By Nick Casey

Dermatologist John Starr, above, examines a sequence of tissue samples from a patient.

May is National Skin Cancer Awareness Month, and with summer just around the corner, area dermatologists are renewing warnings about the disease that claims nearly 10,000 lives each year.

“I often encourage people to ask themselves whether they would want to sleep next door to a nuclear power plant,” said Dr. John Starr, a Palo Alto dermatologist. “What we don’t realize is that the sun is the same - it’s a big radiation emitter.”

According to the Skin Cancer Foundation, more than 1.5 million new cases of skin cancer are diagnosed every year in the United States. One in five Americans and one in three Caucasians will develop skin cancer in their lifetimes. Incidences of melanoma - the deadliest form of skin cancer - are rising faster than those of any other cancer. Approximately 8,000 people die of melanoma every year.

“This is the month to start taking measures,” Starr said. “This means sunblock and a hat with at least a 3-inch brim.”

The summer poses a serious threat not just because high temperatures encourage lighter clothing. As the Earth’s position to the sun changes during the weeks following spring, UVA and UVB radiation levels skyrocket as the sun’s ultraviolet light strikes the planet’s surface more directly. The emissions between 10 a.m. and 4 p.m. are the strongest.

While UVA is considered the primary threat to the skin - constituting 99 percent of UV radiation reaching the Earth’s surface - the remaining 1 percent of UVB is also quite harmful. UVB has a shorter wavelength and carries more energy, so even small quantities can cause significant damage.

Starr’s office has a variety of hats that the dermatologist sells his patients. He cautioned against wearing baseball caps because they offer limited protection.

In addition to a good hat, people should not forget sunscreen with a sun protection factor (SPF) of at least 15, he said. At least 1 teaspoon should be applied to each arm, 2 teaspoons for each leg, with at least 1 to 2 ounces of lotion to cover the body overall.

Sunscreen is not a one-time-only affair, however. Most sunscreens sold in the United States are made using Parsol 1789, a chemical that becomes ineffective 90 minutes after application.

“What’s important then is the reapplication,” Starr said.

Sunshine may not be the only contributor to skin cancer. Tanning salons have recently taken some heat. While their machines offer an ideal tan without the risk of burning the skin, the risk of cancer actually may be increased, experts say.

“They typically run UVA radiation into the skin,” said Dr. Siavosh Vossough, a Los Altos-based dermatologist. “Usually people think this isn’t harmful because it’s the UVB that causes sunburning. But there’s plenty of evidence to prove that UVA is also harmful to the skin.”

Despite the risks, tanning salons remain popular. Last year, an estimated 28 million Americans visited one of the more than 25,000 tanning salons in the country.

If skin cancer does develop, it can take a variety of forms. Most new skin cancers - roughly 800,000 cases every year - are basal cell carcinomas, a form of cancer arising in cells at the bottom of the epidermis, or outer skin layer. In the past, basal cell carcinomas were typically found among older men working outdoors. But recent years have seen a sharp decline in the average age of onset as well as an increased incidence among women.

The second leading skin cancer is squamous cell carcinoma, which affects approximately 200,000 Americans a year. While basal cell carcinomas originate from the bottom of the epidermis, squamous cell carcinomas develop on its outermost layer. If not treated immediately, squamous cell carcinomas may penetrate deeper into underlying tissues and cause permanent disfigurement.

Most carcinomas can be removed surgically; only in rare cases do they spread to other parts of the body. Doctors become highly concerned when the pigment-producing melanocyte cells become damaged, resulting in a third form of cancer known as melanoma.

If treated early, melanoma is almost 100 percent curable. But if allowed to metastasize, treatment becomes difficult and the cancer may prove fatal. Melanoma claims roughly 80 percent of annual skin-cancer related deaths. Last year, California was ranked third-highest in number of melanoma diagnoses, after Texas and Florida. Nationally, the number is on the rise: In 2005, there was a 10 percent increase in new melanoma cases from the previous year.

Dermatologists suggest patients learn the warning signs of cancerous tumors. Individuals are encouraged to check all new moles frequently for signs of asymmetry and border irregularity.

Color and size are also key warning signs. Moles displaying multiple colors should be given immediate attention, as should any growths with a diameter of more than 6mm, roughly that of a pencil eraser. Cancerous moles may also exhibit bleeding, scabbing or a slow changing of position on the body.

“Obviously, early detection is key,” Starr said.

It’s not only dermatologists who are encouraging us to protect ourselves against the sun. “Our eyes are getting exposed to more UV than they used to,” said Dr. Alejandro Zaffaroni, a Los Altos-based ophthalmologist.

Zaffaroni encourages residents to remember a pair of sunglasses in addition to their hat and sunscreen this summer. Studies show expensive and inexpensive sunglasses provide about the same level of protection. But people should be sure that their sunglasses indicate 400 UV protection, the highest level.

In light of the dangers, it’s easy to forget that sunshine - which provides the stimulant of serotonin and Vitamin D - is a very pleasurable part of life. With a few simple safety precautions and greater awareness about skin protection, most people will not have to worry about the frightening consequences of epidermal damage.

“Our tag-line is this,” Starr said. “We’re living longer these days. If you expect to live to 100, you take good care of your teeth. If you want your skin to last a century, the same goes for it, too.”

For more information, visit the American Academy of Dermatology at www.aad.org or the Skin Cancer Foundation at www.skincancer.org.