Volcano May Cut Protective Ozone Layer

The eruption of Mt. Pinatubo could lead to reduced levels of protective ozone over North America and Europe this winter and next summer, possibly increasing the risk of skin cancer, a study suggests.

In a band stretching across the northern United States, ozone levels may decline by about 12% from January to March, compared to normal levels for the period, researcher Guy Brasseur said.

The reductions next summer may be about half of those of this winter, said Brasseur, director of the atmospheric chemistry division at the National Center for Atmospheric Research in Boulder, Colo.

Ozone is a pollutant at ground level, but at high altitudes it shields the Earth from solar ultraviolet light that can cause skin cancer.

Brasseur said that the ozone depletions would last perhaps two or three years, diminishing over time.

The new projections are only estimates and should be considered upper limits for ozone destruction, Brasseur said.

Researchers said that the projections for next summer, despite being lower than those for the winter, are more worrisome for the risk of skin cancer because more sunlight reaches the Northern Hemisphere in the summertime.

Ozone researcher Richard Stolarski of the National Aeronautics and Space Administration’s Goddard Space Flight Center in Greenbelt, Md., said Friday that the projections are plausible.

“My suspicion is that there’s going to be less ozone depletion than that, because I don’t think we saw as much from El Chichon (a Mexican volcano that erupted in 1982) as a similar calculation would have shown,” he said.

Susan Solomon of the National Oceanic and Atmospheric Administration, who has studied the effect of El Chichon on ozone, said that she expects ozone depletions from January through May from Mt. Pinatubo.

The resulting extra dose of ultraviolet light could harm crops and other plants in the spring, she said.

She would not predict the amount of ozone depletion. But she said that she expects little if any depletion during the summer.

Other researchers said that even short-term loss of summertime ozone may raise the risk of a deadly skin cancer called melanoma. Sunburns are considered a major risk factor for melanoma, especially in young people, and the ozone loss could raise the number and severity of sunburns, researchers said.

Children ages 6 to 15 could be at particular risk, said Janice Longstreth of Pacific Northwest Laboratories in Washington, D.C., who has studied skin cancer in relation to ozone depletion.