The stratospheric ozone layer, which protects us from the sun’s ultraviolet radiation, has recovered considerably from past depletion since the implementation of the 1987 Montreal Protocol in 1987 and subsequent amendments, which phased out the production and consumption of major ozone-depleting substances (ODSs). But unexpected observed and potential emissions of long- and short-lived ODSs could delay the return of stratospheric ozone levels to 1980 levels by years to decades.

Recognizing the threat that unconstrained ODSs pose to the continued restoration of the ozone layer, this study provides an overview of these substances and the steps needed to control them in alignment with the Montreal Protocol.