When it comes to exposure to ultraviolet (UV) light, there are no regulations set by the US Department of State. However, the American Conference of Government Industrial Hygienists (ACGIH) has issued limit values (TLV) for occupational exposure to UV rays, which are widely used as guidelines. This requires the strict application of exposure limit values, taking into account the effectiveness of different wavelengths of UV light in causing biological effects, in order to protect against overexposure in the workplace. It is important to understand that some wavelengths of ultraviolet light have a very significant effect, while others have a proportionately lower effect and others have virtually no effect, depending on the effect in question.
If there is a possibility that the eyes and face are exposed to UV radiation, a polycarbonate face protector with ANSI Z87.1-1989 UV certification should be used for protection. Most UV light sources will be broadband; however, single-emission lines can be produced from low-pressure gas discharges. The question is not whether an UV light source exceeds exposure limits, but whether exposure to an UV light source could cause a person to exceed exposure limits. Therefore, by definition, the effectiveness of ultraviolet light at this 270 nm wavelength is set at value 1.UV light exposure limits apply to personal exposure to incoherent UV light sources, such as arcs, gas and vapor discharges, fluorescent tubes, incandescent lamps, and LEDs.
Acute effects usually only occur if exposure to UV light exceeds a threshold, which usually varies from person to person. Broadband UV light sources consist of several monochromatic lines or a continuous spectral distribution, often with overlapping lines. UV exposure limit values are not intended to draw a dividing line between “safe” and “dangerous” UV light levels. What they do is define a level of exposure to ultraviolet light, below which it is believed that almost all people can be repeatedly exposed without adverse health effects.
The level of risk of adverse skin and eye health effects from exposure to UV light is determined by the wavelengths of UV light present, the irradiation values of UV light, and the time of personal exposure. This includes not only processes involving UV light, but also exposure to other artificial sources, including general lighting, which can contribute to a person's total exposure to UV light. The maximum allowable values of exposure to UV radiation are obtained from an enveloping action spectrum that combines the action spectra of photokeratitis and skin erythema. This provides the exposure to UV radiation necessary to produce these biological effects depending on the wavelength.
The limit values for exposure to ultraviolet light are intended to avoid any significant acute photobiological effects and reduce the risks of chronic effects (delayed effects) as far as possible by limiting lifetime exposure to UV rays. Exposure limit values apply to workers and people exposed to artificial sources of UV light where UV light irradiance values and duration of exposure can be controlled.
