According to scientists, human-produced gases such as bromine and chlorine damage the ozone layer, which in turn has caused the hole and allowed it to increase in size over time. This is a major reason why many compounds -- such as components of spray-can propellants -- have been banned in recent years.
"From September 21 to 30, the average area of the ozone hole was the largest ever observed, at 10.6 million square miles," said Paul Newman, atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. That means the area of the hole is larger than North America.
David Hoffman, director of the Global Monitoring Division of the National Oceanic and Atmospheric Administration's Earth System Research Laboratory, stated that "These numbers mean the ozone is virtually gone in this layer of the atmosphere."
Hoffman added that "The depleted layer has an unusual vertical extent this year, so it appears that the 2006 ozone hole will go down as a record-setter." However, the size and thickness of the ozone hole varies from year to year, becoming larger when temperatures are lower.
Due to international agreements banning ozone-depleting substances, researchers calculated that ozone-depleting chemicals peaked in Antarctica in 2001 and have been declining since. However, many of them have extremely long lifetimes once released into the air. While there are year-to-year variations, scientists expect a slow recovery of the ozone layer until the year 2065, anticipating declines in the use of damaging chemicals from this point forward.