U V is the initialism for ultraviolet light. UV light is a small band on the electromagnetic spectrum between visible light and X-rays. Sunlight is our largest source of UV light. However, UV light is important in research, medical, and indoor air quality applications. UV light equipment in biological safety cabinets, germicidal lamps, transluminators, and Wood’s lamps can all have harmful effects.
UV, a form of nonionizing radiation, is generally divided into three classes based on wavelength: UV-A, with a wavelength of 315 to 400 nm (a black light, for example); UV-B, with a wavelength from 280 to 314 nm (eurythermal), prevalent in sunlight; and UV-C, with a wavelength from 180 to 280 nm (germicidal), such as the germicidal lamps found in biosafety cabinets (BSCs), laminar flow hoods, and large commercial air handler units. Sunlight is a major source of UV-A and UV-B light. UV-C is almost never observed in nature because it is absorbed completely in the atmosphere before reaching the Earth’s surface.
Hazards of UV light
The hazards of UV light from sunlight are well publicized. However, UV light sources are also found in the workplace, including labs, mechanical rooms, and shops. Sources include BSCs, certain types of handheld light sources, transilluminators, crosslinkers, and laboratory instruments such as spectrophotometers. According to the Health Physics Society: “Accidental UV overexposure can injure unaware victims due to the fact UV [light] is invisible and does not produce an immediate reaction.… Reported UV accident scenarios often involve work near UV [light] sources with protective coverings removed, cracked, or fallen off. Depending on the intensity of the UV [light] source and length of exposure, an accident victim may end up with a lost-time injury even though totally unaware of the hazardous condition.”1
UV germicidal lamps, such as in BSCs and HVAC air handlers, are designed to emit UV-C radiation because of its ability to kill bacteria and molds. Welding operations associated with maintenance activities also produce UV-C. Overexposure to UV-C can cause corneal burns, commonly termed welder’s flash.
UV burns to the eye are often described as a “sand in the eye” feeling and are often reported to be very painful. One should never work in a BSC with the UV lamps on, and the UV lamps should not be on when the room is occupied.
Transilluminators or UV light boxes are used for visualization of DNA on gels. They typically look like flat boxes with glass tops and UV lamps inside. The glass top allows the light to shine on the gel, causing the DNA to “glow,” which potentially exposes the user. To reduce risk of injury, most models today come equipped with a shield to block the UV light. For older models, install after-market shields rated for UV light to provide protection. Check the UV shields/cover regularly for cracks or other damage.
Related Article: Don't Get Burned!
Control access to rooms with open source transilluminators and post a warning sign indicating face and other skin protection is needed to enter when a transilluminator is in use. The protection required is standard laboratory apparel including a fully buttoned lab coat, gloves, long pants, and closed-toe shoes. In addition to the standard lab attire, a polycarbonate face shield labeled for UV protection (as opposed to just glasses/goggles) is needed to protect the eyes and face and prevent facial burns. In addition, lab workers should take care to prevent gaps in clothing that will expose the skin, such as around the neck and wrists.
Safety glasses that protect from laboratory-generated UV radiation must be stamped with ANSI Z87.1. It is important to note that polycarbonate safety glasses will not protect from high-radiant UV energy sources such as torch cutting, welding, or lasers. Specialized safety glasses are required for safe operation of these devices.
Another warning: there are many common medications that increase an individual’s photosensitivity and a resultant susceptibility to UV-related burns. Review all your medications with your pharmacist or physician to determine whether any increased risk for UV-induced damage is associated with your medication.
In the United States, occupational exposure guidelines for UV radiation have been established by the American Conference of Governmental Industrial Hygienists.2 Handheld meters for measuring UV radiation are commercially available, but expert advice from a qualified industrial hygienist or health physicist is recommended to ensure selection of the correct detector and diffuser for the UV wavelengths emitted by the source.
Let’s not forget about sunlight
Exposure to sunlight can be a concern for anyone working in outdoor locations. The American Cancer Society3 offers the guidance summarized below to help prevent skin cancer:
Cover up: Wear long pants and long sleeves when working in the sun. There are now lightweight fabrics that are cool yet provide good UV protection.
Use a sunscreen with a sun protection factor of 15 or higher: Sunscreens labeled as “broad spectrum” protect against both UV-A and UV-B radiation. Apply the sunscreen properly and often: Almost all sunscreens require reapplication for effective protection throughout the day.
Wear a hat: A hat with at least a 2- to 3-inch brim all around is ideal because it protects areas often exposed to the sun, such as the neck, ears, eyes, forehead, nose, and scalp.
Wear sunglasses that block UV rays: Long hours in the sun without protecting your eyes increase your chances of developing eye disease.
Limit direct sun exposure during midday: UV rays are most intense during the middle of the day, usually between the hours of 10 a.m. and 4 p.m. If possible, schedule outdoor work in the early morning and late afternoon instead.
1. Ultraviolet Radiation, Gary Zeman, Health Physics Society, MacLean, VA. August 2011 http://hps.org/hpspublications/articles/uv.html
2. Threshold Limit Values and Biological Exposure Indices, American Conference of Governmental Industrial Hygienists, Cincinnati, OH. 2011 http://www.acgih.org/
3. Be Safe in the Sun, American Cancer Society, Atlanta, GA. 2013 http://www.cancer.org/healthy/besafeinthesun/
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