September 16 marks the International Day for the Preservation of the Ozone Layer. What exactly is the ozone and why does it need to be protected?

Ozone (O3) is a highly reactive gas that resides in a layer about 6 to 10 miles above the Earth’s surface. It extends up to 30 miles creating a stratosphere.The ozone layer absorbs the majority of the harmful ultraviolet sunlight, protecting humans from increased risk of skin cancer and cataracts and preventing damage to plants, animals and disruptions in marine systems. The absorption of UV by the ozone enables it to play a key role in moderating the temperature of the Earth. 

Picture Courtesy of the United Nations

In the late 20th century, data showed that the ozone layer was starting to thin. Evidence linking the thinning of the ozone to the chlorofluorocarbons (CFCs) and other halogen-source gases in the stratosphere. Collectively known as ozone depleting substances, these substances were used in many industrial and consumer appliances such as refrigerators, air conditioning, aerosols and fire extinguishers.

The Montreal protocol is a global agreement established in 1987 that strived to protect the ozone layer. To do so, substances that would deplete the ozone, such as chlorofluorocarbons, would be phased out. The Protocol has proven to be successful, eliminating 98% ozone depleting substances (ODS) which helps to reverse the damage done to the ozone. Full implementation is expected to result in avoiding nearly 280 million cases of cancer and 45 million cases of cataracts in the United States alone.

Ozone depletion (blue) in the South hemisphere in 2006.
Picture Courtesy of National Aeronautics and Space Administration (NASA) – Goddard Space Flight Center 

While significant progress has been made, hydrofluorocarbons (HFCs) still account for 98% of gas emissions and are actively being used despite available alternatives. Although the Montreal Protocol has phased out many ODS, large quantities of them still exist in old industrial and commercial equipment. Additionally, ODS are still used to produce niche goods such as feedstock. To further climate benefits, we need to develop cost effective alternatives and develop regulation methods for existing equipment.

Today also marks the launch of the ILHAM Transforming Our World Competition. Have you formed a team yet?



Urooj is an undergraduate at Hunter College. She's involved with Come Be Brainy as the Social Media Manager. She is a Group Leader with the 1000 Girls 1000 Futures Program at The New York Academy of Sciences.

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