Overexposure to the Sun Can Happen Indoors and Outdoors

Skin and Daily Sun Exposure

In the car, at work or walking to and from a store, you can't escape the sun's ultraviolet (UV) rays. However, new research about the transmission of UV light through window and automobile glass and through sunglasses, has led to developments that can help protect people from the sun.

"People should realize that even during everyday activities they are receiving incidental sun exposure which harms the skin as it accumulates and can result in premature aging, wrinkles and even skin cancer," said dermatologist Henry W. Lim, M.D., chairman of the department of dermatology, Henry Ford Hospital in Detroit, Mich., and co-author of the Journal of the American Academy of Dermatology article entitled, "Photoprotection by window glass, automobile glass and sunglasses." "Dermatologists and manufacturers of glass products and sunglasses are continually working to find better ways to decrease the amount of UV radiation being filtered through these items to the skin and eyes. These advances are helping to reduce the amount of UV exposure that a person receives on a daily basis.

UV radiation from the sun comes in two forms: ultraviolet A (UVA) and ultraviolet B (UVB). UVB has long been associated with sunburn while UVA has been recognized as a deeper penetrating radiation that contributes to premature aging and wrinkle formation. Both of these types of rays have been linked to the development of skin cancer. More than 1 million new cases of skin cancer are diagnosed each year.

Window Glass and Photoprotection
Window glass filters out UVB rays, but UVA rays are still transmitted to the skin through the panes. The type of glass and the type of coating on the glass can affect the percentage of UV radiation that is transmitted to the body.

Most residential buildings have one of three types of glass: clear, tinted or reflective. Of these three, reflective glass, the kind that eliminates the ability to see the interior of a building from the outside during the day, minimizes unwanted solar heat gain and reduces UV transmission to less than 25 percent. This means nearly one-quarter of the UV exposure, exclusively the longer wavelength UVA, is reaching the inside though, remarked Dr. Lim.

"Most Americans spend 80 percent of their day indoors at work or school," stated Dr. Lim. "With the new trend in architecture toward more and larger windows in buildings, protection from UV exposure when indoors has become an important issue for not only the cost-effectiveness of cooling a building, but also for the health and safety of the employees who work within it."

Recent developments in window glass include low-emissivity (low-E) glass which has a special surface coating between layers of antireflective glass. This type of glass reflects up to 70 percent of solar heat and reduces UV transmission through the panes to 20 percent.

To protect the skin from the damaging rays of the sun when working indoors, it is important to: arrange workspace so that the body is not in direct sunlight; and use blinds or shades on the windows during peak sun hours.

Automobile Glass and Photoprotection
In studies of UV exposure in cars, it was shown that the parts of the driver's and passenger's bodies closest to the window received the greatest UV exposure. Side and rear windows are usually made from non-laminated glass, allowing a significant amount of UVA to pass through to the passengers in the car. Most windshields are made from laminated glass, the type of glass designed to prevent fragments from shattering onto the occupants during an accident and which can filter both UVB and a large portion of the UVA rays.

Tinting automobile glass is an option that allows 3.8 times less UVA light to be transmitted to the interior of the car as compared to untinted window glass. In a 2004 study of UV transmission and color tint, grey tinted laminated glass provided the highest UV protection with only 0.9 percent of UVA light transmitted versus 62.8 percent transmitted through non-laminated clear glass. People who are considering tinting their windows should take their car to a professional auto detailing shop, in order to ensure that the tinting meets the federally mandated 70 percent of minimum visible light transmittance through the windshield.

"Obviously UVA exposure in a car is influenced by non-glass-related factors such as position of the individual in the vehicle, direction of travel with respect to the sun, and time of day," stated Dr. Lim. "However, the more time a person spends in a car, especially at the same time of day such as during a regular commute, can greatly affect the amount of UV exposure their skin receives."

To reduce sun exposure while driving, wear protective clothing, such as a long-sleeved shirt and pants, especially when the body is in the sun; apply sunscreen generously to any exposed skin before driving, especially the hands, forearms and face; and wear protective sunglasses to reduce glare and protect the eyes from UV exposure.

Sunglasses and Photoprotection
UV radiation is potentially hazardous to the structure of the eyes, particularly the cornea, lens and retina, which is why the U.S. developed a "sunglass standard," with the latest version published in 2001. Sunglasses are classified into three categories: cosmetic sunglasses providing minimal UV protection; general purpose sunglasses designed to reduce glare in bright light or when driving; and special purpose sunglasses for activities such as skiing or going to the beach.

"The ideal sunglasses should substantially reduce UV exposure of the cornea and the lens, including any UV coming from lateral directions, and should wrap around the eyes, thereby maximizing eye and eyelid protection," said Dr. Lim. "For even better protection, wear a broad-brimmed hat which can help reduce the level of UV radiation reaching the eyes and the surrounding area."

In addition, Dr. Lim recommended the following tips when purchasing sunglasses to maximize UV protection:

• Look for neutral gray and amber brown lenses that give true color rendition, particularly to red and green stoplights.

• Seek glasses with a large frame and lenses that cover the entire eye and wrap around the side of the eye.

• Look for the "100% UV Protection" sticker to ensure that the sunglasses meet standards for safe levels of UV protection.

Expensive sunglasses do not necessarily provide better UV protection, according to Dr. Lim. Darkly tinted sunglasses can make pupils dilate and increase lid opening, thereby resulting in increased UV exposure to the lens of the eye.

In addition to wearing sun protective clothing, including sunglasses, you should follow these sun protection tips and Be Sun SmartSM:

• Generously apply sunscreen to all exposed skin using a Sun Protection Factor (SPF) of at least 15 that provides broad-spectrum protection from both ultraviolet A (UVA) and ultraviolet B (UVB) rays. Re-apply every two hours, even on cloudy days, and after swimming or sweating.

• Seek shade when appropriate, remembering that the sun's rays are strongest between 10 a.m. and 4 p.m.

• Use extra caution near water, snow and sand as they reflect the damaging rays of the sun which can increase your chance of sunburn.

• Protect children from sun exposure by applying sunscreen.

• Get vitamin D safely through a healthy diet that includes vitamin supplements. Don't seek the sun.

• Avoid tanning beds. Ultraviolet radiation from the sun and tanning beds causes skin cancer and wrinkling. If you want to look like you have been in the sun, consider using a sunless self-tanning product, but continue to use sunscreen with it.

• Check your birthday suit on your birthday. If you notice anything changing, growing, or bleeding on your skin, see a dermatologist. Skin cancer is very treatable when caught early.