Ozone layer depletion
The fragile shield of ozone is being damaged by chemicals released on earth. The main chemicals that are depleting stratospheric ozone are chlorofluorocarbons which are used in refrigerators, aerosols, and as cleaners in many industries, and halons, which are used in fire extinguishers. The damage is caused when these chemicals release highly reactive forms of chlorine and bromine. Over the past 30 years ozone levels over parts of Antarctica have dropped by almost 40 % during some months and a 'hole' in ozone concentrations is clearly visible in satellite observations.