Carcinogens in the environment
Carcinogens in the environment are substances or physical agents that can cause or exacerbate cancer, posing significant health risks globally. These agents can stem from various origins, including naturally occurring chemicals, synthetic compounds, physical sources like radiation, and infectious diseases. Chemical carcinogens include both naturally found compounds, such as aflatoxins and arsenic, and synthetic substances like benzene and formaldehyde. Furthermore, certain minerals like asbestos and gases such as radon are recognized as carcinogenic.
Physical agents contribute to the carcinogenic landscape as well, with ultraviolet radiation and gamma rays being notable examples. Additionally, infectious agents like human papillomavirus (HPV) and various hepatitis viruses have been linked to specific cancers. Exposure to these carcinogens can occur through occupational settings, contaminated environments, or lifestyle factors, with tobacco smoke being a pervasive environmental risk factor.
The mechanisms by which carcinogens induce cancer vary: they may damage DNA directly, alter metabolic processes, or involve viral interactions with host genetic material. Individual susceptibility to these agents is influenced by exposure duration, frequency, and genetic predisposition, underlining the complexity of cancer development in relation to environmental carcinogens.
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Subject Terms
Carcinogens in the environment
DEFINITION: Substances or physical agents that cause or worsen cancer
The effects of human exposure to carcinogens in the environment may include the development of different types of illness, deaths, and economic obligations on a national and global scale.
Cancer is a leading cause of death throughout the world. Environmentalists and others have raised concerns regarding the cancer-causing (carcinogenic) potential of to a constantly growing number of both newly developed and long-existing chemicals in the environment. In addition, humans seem to be increasingly exposed to various sources of electromagnetic waves, such as microwaves, and some groups and individuals are concerned about the possible carcinogenicity of these physical phenomena.
Carcinogens can be categorized based on their origin as chemicals (naturally occurring or synthetic), physical agents, or infectious agents. Chemical carcinogens can be classed as compounds that occur naturally, such as aflatoxins, chromium 6 compounds, and arsenic compounds; and others that are largely synthetic in origin, such as benzene, formaldehyde, vinyl chloride, and dioxins. In addition there are carcinogenic minerals, such as asbestos. Other carcinogenic chemicals are elements or substances such as radon (a radioactive gas), beryllium, and cadmium. Some carcinogens—such as tobacco and alcoholic beverages—are mixtures of compounds. Physical agents that are carcinogens include solar (primarily ultraviolet radiation), gamma rays, and x-rays.
Infectious disease agents that have been implicated as carcinogens include human papilloma virus (HPV), which can cause cervical cancer; Helicobacter pylori (H. pylori), a bacterium causally associated with stomach cancer; the hepatitis C and hepatitis B viruses, which can cause liver cancer; Epstein-Barr virus, which is associated with Burkitt’s lymphoma; and human T-lymphotrophic virus type 1 (HTLV-1), which has been linked to leukemia in adults. The human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), has been associated with Kaposi’s sarcoma. Viruses have also been shown definitively to cause tumors in animals such as mice (mammary tumor virus), chickens (Rous sarcoma virus), and Tasmanian devils.
Exposure to carcinogens can be related to work environments, such as in the case of workers in the nuclear power and medical radioisotope industries. Sometimes carcinogenic agents happen to be concentrated in particular geographic regions; for example, widespread exposure to the carcinogen arsenic occurred in Bangladesh as the result of contaminated drinking water from a large number of wells that accessed in which arsenic was uncommonly abundant. Exposure to H. pylori is believed to occur through contaminated water supplies and thus is considered to be environmental in origin. Tobacco smoke, a major cause of lung cancer, is an environmental carcinogen to which people are widely exposed.
Carcinogens may lead to cancer by directly damaging deoxyribonucleic acid (DNA), as in the case of radiation; through conversion through metabolism; or through effects on metabolism. In the case of viruses, viral genetic material may be incorporated into host DNA at sites of oncogenes, which are genes whose altered function or disruption leads to cancer. Different carcinogens often lead to effects on different organs, thus H. pylori is associated mainly with stomach cancer, whereas tobacco smoking or use is associated with lung, oral, and laryngeal cancers (and also bladder, colon, and kidney cancers, among others), and is primarily linked to lung cancer. The time period and frequency of exposure to carcinogens as well as a person’s genetic background can also influence the likelihood that a carcinogen causes cancer.
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