Other man-made substances besides CFCs are destroying Earth's ozone. Most any compound containing chlorine or bromine that finds its way into the stratosphere is a threat. Chemists call these substances 'halocarbons'. Examples of halocarbons are CFCs, HCFCs, Halons (these contain bromine), carbon tetrachloride, methyl chloroform and others. Methylbromide (CH3Br) occurs naturally in the atmosphere, but has a lifetime of only 1.5 years. ***