Health effects of ozone hole studied Ultraviolet radiation at heart of problem

December 16, 1991|By Liz Bowie

Reports from southern Chile that the ozone hole has left sheep blinded by cataracts and some people blistered by sunburn are probably tall tales, scientists say, but they do expect skin cancer and cataract cases to begin rising sharply worldwide by the end of the century.

In addition, the planet may see infectious diseases spread more quickly, the loss of animal and plant species and a reduction in crop yields, they say.

Why? Because more ultraviolet radiation is now reaching the Earth as the protective ozone shield thins over most of the world.

And since the Earth's shield against the sun's ultraviolet rays probably won't begin to repair itself for 30 or 40 years, people will have to learn to live with the changes.

A recent United Nations report estimates that the world will see a 26 percent increase in skin cancer cases by the end of the decade and 1.6 million more cases of cataracts.

For Marylanders, the increase in the amount of ultraviolet radiation compared with 10 years ago is slight -- the equivalent of moving to Richmond, Va., or of staying in the sun three minutes more each hour, said John E. Frederick, a professor of atmospheric science at the University of Chicago.

"It is going to be another 10 years before we could possibly see an impact, and that is for skin cancer," said Janice Longstreth, who helped write the U.N. report.

The most common type of skin cancer develops after years of exposure to the sun and is usually not fatal if treated.

But melanoma, a more often deadly form, also is expected to rise and cause an estimated 3,000 deaths a year worldwide by the end of the century.

For most Americans, the best protection against the effects of ozone depletion may be a good sunscreen and a hat.

Those who are most susceptible to skin cancer are fair-skinned people living in southern North America, southern Europe, Australia and South America.

Scientists also suspect there may be other human health effects, including a suppression of the immune system.

One of the few laboratories doing work on this is at the M.D. Cancer Center in Houston. There, Margaret Kripke, an immunology professor, is trying to find out if infectious diseases such as tuberculosis, malaria and leprosy will spread more rapidly as the ozone layer is depleted.

Already it is clear that the herpes virus that causes cold sores on the mouth is activated with exposure to the sun. But Ms. Kripke now is exposing mice to bacteria in the same family as tuberculosis and leprosy, and finding that the animals take longer to get over the diseases and are more likely to get them a second time.

In addition, laboratory animals infected with Leishmania, a parasite common in the Third World that was picked up by some military personnel during the Persian Gulf war also have been slow to recover.

But she cautioned that much more research is needed before scientists can say if more ultraviolet radiation will speed the spread of disease in the next several decades.

"We have a lot of information about skin cancer. We have almost no information about the more serious impact," she said. "There are just not a lot of people out there studying this problem."

Researchers are also just beginning to look at the effect more sunshine will have on people with the human immunodeficiency virus.

There is some evidence to suggest that it will speed up the progression of the disease from infection to acquired immune deficiency syndrome, although not effect its spread.

Even less is known about how the uninhabited parts of the planet will react.

For instance, crop yields were reduced 25 percent in a University of Maryland laboratory study, but the question remains about whether crops will react the same way out in the field, said Robert C. Worrest of the U.S. Environmental Protection Agency.

Even if they do, it may be that farmers will find species that are more resistant to the additional sunlight than others.

In addition to the effects on crops, an impact is expected in the sea.

A decrease in phytoplankton, a microscopic plant that is the basis of the food chain in the oceans, could mean a decrease in the amount of fish. Scientists also are concerned about the balance that phytoplankton provides for the atmosphere. By consuming large amounts of carbon dioxide from the atmosphere, phytoplankton use up one of the gases that are believed to cause the greenhouse effect or warming of the planet.

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