Chlorofluorocarbons environmental impact

Refngeration technology is moving into a new phase with the introduction of hydrofluorocarbons that combme the safety of chlorofluorocarbons with a much lower environmental impact The considerable care bemg taken to choose the new refngerants under the close scrutmy of the public and regulatory bodies will ensure that the new products wiU benefit mankind for years to come... 

Over the past several decades, there has been increasing recognition in a number of areas of the environmental impacts, both realized and potential, of human activities not only on local and regional scales but also globally. This is particularly true of changes to the composition and chemistry of the atmosphere caused by such anthropogenic activities. One example, for which there is irrefutable evidence, is stratospheric ozone depletion by chlorofluorocarbons, discussed in detail in Chapters 12 and 13. 

The half-life, tm, of a substance is the time needed for its concentration to fall to one-half its initial value. The half-lives of pollutants such as chlorofluorocarbons are important for assessing their environmental impact. If their half-lives are short, they may not survive long enough to reach the stratosphere, where they can destroy ozone. 

Because of their environmental impact, chlorofluorocarbons (CFC) represent a separate category of volatile organic halides. 

The replacement of chlorofluorocarbon (CFC) propellants with the non-ozone-depleting hydrofluorocarbons (HFCs) merit mention for two reasons. First, it illustrates how environmental impact can be an important selection criterion at a time when green issues are high profile. Second, HFCs were developed and evaluated for safety and delivery capability by a consortium of pharmaceutical companies, with costs shared and evaluation programs defined by prior agreement between end-users and propellant manufacturers. Such collaboration could be employed usefully in the future to develop novel excipients for delivery or targeting. The benefits would undoubtedly accrue to all. 

Moreover, COCs present high toxicity (often being carcinogenic) and high environmental impact. Particularly insidious are volatile organic halides, often used as solvents, whose emissions were limited by the European Community in 1999 [3]. In the past, they were the cause of significant accidents hexachlorobenzene fatally poisoned 500 people in Turkey between 1955 and 1959 chlorofluorocarbons (CFCs) represented the main compounds responsible for the ozone layer depletion dioxins caused several large-... 

Cj Derivatives. The clilorinated methanes, chloroform, methylene chloride, and carbon tetrachloride, consumed approximately 0.8 million tons of clilorine in 1987 and aggregate growth rates from this segment of the industry are expected to remain relatively flat through 1992. Because of its contribution to ozone depletion, carbon tetrachloride use in chlorofluorocarbon manufacture will be phased out in compliance with the recent Montreal Accord. In addition, environmental pressures are expected to continue to impact the use of methylene chloride in aerosol and paint remover applications. Some of the decreases in C1 derivatives should be offset by positive growth for chloroform in HCFC-22 manufacture, which has not been implicated in ozone depletion (see CHLOROCARBONS AND CHLOROHYDROCARBONS, METHYL CHLORIDE METHYLENE CHLORIDE CHLOROFORM CARBON TETRACHLORIDE). 

Most people are familiar with CFCs (chlorofluorocarbons) and how they eventually became doomed as an input into modern industrial products. Ironically, these compounds were initially introduced as environmentally perfect alternatives due to their nontoxic and nonbioaccumulative nature. This is one of many examples of decisions - in this case about safe materials - that have been made on large scale, only to be followed by a late awakening and significant costs to society and individual organizations. Some of the more recent examples now looming on the horizon may be even worse due to their direct impacts on humans - antibiotic-resistant strains of microbes from antibiotics in biota, hampered kidney function from cadmium in foods, and endocrine disruption from plastic additives, to mention just a few. 

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