carcinogenicity

Carcinogenicity is the property of a substance or agent that has the potential to cause cancer. Carcinogens can be chemicals, physical factors such as ionizing or ultraviolet radiation, or biologic agents such as certain viruses. Carcinogenesis usually results from a series of genetic and epigenetic changes that lead to uncontrolled cell growth and tumor formation. The risk depends on the level and duration of exposure as well as individual susceptibility.

Most carcinogens act through one or more mechanisms. Some are genotoxic, damaging DNA directly or causing mutations that can initiate cancer. Others are non-genotoxic, promoting tumor development by chronic inflammation, hormonal disruption, or enhanced cell proliferation. Cancer development typically involves initiation, promotion, and progression, and there may be long latency between exposure and disease onset. Dose, timing, and coexisting risk factors influence risk.

Evidence for carcinogenicity comes from epidemiologic studies, laboratory animal experiments, and mechanistic data. Regulatory agencies summarize this evidence in classification schemes such as the International Agency for Research on Cancer (IARC) groups. Group 1 includes agents carcinogenic to humans; Group 2A probable; Group 2B possible; Group 3 not classifiable; Group 4 probably not carcinogenic. Well-known examples include tobacco smoke, asbestos, certain ultraviolet rays, hepatitis B and C viruses, and aflatoxins. Alcohol consumption is also considered carcinogenic to humans for several cancer types.

Public health responses focus on reducing exposure, substituting safer alternatives, and regulatory limits. Communication to workers and consumers, along with surveillance and risk assessment, guide policies aimed at preventing cancer without imposing unnecessary burdens.