International Regulation of Urban Smog Since the 1940s - Air Pollution and Global Warming: History, Science, and Solutions - page 183

pollution (previously, states were responsible for per-
mits), and mandated reductions in the emission of CFCs
to combat stratospheric ozone reduction. With respect
to acid deposition, CAAA90 required a 10-million-ton
reduction in sulfur dioxide emissions from 1980 lev-
els and a 2-million-ton reduction in nitrogen oxide
emissions from 1980 levels. With respect to CFCs,
CAAA90 required a complete phase-out of CFCs,
halons (synthetic bromine-containing compounds), and
carbon tetrachloride by 2000 and methyl chloroform by
2002. CAAA90 also required the U.S. EPA to publish a
list of safe and unsafe substitutes for these compounds
and a list of the ozone depletion potential, atmospheric
lifetimes, and global warming potential of all regulated
substances suspected of damaging stratospheric ozone.
CAAA90 banned the production of nonessential prod-
ucts releasing ozone-depleting chemicals. Such prod-
ucts included aerosol spray cans releasing CFCs and
certain noninsulating foam.

global warming agent, were also regulated through
NAAQS.
Nevertheless, CAAA70 permitted the U.S. EPA to
regulate motor vehicle emissions of pollutants that
“cause, or contribute to, air pollution which may rea-
sonably be anticipated to endanger public health or
welfare” [Section 202(a)(1)], implying that emissions
of CO 2 (g) and other long-lived global warming agents
could be regulated if the U.S. EPA were convinced that
such agents endangered public health or welfare. The
issue of whether the U.S. EPA could consider emissions
of such chemicals was settled by the U.S. Supreme
Court in April 2007. It ruled in Massachusetts v. Envi-
ronmental Protection Agency (549 U.S. 497) that car-
bon dioxide and other greenhouse gases are air pollu-
tants covered under CAAA70; thus, the U.S. EPA had
the authority to consider regulating these gases. More
specifically, the U.S. EPA must determine whether

emissions of greenhouse gases from new motor vehi-
cles cause or contribute to air pollution which may
reasonably be anticipated to endanger public health or
welfare.

8.1.11. Clean Air Act Revision of 1997
In 1997, the U.S. Congress passed the Clean Air Act
Revision of 1997 (CAAR97), by which it modified the
NAAQSs for ozone and particulate matter (Table 8.2).
The revised federal ozone standard was based on an
8-hour average rather than a 1-hour average. The new
averaging time was intended to protect those who spend
along time each day working or playing outdoors, the
people most vulnerable to the effects of ozone.
The particulate standard was modified to include a
new PM 2.5 standard because studies have shown that
aerosol particles

The basis for this ruling was the fact that vehicles
enhanced 30,000 premature mortalities per year in the
United States, and the Court determined that the U.S.
EPA had the authority to determine whether greenhouse
gases contributed to such mortality.
In the meantime, on September 27, 2006, California
passed the Global Warming Solutions Act of 2006
(AB32), which mandated that the state prepare a plan
to reduce greenhouse gas emissions in the state by 2020.
On February 21, 2007, the state subsequently requested
the U.S. EPA to grant a waiver of Clean Air Act pre-
emption to allow the state to set carbon dioxide emis-
sion standards for passenger vehicles, light-duty trucks,
and medium-duty passenger vehicles sold in the state.
The CAAA70 gives California authority to set stricter
motor vehicle emission standards than the federal gov-
ernment, but only if the state submits a waiver request to
the U.S. EPA to do so and if the U.S. EPA approves the
waiver. The waiver can be granted as long as California
can demonstrate that the standard is at least as tough as
the federal standard, that the state needs the standard
“to meet compelling and extraordinary conditions,”
and that the standard complies with the Clean Air Act
Amendments of 1970. Historically, waivers have been
granted regularly to California because the state has had
the most severe air pollution in the United States.
Following the U.S. Supreme Court ruling permitting
the U.S. EPA to consider long-lived greenhouse gas

mindiameter have more effect
on respiratory illness, premature death, and visibility
than do larger aerosol particles (Section 5.6). The pur-
pose of the new PM 2.5 standard was to reduce risks
associated with disease and early death associated with
PM 2.5 .

≤ 2.5

8.1.12. California Waiver
By 2007, neither the United States nor any state had
set an emission standard for carbon dioxide or other
long-lived gases that cause global warming. Emissions
of some global warming agents, including black car-
bon and carbon monoxide, were regulated as health-
damaging air pollutants. Black carbon, for example, was
indirectly regulated through automobile and stationary
source particulate matter emission standards. Carbon
monoxide was regulated directly under emission stan-
dards. Outdoor concentrations of PM 2.5 (which contains
black carbon), carbon monoxide, and ozone, another