troposphere ozone layer Basic Ozone Layer Science Basic Ozone Layer Science Source EPA-EUA CFCs ozone layer about 9 to 18 miles (15 to 30 kilometers) the Earth’s vital ozone layer EPA-EUA substances to reach the atmosphere increasing concentrations of ozone-depleting chemicals ozone layer Source the ozone layer EPA Website: Basic Ozone Layer Science stratosphere ozone layer 复臭氧层