Preventing ozone depletion comes down to eliminating the chemicals that destroy ozone molecules in the stratosphere, and humanity has already proven this works. The Montreal Protocol, signed in 1987, phased out the worst offenders and put the ozone layer on track to fully recover by mid-century. But the job isn’t finished. New threats from agriculture, the space industry, and legacy equipment still require action at both the policy level and in everyday life.
Why Ozone Breaks Down
The ozone layer sits in the stratosphere, roughly 10 to 30 miles above Earth’s surface, where it absorbs most of the sun’s ultraviolet radiation. Certain chemicals released at ground level are stable enough to drift upward for years until they reach the stratosphere, where intense UV light breaks them apart and frees chlorine or bromine atoms.
Those freed atoms are the problem. A single chlorine atom reacts with an ozone molecule, stripping away one oxygen atom and leaving ordinary oxygen behind. The chlorine then releases that oxygen atom in a second reaction, regenerating itself to attack another ozone molecule. This catalytic cycle repeats thousands of times before anything interrupts it. Bromine works the same way but is even harder to neutralize. One kilogram of halon 1211, a bromine-containing fire suppressant, can destroy 50 tonnes of ozone.
The Chemicals That Cause the Damage
The primary ozone-depleting substances are chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl chloroform, hydrochlorofluorocarbons (HCFCs), and methyl bromide. For decades, these chemicals were everywhere: CFCs and HCFCs cooled refrigerators and air conditioners, propelled aerosol sprays, and puffed up insulation foam. Halons filled fire extinguishers. Methyl bromide fumigated agricultural soil and shipping containers.
Each substance is rated by its ozone depletion potential (ODP), a score comparing its destructive power to CFC-11, which is set at 1.0. Halon 1301 scores a 10.0, meaning pound for pound it does ten times the damage. Some of these chemicals persist in the atmosphere for decades, so even substances released years ago are still contributing to ozone loss today.
How the Montreal Protocol Changed the Trajectory
The Montreal Protocol remains the most successful international environmental agreement ever enacted. It set binding timelines to phase out production and import of ozone-depleting substances, starting with CFCs and expanding to cover HCFCs, halons, and methyl bromide. Nearly every country on Earth has ratified it.
The results are measurable. NASA and NOAA ranked the 2025 Antarctic ozone hole as the fifth smallest since 1992, with an average extent of about 7.23 million square miles during peak depletion season. That’s roughly 30% smaller than the largest hole ever observed in 2006, which averaged 10.27 million square miles. Ozone concentrations at their lowest point this year reached 147 Dobson Units, compared to the record low of 92 Dobson Units in October 2006.
If current policies hold, the ozone layer is expected to recover to 1980 values (before the hole appeared) by around 2040 for most of the world, by 2045 over the Arctic, and by 2066 over the Antarctic. That timeline depends on continued enforcement and on addressing threats the original treaty didn’t anticipate.
Switching to Safer Refrigerants and Chemicals
The transition away from ozone-depleting refrigerants has happened in stages. CFC-12, the original automotive refrigerant, had a global warming potential of 10,900 and destroyed ozone. It was replaced by HFC-134a, which doesn’t touch the ozone layer but still traps heat with a global warming potential of 1,430. Starting in 2012, automakers began shifting to HFO-1234yf, a refrigerant with a global warming potential of just 4 and zero ozone depletion. CO2-based systems (R-744) take this further with a global warming potential of 1, though they operate at much higher pressures and are more complex to engineer.
This progression shows the broader strategy: first eliminate ozone destruction, then reduce climate impact. The same pattern applies in foam manufacturing, air conditioning, and commercial refrigeration, where natural refrigerants like ammonia and hydrocarbons are increasingly replacing synthetic alternatives.
Disposing of Old Appliances Safely
Millions of older refrigerators, freezers, window air conditioners, and dehumidifiers still contain CFCs or HCFCs in their refrigerant lines and insulation foam. If these appliances are crushed in a landfill without proper handling, those chemicals escape directly into the atmosphere.
U.S. law requires that refrigerant be recovered from any appliance before final disposal. If you’re getting rid of an old unit, start by checking whether your electric utility offers a rebate or appliance turn-in program. Many utilities will pick up the appliance and handle disposal for you. Your local municipality may also accept bulky items, though some require the refrigerant to be professionally removed first, typically by an appliance repair technician. Retailers that deliver new appliances often haul away the old one as part of the sale. However you handle it, the key is making sure the refrigerant gets captured rather than vented.
Nitrous Oxide Is Now the Biggest Threat
As CFCs and halons decline, nitrous oxide has become the largest ozone-destroying compound currently being emitted by human activity, measured by ozone depletion potential-weighted emissions. It reached that status by 2008, and it isn’t covered by the Montreal Protocol.
Nitrous oxide rises into the stratosphere and breaks down into nitrogen-containing radicals that catalytically destroy ozone through the same type of chain reaction as chlorine. The largest source is microbial activity in agricultural soil, amplified by heavy use of nitrogen fertilizers. Smaller contributions come from industrial processes and livestock waste. Reducing these emissions likely requires changes in farming practices: precision fertilizer application, cover cropping, and better manure management. Cutting anthropogenic nitrous oxide offers a larger opportunity to reduce future ozone depletion than controlling any of the remaining unregulated halocarbons.
Rocket Launches as a Growing Concern
The commercial space industry is scaling up rapidly, and rocket emissions deposit ozone-destroying chemicals directly into the stratosphere, bypassing the years-long drift that ground-level pollutants require. Solid rocket motors combust aluminum and release both chlorine and alumina particles. The alumina surfaces accelerate chlorine-driven ozone loss. Soot (black carbon), emitted by most propellant types, warms the stratosphere and disrupts air circulation patterns that help distribute ozone.
Current launches already thin upper stratospheric ozone by about 1.5%. Modeling of an ambitious growth scenario with roughly 2,040 launches per year by 2030 projects upper stratospheric ozone losses of around 3%, with Antarctic springtime losses potentially reaching 3.9%. Black carbon is particularly concerning because it causes both direct ozone depletion and atmospheric warming that alters stratospheric dynamics. Propellant choices matter: shifting away from solid rocket motors and high-soot fuels could significantly reduce the industry’s impact.
What Individuals Can Do
Most of the heavy lifting on ozone protection happens through international policy, but individual actions still contribute. Properly maintaining air conditioning and refrigeration systems prevents refrigerant leaks. When replacing old cooling equipment, choosing units with low-impact refrigerants keeps demand for ozone-safe technology growing. Ensuring old appliances go through proper recycling channels rather than informal scrap dealers prevents legacy chemicals from escaping.
Supporting sustainable agriculture matters too, since nitrogen fertilizer overuse is the primary driver behind rising nitrous oxide emissions. Buying from farms that use precision fertilization or organic practices creates market pressure for the farming changes needed to address the ozone layer’s newest threat. Even something as simple as avoiding products containing methyl bromide, still used under exemptions for quarantine fumigation and certain critical agricultural uses, keeps pressure on industries to adopt alternatives like steam sterilization and integrated pest management.
The ozone layer is healing, but the pace of that recovery depends on whether the world continues to enforce existing bans, addresses nitrous oxide emissions that current treaties ignore, and manages emerging risks from industries like commercial spaceflight before they erode the progress already made.