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What are Carcinogens in Cigarettes? How Do They Cause Cancer?

Carcinogens and Cancer


Updated October 18, 2005

Carcinogens are any substance that cause cancer. Carcinogens are classified by a health organization called the International Agency for Research on Cancer (IARC). IARC is part of the World Health Organization.

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

  • Group 2A: Probably carcinogenic to humans.

  • Group 2B: Possibly carcinogenic to humans.

  • Group 3: Unclassifiable to humans

  • Group 4: Probably not carcinogenic to humans.

One of the best way to protect yourself from cancer is to avoid smoke and second hand smoke. Cancer death from smoking is one of the most preventable types of death. Avoiding other known carcinogens is beneficial as well.

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.

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