Virginia Commonwealth University

VCU Massey Cancer Center

Causes, risk factors and prevention

What are the risk factors for lung cancer?

A risk factor is anything that increases a person’s chance of developing a disease such as cancer. Different cancers have different risk factors. Several risk factors make a person more likely to develop lung cancer:

  • Smoking is the leading cause of lung cancer, with more than 90 percent of lung cancers thought to be a result of smoking.

Additional risk factors include:

  • Secondhand smoke – breathing in the smoke of others.
  • Smoking marijuana cigarettes, which:
    • Contain more tar than tobacco cigarettes.
    • Are inhaled very deeply. 
    • Are smoked all the way to the end where tar content is the highest.

Because marijuana is an illegal substance, it is not possible to control whether it contains fungi, pesticides and other additives.

  • Recurring inflammation, such as from tuberculosis and some types of pneumonia.
  • Asbestos exposure – one of the most common causes of mesothelioma. More than 50 percent of mesothelioma patients have a history of exposure to asbestos, which could occur while directly handling the fibrous material, or through random environmental exposure.

    To learn about malignant mesothelioma visit www.allaboutmalignantmesothelioma.com, a comprehensive resource about mesothelioma symptoms, treatments, and causes. 
  • Talcum powder – while no increased risk of lung cancer has been found from the use of cosmetic talcum powder, some studies of talc miners and millers suggest a higher risk of lung cancer and other respiratory diseases from their exposure to industrial-grade talc. Talcum powder is made from talc, a mineral that, in its natural form, may contain asbestos. Although, by law, all home-use talcum products (baby, body and facial powders) have been asbestos-free.
  • Cancer-causing agents in the workplace, including:
    • Radioactive ores such as uranium 
    • Arsenic 
    • Vinyl chloride 
    • Nickel chromates 
    • Coal products 
    • Mustard gas 
    • Chloromethyl ethers 
    • Fuels such as gasoline 
    • Diesel exhaust 
  • Radon – a radioactive gas that cannot be seen, tasted or smelled. It is produced by the natural breakdown of uranium.
  • Personal history of lung cancer. 
  • Air pollution – in some cities, air pollution may slightly increase the risk of lung cancer.

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Facts about smoking and respiratory diseases

Diseases caused by smoking kill more than 430,000 people in the United States each year. In fact, smoking is directly responsible for the majority of lung cancer cases (87 percent), emphysema cases and chronic bronchitis cases. Even with anti-smoking campaigns and medical health disclaimers in place, many people continue to smoke or start to smoke every year. According to the American Cancer Society, 90 percent of new smokers are children and teenagers, in many cases, replacing the smokers who quit or died prematurely from a smoking-related disease.

What are the risks associated with smoking?

Smokers not only increase their risk of lung disease, including lung cancer, but they also increase their risk of other illnesses, including heart disease, emphysema, stroke and oral cancer. Risks from smoking, as they relate to lung disease, may include, but are not limited to, the following:

  • Chronic bronchitis – a long-term inflammation of the bronchi (large airways), is characterized by coughing productively over a long period of time.
  • Emphysema – a chronic lung condition that affects the air sacs in the lungs (alveoli), is characterized by shortness of breath, coughing, fatigue, sleep and heart problems, weight loss, and depression. 
  • Lung cancer – an abnormal, continual multiplying of cells that can result in lumps, masses or tumors, can begin in the lining of the bronchi (large airways) or other areas of the respiratory system. Lung cancer may cause a cough as the tumor grows. Other symptoms may include constant chest pain, shortness of breath, wheezing, recurring lung infections, bloody or rust-colored sputum, hoarseness, swelling of the neck and face, pain and weakness in the shoulder, arm or hand, and unexplained fever. Smoking, including secondhand smoke, is the leading cause of lung cancer.

The symptoms of smoking-related lung diseases may resemble other lung conditions or medical problems. Always consult your physician for a diagnosis.

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How dangerous is secondhand smoke?

Secondhand smoke, smoke that is exhaled by smokers and smoke emitted from the burning end of a lit cigarette, cigar or pipe, causes nearly 3,000 lung-cancer deaths each year in persons who do not smoke themselves. Also called involuntary or passive smoking, secondhand smoke also can lead to heart disease. The following symptoms are some of the most common associated with exposure to secondhand smoke; however, each individual may experience symptoms differently:

  • Irritation of the eyes, nose and throat.
  • Coughing. 
  • Excessive phlegm (mucus in the airways). 
  • Chest discomfort or pain.

Children and infants exposed to tobacco smoke are more likely to experience ear infections and asthma and are at a higher risk for sudden infant death syndrome than children and infants without the same exposure.

The symptoms of secondhand smoke may resemble other medical conditions and problems. Always consult your physician for a diagnosis.

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How does cigar smoking affect a person’s risk of lung cancer and other types of cancer?

Cigars became a trend in the 1990s, attracting adults of all ages. Perceived as less detrimental to one’s health, cigars actually pose the same, if not greater, risk as cigarettes for oral cancer. Although many cigar smokers do not inhale, their risk for oral, throat and esophageal cancers is the same as for cigarette smokers. Consider these facts:

  • Compared with nonsmokers, cigar smokers who inhale are eight times more likely to develop oral cancer, four to 10 times more likely to develop esophageal cancer and 10 times more likely to develop laryngeal cancer.
  • Cigar smokers who inhale and smoke five cigars a day run the same lung cancer risk as one-pack-a-day cigarette smokers. 
  • Secondhand smoke from cigars contains toxins and cancer-causing agents (carcinogens) similar to secondhand cigarette smoke, but in higher concentrations.

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What are the benefits of quitting smoking?

People who quit smoking can actually reverse some of the damage that has been done to their lungs over an extended period of time. Other benefits of quitting smoking may include:

  • Decreased risk of lung disease.
  • Decreased risk of heart disease. 
  • Decreased risk of cancer. 
  • Reduced cigarette stains on fingers and teeth. 
  • Reduced occurrence of a hacking cough. 
  • Elimination of stale cigarette smell on clothing and hair. 
  • Improved smell and taste.

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Quitting smoking

Quitting smoking is both a mental and a physical undertaking. Mentally, you should be ready and relatively stress-free. Physically, you need to commit to exercising daily and getting plenty of sleep. A person trying to quit must overcome two obstacles: a physical addiction to nicotine and a habit. The American Academy of Otolaryngology and the American Lung Association offer the following tips to help users quit using tobacco products:

  1. Think about why you want to quit.
  2. Pick a stress-free time to quit.
  3. Ask for support and encouragement from family, friends and colleagues. 
  4. Begin a daily exercise or activity to relieve stress and improve your health. 
  5. Get plenty of rest. 
  6. Eat a balanced diet. 
  7. Join a smoking cessation program, or other support group.

In some cases, smokers benefit from nicotine replacement products to help break their smoking habit. Nicotine replacement products continue to give the smoker nicotine, although in smaller quantities than a cigarette, to meet their nicotine craving. However, the benefit of nicotine replacement products is the elimination of tars and poisonous gases that cigarettes emit. Pregnant or nursing women and people with other medical conditions should consult with their physician before using any nicotine replacement products. Some examples of nicotine replacement products include:

  • Nicotine chewing gum – an over-the-counter chewing gum that releases small amounts of nicotine to help reduce nicotine withdrawal symptoms.
  • Nicotine patch – an over-the-counter patch applied to the upper body once a day that releases a steady dosage of nicotine to help reduce the urge to smoke. 
  • Nicotine inhaler or nasal spray – a prescription nicotine replacement product that releases nicotine to help reduce withdrawal symptoms (requires a physician’s approval before use).

Zyban, a non-nicotine alternative to help people stop smoking, was approved in 1996 by the U.S. Food and Drug Administration. Offered to smokers who want to quit, Zyban (Bupropion HCI), in pill form, has been shown to alter mood transmitters in the brain that are linked to addiction. Zyban must be prescribed by a physician and may not be appropriate for everyone. Consult your physician for more information.

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The genetics of lung cancer

The majority of lung cancers (90 percent) are due to cigarette smoking. A number of diverse genetic abnormalities have been identified in lung cancer cells. Some of these genetic abnormalities may be causal (i.e., responsible for initiating the development of cancer), while others may instead indicate the progression of the cancer.

Not everyone who smokes will develop lung cancer. Studies have identified that normal genetic variations in the population, known as “polymorphisms,” may make some individuals more likely to develop lung cancer if they smoke than other smokers without the polymorphism.

Genetic polymorphisms also may be important for nonsmokers. About one in six nonsmokers are exposed to tobacco smoke from smokers in their own homes. Certain genetic polymorphisms have been found to be associated with a statistically greater risk of lung cancer development, even in a person who has never smoked. This association may explain why relatives of persons with lung cancer, regardless of whether they smoke, have an increased chance (about double the general population) to develop lung cancer. Additional studies are needed to better understand these gene-environment interactions. Also, certain syndromes are associated with higher chances of lung cancer, such as Li-Fraumeni syndrome and Peutz-Jeghers syndrome.