How do carcinogens cause cancer?
Carcinogens cause damage to our DNA, or cause cells to divide faster than their normal rate, thus causing cancer. See how cancer develops in "Cancer 101"
Carcinogens have different levels of cancer causing potential.
How are carcinogens classified?
- Group 1: Carcinogenic to humans
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Group 2A: Probably carcinogenic to humans.
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Group 2B: Possibly carcinogenic to humans.
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Group 3: Unclassifiable to humans
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Group 4: Probably not carcinogenic to humans.
Learn How Cancer Develops
Lung Cancer Symptoms
Lung Cancer 101: Understanding Lung Cancer
Smoking and Cancer from the National Cancer Institute
- Cigarette smoking causes 87 percent of lung cancer deaths and is responsible for most cancers of the larynx, oral cavity and pharynx, esophagus, and bladder.
- Secondhand smoke is responsible for an estimated 3,000 lung cancer deaths among U.S. nonsmokers each year.
- Tobacco smoke contains thousands of chemical agents, including over 60 substances that are known to cause cancer.
- The risk of developing smoking-related cancers, as well as noncancerous diseases, increases with total lifetime exposure to cigarette smoke.
- Smoking cessation has major and immediate health benefits, including decreasing the risk of lung and other cancers, heart attack, stroke, and chronic lung disease.

