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Both UVA and UVB destroy vitamin A in skin, which may cause further damage. [64] UVB radiation can cause direct DNA damage. [65] This cancer connection is one reason for concern about ozone depletion and the ozone hole. The most deadly form of skin cancer, malignant melanoma, is mostly caused by DNA damage independent from UVA radiation.
While low, there is still some power of a conventional blacklight in the UVB range. [14] UVA is the safest of the three spectra of UV light, although high exposure to UVA has been linked to the development of skin cancer in humans. The relatively low energy of UVA light does not cause sunburn.
There are four UVB types of lamps: Fluorescnt Broad-Band UVB that emit 280-330 nanometer, Fluorescent Narrow-Band that emit 312 nanometer, Excimer that emit 308 nanometer and LED that emit 290-300 nanometer. PUVA means UVA + psoralen. It consists of irradiation of the skin with the UVA ultraviolet light, from a fluorescent bulb or LED lamps.
UVA light presents at wavelengths longer than UVB (between 400 and 315 nm); and it can also be absorbed directly by DNA in skin cells, but at lower efficiencies—about 1/100 to 1/1000 of UVB. [25] Exposure to radiation (UVA and UVB) is a major contributor to developing melanoma. [26]
It is important to use sunscreen because psoriasis patients can be at a higher risk for developing certain types of cancer, ... spectrum” to indicate protection against UVA and UVB rays. SPF 30 ...
In contrast, fluorescent UVB lamps come in two types: broadband (or wideband) and narrowband. Broadband UVB lamps have a peak wavelength of 306 nanometers. Since only a small portion of their spectrum falls near the optimal 297 nanometers, these lamps require a higher dose of 0.5 joules per square centimeter.
Light therapy for skin conditions like psoriasis usually use 313 nanometer UVB though it may use UVA (315–400 nm wavelength) or a broader spectrum UVB (280–315 nm wavelength). UVA combined with psoralen, a drug taken orally, is known as PUVA treatment. In UVB phototherapy the exposure time is very short, seconds to minutes depending on ...
However, UVB will cause the formation of freckles and dark spots, both of which are symptoms of photoaging. With constant exposure to UVB rays, signs of photoaging might appear and precancerous lesions or skin cancer may develop. UVA rays are able to penetrate deeper into the skin as compared to UVB rays.