Organic Chlorofluoro Hydrocarbons

• Main Author: Rusch, George M.
• Format: Other/Unknown Material
• Language: English
• Published: Wiley 2001
• Subjects: Antarctic; Molina; Rowland; The Antarctic; Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1002/0471435139.tox068; https://onlinelibrary.wiley.com/doi/full/10.1002/0471435139.tox068

Abstract The chlorofluorocarbons (CFCs) were introduced in the 1930s as “safe” replacements for refrigerants such as sulfur dioxide, ammonia, carbon tetrachloride, and chloroform. In World War II, they were used to produce insecticide aerosols to protect the troops in tropical areas against malaria and other insectborne diseases. During the next 40–50 years, the number and type of applications expanded to include foam blowing, precision cleaning, and propellants for medicinal, cosmetic, and general‐purpose aerosols, air conditioning, and refrigeration. These uses eventually resulted in emission of the CFCs into the atmosphere. Because of their low chemical reactivity, they typically have long atmospheric residence times, and as a consequence, they are distributed globally. In 1974 Molina and Rowland hypothesized that, once the CFCs reach the stratosphere, they will undergo breakdown to release chlorine atoms. The chlorine atoms could then react with the stratospheric ozone breaking it down into oxygen. Since the stratospheric ozone absorbed much of the sun's ultraviolet β radiation (UVB), decreased ozone levels would lead to increases in ground‐level UVB. This could affect crop growth and lead to increases in cataracts and nonmelanoma skin cancers. Following reports of a marked drop in column ozone over Antarctica (the “ozone hole”) during the Antarctic winter, in 1987 most of the nations of the world drafted and signed an agreement calling for the phaseout of CFCs. This agreement is known as the Montreal Protocol . Development was initiated on two types of “in‐kind” replacements. The first were the hydrochlorofluorocarbons (HCFCs) and the second were the hydrofluorocarbons (HFCs). Both contain hydrogen and are susceptible to attack by hydroxyl radicals present in the atmosphere. Therefore, they have a shorter atmospheric lifetime and either are not transported to the stratosphere or are transported there only in small amounts. The HCFCs contain chlorine and are still capable of causing ozone depletion, ...