“Let us take encouragement from how we have worked together to preserve the ozone layer and apply the same will to healing the planet and forging a brighter and more equitable future for all humanity.” —António Guterres, Secretary-General of the UN

The ozone layer plays a critical role in protecting our planet—and it should therefore be our priority to protect in return. To recognize this important part of the atmosphere, the UN General Assembly has proclaimed September 16th the International Day for the Preservation of the Ozone Layer.

So how much do you know about this vital shield and the significance of this day? Let’s dive in to learn more about World Ozone Day.

What is the significance of World Ozone Day?

The International Day for the Preservation of the Ozone Layer commemorates the signing of the Montreal Protocol on September 16, 1987. The day is intended to celebrate the global cooperation to protect the ozone layer, showing that groups around the world can come together, guided by science, and work to achieve collective good.

What is the ozone layer?

Ozone is a gas that is naturally present in our atmosphere, with each ozone molecule containing three atoms of oxygen. Ozone is formed when sunlight hits oxygen molecules and breaks them up into individual atoms, which then join up with O2 molecules to create O3.

Ozone molecules are primarily concentrated in the stratosphere, which is located about 50 kilometres above the Earth’s surface—this layer of atmospheric gas is called the ozone layer. About 90 percent of atmospheric ozone can be found here. The remaining 10 percent exists in the troposphere, which is the part of our atmosphere that is closest to Earth.

Why is the ozone layer so important?

This shield of gas protects life on our planet as we know it. It protects the Earth from the sun’s ultraviolet radiation, which can be harmful to people through conditions like sunburn, skin cancer and cataracts, and also poses serious risks to plants and ecosystems on our planet. The ozone layer absorbs about 98 percent of the ultraviolet light. Think of it as a giant layer of sunscreen for our planet (although that’s not an excuse to not wear sunscreen!)

What is threatening the ozone layer?

In 1985, it was reported that a “hole” or depletion was forming in the ozone layer over Antarctica. Certain molecules that were dispensed by human-made products were coming into contact with ozone molecules, causing them to break up and lose their ability to absorb the UV light.

The biggest offenders of depleting the ozone are found in chlorofluorocarbons, chemicals used in the manufacturing of aerosol sprays, air conditioners, refrigerants, fire extinguishers and manufacturing foams.

What is the solution?

After the ozone depletion over Antarctica was discovered, scientists, governments, and industry experts around the world came together to save the ozone layer. The Montreal Protocol on Substances that Deplete the Ozone Layer was created in 1987, limiting substances that harm the ozone layer and focussing on saving it as a vital protector for our planet.

Nations mobilized and took measures to control global production and consumption of the substances that deplete the ozone layer, with the ultimate goal of eliminating them. Though existing products continue to emit ozone-depleting substances, the vast majority of these substances have been cut out and the ozone layer is healing and expected to return to pre-1980 values by mid-century, according to the United Nations.


The International Day for the Preservation of the Ozone Layer is a reminder and source of encouragement to continue protecting the ozone layer and the rest of our planet today and for future generations.