Environmental Protection Agency (EPA) MVAC Certification

What percentage of stratospheric chlorine comes from ozone-depleting substances?

1. 50%

2. 65%

3. 75%

4. 82%

The correct answer is: 82%

The correct answer indicates that 82% of stratospheric chlorine is attributed to ozone-depleting substances (ODS). This high percentage underscores the significant role that human-made chemicals, particularly chlorofluorocarbons (CFCs), halons, and other ozone-depleting compounds, have played in the depletion of the ozone layer. These substances, once widely used in refrigeration, air conditioning, aerosol propellants, and foam-blowing agents, release chlorine when they are broken down in the stratosphere. Chlorine is highly effective at destroying ozone molecules, which are crucial for protecting life on Earth from harmful ultraviolet radiation. The alarming percentage reflects the cumulative impact of these chemicals on stratospheric chlorine levels, emphasizing the importance of regulatory measures and global cooperation (like the Montreal Protocol) to reduce and phase out the use of ODS. Understanding this percentage is vital for recognizing the ongoing effects of past industrial practices on ozone depletion and the need for continued vigilance and policy action to protect the ozone layer for future generations.