International Regulation of Urban Smog Since the 1940s - Air Pollution and Global Warming: History, Science, and Solutions - page 182

the removal of the greatest amount of emissions from a
particular industry or process.
CAAA77 also mandated that computer modeling be
performed to check whether each proposed new source
of pollution could result in an exceedance of emission
limits or in a violation of an NAAQS. CAAA77 con-
tained the first regulations in which the U.S. government
attempted to control the emissions of CFCs, precursors
to the destruction of stratospheric ozone.

although slightly less so, and given until 2005 to reach
attainment.
Forattainment to be achieved, all new pollution
sources in nonattainment areas, regardless of size,
were required to obtain their lowest achievable emis-
sions rate (LAER) ,which is the lowest emissions rate
achieved for a specific pollutant by a similar source in
any region. LAERs were required to be less stringent
than NSPSs for the source. To achieve LAERs, states or
ACQRs were required to adopt reasonably achievable
control technologies (RACTs) for all existing major
emission sources. RACTs are control technologies that
are reasonably available and technologically and eco-
nomically feasible. They are usually applied to existing
sources in nonattainment areas.
Per CAAA90, state or local air quality districts over-
seeing a nonattainment area were required to develop
emission inventories for ROGs, NO x (g), and CO(g).
Emissions from mobile, stationary point, area, and bio-
genic sources were to be included in the inventories.
The act also mandated that computer modeling be car-
ried out with current and projected future inventories
to demonstrate that attainment could be obtained under
proposed reductions in emissions.
CAAA90 also created a list of 189 hazardous air
pollutants (HAPs) from hundreds of source categories.
Under CAAA90, the U.S. EPA was required to develop
emission standards for each source category under a
timetable. For each new or existing source anticipated
to emit more than 9.1 tonnes per year of 1 HAP, or 22.7
tonnes per year of a combination of HAPs, the U.S.
EPA was required to establish a maximum achievable
control technology (MACT) to reduce hazardous pol-
lution from the source. In selecting MACTs, the U.S.
EPA was permitted to consider cost, non-air quality
health and environmental impacts, and energy require-
ments. Because the use of a MACT does not necessarily
mean that hazardous pollutant concentrations will be
reduced to a safe level, the U.S. EPA was also required
to consult with the Surgeon General to evaluate the risk
resulting from the implementation of each MACT.
The control of toxic air pollutants under CAAA90
differed from the control of criteria air pollutants. In
the former case, the U.S. EPA was required to develop
aprogram to control toxic emissions; in the latter, states
were required to develop programs to control criteria air
pollutant emissions and their ambient concentrations.
CAAA90 also tightened emission standards for auto-
mobiles and trucks, required additional reductions in
emissions of acid deposition precursors, established
afederal permitting program for point sources of

8.1.10. Clean Air Act Amendments of 1990
The overall financial benefit-to-cost ratio of the Clean
Air Act Amendments between 1970 and 1990 has been
estimated as 4:1 (U.S. EPA, 2010). The benefits have
been in the form of reduced damage to human health,
agricultural crops, timber yields, aquatic ecosystems,
and coastal estuaries due to reduced particulate matter,
ozone, acid deposition, nitrogen deposition, ultraviolet
radiation exposure, and stratospheric ozone loss.
Despite air quality and financial benefits of the
CAAA70 regulations, problems related to urban air
pollution, air toxics, acid deposition, and stratospheric
ozone reduction persisted through the 1980s. For exam-
ple, in 1990, 96 U.S. cities were still in violation of the
NAAQSfor ozone, 41 were in violation of the NAAQS
for carbon monoxide, and 70 were in violation of the
NAAQS for PM 10 .Only seven air toxics had been regu-
lated with NESHAPS between 1970 and 1990, although
many more had been identified.
In response to these continued problems, the U.S.
Congress passed the Clean Air Act Amendments of
1990 (CAAA90, PL 101-549) on November 15, 1990.
This was described as an act

to amend the Clean Air Act to provide for attainment
and maintenance of health protective national ambient
air quality standards, and for other purposes.

CAAA90 was similar to CAAA70 with respect to
NAAQS, NSPS, and PSD standards. However, some
major changes were enacted. In particular, nonattain-
ment areas for O 3 (g), CO(g), and PM 10 were divided
into six classifications, depending on the severity of
nonattainment, and each district in which nonattain-
ment occurred was given a different deadline for reach-
ing attainment. For ozone, only Los Angeles was des-
ignated as “extreme” and given until 2010 to reach
attainment of the NAAQS. Baltimore and New York
City were designated as “severe” and given until 2007.
Chicago, Houston, Milwaukee, Muskegon, Philadel-
phia, and San Diego were also designated as “severe,”