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Thursday, Feb. 17, 2005 11:03 am

earth talk 2-17-05

Dear “Earth Talk”: What has been causing holes in the Earth’s ozone layer, and what is being done about it? — Marcin Wasilewski, Delray Beach, Fla.

Chemicals called chlorofluorocarbons (CFCs), of which there are many variations, are the prime culprits in the depletion of the Earth’s ozone layer. The ozone layer is composed of ozone molecules, which bind together in the Earth’s stratosphere to serve as Earth’s sunglasses, shielding us from damaging ultraviolet rays. Meanwhile, CFCs, commonly used in refrigerants and aerosol sprays, are virtually indestructible and linger in the atmosphere, destroying ozone molecules faster than they can regenerate.

The problem is most acute over Antarctica, where, in 2004, an area of more than 9 million square miles — two-and-a-half times the area of Europe — was affected. Australia, North America, and Europe are also at great risk from ozone depletion. Greater exposure to ultraviolet light resulting from a thinning ozone layer leads to an increased incidence of skin cancers and eye cataracts, as well as lessened disease immunity. Ozone depletion also causes damage to ocean ecosystems and reduces agricultural yields, and it may be affecting the reproductive abilities of some amphibians, especially frogs, whose populations are falling rapidly around the globe.

In 1987, 24 countries signed the Montreal Protocol, an agreement to reduce CFC production worldwide through a phase-out of 96 different chemicals. CFC production is now banned in most countries, and use began to decline after peaking in 2000. According to the United Nations Environment Programme, which oversees implementation of the Montreal Protocol, the ozone layer should be able to repair itself by 2050 as long as CFC production trails off as planned.

Despite widespread ratification and implementation of the Montreal Protocol, some environmental groups do not think enough is being done to protect the ozone layer. For one, black-market trading in CFCs is a big problem that perpetuates the discharge of these chemicals into the atmosphere. And a growing number of scientists are concerned that newer, increasingly popular chemicals such as n-propyl bromide and halon-1202, neither of which is controlled by the Montreal Protocol, could contribute significantly to ozone depletion. n-Propyl bromide is used primarily as a degreasing solvent in metal cleaning, and halon-1202 is used in military firefighting equipment. In fact, the presence of halon-1202 in the atmosphere has increased fivefold since the late 1970s.

“At the moment I believe we do not have a big problem with these new substances,” says Massachusetts Institute of Technology professor Mario Molina, who is credited with discovering the problem of ozone depletion caused by CFCs in the 1970s, “but we cannot be complacent. If enough of them are manufactured and emitted, we will delay the recovery of the ozone layer quite significantly.”

“Early recovery is possible with an aggressive commitment,” agrees Beatrice Olivastri, CEO of Friends of the Earth Canada. “Governments need to stop rolling back legislation for a total ban on these chemicals.”

For more information: Montreal Protocol, www.undp.org/seed/eap/montreal/; United Nations OzoneAction Programme, www.unep.org/themes/atmosphere; Friends of the Earth Canada, 613-241-0085, www.foecanada.org.

Send questions to “Earth Talk” in care of E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881; or e-mail earthtalk@emagazine.com.

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