Researchers this week identified three new ozone-depleting gases in the atmosphere, bringing the total number of such gases discovered this year to seven.Alone, none of the three gases were found in concentrations high enough to harm the ozone layer, researchers from the University of East Anglia. But the scientists believe more such gases will likely be discovered, and, cumulatively, they could have a significant impact. Two of the newly discovered gases are chlorofluorocarbons (CFCs) and one is a hydrochlorofluorocarbon (HCFC), both of which were once widely used in refrigerants. All three of the newly discovered gases are likely man-made, researchers said. Both CFCs and HCFCs fall under the Montreal Protocol, an international agreement that bans the use of 13 such compounds. Including the four new gases discovered earlier this year, there are now a total of 20 known ozone-depleting gases.