The sun and skin

by Larry G. Barratta, M.D., Ph.D.

Traveling to any exotic destination where sun, surf and beach activities are involved and where there are concerns of being overexposed by the sun can be the beginning of more than just a bad case of sunburn. Skin cancer is a serious health condition that comes in several forms, melanoma being the most aggressive and a potentially deadly type. Other skin cancers include basal and squamous cell carcinoma.

Nearly 50,000 cases of melanoma are diagnosed in the U.S. each year. It has afflicted luminaries like Senator John McCain and the late Maureen Reagan. But before I get into describing the disease, it is important for you to know that the sun emits several types of radiation.

The radiation is known as ultraviolet (UV) radiation or invisible rays or, more commonly, “sunburn rays,” which cannot be seen by human eyes. They are classified in three types: UV-A, UV-B and UV-C. The differences between the three are related to their individual wavelengths. UV-C, for example, cannot reach Earth’s surface because it is trapped by the atmospheric ozone layer.

Although small amounts of UV radiation are beneficial to people and play an essential role in the production of vitamin D, overexposure to UV radiation from UV-A and UV-B leads to a bad case of sunburn and skin cancer.

UV-A rays are the main cause of premature aging of the skin. They cause wrinkles, age spots and loss of skin elasticity.

UV-B rays cause the most immediate damage to skin in the form of sunburn. These rays penetrate the skin and activate the pigmented cells that produce melanin, which results in a darker complexion or tan. UV-B rays are the primary cause of skin cancer, especially when combined with the UV-A rays. Interestingly, the fatigue that one feels after laying out in the sun all day is a result of the effects of UV-B rays, as it depresses the immune system.

Several factors that influence the effects of ultraviolet radiation include cloud cover, under which UV radiation levels are lower; altitude, where higher altitudes’ thinner atmosphere absorbs less UV radiation, and the ozone layer, which absorbs some UV radiation that would otherwise arrive at the Earth’s surface.

Among resultant problems of prolonged UV ray exposure is skin cancer. Although there are other types of skin problems that can develop from sun exposure, melanoma will claim over 7,500 lives per year in the U.S.

Even though it is the least common type of skin cancer, melanoma is the most serious form and its frequency in the U.S. is increasing considerably. Characteristically, melanoma is curable if caught in the early stages and is rarely curable if it is diagnosed later.

Melanoma is more frequently seen in white or fair-skinned individuals, older adults and men. Several risk factors have been identified that attribute to the development of melanoma. They include a family history of melanoma; presence of abnormal-looking moles; an increase in the number of moles on an individual’s body, usually 50 or more; having light-colored skin, and having a history of severe sunburns as a child that have had blistering characteristics.

The single most important cause of melanoma is overexposure to the sun. The sun, through the emission of UV radiation, damages the DNA in the skin cells, or melanocytes, that contain the pigment melanin. As the melanocytes become abnormal, they grow frenziedly and invade surrounding tissue aggressively. Melanoma may only affect the skin, but it has been known to travel to other organs via the lymphatic system or the blood.

Early warning signs of melanoma consist of a change in a mole or other skin growth. Any change in the shape, size or color may indicate melanoma.

Typically, melanoma has the appearance of a flat brown or black mole with uneven or irregular borders, and the skin lesion does not have a symmetrical or regular appearance. However, melanomas have been known to change color and to be rounded or lumpy and may bleed and ooze and have a crusty appearance.

A melanoma is diagnosed by physical examination of the skin; if suspected, a skin biopsy is conducted.

Protection from the sun to help prevent or decrease an individual’s risk to developing any skin cancer, particularly melanoma, can take several forms.

• Avoid the sun. The sun and UV radiation is most intense between 10 a.m. and 2 p.m. An incredible 50% of daily UV exposure is received two hours before and two hours after 12 noon.

• Clothing is an excellent tool for sun protection. Wearing garments that are tightly woven and loose fitting can repel UV-A and UV-B rays. Clothing provides a physical block that does not wash or wear off, and protection lasts all day.

A wide-brimmed hat that covers the neck and ears and is made of sun-protective material is beneficial. A hat with at least a 4-inch brim all the way around is preferred; baseball caps do not protect the back of the neck or the ears.

• Sunglasses can block both UV-A and UV-B rays. Wearing sunglasses protects eyes from cataracts, damage to the retina, macular degeneration and cancer of the eyelid.

• Limit exposure to surfaces that have reflective properties such as water, snow, sand and concrete. Water activities such as swimming, boating and fishing will significantly increase exposure to reflected UV rays.

Sunscreens have emerged onto the market as a panacea for preventing skin cancer and reducing the amount of sun exposure. Sunscreens have been rated according to what is commonly known as SPF. SPF stands for “sun protection factor.”

The SPF number is determined through an indoor experiment that exposes human subjects to a light spectrum meant to imitate noontime sun. Some of the subjects wear sunscreen and others do not. The amount of light that provokes redness in sunscreen-protected skin divided by the amount of light that causes redness in unprotected skin is the SPF. It is predominately a calculation of UV-B protection and ranges from one to 45 or above.

Some sunscreens contain a chemical known as PABA. PABA stands for para-aminobenzoic acid. This chemical has been known to cause allergies. Check the labels of sunscreen and if you are allergic to this chemical, make sure to purchase PABA-free products.

A sunscreen with an SPF of 15 filters 92% of the UV-B. In other words, a sunscreen with an SPF of 15 will delay the onset of sunburn in a person who would otherwise burn in 10 minutes to burn in 150 minutes. The SPF 15 sunscreen allows a person to stay out in the sun 15 times longer.

Clothing also can be a measured by SPF, and some has SPF protection, like nylon stockings, SPF 2; hats, SPF 3-6; summer-weight clothing, SPF 6.5, and sun-protective clothing, up to SPF 30.

Dr. Larry G. Baratta is chief medical officer of Passport Health (www.passporthealthusa.com), with clinics nationwide.

Next month in this column, Dr. Alan M. Spira will write on medical organizations that help keep travelers healthy and safe.