#98-09 Contact: Mona S. Rowe, or Kara Villamil
EMBARGOED UNTIL 2/17/98, 12:30 p.m.
SUNSCREENS THAT STOP SUNBURN
DON'T ALWAYS PREVENT SKIN CANCER
Melanoma Rates May Have Risen Due to Inadequate Protection
PHILADELPHIA - Just because a sunscreen keeps you from getting sunburned doesn't necessarily mean it will prevent all skin cancers, a researcher from the U.S. Department of Energy's Brookhaven National Laboratory reports.
In fact, says noted radiation effects researcher Richard Setlow, the use of sunscreens that don't block all the harmful rays in sunlight may actually be partly to blame for the steady five percent annual rise in melanoma rates among whites. And, he says, any depletion of the global ozone layer may not lead to more melanomas after all because the most cancer-causing rays already pass through the layer.
Dr. Setlow, a senior biophysicist at BNL, presented his team's findings today at the annual meeting of the American Association for the Advancement of Science. "Traditionally, sunscreens have only blocked the transmission of a kind of ultraviolet light in sunlight that's known as UV B," Setlow said. "That's the range of wavelengths that cause sunburn, or erythema. It's also the kind of UV that the DNA in our cells absorbs most easily."
"But we have found that another range of wavelengths, collectively called UV A, may be much more powerful in causing skin cancers called melanoma," Setlow continued. "Our research shows that about 90 percent of sunlight's melanoma-causing effect may come from UV A and only 10 percent from UV B." Still, he said, UV B is the chief cause of other skin cancers besides melanoma.
The distinction between the two kinds of UV light makes a difference, Setlow said, when sunlight encounters the Earth's dwindling ozone layer. "Since the ozone layer only blocks UV B, depleting it probably won't cause melanoma rates to rise any faster than they are already." But, he added, ozone depletion will probably still worsen other effects in humans, animals and plants alike.
"Brookhaven researchers such as Dr. Setlow have contributed immeasurably to our knowledge of the health effects of radiation," said Energy Secretary Federico Peña. "I'm glad that the Department of Energy's expertise in this area can help educate Americans on important public health issues."
Because studying skin cancer causes in humans would take decades, Setlow and his team reached their conclusions about UVA's danger by studying a special hybrid fish. Called Xiphophorus, the fish lack most of the genes needed to prevent melanoma.
After extrapolating their fish results to humans, Setlow and his colleagues found confirmation for their theory in a comparison of epidemiological studies of melanoma rates among Australians and Norwegians, and in a study of melanoma among sunscreen users and non-users in Europe.
Melanoma, called "the most serious form of skin cancer" by the American Cancer Society, is a cancer of pigment-producing skin cells that is expected to strike about 41,600 persons in 1998. Since 1973, the incidence rate of melanoma has increased about 4% per year from 5.7 per 100,000 people in 1973 to 12.5 per 100,000 people in 1994. The ACS says it expects an estimated 9,200 skin cancer deaths this year, 7,300 from melanoma and 1,900 from other skin cancers.
Setlow has devoted decades to the study of the biological effects of UV light and other forms of radiation. Most recently, he chaired the Committee on Health Risks of Exposure to Low Levels of Ionizing Radiation, Phase I, convened by the National Research Council of the National Academy of Sciences. In 1996, he chaired the NRC committee that studied the potential health effects from long-term exposure to space radiation.
A 1988 winner of the Enrico Fermi Award, the most prestigious scientific honor given by DOE, Setlow is also BNL's Associate Director for Life Sciences. He holds a 1947 Ph.D. in physics from Yale University, and has worked at BNL since 1974.
Brookhaven National Laboratory carries out basic
and applied research in the physical, biomedical and environmental sciences
and in selected energy technologies. Brookhaven is operated by Associated
Universities, Inc., a nonprofit research management organization, under
contract with the U.S. Department of Energy.