Q: In my office, I sit under a large skylight atrium window. You’ve said that ultraviolet rays penetrate windows. How can I can tell how much I’m being exposed to?
A: You should ask the building manager whether the skylight is made of glass or plastic (usually acrylic or polycarbonate) and whether it has been treated to reduce ultraviolet (UV) transmission.
Some plastics used in skylights naturally block a substantial amount of UV, and many are treated in addition. Plain glass screens out nearly all ultraviolet-B rays (most responsible for sunburn), but less than half of ultraviolet-A rays (the cause of premature skin aging); both kinds increase the risk of skin cancer. Like other glass windows, skylights can be treated with a film that blocks more than 99 percent of all UV rays.
Building and home owners generally choose skylights that filter out some sunlight (and block most of its UV) because the light can fade furniture, curtains, artwork, and rugs as well as heat up rooms in the summer.
Research has shown that workers stationed near untreated glass windows have more signs of skin aging such as wrinkles and sagging skin on the side of the face usually exposed to the sunlight, according to the Skin Cancer Foundation. The low-level skin damage accumulates over the years. The amount of your UV exposure depends in part on your distance from and orientation to the skylight.
If you are getting a lot of direct light through the skylight (or from a south-facing window), and the building manager says it is untreated glass, ask to have it treated—or ask if you can be moved. Installers of window film can be found online or in the Yellow Pages under “glass tinting” or “glass coatings.” Some products carry a seal of recommendation from the Skin Cancer Foundation. For more information about how to make your home and office sun-safe, go to the Foundation's website.
Keep in mind, however, that natural light in workplaces is generally a good thing. Studies have found that workers exposed to natural light report improved mood, sleep, vitality, and mental performance as well as higher quality of life overall, which is why some companies design their offices with skylights and large windows.