Sun, Skin & Cancer : On Beach, Slopes or in Salons, Tanning Is Dangerous, 14 Science Experts Conclude
Zonker Harris, the Doonesbury comic-strip character known for his great tan, got the message and went “pale” a few months ago. But for sun worshipers still denying the dangers of too much sun, a government panel issued a report recently that left no more room for doubt.
The 14-member panel, sponsored by the National Institutes of Health, spent two days examining the scientific evidence on the effects of sunlight and ultraviolet radiation on the skin. They concluded that tanning, whether it occurs on the beach, in a tanning parlor or on the ski slopes, is “deleterious to the skin.”
“Tanning is visible evidence of injury to the skin,” said David Bickers, chairman of the panel and director of the Skin Diseases Research Center at Case Western Reserve University in Cleveland.
That damage can be measured not just by sagging and wrinkling--signs of early aging--but also by an increased risk of skin cancer. Skin cancers caused by ultraviolet-radiation exposure, the kind found in sun rays, are now the most common form of cancer in the United States. In 1978, the latest year for which figures are available, half a million new cases of skin cancer were diagnosed.
The panel said recently that this figure is “probably a gross underestimate (for the number of cases) in 1989.” The reason: visits to the doctor for non-melanoma skin cancer treatment rose 50% in the past 10 years, at a time when visits for other ailments increased just 11%, reported Kenneth Kraemer, a dermatologist with the National Cancer Institute.
The amount of time spent baking in the sun is directly correlated with the risk of skin cancer. That is one reason why basal-cell carcinomas, the most common skin cancer found in Caucasians, form primarily on sun-exposed areas of the body, such as the face and neck.
Basal-cell carcinoma and squamous-cell skin cancer are far less deadly than melanoma--the most virulent type of skin cancer. “While the risk factors for melanoma . . . are less clear, it too has been associated with exposure to ultraviolet radiation,” the panel concluded.
Too much sun also causes changes in the immune system, and that may in turn increase the risk of other forms of cancer. Margaret L. Kripke, a researcher with M. D. Anderson Cancer Center in Houston, told the panel that only in the past several years have researchers discovered that ultraviolet radiation can modify immune function in animals. “There is increasing evidence that similar effects occur in humans exposed to UV radiation,” Kripke said.
For those who thought that they could simply slather on Retin-A to help erase sun-caused wrinkles and other damage, the panel’s advice is that there is no proof that it works. “Available evidence is insufficient to recommend the use of Retin-A and similar compounds for treating sun-induced wrinkles,” the panel concluded.
Because people who use Retin-A must continue it for the rest of their lives, one concern about the drug is whether its long-term use also could pose a cancer risk.
Ortho Pharmaceutical Co., the maker of Retin-A, said the company has completed studies of 2,000 patients who have used the drug to treat sun damage since 1985. The results, not yet made public, will be submitted later this year to the Food and Drug Administration. “We are very confident about that data,” an Ortho spokesman said.
The best bet for preventing both premature aging and skin cancer is to minimize sun exposure, especially between the peak hours of 10 a.m. and 3 p.m., the panel advised. More than 60% of the ultraviolet rays reaching the Earth’s surface do so during midday.
Children and adolescents who spend a lot of time outdoors playing or involved in sports are the most likely to be affected during these peak hours. Studies show that more than half of all lifetime sun exposure occurs before age 18.
For this reason, the panel advised parents and schools to change the time of outdoor activities. “Keep recess and recreation time away from those peak hours,” Bickers said.
Those who cannot avoid the sun need to take precautions when exposed, the panel said. They should start by wearing clothing “constructed of tight woven fabrics, long sleeves, long pants, (and the like),” they advised.
The next step is frequent and liberal use of sunscreens, with sun-protection factors (SPF) of 15 or higher. But a sunscreen with a very high SPF rating is not necessarily that much more protective. “There is no evidence to suggest that a sunscreen with an SPF of 44 is twice as good as one with an SPF of 22,” Bickers said.
What most sunscreens do not do is guard against the effects of ultraviolet A radiation--the longer-wave type known as UVA. Many studies in animals and humans suggest that UVB--the shorter-wave ray--is the more dangerous as far as causing cancer. But both types of rays penetrate the skin, and UVA is not without damaging effects, the panel noted. Studies of mice and guinea pigs show, for example, that UVA can damage DNA, cause redness and produce squamous-cell carcinoma.
For this reason, the panel said, “combination sunscreens that are effective against UVB and UVA are preferable.” Currently only one--Photoplex, which offers extensive protection against both--is on the market. It is available without prescription. Whatever sunscreen consumers choose, the panel said, should “be applied 30 minutes before exposure” and then frequently reapplied. Those living in the Sun Belt were advised to consider daily use of sunscreens for the best protection.
The panel also advised people taking regular medication of any sort to check with their doctor before going into the sun. Among the drugs that can react to sunlight are some oral antibiotics, blood pressure medicine, drugs to suppress the immune system and anti-inflammatory medication.
Worries about the possible cancer-causing effects of sunscreens themselves also surfaced in recent weeks. Lester Gurelik, a photochemist with the National Cancer Institute’s Cancer Prevention and Control Branch, told the panel that a class of chemicals called benzophenones, which are found in many sunscreens, may themselves help promote cancer. With sun exposure, benzophenones “produce intermediate chemicals that cause reactions in the skin that normally cannot occur,” Gurelik said. “These chemicals could potentially cause damage that might promote cancer.”
After reviewing the current scientific evidence, however, the panel said benefits of sunscreens clearly outweigh their risks. Benzophenones have been used for 10 to 15 years, Bickers said. “The panel has considered this at great length,” he said. “At the moment, the use of sunscreens is (deemed) safe.”
Despite all their precautionary warnings about sun exposure, the panel said they are not advising Americans to live hermit-like existences indoors.
“You have to lead a normal life,” said Maria Turner, a panel member who practices dermatology at George Washington University Medical Center. “I tell my patients to adopt a more Spanish life style. Play tennis at 4 p.m. Swim at 5 p.m., and children should not be out in the sun at noon.”
ANATOMY OF SKIN CANCER
BASAL-CELL CARCINOMA
May be a small pearly nodule, a red patch, or a smooth growth with a rolled border and an indented center. There may also be tiny blood vessels on the surface. Often on exposed areas, such as the back of hands and face, but may be elsewhere.
SQUAMOUS-CELL CARCINOMA
May be a thick, hard nodule with white or yellow scales, or a red, crusty patch. May ulcerate or bleed easily. Usually on exposed areas, including lips, but may be elsewhere.
MALIGNANT MELANOMA
Can be a lethal form of skin cancer. Usually a brown-black or multi-colored patch or nodule. Asymmetrical, raised shape, with an irregular border which may bleed easily. Usually on the upper back and also on the legs of women.
SOURCE: American Cancer Society, American Academy of Dermatology and Anatomy and Physiology by Dr. James Bevan
DANGER SIGNS: Asymmetry & Irregular Borders-- One half unlike the other half; scalloped or poorly circumscribed border.
Multicolored-- Color changes from one area to another. Shades of tan and brown; black; sometimes white, red or blue.
Size-- Diameter larger than 6mm as a rule, about the size of a pencil eraser. ULTRAVIOLET RAYS
Ultraviolet radiation from the sun is the main cause of skin cancer.
Ultraviolet A rays: Penetrate deeper than B rays. Harm is more long-term.
Ultraviolet B rays: Main cause of sunburn, they burn just the upper layers of the skin.
Ultaviolet C rays: Toxic to life, they are filtered out by the earth’s ozone layer.
