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Title : SKIN CANCER INCIDENCE, ULTRAVIOLET RADIATION BENCHMARKS SET Type : Press Release NSF Org: OD / LPA Date : November 18, 1993 File : pr9386 Cheryl Dybas December 18, 1993 (202) 357-9498 NSF PR 93-86 SKIN CANCER INCIDENCE, ULTRAVIOLET RADIATION BENCHMARKS SET Significant increases in ultraviolet (UV) radiation and skin cancer incidence are expected from the depletion of stratospheric ozone between 1979 and 1992, according to new estimates published in the November 4 issue of the British journal, Nature. The report is authored by Sasha Madronich, a scientist with the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, and F.R. de Gruijl, a dermatologist with Utrecht University in the Netherlands. The National Science Foundation supported the research. "UV radiation has been implicated in the induction of skin cancers in fair-skinned people," explains Madronich. "Reductions in stratospheric ozone are expected to allow more solar ultraviolet to reach the earth's surface." The figures are based on an analysis of the 14-year record of atmospheric ozone from the Total Ozone Mapping Spectrometer (TOMS) aboard the Nimbus 7 satellite. They update an earlier calculation published by Madronich, and based on the 1979-89 TOMS data. By combining ozone data with a computer model of the UV propagation through the atmosphere, Madronich estimated the long-term increase for several UV wavelengths known to cause erythema (sunburn) in humans, damage to in vitro DNA molecules and skin cancer in laboratory mice. The UV increases were then combined with data on skin cancer induction to calculate the percentage of increases in non-melanoma skin cancer incidence for different latitudes. The results are shown in the attached table. Madronich and de Gruijl found statistically significant increases at middle and high latitudes of both hemispheres. They found no significant changes for the tropics. Although the highest percentage increases are found in the polar region, skin cancer is relatively uncommon there because of the low natural levels of UV radiation and the relatively sparse population. Thus, these large-percentage increases translate to relatively few new cases of skin cancer. More important, according to the authors, are the increases in mid-latitudes, because much of the fair-skinned population is concentrated here. (See attached sheet for a few major midlatitude cities in the Northern Hemisphere with their 1990 census population figures.) "Increases in annually integrated ultraviolet doses, shown in the table, are within one standard deviation of zero only within about 10o latitude of the Equator and become significant at the two standard deviation level polewards of 35o in both hemispheres," reports Madronich. "Relative to the 1979-89 changes, trends at middle and high latitudes are generally persisting but now carry substantially greater certainty." Madronich and de Gruijl note several important assumptions in their study: 1. The calculations considered ozone change only and do not account for any long-term changes in cloud cover and local pollution, both of which are known to block some of the UV light. Cloudiness and pollution may have increased at some locations but decreased at others, so the actual net UV change may vary among places even at the same latitude. 2. The calculation is based only on ozone depletion that has actually occurred between 1979 and 1992 and assumes that no additional ozone depletion will occur. Because skin cancer may take several decades to develop, the effects of the 1979-1992 UV increase will not be manifested immediately. In the meantime, additional ozone depletion may occur. 3. The most critical unknown in this study is how human behavior will change in the future decades. According to Madronich, it is perhaps optimistic but entirely possible that, with more awareness about the connection between UV and skin cancer, people will increasingly protect themselves from UV through the use of appropriate clothing, sunglasses and sunscreens and by minimizing outdoor exposure two hours before and after solar noon. NCAR is sponsored by the National Science Foundation. -end- The National Science Foundation is an independent agency of the federal government established in 1950 to promote and advance scientific progress in the United States. NSF accomplishes its mission primarily by competitively awarding grants to educational institutions for research and education in the sciences, mathematics, and engineering. This and other information is available electronically on STIS, NSF's Science and Technology Information System. For more information about STIS contact the Publications Section at (202) 357-7861 and request the "STIS Flyer," NSF Publication #91-10, or send an E-mail message to stisinfo@nsf.gov (INTERNET) or stisinfo@NSF (BITNET).


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