UVC Safety and Health Effects

UVC Safety & Health Effects

Remember the Three Ps: People, Plants, Pets

• While the UVC light is being operated, the area being disinfected must be clear of People, Plants, and Pets.
• The disinfected area should remain unoccupied for a minimum of 30 minutes after the UVC light is turned off.
• When entering an area where a UVC light is operating (to turn the light off), always wear PPE (see below)

UVC Effects on Skin

Acute (short-term) effects of UVC exposure include redness and/or ulceration of the skin. With high levels of exposure, such burns can be quite serious. With chronic (long-term, repeated) exposure, there is also a cumulative risk, which varies depending on the amount of exposure through your lifetime. These long-term risks associated with large, cumulative exposure include skin cancer and premature aging of the skin.

Personal Protective Equipment (PPE)

UV radiation is readily absorbed by plastic, glass, or clothing, and once absorbed, it is no longer active. Therefore, when working with open UV radiation during operation, maintenance, service, or other situations, personal protective equipment to cover all exposed areas is recommended. When working around UVC light devices, one should:

• Wear UV goggles and/or a full-face shield
  

  Note: Prescription glasses and regular safety glasses DO NOT protect the eyes against UV exposure, so ANSI Z87 rated eyeglasses with wrap around lenses to protect the eyes from side exposure are recommended. It is advisable to consult with ANSI Z87 manufacturers to ensure that you have proper UV exposure protection equipment.

• Cover any exposed skin by wearing lab coats, nitrile gloves, and/or other lab attire.

Safety Design/Control/Monitoring/Maintenance

UVC exposure and risk can be reduced through product safety design considerations and controls. For example, wiring safety switches in series allows UVC light sources to be turned off without exposing operators to UV light. Placing ON/OFF switches for UVC light sources in a location separate from general room lighting, accessible only by authorized persons, and ensuring that switch locations are locked or password protected ensures that the UVC source will not be accidentally turned on. Each UVC system installation should have the option of a viewport so that operators can monitor the lamp assembly without the risk of overexposure to UVC.

Proper installation and monitoring, use of safety switches, education of maintenance personnel, and signage can all help to prevent overexposure. Operating instructions and recommendations for proper use of any UVC light system should be retained for reference. These should be clearly accessible for the operators and maintenance personnel and should include the specified temperature and relative humidity ranges for the system design to ensure safe operation and reduce hazardous exposure. Maintenance must be performed in accordance with the manufacturer’s instructions and electric power should always be shut off to prevent accidental activation and exposure. There are currently no standard guidelines related to monitoring UV equipment, but there are commercial UV monitors available that will detect output or leakage.

Response in the event of UV Exposure

The effects of acute (short-term) exposure to UV radiation are not usually severe and many symptoms will be delayed. In the event of UV exposure, it is recommended to take the following actions:

• If eye damage is suspected, visit an ophthalmologist.
• Immediately treat skin lesions.
• Follow your organization’s EHS incident reporting procedure. These will often require documentation indicating the date and time of the incident, the person(s) involved, the equipment involved, and the type of injury.

UV Light and Health Effects

Deep ultraviolet (UVC) light-emitting diodes (LEDs) are irradiation sources and they require appropriate precautions to ensure safe usage. This page contains information prepared to familiarize users with an understanding of many of the general practices and safety precautions recommended most often in the literature pertaining to UV irradiation sources It is not meant as a complete review on the topic. Currently, there are no workplace-related rules and regulations in regard to UVC health and safety that are set by OSHA (Occupational Safety and Health Administration).

UV Light Spectrum

The electromagnetic radiation spectrum has a UV range that extends from 10 nm to 400 nm. Depending on the wavelength and exposure time, UV radiation can cause harm to the skin and eyes.

The UV spectrum is broken into four parts:

• UVA (315 nm to 400 nm)
• UVB (280 nm to 315 nm)
• UVC (200 nm to 280 nm)
• UV Vacuum (100 nm to 200 nm)

Lower wavelengths correspond to higher frequency radiation and a increased energy per photon.



Biological Effects of UV Light

While UVB radiation is commonly known for its harmful effects on human skin and its links to skin cancer, all of the UV bands (UVA, UVB and UVC) present different risks for humans.

UVC radiation refers to wavelengths that are shorter than 280 nm. In nature, these wavelengths are entirely absorbed by Earth’s atmosphere, so no natural UVC radiation can reach the surface. However, these wavelengths are available for us to use through artificial sources, such as UVC LED lights, or mercury lamps. The intensity from point sources, such as UVC LEDs, falls off as 1/d2 (1 over distance squared), and once it gets past the scattering length, the intensity falls off exponentially. In simple terms:

1) The further away the UVC source is from a person, the lower the dose they are exposed to, and

2) The absorption length in human skin of UVC radiation is extremely short, so almost no UVC radiation can penetrate to the living cells in the skin. All the absorption occurs in the surface dead cell layers.

In rare cases, prolonged, direct exposure to UVC light has been shown to cause temporary eye and skin damage, such as cornea damage (sometimes called “welder’s eye”) This usually heals after a few days. Safety recommendations for UVC LEDs include protecting the skin (particularly open wounds) and, more importantly, the eyes from exposure to UVC radiation.

“In any case, UVC is strongly attenuated by chromophores in the upper epidermis (Young, 1997) and UVC-induced DNA damage in the dividing basal layer of human epidermis is not readily detected (Campbell et al, 1993; Chadwick et al, 1995) which may explain why the dose response curve for UVC erythema in human skin is very much less steep than for UVB (Diffey and Farr, 1991). It is unlikely that UVC from artificial sources presents an acute or long-term hazard to human skin. However, UVC is likely to cause acute photokeratitis… UVC exposure is unlikely to cause acute or long-term damage to the skin but can cause severe acute damage to the eye and should not be permitted at all from any tanning device.”

The same study referenced above laid out the minimum health and safety requirements relating to the exposure of workers to risks stemming from artificial optical radiation (2006/25/EC) - albeit regarding all UV bands combined: “Exposure limit value for UV (180-400nm) is 30 J/m2 (= daily value of 8h)”

Ultraviolet Germicidal Irradiation: Current Best Practices

"Ultraviolet germicidal irradiation (UVGI) is the use of ultraviolet (UV) energy (electromagnetic radiation with a wavelength shorter than that of visible light) to kill or inactivate viral, bacterial, and fungal species. The UV spectrum is commonly divided into UVA (wavelengths of 400 nm to 315 nm), UVB (315 nm to 280 nm), and UVC (280 nm to 200 nm). The entire UV spectrum can kill or inactivate many microorganisms, but UVC energy provides the most germicidal effect, with 265 nm being the optimum wavelength."




"Scenario: Workers using ultraviolet (UV) lamps may have skin or eye exposure to stray ultraviolet light emissions. Such workers need to know acceptable levels of irradiance (measured in milliwatts per square centimeter (mW/cm2)) and how to monitor for stray radiation. The exposed UV dose would be in units of millijoules per square centimeter (mJ/cm2). [In most cases, the UV lamp would be a low pressure mercury lamp, so almost all the UV light is at 253.7 nanometers (nm).]"

"The ionizing radiation standard covers alpha, beta, gamma, and X-rays; neutrons; high-speed electrons and protons; and other atomic particles; but does not include sound or radio waves, or visible, infrared, or ultraviolet light. Therefore, there are no OSHA-mandated employee exposure limits to ultraviolet radiation."