Ozone Depletion and Restoration

Previous article in this series: March 15, 2016, p. 278. In the late 1800s and early 1900s, highly toxic gases, such as ammonia, methyl chloride, and sulfur dioxide, were used as refrigerants. Due to their toxicity and a number of fatalities in connection with leaks of these chemicals, they were replaced by chlorofluorocarbons (CFCs) -- laboratory-built compounds composed of carbon, hydrogen, fluorine, and chlorine atoms. In 1928, Thomas Midgley, Jr. from General Motors synthesized the first...