An international agreement, given the expanding ozone hole, bans hydrofluorocarbons. The treaty is ratified by 197 countries. The ozone hole is shrinking, and it is estimated that it will close completely by the mid-21st century. CFCs were discovered in 1930 by Thomas Midgley and his team, who were searching for a non-toxic, non-flammable compound with a boiling point that would make it usable in refrigeration. After countless attempts, they tried chlorofluorocarbons (CFCs), which proved very promising and very stable, interacting with almost nothing. Dramatically, to demonstrate the non-toxicity and non-flammability of CFCs, Midgley, in a public demonstration, inhaled CFCs and blew them on a lit candle, extinguishing the flame. They seemed like the perfect gas for refrigerators, and would be used in billions of household refrigerators for decades, dramatically changing our lives for the better. In the 1970s, One million tons of CFCs will be produced annually. Then, in 1974, at a meeting of the American Chemical Society in Atlanta, Sherwood Rowland and Mario Molina announced worrying results. Precisely because of the stability of the CFC molecule, they wander unperturbed in the atmosphere for decades, rising into the stratosphere and finally being broken down by solar radiation. Chlorine atoms in the stratosphere increase the rate of decomposition of the thin ozone layer that protects us from the sun’s harmful ultraviolet rays. Chlorine, moreover, acts only as a catalyst, so it then continues unperturbed to cause further ozone decomposition, undestroyed, thousands of times. The news didn’t cause much alarm until 1985, when increasing depletion of the ozone layer over Antarctica was measured, and in 1987, chlorine monoxide (ClO) was discovered: the smoking gun. In 1987, an agreement called the Montreal Protocol obligated signatory nations to gradually reduce CFCs until they were completely phased out. In 1995, Rowland and Molina won the Nobel Prize. The Montreal Agreement is the greatest environmental success of the 20th century, even though the CFCs released into the atmosphere (and the millions of refrigerators still in operation with CFCs—not all nations have signed) will continue to cause harm, perhaps for centuries to come.
