Detecting high levels of these chemicals seven 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."
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