Sun Protection Simplified

Posted on Wed., June 17, 2009
By Sonika Shah, M.D.

MRS. BIRDIE, an avid golfer, was shocked to learn that the rough patches on her face and arms were not only pre-cancerous but also the result of decades of sun exposure. She, like many, believed her darker skin tone protected her.

Sun exposure is the most preventable risk factor for all skin cancers, including the most deadly form: malignant melanoma. However, you can still have fun in the sun while lowering your risk of skin cancer.

Sunlight contains two types of harmful ultraviolet rays: UVA and UVB. UVA rays, which pass through window glass, comprise 98.7% of the ultraviolet radiation that reaches Earth's surface. Thought of as the sun's aging rays, UVA rays cause wrinkling and age spots as well as weaken the immune system. UVB rays, the sun's burning rays, which are blocked by window glass, are the primary cause of sunburns. Both UVA and UVB radiation can cause skin cancer. A tan is the skin's response to injury caused by UV radiation, both natural and artificial. Unfortunately, there is no safe way to tan.

Clothes are your best form of protection from the sun. Wear light-colored, long-sleeved clothing, a wide-brimmed hat and UV light-blocking sunglasses, ideally, ones that wrap around the sides of the eyes. Most fabrics that are not see-through provide reasonable protection, but the new microfiber nylons are very sun protective.

Sun Protection Factor (SPF) is a rating based on UVB blocking ability. The higher the SPF, the greater the protection from UVB rays, but not proportionately. For example, SPF 15 screens 93% of UVB rays, while SPF 30 screens 97% of UVB rays. Think of SPF as a time multiplier; i.e. if a person typically burns in 10 minutes, using an SPF of 15 means that it would take 15 times longer to burn, in this case 150 minutes. Dermatologists recommend a sunscreen and lip balm with SPF 30 or higher.

Most people only apply 20-60% of the amount of sunscreen required to obtain the labeled SPF rating. It takes at least 1 ounce (about the amount to fill a shot glass) to cover an average adult.

To achieve the SPF factor labeled, you will need:

More than ½ teaspoon for each: head and neck, right arm, left arm
More than 1 teaspoon for each: chest and abdomen, back, right leg, left leg
A broad-spectrum (UVA and UVB protection) sunscreen, ideally water-resistant, should be applied every day to exposed skin of all types 15-30 minutes before going outdoors. Even on cloudy days up to 80% of the sun's UV rays can reach the earth.

Remember the word "BLOCKED" to be sun smart:

Broad spectrum (UVA/UVB) sunscreen with SPF 30 or higher.
Look over your birthday suit on your birthday. If you notice anything growing, changing or bleeding, see your health care provider.
One ounce of sunscreen is the minimum needed to cover the average adult.
Clothes are the best protection when in the sun.
Keep out of the sun between 10 a.m. and 4 p.m., when the sun's rays are strongest. If your shadow is shorter than you are, seek shade.
Eyes — Use sunglasses with 100% UVA/UVB protection.
Daily sun protection is a year-round habit for all ages and skin types.

Dr. Shah is a board-certified internist affiliated with Contra Costa Regional Medical Center in Martinez.