Chlorofluorocarbons, commonly called CFCs, are entirely synthetic. They do not exist in nature and have no natural background concentration in the atmosphere. Every CFC molecule on Earth was manufactured in a factory, starting in the late 1920s and continuing on a massive scale through the late 20th century. Today, CFCs still enter the atmosphere from old products that contain them, and in some cases from illegal production.
How CFCs Were Invented
CFCs were first synthesized in 1928 by Thomas Midgley Jr. and Albert Leon Henne, working for the Frigidaire division of General Motors. At the time, refrigerators relied on toxic, flammable gases like ammonia and sulfur dioxide, which occasionally leaked and poisoned people. GM wanted something safer.
Midgley’s team focused on combinations of carbon chains and halogens, chemicals known to evaporate easily, which is essential for a refrigerant. They zeroed in on adding fluorine to hydrocarbons, reasoning that the strong bond between carbon and fluorine would keep the compound stable and nontoxic. The result was dichlorodifluoromethane, the first CFC, which they branded “Freon.” By 1935, Frigidaire and its competitors had sold 8 million refrigerators in the United States using it.
What CFCs Are Made From
Producing the two most common CFCs (CFC-11 and CFC-12) requires two raw materials: carbon tetrachloride and hydrogen fluoride. In both the liquid-phase and vapor-phase manufacturing processes, these two chemicals react together, swapping chlorine atoms for fluorine atoms. Replacing one chlorine produces CFC-11; replacing two produces CFC-12. Hydrochloric acid is generated as a byproduct. The ratio of CFC-11 to CFC-12 coming out of the reactor can be adjusted by changing temperature, pressure, and the proportion of the two inputs.
Where CFCs Were Used
Refrigeration was just the beginning. In 1932, Carrier Engineering Corporation used CFC-11 in the world’s first self-contained home air conditioning unit, called the “Atmospheric Cabinet.” Through the 1950s and 1960s, CFCs made affordable air conditioning possible in cars, homes, and office buildings. Their reputation for being nontoxic and nonflammable made them the default coolant for large commercial systems.
After World War II, use expanded well beyond cooling. CFCs became the propellant gas in aerosol cans for bug sprays, paints, hair products, and other consumer goods. They served as blowing agents for foam insulation and packing materials. They were used as solvents for degreasing metal parts and cleaning electronic circuit boards. At their peak, CFCs were embedded in daily life in ways most people never noticed.
Why They Were Banned
The same chemical stability that made CFCs safe to breathe turned out to be catastrophic for the atmosphere. CFC-11 persists in the atmosphere for about 52 years. CFC-12 lasts even longer, roughly 102 to 113 years. During that time, the molecules drift up into the stratosphere, where intense ultraviolet radiation finally breaks them apart, releasing chlorine atoms that destroy ozone molecules. A single chlorine atom can break down thousands of ozone molecules before it’s neutralized.
The 1987 Montreal Protocol established a global timeline to phase out CFC production. By 2010, production for direct uses like refrigeration and aerosols was banned worldwide. The treaty did include one exception: CFCs could still be produced as an intermediate step in manufacturing other chemicals, including the hydrofluorocarbons (HFCs) designed to replace them.
Where CFCs Come From Today
Even though production is largely banned, CFCs are still entering the atmosphere from two main sources.
Old Products and Buildings
The biggest ongoing source is what scientists call “banks,” the CFCs still trapped inside products made decades ago. As of 2008, the estimated global bank of CFC-11 alone was about 1.42 million tonnes. Most of it sits in closed-cell polyurethane foam used to insulate buildings and old refrigerators. These foams slowly leak their CFC content throughout their useful life, releasing small amounts year after year.
The problem gets worse at end of life. When old buildings are demolished or appliances are scrapped, the insulating foam is often crushed or shredded to recover metal and plastic, releasing the trapped CFC in the process. Foam that ends up in landfills continues to emit at a rate of roughly 0.5% per year, though some bacteria in landfills can break down a portion of the CFC over time. These bank emissions are expected to decline gradually as less and less CFC-containing material remains in circulation, but the process will take decades.
Illegal Production
In 2018, atmospheric measurements revealed something alarming: the expected decline in global CFC-11 concentrations had slowed significantly starting around 2013. Emissions had increased by a substantial amount, pointing to unreported production somewhere in the world. A 2018 investigation by the Environmental Investigation Agency traced much of this to China’s foam-blowing industry, where some manufacturers were illegally producing and using CFC-11 because it was cheaper than legal alternatives.
International pressure and enforcement appear to have worked. By 2019, global CFC-11 emissions dropped by about 26%, falling back to levels similar to the 2008 to 2012 average. A study published in Nature estimated the 2019 emissions at roughly 52 gigatonnes per year. If this decline holds, the damage to the ozone layer from the episode of illegal production is expected to be limited, though the extra CFC-11 that was produced and stored in foam banks (an estimated 90 to 725 additional gigatonnes) will continue leaking slowly for years to come.
No Natural Sources Exist
Unlike some other halogen-containing gases, CFCs have no known natural sources. Volcanoes, ocean processes, and biological activity produce various chlorine and bromine compounds, but none of them produce CFCs. Every measurement of CFC concentrations in the atmosphere traces back to human manufacturing. Ice core samples from before the industrial era show zero CFCs, confirming that these molecules simply did not exist on Earth until chemists created them in the 20th century.