According to the website All Business, federal EPA is banning the use of the common refrigerant R-22 for use in air conditioning units. The ban will take effect in 2010. R-22 is being banned because it releases hydrocarbons into the air, harming the ozone layer.
New air-conditioning units manufactured after the ban will contain substitute gases such as R-410A, which supposedly have less of an environmental effect. The problem, as always, is that there is no "free lunch": while lessening the threat to the ozone layer, the substitute gas runs at a much higher pressure than does R-22. According to the article, this will mean greater wear-and-tear on air-conditioning equipment, resulting in more frequent repairs.