Ozone-Depleting Chemicals Found to Be Declining

Ozone-destroying chemicals are declining in the atmosphere for the first time, according to researchers who say that means the ozone hole high above the Earth could start closing within 10 years.

“A detectable signal for ozone recovery is expected around 2005 or 2010,” said Stephen A. Montzka, a researcher in the National Oceanic and Atmospheric Administration laboratory in Boulder, Colo., and one of eight coauthors of a study published today in the journal Science.

The high-altitude natural ozone layer forms a barrier against ultraviolet radiation from the sun. Excessive levels of UV radiation can cause skin cancer in humans.

Thinning of the ozone layer in the stratosphere is thought to be caused by some industrial compounds containing chlorine and bromine. The most common chemicals include chlorofluorocarbons, halons and chlorine-based solvents that have been used as refrigerants, cleaning agents and spray propellants.

Erosion of the ozone layer has been particularly severe over the South Pole, forming what has been called an “ozone hole.”

In 1987, 23 nations signed an agreement to gradually phase out ozone-destroying chemicals. Montzka said tests now show it is beginning to have an effect.