Word: cfcs
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Dates: during 2000-2009
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Humankind doesn't have a great track record when it comes to cleaning up environmental messes, but there was one time we really outdid ourselves. That was back in 1989, when over 190 nations signed the Montreal Protocol, phasing out the use of chlorofluorocarbons (CFCs). The decade before, scientists had discovered that CFCs were blowing a hole in the ozone layer over Antarctica, exposing us to dangerous ultraviolet radiation and boosting the risk of skin cancer. Today, CFCs are no longer in widespread use, and the ozone layer appears to be on the mend...
...study published in the Aug. 28 Science found that N2O - a by-product of agricultural fertilizer and a number of other industrial processes - is now the biggest ozone-depleting gas in the air, and could present a real threat to the ozone layer in coming decades. And worse, unlike CFCs, N2O - which also adds to global warming - is not regulated by the Montreal Protocol, meaning there is no global effort to try to reduce emissions. (See pictures of the world's most polluted places...
...idea that N2O poses a threat to the ozone layer is not new, but the Science study is the first comprehensive look at the exact concentrations and consequences of the gas. The investigators found that although N2O is only one-sixtieth as dangerous to the ozone layer as CFCs on a gram-by-gram basis, the sheer amount of N2O - each year nearly 1 billion metric tons of CO2 equivalent are released globally - means that it now poses a more significant threat to the atmosphere. (N2O emissions are calculated in terms of their impact on global warming...
...news isn't all bad: the fact that scientists can now turn so much of their attention to the dangers of N2O is in part because CFC levels have dropped so low, thanks to the Montreal Protocol. But N2O is likely to prove much more difficult than CFCs to phase out. While CFCs had a relatively narrow range of uses - and chemical companies like DuPont were able to come up with replacements quickly - N2O is all around us, tied intimately to our industrial way of life. The millions of tons of soil fertilizer used in U.S. agriculture alone...
...Montreal Protocol, meanwhile, provided an important example of successful trade controls: firms were discouraged from relocating to evade standards through the imposition of non-discriminatory controls placed on industries that release CFCs, ozone-depleting compounds...