On the electromagnetic spectrum, ultraviolet radiation (UVR) is found between visible light and x-rays, and is divided into three components: UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm).[1,2] Based on genotoxicity studies, UVC is the most genotoxic of the three components; UVA is the weakest. Artificial sources of UVR emit a range of wavelengths specific to each source. Artificial UVR may be used in occupational settings (medicine, industry, business and research) as well as for cosmetic and domestic purposes (sunlamps and sunbeds). Welding arcs and UV lasers are also sources of artificial UVR.
Ultraviolet radiation with wavelengths in the range of 100 nm to 400 nm (including UVA, UVB and UVC), along with UV-emitting tanning devices, have been classified by IARC as Group 1 carcinogens, carcinogenic to humans, with links to skin and ocular melanoma. For artificial tanning devices, the risk for developing melanoma was prominently and consistently increased in people who first used the equipment in their twenties or teen years. There is also sufficient evidence for ocular melanoma in welders, but a causal relation between UV exposure in welding and ocular melanoma cannot be established due to concurrent exposures during welding. Fluorescent lights also emit UVR. However, studies examining the relationship between melanoma of the skin and exposure to fluorescent lights at work have produced conflicting results and fluorescent lights were classified by IARC as Group 3, not classifiable as to its carcinogenicity to humans.[1,5]
Exposure to UVR may result in short term skin damage such as burning, fragility and scarring; in addition to carcinogenic effects, long term exposures may result in collagen breakdown and decreased skin elasticity. Data suggest that the use of indoor tanning facilities may produce detrimental effects on the skin's immune response. The use of certain prescription drugs or exposure to industrial chemicals such as coal tar distillates may cause hypersensitivity to UVR, and fair skinned individuals are at greater risk of adverse outcomes following UVR exposure.
The American Conference of Governmental Industrial Hygienists (ACGIH) recognizes ultraviolet radiation as an occupational hazard and recommends different exposure threshold limit values (TLVs) for different UV with wavelengths in air between 180 and 400 nanometres. The recommend TLVs published in 2011 are shown in a figure below. Many Canadian provincial jurisdictions, such as British Columbia, Saskatchewan, Manitoba, New Brunswick, Nova Scotia, and Newfoundland and Labrador adopt ACGIH TLVs as occupational exposure limits.
Guidelines for Tanning Salon Owners, Operators and Users
Food and Drugs Act: Medical Devices Regulations
Radiological Health Protection Act (NB)
Radiation Health and Safety Regulations (SK)
Guidelines for Tanning Salon Operators (BC)
Major Sources of Artificial UVR
Electric welding arcs can produce significant levels of UVR within a radius of several metres; gas welding and cutting torches do not produce high levels of UVR.
Artificial UVR is used in medical and dental practices for procedures such as the treatment of skin diseases and neonatal jaundice, cavity detection and treatment, and for chronic conditions such as seasonal affective disorder (SAD) and sleep disorders.
Curing lamps emit intense artificial UVR to harden resins and dry paints; these processes are usually enclosed but openings in the enclosure may lead to overexposure. Germicidal lamps, commonly used for sterilizing materials in hospitals, are strong emitters of UVB and UVC radiation. Halogen, xenon and metal halide lamps can emit artificial UVR; black lights, incandescent and fluorescent lamps do not generally present a high exposure risk.
Ultraviolet lasers, which emit a single invisible wavelength of UVR, are used industrially and medically.
Occupations with potential for exposure to artificial UVR include welders and tanning appliance operators, as well as workers in industrial photo-processes, sterilization and disinfection (sewage effluents, drinking water, swimming pools, operating rooms and research laboratories), non-destructive testing, printing, phototherapy, UV photography, UV lasers, food industry quality control, and discotheques.[3,4]
Artificial UVR exposure may be mitigated through engineering controls (such as enclosures), however in some applications workers can be exposed by reflection or scattering from adjacent surfaces, a phenomenon which is of particular concern for tanning appliance operators.
Cosmetic tanning appliances, which may be referred to as sunbeds, sunlamps, or tanning beds, are the main source of artificial UVR exposure for the general public.[1,3] It has been estimated that powerful tanning units may emit UVR with an intensity 10-15 times greater than that of the midday sun.
Current tanning appliances emit primarily UVA radiation, although recently tanning lamps have been manufactured to produce higher levels of UVB in order to mimic the solar spectrum and speed the tanning process. Indoor tanning facilities are most commonly used by younger women (< 35 yrs) in North America and Northern Europe.
The Canadian Cancer Society has endorsed the World Health Organization's recommendation that no person under 18 should use artificial tanning equipment.