World Ozone Day, which is observed every year on September 16, marks global efforts to protect the ozone layer, which helps protect the Earth by acting as a shield from harmful Ultraviolet (UV ) radiation.
This day is marked by the adoption of the Vienna Convention (1985) and the Montreal Protocol (1987), in 1994 by the UN General Assembly as the International Day for the Preservation of the Ozone Layer, which is a landmark agreement to phase out ozone-depleting substances.
In 2025, these two protocols marked a very significant step toward the safety of the Ozone layer, depletion from many harmful gases like CFCs, HFCs and many other chemicals that are destroying the Ozone layer.
What is the Theme of World Ozone Day 2025?
As per the UNEP, the theme for World Ozone Day 2025 is “From Science to Global Action”
Source: ozone.unep.org
Four decades ago, there were many countries around the world that united through the Vienna Convention for the Protection of the Ozone Layer, which pledged together to safeguard humanity and to protect the environment from the danger of excessive Ultraviolet radiation caused by a thin layer of the ozone layer.
This global commitment toward making climate protection made the landmark Montreal Protocol, which is based on advancing scientific research with its knowledge, and this protocol led to the phase-out of chlorofluorocarbons (CFCs), which are very harmful human-made chemicals that are commonly used in refrigeration, aerosols, and foam products.
Source: ozone.unep.org
Thanks to these efforts, the ozone layer has been set on a path to healing.World Ozone Day is a reminder of this remarkable achievement and a call to continue the journey. Today, the Vienna Convention and Montreal Protocol remain essential in tracking ozone health, monitoring UV radiation, and eliminating ozone-depleting substances. With the Kigali Amendment, the fight has expanded to include hydrofluorocarbons—potent greenhouse gases that worsen climate change.
Source: ozone.unep.org
What is the ozone layer?
The ozone layer is a concentrated band of ozone gas which lies in the stratosphere, around 15 to 35 kilometres above Earth’s surface. The ozone layer acts like an invisible shield in our Earth's atmosphere, playing a crucial role in protecting life on Earth by filtering harmful Ultraviolet (UV) radiation from the sun.
It also blocks the UV-B rays, which are very harmful for the skin, causing sunburn, and, for long-term exposure, can lead to serious health problems like skin cancer. Without the Ozone layer, not only humans, but also animals, plants, and even microorganisms would face severe threats to their survival.
When did the problem of ozone depletion arise?
In the 1970s, scientists discovered that ozone levels were being seriously affected by manmade chemicals containing chlorine and bromine. By the mid-1980s, they confirmed the existence of a dramatic thinning—known as the “ozone hole”—over Antarctica.
This depletion is primarily caused by substances known as ozone-depleting substances (ODSs). For decades, these chemicals were present in countless everyday products. Chlorofluorocarbons (CFCs), the most notorious ODSs, were used widely in refrigerators, air conditioners, aerosol sprays, and even medical inhalers. Other harmful compounds included hydrochlorofluorocarbons (HCFCs), halons used in fire extinguishers, and methyl bromide used in agriculture. From cleaning electronics to producing plastic foams and insulation, these chemicals became deeply embedded in modern life.
How do these chemicals destroy ozone?
When CFCs and similar chemicals rise into the stratosphere, they are broken down by sunlight, releasing chlorine or bromine atoms. These atoms are highly destructive. A single chlorine atom can react with and destroy up to 100,000 ozone molecules before it becomes inactive. As these reactions multiply, the chemical balance of the stratosphere is disrupted, leading to faster ozone destruction than creation—causing the layer to thin.
Source: ozone.unep.org
Vienna Convention for the Protection of the Ozone Layer (1985)
When the scientific community confirmed ozone depletion, countries realised the urgency of collective action. This led to the Vienna Convention, adopted on 22 March 1985 by 28 nations. The Convention established a framework for global cooperation to protect the ozone layer and later became the foundation for the Montreal Protocol (1987).
Montreal Protocol (1987)
The Montreal Protocol was a landmark agreement designed to protect the ozone layer by regulating the production and consumption of ozone-depleting substances (ODS).
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It groups harmful chemicals into categories based on their chemical family and sets phase-out schedules for each group.
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Nearly 100 chemicals are covered under its control measures.
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Phase-outs are defined relative to baseline years and apply to consumption (production + imports – exports – verified destruction).
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While it restricts new production and use, existing or recycled substances can still be used.
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Essential exemptions were granted in cases where substitutes were not available, such as in inhalers for asthma patients or halon systems in submarines and aircraft.
In 1994, the UN General Assembly designated 16 September as the International Day for the Preservation of the Ozone Layer, marking the signing of the Protocol.
Implementation and Progress
The Montreal Protocol has been hailed as one of the most successful environmental treaties.
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Developed and developing countries both adhered to their commitments, often meeting targets earlier than expected.
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The first focus was on high-risk substances like CFCs and halons.
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HCFCs, considered less damaging but still harmful, were given a more gradual phase-out schedule.
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Freeze for developing nations began in 2015.
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Complete phase-out deadlines: 2030 for developed nations and 2040 for developing nations.
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In 2007, the timeline for HCFCs was further accelerated.
Source: ozone.unep.org
Universal Ratification
On 16 September 2009, the Vienna Convention and the Montreal Protocol made history by becoming the first treaties in the UN system to be universally ratified.
This milestone reflects the exceptional success of international cooperation in addressing a global environmental crisis.
Conclusion
September 16, which is observed every year as the “World Ozone Day”, is very significant for climate safety in remembrance of the two important protocols, which were the Vienna Convention for the Protection of the Ozone Layer (1985) and the Montreal Protocol (1987), which were the landmark agreements. While these protocols have played a crucial role in protecting us from harmful radiation, we cannot rely on them to be safe and protected from this Ultraviolet radiation. But it is our responsibility to contribute to climate safety and sustainable development to achieve a safe climate in our environment.
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