Hazards of Ultraviolet Light


UV or ultraviolet lamps are used in biological safety cabinets, light boxes, and cross linkers in many University laboratories and in some patient care rooms. One of the problems in working with UV radiation is that the symptoms of overexposure are not immediately felt so that persons exposed do not realize the hazard until after the damage is done.

UV radiation is that radiation just outside the visible range, or under 400 nanometers (nm). There are three ranges of UV (see table below).

Region Also known as *Range in nm Hazard Potential Damage Mechanism (High Exposures)
UV-A near UV 320-400 lowest cataracts
UV-B mid UV 290-320 mid to high **skin or eye burns
UV-C far UV 190-290 highest skin or eye burns

*Early "black lights" emitted in the range of 360-390 nm.
** Increased risk of some types of skin cancer.


A University lab employee received skin and eye burns while using an acrylic plastic shield for protection against UV. The lab did not realize that the shield had not been manufactured for this use and was not rated for protection against UV light. Please check your safety equipment to ensure that it is rated for the wavelength in use.

Ineffective shielding


Germicidal lamps emit radiation almost exclusively in the far-UV range of 254 nm, and are commonly used in Laminar Air Flow hoods or biological safety cabinets and should be treated with extreme caution. DO NOT expose yourself to these lights!

The UV light box is another source in use in the laboratory. This instrument is literally a box with a glass top and a UV lamp inside. Some units have multiple lamps that allow a choice of wavelength. Most of these instruments are stationary, but there are a few hand held types that carry the same hazards as the stationary models. Nucleic acid (DNA or RNA) which has been stained with the chemical Ethidium Bromide, lights up when exposed to UV light.

What makes Ethidium Bromide an excellent stain, also makes it toxic and mutagenic. It should never be used without gloves!

An apparatus called a UV-Crosslinker is used to literally "cross-link" to covalently attach nucleic acid to a surface or membrane following Southern blotting, Northern blotting, dot blotting, and Colony/Plaque lifts. Since the DNA will be used in place, a 254 nm wavelength is used to maximize adherence.

Adapted from the California Campus Environmental Health & Safety Association Winter 1995 Newsletter What You Should Know About UV Light.

UV Warning Sign


The biological effects of the 3 regions vary greatly as implied by the "hazard potential" column in the table. The health effects of exposure to UV light are familiar to anyone who has had a sunburn. However, the UV light levels around some UV equipment greatly exceeds the levels found in nature. Acute (short-term) effects include redness or ulceration of the skin. At high levels of exposure, these burns can be serious. For chronic exposures, there is also a cumulative risk of harm. This risk depends upon the amount of exposure during your lifetime. The long-term risk for large cumulative exposure includes premature aging of the skin and even skin cancer.

UV exposure is not immediately felt . . . the user may not realize a hazard until after the damage is done.

The eyes are also susceptible to UV damage. Like the skin, the covering of the eye or the cornea, is epithelial tissue, too. The danger to the eye is enhanced by the fact that light can enter from all angles around the eye and not only in the direction you are looking. The lens can also be damaged, but since the cornea acts as a filter, the chances are reduced. This should not lessen the concern over lens damage however, because cataracts are the direct result of lens damage.

Burns to the eyes are usually more painful and serious than a burn to the skin. Make sure your eye protection is appropriate for this work. There are specially-made safety glasses for the different UV ranges. NORMAL EYEGLASSES OR CONTACTS OFFER YOU VERY LIMITED PROTECTION!!

You must not forget to protect the rest of your face, too. Severe skin burns can happen in a very short time, especially under your chin (where most people forget to cover). Full-face shields are really the only appropriate protection when working with UV light boxes for more than a few seconds.

Be sure to protect your arms and hands by wearing a long-sleeve lab coat and gloves.


How do I know if my eye protection is rated for UV safety? Look for a symbol indicating a rating for UV protection or check with the manufacturer. If no information is available, you may contact by phone: Radiation Safety Office or by e-mail: radsaf@u.washington.edu to arrange for test measurements.

How can I work safely around a bio cabinet or germicidal lamp? The UV lamp should never be left on when the hood is open. Even a small opening at the bottom of the cabinet can exceed occupational exposure standards several feet away.

What if our lab has overhead germicidal lamps and/or area sterilizer? These devices are extremely hazardous. They should never be left on when the room is occupied. Contact radsaf@u.washington.edu for appropriate signage if you have overhead or area UV germicidal lamps.

How would I know if exposure from a UV emitting device is excessive? Call Radiation Safety at 206.543.0463 or e-mail: radsaf@u.washington.edu to schedule a UV safety survey. Be sure to mention your name, telephone number, the room number, and the type of device you are working with.