2.1 HISTORY OF THE CLEAN AIR ACT
2.2.1 T ITLE I: P ROVISIONS FOR A TTAINMENT AND M AINTENANCE OF NAAQS The 1990 CAAA recognized that many urban areas were not in attainment of the The 1990 CAAA recognized that many urban areas were not in attainment of the
NAAQS, and that there were major problems with high levels of tropospheric ozone and CO. To address the problems practically, the amendments extended the time for states to achieve compliance, but required constant progress in reducing emissions and established provisions for sanctions on areas of the country that do not meet the conditions.
The new amendments also established degrees of severity for nonattainment for O3, CO, and particulate matter with an aerodynamic diameter of less than 10 μ (PM10).
Ozone nonattainment was broken into five degrees of severity, as listed in Table 2.3.
Areas of extreme severity were allowed more time to achieve attainment, but receive increased federal scrutiny for new source review of major sources. The definition of major stationary source, discussed further in new source review permit applications in Chapter 3, applies to smaller sources, and the emission offset ratio requirement for new sources is increased.
Carbon monoxide and particulate matter degrees of severity for nonattainment were established at two levels as shown in Table 2.4.
Also in 1990, Congress added Section 169B, Visibility, to better address regional haze issues, which were not sufficiently addressed with Section 169A. Pursuant to
TABLE 2.4
Degrees of Severity for CO and PM Nonattainment
CO PM
Moderate 9–16.5 ppm Area that can achieve attainment by November 1996 Serious >16.5 ppm Area that cannot achieve compliance by November 1996
TABLE 2.3
Degrees of Severity for Ozone Nonattainment
1-h Avg.
Attainment Date
Major Source Threshold (tons/year)
Offset Ratio for New Sources
Marginal 0.12–0.138 11/15/1993 100 1.1
Moderate 0.138–0.16 11/15/1996 100 1.15
Serious 0.16–0.18 11/15/1999 50 1.2
Severe 0.18–0.19 11/15/2005 25 1.3
0.19–0.28 11/15/2007
Extreme >0.28 11/15/2010 10 1.5
Section 169B, the EPA promulgated additional visibility protection requirements within 40 CFR 51.300–309, requiring states to submit state implementation plans addressing regional haze visibility impairment no later than December 17, 2007 and creating the Grand Canyon Visibility Transport Commission.
2.2.1.1 NAAQS Revisions
Current NAAQS as of December 2014 are listed in Table 2.5. The CAA Section 109(d)(1) requires that the EPA review all its criteria published under Section 108, and NAAQS published under Section 109 every five years to determine if new stud- ies and scientific evidence warrant revisions to the standards. In 1997, the EPA issued a new primary and secondary ozone standard of 0.08 ppm for an 8-h average in addition to the existing standard of 0.12 ppm for a 1-h average. The EPA determined that longer term exposures to lower levels of ozone caused health effects including asthma attacks, breathing and respiratory problems, loss of lung function, and pos- sible long-term lung damage and decreased immunity to disease. This was the first update of the ozone standard in 20 years.
Also in 1997, the EPA established a new particulate matter standard for fine par- ticulates with an aerodynamic diameter of less than 2.5 μ (PM2.5). The standard was established at 65 μg/m3 for a 24-h average and 15 μg/m3 for an annual average. The new standards followed a lawsuit by the American Lung Association that the EPA missed the deadline for the required review of the particulate standard. The previous review of the particulate standard was conducted in 1987. A new court-ordered dead- line of July 1997 was established to finalize the particulate standard, and the EPA finalized the ozone standard simultaneously.
In May 1999, the new ozone and particulate standards were remanded by the Court of Appeals following a lawsuit by the American Trucking Association. The key issue was neither the quality of the health-based review, the review process, nor the degree of public health concern. Indeed, the Court of Appeals agreed that there was growing
TABLE 2.5
National Ambient Air Quality Standards
Primary Secondary
Level Averaging Time Level Averaging Time
O3 0.075 ppm 8 h Same Same
PM10 150 μg/m3 24 h Same Same
PM2.5 CO
35 μg/m3 12 μg/m3 35 ppm
24 h Annual 1 h
35 μg/m3 15 μg/m3
24 h Annual
9 ppm 8 h
SO2 0.075 ppm 1 h 0.5 ppm 3 h
NO2 0.100 ppm 0.053 ppm
1 h Annual
0.053 ppm Annual
Lead 0.15 μg/m3 Rolling 3 month Same Same
adverse health effects that justified a new fine particle standard. Instead, the key issue centered around EPA’s authority to establish a standard for a nonthreshold pollutant that weighs health with the cost of implementing the standard.
A threshold pollutant is one that exhibits a minimum level, or threshold, below which no health effects are observed. A nonthreshold pollutant has diminishing health effects with decreasing concentration, but there will always be some effect even at extremely low concentrations. Threshold and nonthreshold pollutant responses are illustrated in Figure 2.1. The data are the difference in mortality between mice exposed to ozone and an unexposed control group, then both subsequently exposed to Streptococcus bacteria.5 Figure 2.1 also demonstrates the difficulty in collecting data to measure and interpret a threshold level. A large number of expensive data at very low concentrations and with very small responses may be required to detect a threshold.
If a pollutant indeed has no health-based threshold, then the only healthy level is zero, which is impractical. Therefore, a judgment that compromises an acceptable level of health risk with a reasonable implementation cost must be reached, and such judgment constitutes establishing policy. In American Trucking Associations, Inc. v.
U.S. EPA, the D.C. Circuit Court of Appeals said that the EPA lacked any determi- nate criterion for establishing where the standard for a nonthreshold pollutant should be set, so choosing a standard was capricious and arbitrary. In a decision of 2 to 1, the Court of Appeals determined that the CAA, as applied and absent further clarifica- tion, is unconstitutional because it gives “an unconstitutional delegation of legislative power”6 to the EPA. The dissenting opinion of the Court was that this interpretation
“ignores the last half-century of Supreme Court nondelegation jurisprudence.”6 The EPA appealed to the U.S. Supreme Court. On February 27, 2001, the Supreme Court unanimously upheld the constitutionality of EPA’s interpretation in setting the 1997 NAAQS revisions. Specifically, the Supreme Court held that the CAA does not
0.0 0.1 0.2
Ozone concentration (ppm) Increased mortality in mice exposed to bacteria (%)
0.3 0.4 0.5 0.6
0 10 20 30 40 50 60 70 80
Data Nonthreshold Threshold
FIGURE 2.1 Threshold versus nonthreshold response. (Adapted from De Neveres, N., Air Pollution Control Engineering, Copyright 1995. The McGraw-Hill Companies, p. 16.)
permit the EPA to consider implementation costs in setting NAAQS, and disagreed that the EPA lacked determinate criteria for drawing the lines that guide the protection of public health.7