Ultraviolet radiation and related exposures
Ultraviolet (UV) radiation is a type of electromagnetic radiation with wavelengths ranging from 100 to 400 nanometers, situated between X-rays and visible light. It is categorized into three types: UVA (315-400 nm), UVB (280-315 nm), and UVC (100-280 nm). This radiation is primarily sourced from sunlight and artificial sources like tanning beds. Exposure to UV radiation is linked to significant health risks, particularly skin cancers such as melanoma and nonmelanocytic skin cancers, caused primarily by DNA damage in skin cells. Factors influencing the risk of UV-induced skin cancer include the intensity and duration of exposure, as well as individual characteristics like skin type.
Historically, the harmful effects of UV radiation have been recognized since the early 20th century, leading to its classification as a known carcinogen by various health organizations. Preventive measures are strongly recommended to mitigate these risks, including the use of broad-spectrum sunscreens, protective clothing, and seeking shade. Awareness of the UV index and avoiding reflective surfaces can further enhance safety. Understanding the nature and risks of UV radiation is crucial for individuals, especially those with fair skin or those who are frequently exposed to sunlight or artificial UV sources.
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Ultraviolet radiation and related exposures
ROC STATUS: Solar radiation and exposure to sunlamps or sun beds, known carcinogens since 2000; broad-spectrum ultraviolet radiation (UVR), known carcinogen since 2002; ultraviolet A, B, and C (UVA, UVB, and UVC), reasonably anticipated carcinogens since 2002
ALSO KNOWN AS: UV, ultraviolet light, black light, UVR, UVA, UVB, UVC
RELATED CANCERS: Melanoma and nonmelanocytic skin cancers
DEFINITION: Ultraviolet light is electromagnetic radiation between X-rays and visible light in the spectrum, with wavelengths between 100 and 400 nanometers (nm). It is divided into long-wave UVA (315–400 nn), UVB (280–315 nm), and short-wave UVC (100–280 nm).
Exposure route: Through skin
Where found: Sunlight, tanning beds
At risk: Individuals chronically exposed to sunlight or occupationally exposed to ultraviolet (UV) light sources, especially those with fair skin
ETIOLOGY AND SYMPTOMS OF ASSOCIATED CANCERS: The damage caused by exposure to UV radiation depends on the intensity and wavelengths of the radiation, the duration of exposure, and many other highly individual factors. Cancers caused by UV radiation are based on damage to cellular deoxyribonucleic acid (DNA) and immune system suppression. Since UV radiation is absorbed efficiently by the skin, this is the primary carcinogenic target, and UV radiation-caused skin cancers occur mostly on sun-exposed areas. The interaction of UV 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 by releasing cytokines, induction of latent viruses, or mutations that cause functional changes in encoded protein molecules. Skin cancers are typically noted and diagnosed by inspection before producing systemic illness.
History:Hippocrates, a physician in Ancient Greece, recognized that depression was more common in winter and recommended sunbathing to treat medical and psychological maladies. Ultraviolet light as a component of sunlight and its interactions with matter were first demonstrated in the early 1800s. Ultraviolet radiation’s ability to injure the eyes was noted in 1843 in welders, and papers from 1889 confirmed that ultraviolet rays caused skin burns. An epidemiologic study published in 1907 first associated sun exposure and skin cancer. A causal relationship was demonstrated in a 1928 publication that described the induction of skin cancer in mice by exposure to UV radiation. In 1941, scientific studies in mice showed that UV light from artificial lamps could induce skin cancer in their ears. Throughout the 1950s and 1960s, scientists became confident that UV radiation led to damage to the DNA of skin cells, which could ultimately lead to cancer. This led to the International Agency for Research on Cancer’s classification of solar radiation as a carcinogen in 1992 and its designation as a known carcinogen by US agencies in the 2000s. The peak carcinogenic response of UVB at 310 nm was identified in 1975. Reducing UVB in favor of UVA rays is a strategy to reduce the carcinogenicity of tanning beds, although their dangers related to skin cancers are widely recognized, and medical professional suggest individuals should avoid their use. Liberal use of sunscreens and the implantation of physical barriers for sun protection are current recommendations to reduce the incidence of melanoma and other UV radiation-related skin cancers. Practical methods include: seeking out shady areas, wearing protective clothing, avoiding reflective surfaces like water and snow, wearing protective eyewear, and noting the forecasted UV index.
Bibliography
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