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Criteria pollutants. The 1970 and 1977 federal Clean Air Acts required
that local metropolitan areas be evaluated to determine whether they met air-quality standards for five pollutants: ozone, carbon monoxide, total suspended particulate matter, sulfur dioxide,
and nitrogen dioxide. Later, the EPA added lead (in 1978) and replaced total suspended particulates with particulate matter less than 10 microns in diameter, known as PM10 (in 1987). In July
1997 the EPA adopted a new standard for PM2.5, particulate matter less than 2.5 microns, as well as a more stringent 8-hour ozone standard.
Two-hundred and thirty metropolitan areas in the United States did not meet the standards for one of the six
criteria pollutants as of April 1993 and were considered "non-attainment"-- including 96 metropolitan areas which did not meet the one-hour ozone standard.* Depending upon the severity of the non-attainment designation, states were required to work with the EPA and metropolitan areas to design "SIPs" State Implementation Plans to help clear the air. Because of actions taken under these plans, as well as other federal and state level requirements, by the end of 1997, EPA data indicated that 38 metropolitan areas still did not meet the 1-hour standard.* Under the 1990 Act amendments, all but 10 of these cities were initially required to meet the 1-hour ozone standard by 1999, with Los Angeles -- the most heavily polluted city – having to comply by 2010. However, by September of 2002, there will still 124 areas designated as non-attainment in 1993 that were still considered non-attainment, including 56 for ground-level ozone-- with some 116 million people living there -- and 67 for particulate matter, potentially impacting another 34 million
(Footnote: U.S. Environmental Protection Agency, National Air Quality and Emissions Trends Report, 2003, Appendix A: Condensed Nonattainment Areas List).
It is important to note that this does not include any metropolitan areas which may be designated non-attainment for the new 8-hour ozone standard or for the new 2.5 particulate matter standard, and EPA estimated that in the 2002 year alone, some 136 million people lived in metropolitan areas that violated the national air quality standards for the 8-hour ozone standard, while 59 million people lived in metropolitan areas violating standards for PM 2.5.
(FOOTNOTE: U.S. Environmental Protection Agency, Latest Findings on National Air Quality: 2002 Status and Trends, 5).
Under programs and regulations implemented because of the 1990 Federal Clean Air Act Amendments, substantial
progress was made in reducing overall emissions. For example, between 1993 and 2002, the EPA estimates that nationwide, industries, cars, trucks and other sources of pollution reduced
emissions of nitrogen oxides by 12 percent; volatile organic compounds by nearly 25 percent; sulfur dioxide by a wopping 31 percent; and particulate matter less than 10 microns by some 22
percent. Despite this progress, overall air quality -- the actual pollution found in the air -- did not improve as much. Thus, monitors indicated that nationwide, one-hour readings of ozone
only declined by two percent, and concentrations of particulate matter less than 10 microns by 13 percent. (FOOTNOTE: U.S. Environmental Protection Agency, Latest Findings on National Air
Quality: 2002 Status and Trends, 3).These numbers -- as well as the large number of cities considered non-attainment -- indicate that even more work is required to produce cleaner cars,
buildings, trucks and industries -- and ultimately cleaner air.
Airborne toxics. The 1990 federal Clean Air Act forced the EPA to identify industries
that release certain toxic chemicals and require major sources of these chemicals to install "maximum achievable control technology" by the year 2003. Sources other than major sources would
be required to install less costly forms of control. Currently, 188 air pollutants have been identified by Congress and the EPA as toxic, and 174 industry classifications that release toxic
compounds and could thus be subject to resulting regulations also have been identified. Despite these improvements, there is still debate about whether the new control technology levels will
be stringent enough to protect those living near industries that emit hazardous air pollutants.* Overall, some chemical toxics have witnessed substantial declines, both in terms of emissions and the pollutants concentrated in the air. Overall, EPA estimates that emissions of the 188 toxic HAPs have been reduced from some 6.0 million tons in 1993 to some 4.7 million tons by 1996
(FOOTNOTE: U.S. Environmental Protection Agency, Latest Findings on National Air Quality: 2002 Status and Trends, 23).
Acid rain. Emissions of sulfur dioxide -- one of the gases that produces acid rain
-- are subject to stronger controls and monitoring. Under the 1990 Clean Air Act, power plants are limited to 8.9 million tons per year of sulfur dioxide emissions by the year 2010, down from
19 million tons per year emitted in 1980. This reduction is being accomplished in two phases. In Phase I, which began in 1995, the 263 "dirtiest" units (at power plants with the most
emissions) had to meet an emissions cap for sulfur dioxide. These units – mostly located in the Mid-west -- reduced sulfur dioxide emission from 9.4 to 4.95 million tons between 1980 and 1999
(REPLACE FOOTNOTE: U.S. Environmental Protection Agency, Latest Findings on National Air Quality: 2002 Status and Trends, 18).* In Phase II, which began in 2000, the remaining power plants, including those in Texas, must reduce sulfur dioxide emissions. Overall, preliminary data shows that all major utilities required to reduce emissions cut emissions from 11.87 million tons in 1995 to 10.19 million tons in 2002. Interestingly, the program uses a cap-and-trade emissions program, where sources are allocated allowances (i.e. one allowance is equal to one ton of emissions of sulfur dioxide) each year, which can be bought and sold or banked for future use. This allows utilities more flexibility in how they meet the emissions cap.
In addition, both Phase I (which began in 1996) and Phase II (which began in 2000) sources must cut nitrogen
oxide emissions by some two million tons by 2010. Preliminary data shows that between 1990 and 2002, the major utilities in the U.S. cut emissions of nitrogen oxides from 6.66 to 4.47 million
tons. (FOOTNOTE: U.S. Environmental Protection Agency, Latest Findings on National Air Quality: 2002 Status and Trends, 18).
Atmospheric ozone. Ozone can be helpful or harmful, depending on where it is. High
above the earth in the stratosphere, an ozone layer protects life on earth from harmful ultraviolet radiation from the sun. The 1990 federal Clean Air Act phases out the production of certain
chemicals such as methyl chloroform and freon that may deplete the stratospheric ozone layer and regulates the use and disposal of other possible ozone-depleting substances.* In 1996, U.S. production of CFCs, carbon tetrachloride and methyl chloroform was virtually ended, while production of halons ended in 1994. However, the production of all ozone-depleting chemicals has not ceased, and some products -- like methyl bromide -- have continued to be produced past their original deadlines.
Mobile sources.
The 1990 federal Clean Air Act amendments imposed reductions in the amount of hydrocarbons and nitrogen oxides present in tailpipe exhaust beginning with 1994 vehicles and required that these standards be maintained for 100,000 miles. The act also required the sale of only cleaner "reformulated" gasoline in cities with the highest levels of ground-level ozone pollution and gasoline with a higher oxygen content in those cities that exceed standards for carbon monoxide. In cities where ozone pollution exceeds certain levels, the federal act requires consumers to have their car or vehicle tailpipe emissions tested. Vehicles that do not meet the emission standards they were built to meet are to be repaired.
The act encourages the development and sale of low-emission vehicles powered by alternative fuels, such as
hydrogen gas, ethanol, liquefied petroleum gas, and natural gas or even electricity. It required manufacturers to begin producing such cars for sale -- starting with the manufacture of
500,000 of these clean-fuel cars for sale in Southern California in 2003.* The act also requires private and government owners of large fleets of cars to purchase certain clean-fuel vehicles for their fleets in those cities with the most severe ozone problems.
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