UV light (specifically, UV‑B) causes the body to produce vitamin D, [46] which is essential for life. Humans need some UV radiation to maintain adequate vitaminD levels. According to the World Health Organization: [47] Coming of Age UV-C LED Technology Update". wateronline.com. Archived from the original on 20 April 2017.

Meyer-Rochow, V.B.; Järvilehto, M. (1997). "Ultraviolet colours in Pieris napi from northern and southern Finland: Arctic females are the brightest!". Naturwissenschaften. 84 (4): 165–168. Bibcode: 1997NW.....84..165M. doi: 10.1007/s001140050373. S2CID 46142866. Scott, K.J.; Wills, R.R.H.; Patterson, B.D. (1971). "Removal by ultra-violet lamp of ethylene and other hydrocarbons produced by bananas". Journal of the Science of Food and Agriculture. 22 (9): 496–7. Bibcode: 1971JSFA...22..496S. doi: 10.1002/jsfa.2740220916. Ultraviolet radiation is used in several food processes to kill unwanted microorganisms. UV can be used to pasteurize fruit juices by flowing the juice over a high-intensity ultraviolet source. The effectiveness of such a process depends on the UV absorbance of the juice. Couteau C, Couteau O, Alami-El Boury S, Coiffard LJ (August 2011). "Sunscreen products: what do they protect us from?". Int. J. Pharm. 415 (1–2): 181–184. doi: 10.1016/j.ijpharm.2011.05.071. PMID 21669263. The most deadly form of skin cancer, malignant melanoma, is mostly caused by DNA damage independent from UV‑A radiation. This can be seen from the absence of a direct UV signature mutation in 92% of all melanoma. [61] Occasional overexposure and sunburn are probably greater risk factors for melanoma than long-term moderate exposure. [62] UV‑C is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic. [63]

Optical properties of lens materials". Optician Online. 6 June 2005. Archived from the original on 26 October 2016.

Juzeniene, Asta; Moan, Johan (27 October 2014). "Beneficial effects of UV radiation other than via vitaminD production". Dermato-Endocrinology. 4 (2): 109–117. doi: 10.4161/derm.20013. PMC 3427189. PMID 22928066. Bhatia, Bhavnit K.; Bahr, Brooks A.; Murase, Jenny E. (2015). "Excimer laser therapy and narrowband ultravioletB therapy for exfoliative cheilitis". International Journal of Women's Dermatology. 1 (2): 95–98. doi: 10.1016/j.ijwd.2015.01.006. PMC 5418752. PMID 28491966. Although rechargeable batteries are preferable, the Esco Lite may be powered by regular disposable cells (three AA standard alkaline batteries, like others on our list). With completely charged batteries, it can operate for four to six hours. The greatest tactical flashlight can benefit from having this accessory. UV Flashlight with 51 LED by Vansky

Torma, H.; Berne, B.; Vahlquist, A. (1988). "UV irradiation and topical vitamin A modulate retinol esterification in hairless mouse epidermis". Acta Derm. Venereol. 68 (4): 291–299. PMID 2459873. Ultraviolet (UV) light has a wavelength between 10 nm and 400 nm, placing it outside of the visible range of electromagnetic energy. Light from UV sources, such as the UV torches listed above, is invisible to the human eye. On the contrary, it emits photons that combine with phosphorus to create a visible substance. Phosphorus reacts with UV radiation to produce the visible light you see.

Vacuum UV, or VUV, wavelengths (shorter than 200nm) are strongly absorbed by molecular oxygen in the air, though the longer wavelengths around 150–200nm can propagate through nitrogen. Scientific instruments can, therefore, use this spectral range by operating in an oxygen-free atmosphere (commonly pure nitrogen), without the need for costly vacuum chambers. Significant examples include 193-nm photolithography equipment (for semiconductor manufacturing) and circular dichroism spectrometers. Solar Water Disinfection". Sodis.ch. 2 April 2011. Archived from the original on 31 August 2012 . Retrieved 8 November 2011. James Bolton, Christine Colton, The Ultraviolet Disinfection Handbook, American Water Works Association, 2008 ISBN 978 1 58321 584 5, pp. 3–4ultraviolet radiation, that portion of the electromagnetic spectrum extending from the violet, or short-wavelength, end of the visible light range to the X-ray region. Ultraviolet (UV) radiation is undetectable by the human eye, although, when it falls on certain materials, it may cause them to fluoresce—i.e., emit electromagnetic radiation of lower energy, such as visible light. Many insects, however, are able to see ultraviolet radiation. In the past, UV‑A was considered not harmful or less harmful than UV‑B, but today it is known to contribute to skin cancer via indirect DNA damage (free radicals such as reactive oxygen species). [ citation needed] UV‑A can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. The DNA damage caused indirectly to skin by UV‑A consists mostly of single-strand breaks in DNA, while the damage caused by UV‑B includes direct formation of thymine dimers or cytosine dimers and double-strand DNA breakage. [64] UV‑A is immunosuppressive for the entire body (accounting for a large part of the immunosuppressive effects of sunlight exposure), and is mutagenic for basal cell keratinocytes in skin. [65] Davies, H.; Bignell, G.R.; Cox, C. (June 2002). "Mutations of the BRAF gene in human cancer" (PDF). Nature. 417 (6892): 949–954. Bibcode: 2002Natur.417..949D. doi: 10.1038/nature00766. PMID 12068308. S2CID 3071547. Archived (PDF) from the original on 5 August 2020 . Retrieved 30 November 2019.