May 12, 1995
Media Contact: Marc Kusintz
Phone: (410) 955-8665
A Johns Hopkins study has dispelled earlier fears that a hole in Chile's protective ozone layer caused an increase in eye and skin diseases among humans and animals.
The researchers found that even though ultraviolet B (UV-B) radiation exposure over Puenta Arenas, Chile increased 1.6 to 2.3 times on individual days during 1992, the total annual exposure increased by only 1 percent.
"We found no convincing evidence to support the earlier reports widely carried in the media that the hole in the ozone layer over southern Chile caused an increase in eye or skin diseases," says Oliver D. Schein, M.D., associate professor of ophthalmology at Wilmer Eye Institute, and lead author of the study. The results, published in a recent issue of the American Journal of Public Health, bore out preliminary findings announced by the team in 1993.
"The annual cumulative UV-B exposure in Punta Arenas, even considering the increase, was less than that recorded in many temperate climates at the same time, including Maryland," says Schein. He added, however, if the UV-B exposure increases any further in Punta Arenas or elsewhere, researchers "should begin long-term surveillance for UV-related disease in humans and animals."
Previous studies had implicated excessive exposure to UV-B radiation in actinic keratitis, an inflammation of the cornea--the transparent, slightly curved tissue that focuses light entering the eye--also called snow blindness. UV-B may also reactivate herpes simplex virus infections in the cornea of the eye, a potentially blinding condition.
The long-term effects of increased UV-B radiation on the eye also include cataract (clouding of the lens) as well as damage to the conjunctiva, the lining of the eyelid. Long-term exposure to UV-B also can cause some skin cancers.
After press reports first alerted the Hopkins researchers to stories of humans and animals developing blinding eye diseases because of the increase in UV-B rays, Schein and his colleagues went to Puenta Arenas in November 1992, one month after the springtime ozone depletion had produced record lows in the ozone layer over the region.
The researchers examined the medical records of 7,228 patients who had visited doctors during periods of known ozone depletion (October 1991 and 1992) and identified seven cases of actinic keratitis, of which five were in men who were welders and had been exposed to the bright light of welding arcs.
Another patient with acute actinic keratitis used a UV tanning device. And a seventh patient did not have the form of keratitis generally seen in caused by excessive exposure to UV-B.
Local veterinarians and team member Kirk Gelatt, a veterinary ophthalmologist, also found no evidence of blinding cataracts among the 224 sheep, 30 Hereford cattle, 29 alpacas, eight hares and nine cottontail rabbits they examined.
Other authors of the study include Hopkins researchers Beatriz Munoz, M.S., Sheila West, Ph.D., James Nethercott, M.D., and Donald D. Duncan, Ph.D.; Cesar Vincencio, M.D. and Juan Honeyman, M.D. (University of Chile, Santiago); Kirk N. Gelatt (Universityof Florida, Gainesville), and Hillel S. Koren, Ph.D. (U.S. Environmental Protection Agency).
The study was supported in part by the U.S. Environmental Protection Agency, the University of Chile, and the National Institutes of Health.