Draft – Do Not Cite or Quote lxxviii June 2012

LEGISLATIVE AND HISTORICAL BACKGROUND

Legislative Requirements for the NAAQS Review

1 Two sections of the Clean Air Act (CAA) govern the establishment and revision of 

2 the National Ambient Air Quality Standards (NAAQS). Section 108 (42 USC §7408) 

3 directs the Administrator to identify and list certain air pollutants and then to issue air 

4 quality criteria for those pollutants. The Administrator is to list those air pollutants 

5 that in her “judgement; cause or contribute to air pollution which may reasonably be 

6 anticipated to endanger public health or welfare;” ... ”the presence of which in the 

7 ambient air results from numerous or diverse mobile or stationary sources” and “for 

8 which ... [the Administrator] plans to issue air quality criteria...” (CAA, 1990a). Air 

9 quality criteria are intended to “accurately reflect the latest scientific knowledge 

10 useful in indicating the kind and extent of identifiable effects on public health or 

11 welfare, which may be expected from the presence of [a] pollutant in ambient air ...” 

12 [42 USC §7408(b)].

13 Section 109 (CAA, 1990b) directs the Administrator to propose and promulgate 

14 “primary” and “secondary” NAAQS for pollutants for which air quality criteria have 

15 been issued. Section 109(b)(1) defines a primary standard as one “the attainment and 

16 maintenance of which in the judgment of the Administrator, based on such criteria 

17 and allowing an adequate margin of safety, are requisite to protect the public 

health.”1 18 A secondary standard, as defined in section 109(b)(2), must “specify a level 

19 of air quality the attainment and maintenance of which, in the judgment of the 

20 Administrator, based on such criteria, is required to protect the public welfare from 

21 any known or anticipated adverse effects associated with the presence of [the] 

pollutant in the ambient air.”2 22

23 The requirement that primary standards include an adequate margin of safety was 

24 intended to address uncertainties associated with inconclusive scientific and technical 

25 information available at the time of standard setting. It was also intended to provide a 

26 reasonable degree of protection against hazards that research has not yet identified. 

27 See Lead Industries Association v. EPA, 647 F.2d 1130, 1154 (D.C. Cir 1980), cert. 

28 denied, 449 U.S. 1042 (1980); American Petroleum Institute v. Costle, 665 F.2d 

29 1176, 1186 (D.C. Cir. (1981), cert. denied, 455 U.S. 1034 (1982). Both kinds of 

 1 The legislative history of section 109 indicates that a primary standard is to be set at “the maximum permissible ambient air level 

. . . which will protect the health of any [sensitive] group of the population,” and that for this purpose “reference should be made to a 

representative sample of persons comprising the sensitive group rather than to a single person in such a group” [S. Rep. No. 91-

1196, 91st Cong., 2d Sess. 10 (1970)].

2 Welfare effects as defined in section 302(h) include, but are not limited to, “effects on soils, water, crops, vegetation, man-made 

materials, animals, wildlife, weather, visibility and climate, damage to and deterioration of property, and hazards to transportation, as 

well as effects on economic values and on personal comfort and well-being” (CAA, 2005).
Draft – Do Not Cite or Quote lxxix June 2012

1 uncertainties are components of the risk associated with pollution at levels below 

2 those at which human health effects can be said to occur with reasonable scientific 

3 certainty. Thus, in selecting primary standards that include an adequate margin of 

4 safety, the Administrator is seeking not only to prevent pollution levels that have 

5 been demonstrated to be harmful but also to prevent lower pollutant levels that may 

6 pose an unacceptable risk of harm, even if the risk is not precisely identified as to 

7 nature or degree. The CAA does not require the Administrator to establish a primary 

8 NAAQS at a zero-risk level or at background concentration levels, see Lead 

9 Industries v. EPA, 647 F.2d at 1156 n.51, but rather at a level that reduces risk 

10 sufficiently so as to protect public health with an adequate margin of safety.

11 In addressing the requirement for a margin of safety, EPA considers such factors as 

12 the nature and severity of the health effects involved, the size of the sensitive 

13 population(s) at risk, and the kind and degree of the uncertainties that must be 

14 addressed. The selection of any particular approach to providing an adequate margin 

15 of safety is a policy choice left specifically to the Administrator’s judgment. See 

16 Lead Industries Association v. EPA, supra, 647 F.2d at 1161-1162; Whitman v. 

17 American Trucking Associations, 531 U.S. 457, 495 (2001).

18 In setting standards that are “requisite” to protect public health and welfare, as 

19 provided in Section 109(b), EPA’s task is to establish standards that are neither more 

20 nor less stringent than necessary for these purposes. In so doing, EPA may not 

21 consider the costs of implementing the standards. [See generally, Whitman v. 

22 American Trucking Associations, 531 U.S. 457, 465-472, 475-76. (2001)]. Likewise, 

23 “[a]ttainability and technological feasibility are not relevant considerations in the 

24 promulgation of national ambient air quality standards.” American Petroleum 

25 Institute v. Costle, 665 F. 2d at 1185.

26 Section 109(d)(1) requires that “not later than December 31, 1980, and at 5-year 

27 intervals thereafter, the Administrator shall complete a thorough review of the 

28 criteria published under section 108 and the national ambient air quality standards ... 

29 and shall make such revisions in such criteria and standards and promulgate such 

30 new standards as may be appropriate...” Section 109(d)(2) requires that an 

31 independent scientific review committee “shall complete a review of the criteria ... 

32 and the national primary and secondary ambient air quality standards ... and shall 

33 recommend to the Administrator any new ... standards and revisions of existing 

34 criteria and standards as may be appropriate ...” Since the early 1980s, this 

35 independent review function has been performed by CASAC.
Draft – Do Not Cite or Quote lxxx June 2012

History of the NAAQS for Ozone

1 Tropospheric (ground-level) O3 is the indicator for the mix of photochemical 

2 oxidants (e.g., peroxyacetyl nitrate, hydrogen peroxide) formed from biogenic and 

3 anthropogenic precursor emissions. Naturally occurring O3 in the troposphere can 

4 result from biogenic organic precursors reacting with naturally occurring nitrogen 

5 oxides (NOX) and by stratospheric O3 intrusion into the troposphere. Anthropogenic 

6 precursors of O3, especially NOX, and volatile organic compounds (VOCs), originate 

7 from a wide variety of stationary and mobile sources. Ambient O3 concentrations 

8 produced by these emissions are directly affected by temperature, solar radiation, 

9 wind speed, and other meteorological factors.

10 NAAQS are comprised of four basic elements: indicator, averaging time, level, and 

11 form. The indicator defines the pollutant to be measured in the ambient air for the 

12 purpose of determining compliance with the standard. The averaging time defines the 

13 time period over which air quality measurements are to be obtained and averaged or 

14 cumulated, considering evidence of effects associated with various time periods of 

15 exposure. The level of a standard defines the air quality concentration used (i.e., an 

16 ambient concentration of the indicator pollutant) in determining whether the standard 

17 is achieved. The form of the standard specifies the air quality measurements that are 

18 to be used for compliance purposes (e.g., the annual fourth-highest daily maximum 

19 8-hour concentration, averaged over 3 years), and whether the statistic is to be 

20 averaged across multiple years. These four elements taken together determine the 

21 degree of public health and welfare protection afforded by the NAAQS.

Table III Summary of primary and secondary NAAQS promulgated for ozone 

during the period 1971-2008

Final Rule Indicator Avg 

Time

Level (ppm) Form

1971 (36 FR 8186) Total 

photochemical 

oxidants

1-h 0.08 Not to be exceeded more than 1 hour per year

1979 (44 FR 8202) O3 1-h 0.12 Attainment is defined when the expected number of days per 

calendar year, with maximum hourly average concentration greater 

than 0.12 ppm, is ≤ 1

1993 (58 FR 13008) EPA decided that revisions to the standards were not warranted at the time.

1997 (62 FR 38856) O3 8-h 0.08 Annual fourth-highest daily maximum 8-h concentration averaged 

over 3 years

2008 (73 FR 16483) O3 8-h 0.075 Form of the standards remained unchanged relative to the 1997 

standard
Draft – Do Not Cite or Quote lxxxi June 2012

1 Table III summarizes the O3 NAAQS that have been promulgated to date. In each 

2 review, the secondary standard has been set to be identical to the primary standard. 

3 These reviews are briefly described below.

4 EPA first established primary and secondary NAAQS for photochemical oxidants in 

5 1971 . Both primary and secondary standards were set at a level of 0.08 parts per 

6 million (ppm), 1-h avg, total photochemical oxidants, not to be exceeded more than 

7 1 hour per year. The standards were based on scientific information contained in the 

8 1970 AQCD.

9 In 1977, EPA announced the first periodic review of the 1970 AQCD in accordance 

10 with Section 109(d)(1) of the Clean Air Act. In 1978, EPA published an AQCD. 

11 Based on the 1978 AQCD, EPA published proposed revisions to the original 

12 NAAQS in 1978 (U.S. EPA, 1978b) and final revisions in 1979 (U.S. EPA, 1979a). 

13 The level of the primary and secondary standards was revised from 0.08 to 0.12 ppm; 

14 the indicator was revised from photochemical oxidants to O3; and the form of the 

15 standards was revised from a deterministic to a statistical form, which defined 

16 attainment of the standards as occurring when the expected number of days per 

17 calendar year with maximum hourly average concentration greater than 0.12 ppm is 

18 equal to or less than one. 

19 In 1982, EPA announced plans to revise the 1978 AQCD (U.S. EPA, 1978a). In 

20 1983, EPA announced that the second periodic review of the primary and secondary 

21 standards for O3 had been initiated (U.S. EPA, 1983). EPA subsequently published 

22 the 1986 O3 AQCD (U.S. EPA, 1986) and 1989 Staff Paper (U.S. EPA, 1989). 

23 Following publication of the 1986 O3 AQCD, a number of scientific abstracts and 

24 articles were published that appeared to be of sufficient importance concerning 

25 potential health and welfare effects of O3 to warrant preparation of a Supplement to 

26 the 1986 O3 AQCD (Costa et al., 1992). Under the terms of a court order, on August 

27 10, 1992, EPA published a proposed decision (U.S. EPA, 1992) stating that revisions 

28 to the existing primary and secondary standards were not appropriate at the time 

29 (U.S. EPA, 1992). This notice explained that the proposed decision would complete 

30 EPA’s review of information on health and welfare effects of O3 assembled over a 

31 7-year period and contained in the 1986 O3 AQCD (U.S. EPA, 1986) and its 

32 Supplement to the 1986 O3 AQCD (Costa et al., 1992). The proposal also announced 

33 EPA’s intention to proceed as rapidly as possible with the next review of the air 

34 quality criteria and standards for O3 in light of emerging evidence of health effects 

35 related to 6- to 8-hour O3 exposures. On March 9, 1993, EPA concluded the review 

36 by deciding that revisions to the standards were not warranted at that time (U.S. 

37 EPA, 1993).
Draft – Do Not Cite or Quote lxxxii June 2012

1 In August 1992, EPA announced plans to initiate the third periodic review of the air 

2 quality criteria and O3 NAAQS (U.S. EPA, 1992). On the basis of the scientific 

3 evidence contained in the 1996 O3 AQCD and the 1996 Staff Paper (U.S. EPA, 

4 1996e), and related technical support documents, linking exposures to ambient O3 to 

5 adverse health and welfare effects at levels allowed by the then existing standards, 

6 EPA proposed to revise the primary and secondary O3 standards on December 13, 

7 1996 (U.S. EPA, 1996d). The EPA proposed to replace the then existing 1-hour 

8 primary and secondary standards with 8-h avg O3 standards set at a level of 0.08 ppm 

9 (equivalent to 0.084 ppm using standard rounding conventions). The EPA also 

10 proposed, in the alternative, to establish a new distinct secondary standard using a 

11 biologically based cumulative seasonal form. The EPA completed the review on July 

12 18, 1997 by setting the primary standard at a level of 0.08 ppm, based on the annual 

13 fourth-highest daily maximum 8-h avg concentration, averaged over 3 years, and 

14 setting the secondary standard identical to the revised primary standard (U.S. EPA, 

15 1997).

16 On May 14, 1999, in response to challenges to EPA’s 1997 decision by industry and 

17 others, the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Cir.) 

18 remanded the O3 NAAQS to EPA, finding that Section 109 of the CAA, as 

19 interpreted by EPA, effected an unconstitutional delegation of legislative authority. 

20 In addition, the D.C. Cir. directed that, in responding to the remand, EPA should 

21 consider the potential beneficial health effects of O3 pollution in shielding the public 

22 from the effects of solar ultraviolet (UV) radiation, as well as adverse health effects. 

23 On January 27, 2000, EPA petitioned the U.S. Supreme Court for certiorari on the 

24 constitutional issue (and two other issues) but did not request review of the D.C. Cir., 

25 ruling regarding the potential beneficial health effects of O3. On February 27, 2001, 

26 the U.S. Supreme Court unanimously reversed the judgment of the D.C. Cir. on the 

27 constitutional issue, holding that Section 109 of the CAA does not delegate 

28 legislative power to the EPA in contravention of the Constitution, and remanded the 

29 case to the D.C. Cir. to consider challenges to the O3 NAAQS that had not been 

30 addressed by that Court’s earlier decisions. On March 26, 2002, the D.C. Cir. issued 

31 its final decision, finding the 1997 O3 NAAQS to be “neither arbitrary nor 

32 capricious,” and denied the remaining petitions for review. On November 14, 2001, 

33 in response to the D.C. Cir. remand to consider the potential beneficial health effects 

34 of O3 pollution in shielding the public from effects of solar (UV) radiation, EPA 

35 proposed to leave the 1997 8-h O3 NAAQS unchanged (U.S. EPA, 2001). After 

36 considering public comment on the proposed decision, EPA published its final 

37 response to this remand on January 6, 2003, reaffirming the 8-h O3 NAAQS set in 

38 1997 (U.S. EPA, 2003). On April 30, 2004, EPA announced the decision to make the 

39 1-h O3 NAAQS no longer applicable to areas 1 year after the effective date of the 
Draft – Do Not Cite or Quote lxxxiii June 2012

1 designation of those areas for the 8-h NAAQS (2004). For most areas, the date that 

2 the 1-h NAAQS no longer applied was June 15, 2005.

3 EPA initiated the next periodic review if the air quality criteria and O3 standards in 

4 September 2000 with a call for information (U.S. EPA, 2000). The schedule for 

5 completion of that rulemaking later became governed by a consent decree resolving a 

6 lawsuit filed in March 2003 by a group of plaintiffs representing national 

7 environmental and public health organizations. Based on the 2006 O3 AQCD (U.S. 

8 EPA, 2006b) published in March 2006, the Staff Paper (U.S. EPA, 2007b) and 

9 related technical support documents, the proposed decision was published in the 

10 Federal Register on July 11, 2007 (U.S. EPA, 2007a). The EPA proposed to revise 

11 the level of the primary standard to a level within the range of 0.075 to 0.070 ppm. 

12 Two options were proposed for the secondary standard: (1) replacing the current 

13 standard with a cumulative, seasonal standard, expressed as an index of the annual 

14 sum of weighted hourly concentrations cumulated over 12 daylight hours during the 

15 consecutive 3-month period within the O3 season with the maximum index value, set 

16 at a level within the range of 7 to 21 ppm-h; and (2) setting the secondary standard 

17 identical to the revised primary standard. The EPA completed the rulemaking with 

18 publication of a final decision on March 27, 2008 (U.S. EPA, 2008e), revising the 

19 level of the 8-hour primary O3 standard from 0.08 ppm to 0.075 ppm and revising the 

20 secondary standard to be identical to the primary standard.

21 In May 2008, state, public health, environmental, and industry petitioners filed suit 

22 against EPA regarding that final decision. At EPA’s request the consolidated cases 

23 were held in abeyance pending EPA’s reconsideration of the 2008 decision. A notice 

24 of proposed rulemaking to reconsider the 2008 final decision was issued by the 

25 Administrator on January 6, 2010. Three public hearings were held. The Agency 

26 solicited CASAC review of the proposed rule on January 25, 2010 and additional 

27 CASAC advice on January 26, 2011. On September 2, 2011, the Office of 

28 Management and Budget returned the draft final rule on reconsideration to EPA for 

29 further consideration. EPA decided to coordinate further proceedings on its voluntary 

30 rulemaking on reconsideration with the ongoing periodic review, by deferring the 

31 completion of its voluntary rulemaking on reconsideration until it completes its 

32 statutorily-required periodic review. In light of that, the litigation on the 2008 final 

33 decision is no longer being held in abeyance and is proceeding. The 2008 ozone 

34 standards remain in effect.
Draft – Do Not Cite or Quote lxxxiv June 2012

References

CAA. Clean Air Act, as amended by Pub. L. No. 101-549, section 108: Air quality criteria and control 

techniques, § 7408 (1990a). http://www.law.cornell.edu/uscode/text/42/7408

CAA. Clean Air Act, as amended by Pub. L. No. 101-549, section 109: National primary and secondary 

ambient air quality standards, § 7409 (1990b). http://www.epa.gov/air/caa/title1.html#ia

CAA. Clean Air Act, section 302: Definitions, § 7602 (2005). http://www.gpo.gov/fdsys/pkg/USCODE2005-title42/pdf/USCODE-2005-title42-chap85-subchapIII-sec7602.pdf

Costa, DL; Folinsbee, LJ; Raub, JA; Tilton, B; Tingey, DT. (1992). Summary of selected new information on 

effects of ozone on health and vegetation: Supplement to 1986 air quality criteria for ozone and other 

photochemical oxidants. (EPA/600/8-88/105F). Research Triangle Park, NC: U.S. Environmental 

Protection Agency. http://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=31093

U.S. EPA (U.S. Environmental Protection Agency). (1971). National primary and secondary ambient air 

quality standards. Fed Reg 36: 8186-8201. 

U.S. EPA (U.S. Environmental Protection Agency). (1978a). Air quality criteria for ozone and other 

photochemical oxidants [EPA Report]. (EPA/600/8-78/004). Washington, DC. 

U.S. EPA (U.S. Environmental Protection Agency). (1978b). Photochemical oxidants: Proposed revisions to 

the national ambient air quality standards. Fed Reg 43: 26962-26971. 

U.S. EPA (U.S. Environmental Protection Agency). (1979a). National primary and secondary ambient air 

quality standards: Revisions to the national ambient air quality standards for photochemical oxidants. 

Fed Reg 44: 8202-8237. 

U.S. EPA (U.S. Environmental Protection Agency). (1982). Air quality criteria document for ozone and other 

photochemical oxidants. Fed Reg 47: 11561. 

U.S. EPA (U.S. Environmental Protection Agency). (1983). Review of the national ambient air quality 

standards for ozone. Fed Reg 48: 38009. 

U.S. EPA (U.S. Environmental Protection Agency). (1986). Air quality criteria for ozone and other 

photochemical oxidants [EPA Report]. (EPA-600/8-84-020aF - EPA-600/8-84-020eF). Research 

Triangle Park, NC. http://www.ntis.gov/search/product.aspx?ABBR=PB87142949

U.S. EPA (U.S. Environmental Protection Agency). (1989). Review of the national ambient air quality 

standards for ozone: Assessment of scientific and technical information: OAQPS staff report [EPA 

Report]. (EPA-450/2-92-001). Research Triangle Park, NC. 

http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=2000LOW6.txt

U.S. EPA (U.S. Environmental Protection Agency). (1992). National ambient air quality standards for ozone; 

Proposed decision. Fed Reg 57: 35542-35557. 

U.S. EPA (U.S. Environmental Protection Agency). (1993). National ambient air quality standards for ozone 

- Final decision. Fed Reg 58: 13008-13019. 

U.S. EPA (U.S. Environmental Protection Agency). (1996d). National ambient air quality standards for 

ozone: Proposed decision. Fed Reg 61: 65716-65750. 

U.S. EPA (U.S. Environmental Protection Agency). (1996e). Review of national ambient air quality 

standards for ozone: Assessment of scientific and technical information: OAQPS staff paper [EPA 

Report]. (EPA/452/R-96/007). Research Triangle Park, NC. 

http://www.ntis.gov/search/product.aspx?ABBR=PB96203435

U.S. EPA (U.S. Environmental Protection Agency). (1997). National ambient air quality standards for ozone; 

final rule. Fed Reg 62: 38856-38896. 

U.S. EPA (U.S. Environmental Protection Agency). (2000). Air quality criteria for ozone and related 

photochemical oxidants. Fed Reg 65: 57810. 

U.S. EPA (U.S. Environmental Protection Agency). (2001). National ambient air quality standards for ozone: 

Proposed response to remand. Fed Reg 66: 57268-57292. 

U.S. EPA (U.S. Environmental Protection Agency). (2003). National ambient air quality standards for ozone: 

Final response to remand. Fed Reg 68: 614-645. 

U.S. EPA (U.S. Environmental Protection Agency). (2004). Final rule to implement the 8-hour ozone 

national ambient air quality standard-phase 1. Fed Reg 69: 23951-24000. 
Draft – Do Not Cite or Quote lxxxv June 2012

U.S. EPA (U.S. Environmental Protection Agency). (2006b). Air quality criteria for ozone and related 

photochemical oxidants [EPA Report]. (EPA/600/R-05/004AF). Research Triangle Park, NC. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=149923

U.S. EPA (U.S. Environmental Protection Agency). (2007a). National ambient air quality standards for 

ozone. Fed Reg 72: 37818-37919. 

U.S. EPA (U.S. Environmental Protection Agency). (2007b). Review of the national ambient air quality 

standards for ozone: Policy assessment of scientific and technical information: OAQPS staff paper 

[EPA Report]. (EPA/452/R-07/003). Research Triangle Park, NC. 

http://www.epa.gov/ttn/naaqs/standards/ozone/data/2007_01_ozone_staff_paper

U.S. EPA (U.S. Environmental Protection Agency). (2008e). National ambient air quality standards for 

ozone. Fed Reg 73: 16436-16514.