Chlorofluorocarbons

Chlorofluorocarbons emerged as a laboratory curiosity in 1890 and became an environmental catastrophe by 1990—a century-long case study in unforeseen consequences. Belgian chemist Frederic Swarts first synthesized these compounds at the University of Ghent, developing techniques for replacing chlorine atoms with fluorine in organic molecules. The chemistry was elegant; the applications were unclear.

The adjacent possible remained unrealized for four decades. Swarts had created the molecules, but the world had no pressing need for non-toxic, non-flammable refrigerants. Existing refrigerators used ammonia, sulfur dioxide, or methyl chloride—all toxic, some explosive. Home refrigeration remained dangerous and rare.

Thomas Midgley Jr. changed that calculation. Working for General Motors' Frigidaire division in 1928, he systematically searched for a safe refrigerant. The search was methodical: he needed a compound that boiled at the right temperature, didn't burn, didn't poison, and didn't corrode. Dichlorodifluoromethane—Freon-12—met every criterion. DuPont commercialized it under license.

CFCs proliferated. Refrigerators became household fixtures. Air conditioning transformed architecture—sealed buildings became possible. Aerosol propellants replaced pumps. The compounds seemed miraculous: stable, inert, and safe to handle.

Too stable, as it turned out. In 1974, Mario Molina and F. Sherwood Rowland published their hypothesis: CFCs were so stable that they survived unchanged through the entire atmosphere until reaching the stratosphere, where ultraviolet radiation broke them apart, releasing chlorine atoms that catalytically destroyed ozone. Each chlorine atom could destroy 100,000 ozone molecules.

The ozone hole over Antarctica confirmed the theory in 1985. The Montreal Protocol of 1987 began phasing out CFCs—the first international environmental treaty to address a global atmospheric threat. The compounds that had made modern comfort possible had also threatened the planetary sunscreen that made complex life possible.

CFCs demonstrated how perfectly designed solutions can harbor invisible catastrophe. The adjacent possible had included not just the molecule but its unintended destination.