The Ozone Layer: International Efforts to Combat Ozone-Depleting Compounds

Since the 1970s, the total volume of ozone in the ozone layer has been decreasing by 4 percent each decade. This depletion leads to higher exposure to harmful UV-B radiation, which can affect all living organisms. Overexposure to UV-B has been linked to various health issues, such as skin cancer, cataracts, and a weakened immune system. Additionally, the reduction in crop yields is associated with changes in plant nutrient distribution and metabolism, as well as developmental phases. Even marine life is affected by this phenomenon, as demonstrated by the decrease in phytoplankton production, which is the foundation of the aquatic food chain. Furthermore, the early developmental stages of fish, shrimp, crabs, and amphibians are also vulnerable to damage caused by this depletion.

 

The purple tinted NASA satellite image from October 1, 1998 displays the ozone hole located over Antarctica.

Ozone is a naturally occurring gas that is relatively scarce. It is mostly concentrated in the ozone layer, which starts around 6-10 miles (10-17 kilometers) above the Earth's surface and extends up to around 30 miles (50 kilometers). The ozone layer is situated in the stratosphere, and it is responsible for filtering out most of the harmful UV-B radiation from sunlight, allowing only a small portion to reach the Earth's surface.

 

One of the consequences of ozone depletion is the appearance of the so-called "ozone hole" above the polar caps during the Antarctic springtime (September through early December), which has decreased the ozone layer by one-third. The depletion is mainly caused by chlorofluorocarbons (CFCs) and hydrofluorocarbons (HCFCs) which were once commonly used as propellants in spray cans, refrigerants, foam and insulating products, and electronic solvents. These substances are carried into the stratosphere where they are broken down by UV radiation, releasing chlorine atoms that can react with ozone (O₃)  causing it to break down and deplete.

 

In 1987, international attention was drawn to the harmful effects of CFCs on the ozone layer, which led to the adoption of the Montreal Protocol on Substances that Deplete the Ozone Layer. This international treaty called for a reduction in the use of CFCs and other compounds that contribute to ozone depletion. By 2010, 190 nations had signed the treaty. If the use of CFCs is discontinued, it is estimated that the ozone layer will return to its normal levels by 2050.