|
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment into the atmosphere. Ever since the beginning of the Industrial Revolution in the United States, America has had much trouble with environmental issues, air pollution in particular. According to a 2009 report, around "60 percent of Americans live in areas where air pollution has reached unhealthy levels that can make people sick".〔(【引用サイトリンク】title=Top Polluted U.S. Cities With the World Air )〕 ==Clean Air Acts== In the 1960s, 1970s, and 1990s, the United States Congress enacted a series of Clean Air Acts which significantly strengthened regulation of air pollution. Individual U.S. states, some European nations and eventually the European Union followed these initiatives. The Clean Air Act sets numerical limits on the concentrations of a basic group of air pollutants and provide reporting and enforcement mechanisms. In 1999, the United States Environmental Protection Agency (EPA) replaced the Pollution Standards Index (PSI) with the Air Quality Index (AQI) to incorporate new PM2.5 and Ozone standards. The effects of these laws have been very positive. In the United States between 1970 and 2006, citizens enjoyed the following reductions in annual pollution emissions:〔(Wall Street Journal article, May 23, 2006 ) on OpinionJournal.com〕 * carbon monoxide emissions fell from 197 million tons to 89 million tons * nitrogen oxide emissions fell from 27 million tons to 19 million tons * sulfur dioxide emissions fell from 31 million tons to 15 million tons * particulate emissions fell by 80% * lead emissions fell by more than 98% In an October 2006 letter to EPA, the agency's independent scientific advisors warned that the ozone smog standard “needs to be substantially reduced” and that there is “no scientific justification” for retaining the current, weaker standard. The scientists unanimously recommended a smog threshold of 60 to 70 ppb after they conducted an extensive review of the evidence.〔(American Lung Association, June 2, 2007 )〕 The EPA has proposed, in June 2007, a new threshold of 75 ppb. This is less strict than the scientific recommendation, but is more strict than the current standard. Some industries are lobbying to keep the current standards in place. Environmentalists and public health advocates are mobilizing to support the scientific recommendations. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Air pollution in the United States」の詳細全文を読む スポンサード リンク
|