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9 Dec 05
Atmospheric Ozone Drop May Lead to More Cataracts
National Geographic 8 Dec 05
Old Fridges, Cars Slow Ozone Hole Recovery, Scientists Say
John Roach for National Geographic News
Running low on sunscreen? Lost your sunglasses? Better buy some more.
The gaping hole in the ozone layer above Antarctica may take decades longer to recover than anticipated, scientists warned Tuesday, adding that old refrigerators and cars may be to blame. The ozone layer prevents harmful ultraviolet (UV) sunlight from reaching Earth.
Without this protective layer, people are more susceptible to skin cancer and eye damage, scientists say. UV rays may also harm wildlife, reduce crop yields, and kink the ocean food chain, research shows.
A hole in the ozone layer above Antarctica was first noted in scientific literature 20 years ago. Prior to those reports, scientists predicted chemicals such as chlorofluorocarbons (CFCs) used in refrigerators and car air conditioners could damage the ozone layer. In 1987, two years after the ozone hole was detected, developed nations around the world agreed under the Montreal Protocol to phase out the production of ozone-depleting chemicals. Doing so, scientists predicted, would enable the hole to recover by about 2050.
But new research presented Tuesday at the annual meeting of the American Geophysical Union in San Francisco, California, shows that the recovery may be delayed, perhaps until 2065.
Paul Newman, an atmospheric scientist at the NASA Goddard Space Flight Center in Greenbelt, Maryland, explained why: "We believed the U.S. was no longer emitting a significant amount of chlorofluorocarbon containing compounds. That's not the case."
Dale Hurst, an atmospheric chemist with the National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado, presented measurements taken in 2003 that show ozone-depleting chemicals are still emitted in the U.S. and Canada.
The measurements, taken from a low-flying aircraft, indicate that the U.S. and Canada are responsible for 7 to 45 percent of the global emissions of various ozone-depleting substances.
"This to us was a surprising result: because these chemicals have not been produced in the U.S. or Canada since 1995. And when they were produced, they were typically released to the atmosphere within one to five years," Hurst said.
Detecting high levels of these chemicals eight years after they were last produced in the U.S. and Canada suggests consumer products emit these substances into the atmosphere over a longer period than expected, he added.
For example, Hurst said cars, refrigerators, and fire extinguishers made with CFCs before the ban took effect must still be in use today, which is illegal, rather than sitting in junkyards.
According to Hurst, the finding means that the Antarctic ozone hole may not completely heal for 10 to 15 years longer than the previous recovery estimate of 2050.
In a separate presentation at the conference, John Austin, a NOAA atmospheric scientist in Princeton, New Jersey, released computer-modeling data that suggests the recovery of the Antarctic ozone layer will now occur by 2065.
Unlike the oxygen in the air we breathe, which is made up of two oxygen atoms, ozone is a molecule made up of three oxygen atoms. Ozone forms both near the ground and high up in the atmosphere as a result of chemical reactions between sunlight and oxygen and other chemicals. Ground-level ozone is the main component of smog and is considered harmful to human health.
Atmospheric ozone collects in the stratosphere between 9 and 22 miles (14 and 35 kilometers) above Earth's surface, forming the ozone layer. "The ozone layer is our protective shield against harmful ultraviolet light form the sun," Hurst said.
CFCs contain chemicals that break down ozone, particularly over the Earth's polar regions during the coldest months of the year. In 1985 scientists discovered that a proliferation of CFCs was creating an annual hole in ozone layer above Antarctica.
Since the hole forms over Antarctica, most people are spared a direct blast of harmful UV radiation, Hurst notes. But in the spring and summer, parts of the ozone hole break off and travel over the southern portions of Australia and South America.
"So a delay in ozone recovery means that risk will be ongoing even into the future," he said. In addition, ozone is being depleted globally, just not as rapidly or thoroughly as at the poles, Hurst adds.
Scientists study the Antarctic ozone hole to understand how it is depleted and predict when it will recover. "In that regard we'll be able to apply similar knowledge to predict when the global ozone will again start to increase," he said. "And that does have an impact on the whole population of the planet, not just penguins in Antarctica."
PlanetArk 9 Dec 05
Atmospheric Ozone Drop May Lead to More Cataracts
NEW YORK - An increase in exposure to ultraviolet radiation as result of ozone depletion in the stratosphere could in future lead to a considerable increase in the incidence of cataracts in the US population, researchers report.
Ozone screens out most of the ultraviolet radiation coming from the sun.
Although progress is being made in reducing the degree of ozone depletion, Dr. Sheila K. West of Johns Hopkins Hospital, Baltimore and colleagues note in the American Journal of Epidemiology that cataracts are still a health effect of particular concern.
They also note that unlike skin cancer, which is much more prevalent in those with light skin, cataracts affect African Americans at higher rate than Caucasians.
The researchers obtained data from a Maryland population-based study, involving more than 2500 subjects, which provided information on cataract and ultraviolet radiation exposure. With this and other data the team was able to create a model of cataract risk in the US population related to increasing ultraviolet radiation arising from falling ozone levels of 5 to 20 percent.
Based on this analysis, the researchers estimated that by 2050 cataract rates would increase by 1.3 percent to 6.9 percent. This could amount to as many as 830,0000 extra cases by 2050 and could result in an extra expenditure of close to $3 billion, calculated using 2003 costs for cataract operations.
The team notes that ozone-depleting substances continue to degrade the stratosphere, and although there is a geographic variability in ultraviolet exposure, they stress "the importance of vigilance in adopting sun avoidance behaviors."
SOURCE: American Journal of Epidemiology, December 2005.
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