

Nonsmokers who breathe the smoke of others also increase their risk of lung cancer. Non-smoking spouses of smokers, for example, have a 30% greater risk of developing lung cancer than do spouses of nonsmokers. Workers exposed to tobacco smoke in the workplace are also more likely to get lung cancer.

Asbestos: Asbestos is another risk factor for lung cancer. People who work with asbestos have a higher risk of getting lung cancer, and if they smoke as well the risk is greatly increased. Although asbestos was used for many years, the government has now nearly stopped its use in the workplace and in home products. The type of lung cancer linked to asbestos, mesothelioma, often starts in the pleura. To learn more about this type of cancer, please see our Cancer Reference Information section on Mesothelioma.

Radon: Radon is a radioactive gas made by the natural breakdown of uranium. Radon can't be seen, tasted, or smelled. Radon can become concentrated indoors and create a possible risk for cancer. The EPA (Environmental Protection Agency) can provide the names of reliable companies that test for radon gas.

Cancer-causing agents in the workplace include substances such as uranium, arsenic, vinyl chloride, nickel chromates, coal products, mustard gas, and chloromethyl ethers., gasoline, and diesel exhaust. People who work with these substances should be very careful to avoid exposure.

Marijuana: Marijuana cigarettes have more tar than regular cigarettes. Many of the cancer-causing substances in tobacco are also found in marijuana. Some medical reports suggest that marijuana could cause cancers of the mouth and throat. But because marijuana is an illegal substance it is not easy to gather information about its effects on the body.

Other diseases: Tuberculosis (TB) and some types of pneumonia often leave scars on the lung. This scarring can increase the risk of developing lung cancer.

Minerals: such as talc may increase the risk of lung cancer in those who mine or work with it. People with diseases caused by breathing certain minerals also have an increased risk.

Personal and family history: If you have had lung cancer, you have a higher risk of developing another lung cancer. Brothers, sisters, and children of people who have had lung cancer may have a slightly higher risk themselves.

Diet: Some reports suggest that a diet low in fruits and vegetables might increase the risk of lung cancer in people who are exposed to tobacco smoke. It is possible that apples, onions, and some other fruits and vegetables could contain a substance that offers some protection against lung cancer.

Gender: Several studies have shown that the lung cells of women are more likely to develop cancer when exposed to tobacco smoke.

During the past few years, scientists have made great progress in understanding how risk factors produce certain changes in the DNA of lung cells, causing the cells to become cancerous. DNA is the genetic material that carries the instructions for nearly everything our cells do.

Current research in this field is aimed at developing tests that can detect lung cancers at an early stage by recognizing DNA changes. Other researchers are working on ways to repair or replace these faulty genes in order to stop the growth and spread of cancer cells. To learn more about risk factors and causes of lung cancer, please see our Cancer Reference Information section on Lung Cancer.