What is electromagnetic radiation?
Related cancers: Skin cancers, especially melanoma; leukemia
Definition: Electromagnetic radiation is a form of energy, composed of individual oscillating photons. The amount of energy carried by each photon is proportional to its frequency. The collection of all possible frequencies of electromagnetic radiation is called the electromagnetic spectrum; this is subdivided (from highest to lowest frequency) into gamma rays, x-rays, ultraviolet (UV) light, visible light, infrared light, microwaves, and radio waves. Alternatively, electromagnetic radiation can be divided into ionizing and nonionizing frequencies based on its ability to disrupt electrons.
Exposure routes: Unshielded incident radiation
Where found: Electromagnetic radiation is pervasive, and life would not be possible without it. Sunlight is the most important source of ultraviolet and visible light. Many devices also emit electromagnetic radiation.
At risk: Individuals with occupational or volitional exposure to ionizing electromagnetic radiation
Etiology and symptoms of associated cancers: When electromagnetic radiation interacts with matter, some of the photons’ energy alters the structure or increases the kinetic energy of atoms. Structural alterations include ionization (loss of electrons) and breakage of covalent bonds. Deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and proteins are all susceptible to damage by radiation. The skin is the primary carcinogenic target, and UV-caused skin cancers occur mostly on sun-exposed areas. Shorter wavelength electromagnetic radiation such as x-rays and gamma rays penetrate the skin and can cause leukemia, lung cancer, and bone cancer. The interaction of electromagnetic radiation with DNA results in abnormal dimerization of adjacent pyrimidine bases, damage to individual bases, strand breakage, and cross-linkages between DNA and adjacent proteins. Such DNA damage contributes to cancer formation through the release of cytokines, induction of latent viruses, or mutations that cause functional changes in encoded protein molecules.
History: The biological effects of electromagnetic radiation in the form of sunlight have been known since antiquity. The understanding of visible light as part of a continuous spectrum was advanced with the discovery of radio waves in 1887 by Heinrich Hertz and of x-rays in 1895 by Wilhelm Conrad Röntgen. One of the first publications on the carcinogenicity of sunlight appeared in 1907, and a causal relationship was demonstrated by study in a 1928 publication that involved induction of skin cancer in mice by exposure to ultraviolet light. Cancers were linked to penetrating electromagnetic radiation (x-rays and gamma rays) shortly after the isolation and characterization of radioactive isotopes in the 1800s.
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