What is Carcinogen?
[[File:Wellasbestdach-233-3358 IMG.JPG|thumb|[[Asbestos]] is a carcinogen. The roof of this house is made of asbestos.]] [[File:Solid benzene.png|thumb|Frozen [[benzene]]. Benzene is a carcinogen]] [[File:Aspergillus flavus 01.jpg|thumb|[[Aspergillus flavus]], a kind of [[mould]], produces [[Aflatoxin]] B1, which is a carcinogen.]] '''Carcinogens''' are [[substance]]s that cause [[cancer]]. Sometimes [[radiation]] or [[radionuclide]] are also considered carcinogens. A common example of a carcinogen is [[tobacco]] smoke. Carcinogens come from both natural and man-made substances.<ref>{{cite journal | doi = 10.1016/S0027-5107(99)00194-3 | title = Paracelsus to parascience: The environmental cancer distraction | year = 2000 | last1 = Ames | first1 = Bruce N | last2 = Gold | first2 = Lois Swirsky | journal = Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis | volume = 447 | issue = 1 | pages = 3–13| pmid = 10686303 }}</ref> ==Carcinogens in radiation== Several radioactive substances are considered carcinogens. The carcinogens in them are caused by the radiation they release, such as [[gamma ray]]s or [[alpha particle]]s. [[CERCLA]] says that all radionuclides are carcinogens. How much of a carcinogen a radiation is depends on the type of radiation, the type of exposure to it and its penetration. For example, alpha radiation has low penetration and is not a danger outside the body. Alpha radiation is a carcinogen when breathed in or eaten. [[Thorotrast]], previously used in [[x-ray]]s, is a human carcinogen. [[Marie Curie]], one of the pioneers of radioactivity, died of a cancer that was caused by the radiation she was exposed to during her experiments. Not all types of electromagnetic radiation are carcinogenic. [[Radio wave]]s, [[microwave|microwave radiation]], [[infrared radiation]], and [[visible light]] are examples of this. Higher-energy radiation, including [[ultraviolet radiation]], usually ''is'' carcinogenic, if a person is exposed to it long enough. ==Carcinogens in food== Recen