Ozone hole history and discovery: ozone depletion: effects, ozone: thinned area over antarctica in blue. Halons: contain bromine and chlorine use in fire retardants. Nitrous oxide: released from burning fossil fuels, ozone depletion: chemical reaction. Cfcs reach the atmosphere and react with uv light and o3. Cfc-ozone reactions occurs more frequently than ozone formation. Continued decline of total ozone over halley, antarctica since 1985 (nature 376: 409-411 august 3, 2002) Better news nasa (fall 2012 smallest ozone in 20 years: why does ozone works, ozone absorbs at uv radiation at specific wavelengths, absorbs most strongly at wavelengths of 250 nm. Very hazardous and is completely absorbed: ozone threats, chlorine: one of the most important catalysts for ozone destructions, natural sources: 25% of chlorine in stratosphere: formed in the oceans by marine phytoplankton and from biomass burning in grasslands and forested areas. Hydrogen chloride (hcl: volcanoes, anthropogenic chlorine sources, chlorocarbons, halocarbons. Family of chemicals usually derived from an organic compound.