1.1　Problem background

Ozone layer can absorb most of the short wavelength of radiation,such as ultraviolet(UV),to make the atmospheric temperature increases,and prevent the Earth's creatures from excessive UV damage,so it is called“the earth's biological umbrella”.The United Nations Environment Program has warned that if the earth's ozone layer continues to decrease at this rate and thinning,then by 2020 the world will increase the proportion of skin cancer by 26%to 300,000 people.And in the next fifty years,then the world's annual cataracts may reach 1.6 million—175 million people.

Ozone depletion by chlorofluorocarbons(CFCs)was first proposed by Molina and Rowland in their Nature paper.Since that time,the scientific connection between ozone losses and CFCs and other ozone depleting substances(ODSs)has been firmly established with laboratory measurements,atmospheric observations,and modeling studies.These science researches led to the implementation of international agreements that largely stopped the production of ODSs.

Figure 1 show the growing hole in the ozone layer over Antarctica for each October from 1979 to 1984.

Figure 2 gives examples of household items containing CFCs.

Figure 1

Figure 2