Chlorofluorocarbons, or CFCs, are synthetic chemicals that were invented in a lab in 1928 and mass-produced for decades as refrigerants, aerosol propellants, and foam-blowing agents. They don’t exist in nature. Every molecule of CFC in the atmosphere got there because humans manufactured it and eventually released it, whether through leaky air conditioners, spray cans, or industrial processes.
How CFCs Were First Created
CFCs were first synthesized in 1928 by Thomas Midgley Jr. at General Motors. The goal was to find a safer refrigerant for commercial cooling systems, which at the time relied on toxic and flammable gases like ammonia and sulfur dioxide. The result was a family of stable, non-toxic, non-flammable compounds that seemed like a miracle solution. By 1935, Frigidaire and its competitors had sold 8 million refrigerators in the United States using CFC-12, commonly known by the brand name Freon-12.
On the manufacturing side, CFCs are made by reacting chlorine-containing carbon compounds (typically carbon tetrachloride) with hydrogen fluoride in the presence of a catalyst. This swaps out some of the chlorine atoms for fluorine, producing the various CFC types. It’s a straightforward industrial process, which is one reason production scaled up so quickly and why illegal manufacturing has been hard to stamp out entirely.
The Products That Released CFCs
Once manufacturers realized how useful these chemicals were, CFCs found their way into an enormous range of everyday products. The major categories were:
- Refrigeration and air conditioning. CFC-12 became the standard refrigerant in home refrigerators, car air conditioners, and commercial cooling systems. In 1932, Carrier Engineering used CFC-11 in the world’s first self-contained home air conditioning unit. By the late 1950s and 1960s, CFCs made affordable air conditioning possible in cars, homes, and office buildings across the country. Millions of automobiles were still using CFC-12 systems well into the early 1990s.
- Aerosol sprays. After World War II, CFCs became the go-to propellant in spray cans for bug sprays, paints, hair conditioners, and other personal care and household products. Every press of the nozzle released a burst of CFC directly into the air.
- Foam and packing materials. CFCs served as “blowing agents,” the gas that creates bubbles in foam insulation, foam packaging, and styrofoam-type products. The gas would slowly leak out of the foam over months or years.
- Industrial solvents. Electronics manufacturers and other industries used CFCs to clean circuit boards, metal parts, and precision equipment because they evaporated cleanly without leaving residue.
Of these, refrigeration and air conditioning were the largest single source of emissions. Large commercial cooling systems were particularly problematic because topping off leaky systems with fresh refrigerant was standard practice, meaning CFC gas was routinely vented straight into the atmosphere.
Why CFCs Became a Global Problem
The same chemical stability that made CFCs safe to use indoors made them devastating outdoors. Once released, CFC molecules don’t break down in the lower atmosphere. They drift upward over years until they reach the stratosphere, where ultraviolet radiation finally splits them apart, freeing chlorine atoms that destroy ozone molecules. A single chlorine atom can break down thousands of ozone molecules before it’s neutralized.
CFCs are also extraordinarily potent greenhouse gases. CFC-11, one of the most common variants, traps roughly 6,230 times more heat per molecule than carbon dioxide over a 100-year period. So even relatively small quantities have an outsized warming effect.
The Global Ban and What Replaced CFCs
The Montreal Protocol, signed in 1987, set the world on a path to phase out CFC production. Developed nations ended production first, and the final global deadline for all CFC production came in 2010. It remains one of the most successful international environmental agreements ever adopted.
The first wave of replacements were HCFCs (hydrochlorofluorocarbons), which still contained some chlorine but broke down faster in the atmosphere, doing less ozone damage. Those were then largely replaced by HFCs (hydrofluorocarbons), which don’t harm the ozone layer at all. The catch is that HFCs are still potent greenhouse gases, so they’re now being phased down as well. In the U.S., the AIM Act authorizes the EPA to reduce HFC production and push industries toward the next generation of climate-friendlier alternatives.
Where CFCs Still Come From Today
Despite the global ban, CFCs haven’t disappeared entirely. Starting around 2012, atmospheric monitoring stations, including the Mauna Loa Observatory in Hawaii, detected a surprising increase in CFC-11 emissions. About 13,000 metric tons per year of new CFC-11 was entering the atmosphere from somewhere in eastern Asia. It was the first sustained rise in CFC emissions since production controls took effect in the late 1980s.
A follow-up study published in Nature traced roughly 7,000 metric tons of those annual emissions to the provinces of Shandong and Hebei on China’s northeastern coast. The source: small factories illegally using CFC-11 as a cheap blowing agent to manufacture foam insulation for refrigerators and buildings. When investigators from the Environmental Investigation Agency visited some of these factories, they found companies keeping canisters of legal alternatives on hand as props for government inspections while actually using CFC-11 in production. Chinese enforcement officers visited over 1,170 production plants but managed to identify only 10 instances of continuing CFC-11 production.
If sustained, emissions at that level could delay the recovery of the ozone layer by a decade or more, potentially pushing full recovery to the end of the century. International pressure and enforcement have since helped reduce these illegal emissions, but the episode showed how difficult it is to completely eliminate a cheap, effective industrial chemical once the knowledge to make it exists.
Beyond illegal production, older equipment and building materials still release stored CFCs. Foam insulation installed decades ago continues to slowly off-gas. Old refrigerators and air conditioning units that were never properly decommissioned can leak residual refrigerant. These “banks” of trapped CFCs represent a lingering source of emissions that will take decades to fully dissipate.