The hole in the ozone over Antarctica still exists, but it is no longer the threat it once was according to an October 2012 NASA press release. According to NASA, the hole appears and disappears every year due to a complex interplay of seasonal weather patterns. Ozone blocks most of the harmful ultraviolet rays from the sun, which would otherwise reach earth's surface and cause more skin cancer. The hole in the ozone, which in reality is more like a region of partial depletion than a complete hole, was dangerously increasing in size in the 1980's and 1990's. Research indicated that use of man-made CFC chemicals such as found in aerosol cans contributed to depleting the ozone. As a result the U.S. banned the use of CFC's in aerosol cans in 1978. Other countries have imposed similar CFC bans and efforts to enact additional bans are under way. As a consequence of these legal measures, the hole in the ozone stopped expanding from year to year and is slowly shrinking back to its 1980's state.