Causes of Lung Cancer

Causes include:

• Tobacco smoke
• Asbestos exposure
• Environmental toxins
• Radon
• Radiation exposure
• Genetic factors also can contribute

Two or more of these factors can work together in synergy to cause cancer.

Smoking

Approximately 78% of men with lung cancer smoke, as do approximately 90% of women with lung cancer. Tobacco is the leading cause of lung cancer, with cigarettes the most common form of tobacco use. The longer a person smokes, and the more cigarettes, the greater the chance of getting lung cancer. Epidemiologists (scientists who study diseases in populations) estimate that 87% of lung cancer cases in the United States can be attributed primarily to tobacco smoke.

Secondhand smoke also causes lung cancer. Of all the lung cancers in nonsmokers, 15% are thought to be caused by secondhand smoke. Chemicals that indicate exposure to cigarette smoke can be detected in nonsmokers who have been around secondhand smoke.

Asbestos and cigarette smoke together act in synergy to cause lung cancer. Current smokers who were exposed to asbestos may have a risk as high as 80% to 90% higher than that of nonsmokers with no asbestos exposure.

The incidence of lung cancer mirrors the incidence of smoking and asbestos exposure, with a latency period which represents the time it takes to develop cancer. After years of increasing lung cancer rates, there are now fewer men smoking, and fewer lung cancer deaths in men than previously. The lung cancer rate for men has been decreasing since 1990. Public health programs to encourage quitting smoking, and OSHA regulations to control asbestos dust in the workplace have resulted in great success, and after decades are finally brining about a decline in lung cancer rates, particularly in the United States.

Asbestos

The U.S. Department of Health and Human Services, the EPA, and the International Agency for Research on Cancer have all classified asbestos as a carcinogen (reference) There are different types of asbestos, but all types that were used commerically can cause cancer.

Asbestos exposure is strongly associated with lung cancer. Asbestos exposure raises the risk of lung cancer five times. Asbestos can also cause mesothelioma, another malignancy inside the chest. Workers in many industries have had asbestos exposure. The long latency period of the cancer means that asbestos-caused cancer rates continue to rise even as asbestos exposure levels are lower than they were in past decades.

It is impossible to predict in advance whether asbestos exposure will cause a person to develop lung cancer. The risk the asbestos poses depends on many things, including how much (were the fibers in the air thick), for how long (some people experienced prolonged exposure in the workplace), the type of asbestos (including how it was processed before use), and the source of the asbestos exposure. source

How are people exposed to asbestos? In many ways. Asbestos was used widely in many products for decades, and is still sold in new products today. Hundreds of thousands of people were exposed to asbestos at work.

Modern workplace regulations are stricter than in past decades, and industial hygienists know to look for to reduce risks.

But many people who were exposed to asbestos at the job in the past are only now developing cancer. This is not surprising, given that cancer can have a long latency period, and that asbestos fibers remain in the lungs for life. Many veterans were exposued during their times in the service, and trademen, factory workers, and auto mechanics all came into contact with asbestos in the workplace.

If you have lung cancer and were exposed to asbestos, even decades ago, you may be eligible for compensation. Click here to learn more.

Environmental toxins

In addition to asbestos, other chemicals that cause lung cancer include tar and soot which contain aromatic polycyclic hydrocarbons, arsenic, chromium, nickel, silica, cadmium and radon. It is very important for individuals to know what they might be exposed to in the workplace, and for employers to take requisite care. These chemicals often show a synergistic effect with cigarette smoke, as with asbestos.

There have been many studies looking at the effects of air pollution. The most recent studies show a slight increased risk of lung cancer for people living in areas with the most air pollution. High sulfates in the air may be the main factor.

Radon and other sources of radiation

Exposure to nuclear radiation causes lung cancer; veterans who were irradiated during the testing of nuclear weapons frequently got cancer. Radon, a gas produced when uranium decays, causes lung cancer in uranium miners. Radon can also be found in small quantities in homes all over the country. Radon is an invisible, odorless gas produced naturally in the ground. It accumulates in the basements of some homes. Radon in the home appears to increase the risk of cancer, again causing an even greater risk in smokers. Radon exposure may account for some 2% to 3% of lung cancers.

Other factors

People who have had tuberculosis may be at higher risk of lung cancer, as are those who have other chronic lung problems, including chronic obstructive lung disease (COPD) which is also caused by smoking.

It was once believed that beta carotene could help prevent lung cancer. However multiple studies have shown that in heavy smokers, high doses of beta carotene are associated with a higher risk of lung cancer. Normal amounts of beta carotene in vegetables are not associated with increased risk.

There are other areas of investigation with unclear results, including the role of vitamins, consumption of fruits and vegetables, and other lifestyle factors including exercise. It is often difficult to separate out these factors from smoking, because heavy smokers may also do insufficient exercise and eat less fruit.

Genetic factors also play a role in the growth of lung cancer. Researchers, looking at animal and human genetics of lung cancer, have found amplified oncogenes and inactivation of tumor suppressor genes in some lung cancers. One area of focus is the ras oncongene family. The K-ras mutation is found in 30% of lung adenocarcinomas, only in smokers. There have been genes found on the fifth and possibly the sixth chromosome that may be involved with lung cancer. There is much more work to be done in this area. Understanding the genetics of lung cancer will help with both prevention and treatment.

Symptoms of lung cancer