Page 477 - Environment: The Science Behind the Stories

As a result of Clean Air Act legislation, the U.S. Environ-
CO 2 CH 4 N 2 O mental Protection Agency (EPA) sets nationwide standards for:
SF 6 HFCs HCFCs
Maximum scale of impact Hemispheric SO 4 2– NO 3 – Tropospheric CO quality and to develop, implement, and enforce regulations
Global
PFCs CFCs
• Emissions of several key pollutants
• Concentrations of key pollutants in ambient air
It is largely up to the states to monitor emissions and air
ozone
Regional
+
NH 4
the EPA for approval, and if a state’s plans are not adequate,
SO 2 NO 2
the EPA can take control of enforcement. If a region fails to
Local NH 3 PM 10 PM 2.5 within their borders. States submit implementation plans to
NO
clean up its air, the EPA can prevent it from receiving federal
Hours Days Weeks Months Years Centuries money for transportation projects.
Residence time in the atmosphere
Agencies monitor emissions
Figure 17.12 Substances with short residence times affect air
quality locally, whereas those with long residence times affect State and local agencies monitor and report to the EPA emis-
air quality regionally or globally. Data from United Nations Environment sions of six major pollutants—carbon monoxide (CO), sulfur
Programme, 2007. Global environmental outlook (GEO-4), Nairobi, Kenya. dioxide (SO ), nitrogen oxides (NO ), volatile organic com-
X
2
pounds (VOCs), particulate matter, and lead (Pb). Across the
United States in 2012, human activity polluted the air with
the atmosphere for so long. Figure 17.12 shows this relation- 85 million tons of these six monitored pollutants. Carbon
ship, with examples.
monoxide was the most abundant pollutant by mass, followed
by VOCs, NO , and SO (Figure 17.13).
X 2
Clean Air Act legislation addresses Carbon monoxide Carbon monoxide is a colorless,
pollution in the United States odorless gas produced primarily by the incomplete combus-
tion of fuel. Vehicles and engines account for most CO emis-
To address air pollution in the United States, Congress has sions in the United States. Other sources include industrial
passed a series of laws, beginning with the Air Pollution processes, waste combustion, and residential wood burning.
Control Act of 1955. The Clean Air Act of 1963 funded Carbon monoxide is hazardous because it can bind irrevers-
research into pollution control and encouraged emissions ibly to hemoglobin in red blood cells, preventing the hemo-
standards for automobiles and for stationary point sources globin from binding with oxygen.
such as industrial plants. Subsequent amendments expanded
the legislation’s scope and established a nationwide air quality Sulfur dioxide Sulfur dioxide is a colorless gas with a
monitoring system. pungent odor. The vast majority of SO pollution results from
2
In 1970, Congress thoroughly revised the law in what the combustion of coal for electricity generation and industry.
came to be known as the Clean Air Act of 1970. This legislation During combustion, elemental sulfur (S) in coal reacts with
set stricter standards for air quality, imposed limits on emis-
sions from new sources, provided new funds for pollution-
control research, and enabled citizens to sue parties violating
the standards. Some of these goals came to be viewed as too
ambitious, so amendments in 1977 loosened some standards Volatile
organic
and extended some deadlines for compliance. compounds
The Clean Air Act of 1990 sought to strengthen regula- (15%)
tions pertaining to air quality standards, auto emissions, toxic Nitrogen
air pollution, acid deposition, and stratospheric ozone deple- oxides
tion. It also introduced an emissions trading program for Carbon (13%)
sulfur dioxide (p. 201). Beginning in 1995, businesses and monoxide
utilities were allocated permits for emitting this pollutant and (62%) Sulfur dioxide
could then buy, sell, or trade these allowances. Each year the (6%)
overall amount of allowed pollution was decreased. This mar-
ket-based incentive program has helped reduce sulfur diox- Particulate
ide emissions nationally (see Figure 7.16, p. 201). It has also matter
spawned similar cap-and-trade programs for other pollutants, Lead (3%)
including greenhouse gases (pp. 530–531). The Los Angeles (0.002%)
region adopted its own cap-and-trade program in 1994. The Figure 17.13 In 2012, the United States emitted 85 million
RECLAIM (Regional Clean Air Incentives Market) program tons of the six major pollutants whose emissions are
helped the L.A. basin reduce emissions of sulfur dioxide and monitored by the EPA and state agencies. These figures omit pol-
476 nitrogen dioxide by over 70% by 2010. lutants from dust and wildfires. Data from U.S. EPA.

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