A number of commonly used chemicals have been found to be extremely damaging to the ozone layer. Halocarbons are chemicals in which one or more carbon atoms are linked to one or more halogen atoms (fluorine, chlorine, bromine or iodine). Halocarbons containing bromine usually have much higher ozone-depleting potential (ODP) than those containing chlorine. The man-made chemicals that have provided most of the chlorine and bromine for ozone depletion are methyl bromide, methyl chloroform, carbon tetrachloride and families of chemicals known as halons, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).
In 1994, the United Nations General Assembly proclaimed 16 September the International Day for the Preservation of the Ozone Layer, commemorating the date of the signing, in 1987, of the Montreal Protocol on Substances that Deplete the Ozone Layer (resolution 49/114).
Theme for 2023 - Montreal Protocol: fixing the ozone layer and reducing climate change
This year Ozone Day is held under the theme Montreal Protocol: fixing the ozone layer and reducing climate change. We celebrate the achievements of the Montreal Protocol on Substances that Deplete the Ozone Layer. This year’s theme highlights and reiterates the positive impact of the Montreal Protocol on ozone layer recovery and reducing climate change. Especially emphasizing the Kigali Amendment, which through the phase-down of hydrofluorocarbons (HFCs) and improved efficiency in the cooling sector, will provide additional climate mitigation benefits.
The principal aim of the Montreal Protocol is to protect the ozone layer by taking measures to control total global production and consumption of substances that deplete it, with the ultimate objective of their elimination on the basis of developments in scientific knowledge and technological information.
The Montreal Protocol is structured around several groups of ozone-depleting substances. The groups of chemicals are classified according to the chemical family and are listed in annexes to the Montreal Protocol text.
The Montreal Protocol requires the control of nearly 100 chemicals, in several categories. For each group or annex of chemicals, the Treaty sets out a timetable for the phase-out of production and consumption of those substances, with the aim of eventually eliminating them completely.
The timetable set by the Montreal Protocol applies to consumption of ozone depleting substances. Consumption is defined as the quantities produced plus imported, less those quantities exported in any given year. There is also a deduction for verified destruction.
Percentage reductions relate to the designated base-line year for the substance. The Protocol does not forbid the use of existing or recycled controlled substances beyond the phase-out dates.
There are a few exceptions for essential uses where no acceptable substitutes have been found, for example, in metered dose inhalers (MDI) commonly used to treat asthma and other respiratory problems or halon fire-suppression systems used in submarines and aircraft.
On 16th September 2009, the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification.
The Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer reached agreement at their 28th Meeting of the Parties on 15 October 2016 in Kigali, Rwanda to phase-down hydrofluorocarbons (HFCs). To access the document, click here.
The Ozone hole and science
What is ozone?
Ozone is a special form of oxygen with the chemical formula O3. The oxygen we breathe and that is so vital to life on earth is O2.
Ozone constitutes a very small part of our atmosphere, but its presence is nevertheless vital to human well-being. Most ozone resides high up in the atmosphere, between 10 and 40 km above Earth's surface. This region is called the stratosphere and it contains about 90% of all the ozone in the atmosphere.
Why do we care about atmospheric ozone?
Ozone in the stratosphere absorbs some of the Sun’s biologically harmful ultraviolet radiation. Because of this beneficial role, stratospheric ozone is considered “good” ozone. In contrast, excess ozone at Earth’s surface that is formed from pollutants is considered “bad” ozone because it can be harmful to humans, plants, and animals. The ozone that occurs naturally near the surface and in the lower atmosphere is also beneficial because ozone helps remove pollutants from the atmosphere.
The Ozone hole and science
Following the publication of the findings of a British Antarctic Survey article in May 1985, the phenomenon of ozone depletion over Antarctica was referred to as the "ozone hole", a phrase first attributed to Nobel Prize winner Sherwood Rowland. The satellite image of the Ozone Hole has become a global symbol of this environmental threat that has helped mobilize public support for the Montreal Protocol.
The work of atmospheric scientists and environmental researchers continues to play a paramount role in informing the policymaking under the Montreal Protocol. Images and scientific bulletins about ozone depletion are useful communication tools to the public about progress made and challenges ahead.
Some Ozone Depleting Substances in Different Industry Sectors
Aerosols, Sterilants and Carbon Tetrachloride : CFCs are used in aerosol products, as sterilants of medical equipment, and in a range of miscellaneous applications including food freezing, tobacco expansion, fumigation and cancer therapy. Carbon tetrachloride is used as a feedstock in the production of CFC-11 and CFC-12, in the production of key pharmaceuticals and agricultural chemicals, and as a catalyst promoter. CFCs and carbon tetrachloride are ozone depleting substances whose production and consumption is controlled under the Montreal Protocol.
Foams : CFCs have been used extensively in the manufacture of polyurethane, phenolic, polystyrene and polyolefin foam polymers, used in many different products. Common blowing agents have included CFC-11, CFC-12, CFC-113 and CFC-114. CFCs are ozone depleting substances whose production and consumption is controlled under the Montreal Protocol.
Halons : Halon 1211 has been widely used in portable fire extinguishers. Halon 1301 has seen widespread use in fixed systems throughout the industrial, commercial, marine, defence, and aviation industries. Halon 2402 has primarily been used in the defence, industrial, marine and aviation sector in some countries. Halons are ozone depleting substances whose production and consumption is controlled under the Montreal Protocol. The strategy for the halon sector essentially consists of two approaches: replacing halons with alternatives, and halon banking. Alternatives to halons include halocarbon alternatives, inert gases, water mist, fine particulate aerosols and streaming agents. In some cases, fire protection strategies may be re-considered and the need for halons eliminated. Halon banking, which includes recovery, recycling and establishing inventories, is used by companies and countries for managing existing halon supplies to cover remaining critical uses.
HCFCs (hydrochlorofluorocarbons) : HCFCs (hydrochlorofluorocarbons) are widely used in the refrigeration, foam, solvent, aerosol and fire fighting sectors as a transitional substance to substitute CFCs. HCFCs are also used as feedstock (raw material) in the production for other chemical products. HCFCs were introduced in the 1990s as alternative chemicals for CFCs and added to the list of substances controlled by the Montreal Protocol. It was acknowledged at the time that these chemicals, with considerably lower ozone depleting potentials (ODP), were transitional and their production and consumption was also to be phased out under the Montreal Protocol. Although having considerably lower ozone depleting potentials than CFCs, many HCFCs have high global warming potentials, of up to 2000 times that of carbon dioxide. In 2006 global HCFC production was 34,400 ODP tonnes and approximately 75% of global HCFC use is in air-conditioning and refrigeration sectors. The main HCFC used is HCFC-22 or chlorodifluoromethane. At the 20th anniversary meeting of the Montreal Protocol on Substances that Deplete the Ozone layer agreement was reached to adjust the Montreal Protocol's HCFC phase out schedule to accelerate the phase-out of production and consumption of HCFCS. This decision will result in a significant reduction in ozone depletion and well as in global warming.
Methyl bromide : Methyl bromide is widely used as a fumigant in agriculture, for pest control in structures and stored commodities, and for quarantine treatments. Fumigation is a technique that allows the gas to reach pests which are in soil, in durables, in perishables, and in structures and vehicles. This chemical controls a wide range of pests, including pathogens (fungi, bacteria and soilborne viruses), insects, mites, nematodes and rodents. Methyl bromide is an ozone depleting substance that is controlled under the Montreal Protocol. Use of methyl bromide can be reduced and eliminated by adopting alternatives, which have been identified for more than 90 percent of applications. These include chemicals, non-chemical measures - - including Integrated Pest Management (IPM) - or a combination of both.
Solvents, Coatings & Adhesives : In the past, CFC-113 use was essential in many industrial applications: in electronic assembly production processes, precision cleaning and general metal degreasing during manufacture, as well as in dry cleaning and other industrial applications. CFC-113 began to be used in the 1970s in metal degreasing and other areas owing to concern over the toxicity of the chlorinated solvents used previously. For many years 1,1,1-trichloroethane was the solvent of choice to replace other more toxic chlorinated solvents for general metal cleaning. Carbon tetrachloride is no longer used as a solvent in most countries because of its toxicity, but it is still used in some parts of the world. CFC-113, 1,1,1-trichloroethane, CTC, and bromochloromethane are ozone depleting substances whose production and consumption is controlled under the Montreal Protocol. With support from the Protocol's Multilateral Fund delivered by UNEP, UNDP, UNIDO, the World Bank and bilateral agencies, developing countries are phasing out these ozone depleting chemicals in this sector.
What You Can Do
Protect yourself from ozone layer depletion by avoiding excessive sun exposure.
Take care of your appliances to minimize ozone layer impact.