Avoiding UV Exposure in the Workplace
Research laboratories are challenging places to work safely. This month the Safety Guys alert you to a potential significant radiation hazard present in the workplace: UV. UV is short for ultraviolet light. And most of us remember from high school science class that UV represents a small band on the electromagnetic spectrum and that the sun is our largest source of UV. Perhaps many of us work with UV daily and are well versed in the science of electromagnetic radiation. But even so, we’ll begin with a basic UV review.
UV is a form of nonionizing radiation found within the electromagnetic spectrum between X-rays and visible light, and is generally divided into three classes based upon wavelength: UV-A with a wavelength of 315 to 400nm (black light); UV-B with a wavelength from 280 to 314nm (erythermal), prevalent in sunlight; and UV-C with a wavelength from100 to 280nm (germicidal), used by the germicidal lamps found in biosafety cabinets and laminar-flow hoods. The sun is a major source of UV-A and UV-B. UV-C is almost never observed in nature because it is absorbed completely in the atmosphere before reaching the Earth’s surface.
Let’s take a look at the indoor stuff
Hazards of UV do not distinguish between work and home, and in addition to sunlight, UV sources are found in the workplace, including in labs, mechanical rooms, and shops. Sources include some biosafety cabinets, certain types of handheld light sources, transilluminators, crosslinkers, and some laboratory instruments, such as spectrophotometers. We do see the occasional accident report resulting from non-sunlight UV exposure. According to the Health Physics Society:1 “Accidental UV overexposure can injure unaware victims due to the fact UV is invisible and does not produce an immediate reaction… Reported UV accident scenarios often involve work near UV sources with protective coverings removed, cracked, or fallen off. Depending on the intensity of the UV source and length of exposure, an accident victim may end up with a lost-time injury even though he or she was totally unaware of the hazardous condition.”
UV germicidal lamps, such as in biosafety cabinets, are designed to emit UV-C radiation because of its ability to kill bacteria. Welding operations, though not common in the lab, can be found associated with maintenance activities, and also produce UV-C. In humans, UV-C is typically absorbed in the outer dead layers of the skin. Overexposure to UV-C can cause corneal burns, commonly termed welders’ flash. UV burns to the eye are often described as a “sand in the eye” feeling and are often reported to be very painful. No one should ever work in a biosafety cabinet (BSC) with the UV lamps on, and in reality, 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 have UV lamps inside. The glass top allows the light to shine on the gel, causing the DNA to “glow,” but this also 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, there are various types of after-market shields that can be attached that may also provide good protection. We have heard of accidents in which lab workers have used inappropriate shielding, thinking it was rated for UV when, in fact, it was not. The UV shields/covers should be checked regularly for cracks or other damage.
Access to rooms with open-source transilluminators should be controlled and posted with a warning sign indicating that face and other skin protection is needed to enter when a transilluminator is in use. The protection required is standard laboratory apparel and includes a fully buttoned lab coat, gloves, long pants, and closed-toe shoes. While working with UV radiation sources, lab workers must be careful to prevent gaps in clothing that will expose the skin, such as around the neck and wrists. In addition to the standard lab attire, a polycarbonate face shield labeled for UV protection (as opposed to just glasses/goggles) should be worn to protect the eyes and face. It is not uncommon for lab workers to receive facial burns in the areas not covered by the goggles or glasses.
One more consideration is that there are many common medications that increase an individual’s photosensitivity and resultant susceptibility to UV-related burns. You should review all your medications with your pharmacist or physician to determine if any of them increase your risk for UV-induced damage.
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.
You might be in for a burn
Exposure to sunlight can be a concern for anyone working in outdoor locations, even those with responsibilities for brief outdoor activities. The exposure guidelines for the general public for sun exposure are certainly applicable to the workplace as well. There is plenty of literature and general information on the use of protective clothing and sunscreens, and on limiting exposure in the middle of the day. 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 good lightweight fabrics that are cool yet provide good UV protection.
Use a sunscreen with a sun protection factor (SPF) of 15 or higher: The SPF number only indicates the protection against UV-B rays. Sunscreens labeled as “broad-spectrum” protect against both UV-A and UV-B radiation, but there is no standard system for measuring protection from UV-A rays at this time. Products that contain avobenzone (Parsol 1789), ecamsule, zinc oxide, or titanium dioxide are likely to offer some protection against most UV-A rays.
Be sure to apply the sunscreen properly: Always follow the label directions. 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. UV-blocking sunglasses can help protect your eyes from sun damage.
Limit direct sun exposure during midday: Another way to limit exposure to UV light is to avoid being outdoors in intense sunlight for too long. UV rays are most intense during the middle of the day, usually between the hours of 10 AM and 4 PM. If possible, schedule outdoor work in the early morning and late afternoon instead. Note: This can also help limit heat exposure.
We have just gotten warmed up
There is no excuse or need for any excess UV exposure in the lab, as it is so easily controllable. We all like some rays of sunshine in our lives, and we would never suggest a vampirelike existence (we Safety Guys do get our share of outdoor time in Florida, surfing, biking, sailing, and kayaking), but we have learned to limit our exposures to the harmful UV rays through timing, sunscreens, effective clothing, and shade. We hope you do the same. Until next issue remember—SAFETY FIRST!
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/