According to researchers at the National Institute of Water and Atmospheric Research in New Zealand, on September 9 and 10 the hole extended over the city of 120,000 people, exposing them to very high levels of ultraviolet radiation. This is the first time the hole has reached over a population center. Low temperatures in the stratosphere are believed to have contributed to the expansion of the ozone hole during the Southern Hemisphere's late winter. Antartic ozone depletion starts in July, when sunlight trigers chemical reactions in cold air trapped over the South Pole during the Antartic winter. Warmer temperatures reduce the ability of chlorine and other gases to destroy ozone.
Ozone protects the Earth from harmful ultraviolet radiation.
SPF 15 is the standard - it blocks 93 percent of UVB and allows you to stay out 15 times longer.