UV Awareness: Beginning to See the Light

Jul. 2, 2018

High summer is the most important time to think about protection from the harmful effects of Ultraviolet (UV) rays, the leading cause of skin cancer in the U.S. 

Two types of UV rays, UVA and UVB, damage the skin, which can lead to premature aging and skin cancers including melanoma, basal cell carcinoma, and squamous cell carcinoma. UV exposure also can cause cataracts and cancers of the eye.

But while most of us think of summer sun and surf when we think of UV dangers, there are other sources of ultraviolet light that are less obvious: sun glare from snow or sand, tanning beds, sunlight through clouds, welding arcs, black-light lamps and laboratory equipment, to name a few. UV exposure is also determined by factors such as time of day, season of the year and elevation. 

Outdoor Exposure

If you can’t stay in the shade, the best way to protect yourself from exposure to UV rays outdoors is to cover up. Especially between the hours of 10 a.m. and 4 p.m., wear wide-brimmed hats, long sleeves and pants, and sunglasses. If your outdoor activity makes this mode of dress impossible (or at least, spoils the fun), use sunscreen with at least SPF 15. Reapply every two hours—more often if sweating or swimming.  

The Centers for Disease Control reports that most t-shirts have an SPF below 15, so even if wearing a light shirt, sunscreen should be applied. In addition, a wet t-shirt offers less protection than a dry one. 

Indoor Exposure

The rumors are true—tanning beds are a bad idea. The CDC advises that indoor tanning is not safe, and that “a base tan is not a safe tan.” Due to health factors including increased risk of melanoma, many states ban the use of tanning beds by minors.

Sources of incidental indoor exposure to UV rays include “basking bulbs” for reptile habitats, black lights, xenon and xenon-mercury lights (used in disinfection, curing and to simulate sunlight) and damaged fluorescent or mercury-vapor lights (where protective outer coating is chipped or broken). 

Workplace Exposure

Plasma torches and welding arcs used in HVAC, plumbing and metalwork emanate intense light across the visible and nonvisible spectrum that includes UV rays. The most significant risk for working with these tools is eye damage; according to OSHA, personal protective equipment to shield workers and observers from light radiation includes safety glasses, goggles, welding helmets or face shields.

A rule of thumb for plasma cutting is to test visibility with a shade that is too dark to see the weld zone, and progress to lighter shades until the weld zone can be clearly seen, without going below the minimum recommended protective shade (determined by the arc current of the torch). 

Minimum shade numbers range from #4 for ampere levels below 20 to #10 for levels above 60 amperes. Approved safety glasses should be worn under a helmet or face shield.

In addition to eyewear, flame-resistant gloves and long sleeves should be worn to protect from UV burns as well as heat and flying sparks. 

Laboratory Exposure

Common sources of UV rays in the lab include transilluminators (for viewing nucleic acids), spectrometers, UV curing lamps, black lights and germicidal lamps. 

While many biosafety cabinets at Princeton are equipped with germicidal UV lamps, EHS discourages their use as a disinfectant because liquid disinfectants can be substituted for such lights. In addition to UV dangers, biosafety cabinet UV lights do not always reach all surfaces as effectively as liquid surface decontamination. 

Other engineering controls to reduce UV exposure include placement of UV-generating equipment away from common areas, minimizing or eliminating reflective areas inside and around UV-generating equipment, and access controls such as interlocks.

Lab workers who work with UV-emitting instruments should cover exposed skin with tightly-woven clothing such as a lab coat and gloves. Polycarbonate safety glasses and a face shield should be used to protect the eyes.

The American Conference of Governmental Industrial Hygienists (ACGIH) publishes Threshold Limit Values (TLVs) that have been adopted by Princeton as recommended exposure limits. UV surveys, conducted by EHS, use a UV detector to measure irradiance at potential exposure points and, if necessary, recommend measures to minimize or eliminate exposure. 

If you have a UV source, contact EHS (ehs@princeton.edu ; 609-258-5294) to set-up a UV survey to determine if you need to take special precautions to protect yourself.