Thinning Arctic Ozone Could Pose Health Threat

An image of polar stratospheric clouds observed over Kiruna, Sweden, in January 2000. Extremely low temperatures allow these clouds to form at altitudes approximately near 12 miles (20 kilometers) in the stratosphere. The low Arctic temperatures enabled PSCs to last longer during the 1999-2000 winter, causing additional ozone loss. Credit: NASA SOLVE Mission

The protective ozone layer is thinning dramatically above the North Pole and could pose a health risk to residents in northern countries like Scandinavia. If the layer gets thinner, the risk could spread to central Europe and the United States, experts say.

Scientists are advising residents of the far north to take precautions. Here's why: Ozone blocks much of the Sun's harmful ultraviolet (UV) radiation, helping to make the planet habitable. Exposure to excessive UV radiation can cause skin cancer. Animals and plants can be adversely affected, too.

Over the South Pole the thinning is worse. Each winter, an Antarctic ozone hole develops. Relatively few people live under that hole, however. Now, scientists fear a similar scenario could unfold over the Arctic, potentially affecting millions of people.

The thinning is exacerbated by cold temperatures in the stratosphere, about 12 miles (20 kilometers) above the Arctic.

Concern began last November when scientists noted the presence of characteristic polar stratospheric clouds, which indicate ozone depletion. The clouds are larger than those seen in 2000, a record year for northern ozone depletion.

When polar stratospheric clouds form, reactions take place between ozone gas and chlorine, bromine and other so-called halogens gases on the surface of ice or water droplets in the clouds, depleting the ozone. Most of the halogens are from chlorofluorocarbons emitted into the atmosphere by industrial processes.

"Large ozone losses are expected to occur if the cold conditions persist,'' said European Commissioner for Science and Research Janez Potocnik.

Temperatures at 12 miles altitude have dropped to an average of minus 112 degrees Fahrenheit (minus 80 degrees Celsius), the lowest over the Arctic in half a century. Oddly, greenhouse gases that warm the atmosphere near Earth's surface cool the stratosphere.

"The meteorological conditions we are now witnessing resemble and even surpass the conditions of the 1999-2000 winter -- when the worst ozone loss to date was observed,'' said Neil Harris of the European Ozone Research Coordinating Unit in Britain.

People in some northern countries who work out in the open should taken special precautions for sun protection in a month, Harris said.

Overall, scientists have observed a decrease in total ozone above the Arctic region since 1980. So far, however, it has not been as dire a situation as exists in Antarctica.

"The concern is that the Arctic appears to be moving into Antarctic-like conditions which will result in an increase in UV radiation levels that will have consequences on human health in northern hemisphere countries,'' the statement of the EU head office said.

It said the hole in the ozone layer could affect areas around the polar zone, Scandinavia and even down to central Europe.

Other groups have estimated that a northern hole as large as its southern sister could affect more than 700 million people.

The Associated Press contributed to this report.