What Are Carcinogens?

Carcinogens are certain substances that are known to be a contributory factor to the development of certain cancers or involved in its propagation. Cancer is a disease where the damaged cells in the body do not go through normal programmed cell death. Instead the damaged cells undergo abnormal growth and metabolism that the body no longer has control of. Carcinogens may help disrupt cellular metabolic processes or damage the DNA in cells directly.

Types of carcinogens

There are many types of carcinogens that exist naturally and with some of them produced through human means. The IARC, or the International Agency for Research on Cancer has classified the different types of carcinogens. The classification depends on their effect to humans.

  • Group 1– consist of substances or mixtures that are definitely carcinogenic to humans.
  • Group 2A– substances or mixture that is probably carcinogenic to humans associated to limited evidence or tests.
  • Group 2B– substances or mixtures that is possibly carcinogenic to humans.
  • Group 3– substances and mixtures unclassified according to its carcinogenicity to humans.
  • Group 4– substances and mixtures known to have no carcinogenic effects on humans.

Classifications of carcinogens are determined through laboratory testing and studies. Most carcinogens are first determined to cause cancer first in animals and then are later found to cause cancer in humans. Although it may not be possible to determine which substances can cause cancer by human and animal tests alone, all of those substances currently considered as carcinogens have been tested adequately to know for certain that they can cause cancer.

One way that scientists try to determine potential carcinogens is by exposing lab animals to high doses of certain substances usually higher than humans are commonly exposed to. If animals develop certain cancers after exposed to higher doses of a potential carcinogen, it is assumed that the same effect can happen to humans. Another way that scientists use to identify potential carcinogens is through epidemiologic studies. Such studies look into human populations and certain instances which can help them determine certain factors that can be attributed to cancer development.

Although such studies might be helpful, they also have their limitations since population studies lack the benefit of a controlled environment such as those that can be provided by laboratory studies. And with virtually thousands of substances to test out, most scientists now use the knowledge of identifying chemical structures of different substances in order to select potential chemicals for testing.


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