As a result of a court challenge to the 1997 ozone and PM2.5 standards, on March 26, 2002, the U.S. Court of Appeals for the District of Columbia decided on the Petitioners' specific challenges to the air quality standards that remained unresolved. The Court rejected the argument that the language and reasoning of their earlier decision determined the outcome of these remaining claims. Finding the challenged air quality standards neither arbitrary nor capricious, the Court of Appeals denied the petitions for review except to the extent the Supreme Court's and their earlier decisions require further action by EPA.

Earlier, on May 14, 1999, the U.S. Court of Appeals for the D.C. Circuit set aside the new air quality standards issued by the Environmental Protection Agency in July 1997. The court remanded the ozone and fine particulate matter (PM2.5) standards to the EPA for redrafting and ordered the agency to explain why its rule-making process was justified under the Constitution. The PM10 standard was revoked.

By a 2 to 1 vote, the court concluded the EPA set the new pollution levels arbitrarily without clear "principles" to support them. The nondelegation doctrine requires such a principle. In their decision, the judges wrote, in adopting the guidelines two years ago, the Environmental Protection Agency had failed to show that additional health protections were justified, ruling that the agency had acted on legal assumptions that amounted to "unconstitutional delegations of legislative power." Judge Tatel dissented from this portion of the opinion, but concurred in the remainder of the decisions.

Some background on the "unconstitutional delegations of legislative power" decision would be helpful here. The decision points out a growing contradiction in air pollution policy. Congress told the EPA to set standards that protect the public's health with "an adequate margin of safety," on the theory that there is a threshold below which any pollutant is safe. But some scientists argue that for contaminants, such as ozone, any exposure level may be harmful.

EPA regards ozone definitely, and particulate matter likely, as non-threshold pollutants (i.e., ones that have some possibility of some adverse health impact, however slight, at any exposure level above zero). Thus the only concentration for ozone and particulate matter that is utterly risk-free, in the sense of direct health impacts, is zero. In its ruling, the court stated

Section 109(b)(1) says that EPA must set each standard at the level "requisite to protect the public health" with an "adequate margin of safety." 42 U.S.C. s 7409(b)(1). These are also the criteria by which EPA must determine whether a revision to existing NAAQS is appropriate. See 42 U.S.C. s 7409(d)(1) (EPA shall "promulgate such new standards as may be appropriate in accordance with ... [s 7409(b)]"); see also infra Part II.A. For EPA to pick any non-zero level it must explain the degree of imperfection permitted. The factors that EPA has elected to examine for this purpose in themselves pose no inherent nondelegation problem. But what EPA lacks is any determinate criterion for drawing lines. It has failed to state intelligibly how much is too much.

As an example of not explicitly determining criteria for basing its decisions, the court provided an example. The judges noted

...that EPA argued that a 0.07 standard would be "closer to peak background levels that infrequently occur in some areas due to nonanthropogenic sources of O3 precursors, and thus more likely to be inappropriately targeted in some areas on such sources." But a 0.08 level, of course, is also closer to these peak levels than 0.09. The dissent notes that a single background observation fell between 0.07 and 0.08, and says that EPA's decision" ensured that if a region surpasses the ozone standard, it will do so because of controllable human activity, not uncontrollable natural levels of ozone." EPA's language, coupled with the data on background ozone levels, may add up to a backhanded way of saying that, given the national character of the NAAQS, it is inappropriate to set a standard below a level that can be achieved throughout the country without action affirmatively extracting chemicals from nature. That may well be a sound reading of the statute, but EPA has not explicitly adopted it.

The court found that EPA is precluded from enforcing a revised primary ozone NAAQS other than in accordance with the classifications, attainment dates, and control measures set out in Subpart 2 of the Clean Air Act. The Court agreed that "because the 1990 amendments extended the time for nonattainment areas to comply with the 0.12 ppm ozone NAAQS, they must preclude the EPA from requiring areas to comply either more quickly or with a more stringent ozone NAAQS."

The appeals court rejected claims by the industry groups that the regulations were based on incomplete and poor science, or that the EPA should have taken costs into account.

In an interesting decision, the court found that EPA must consider health disbenefits of proposed standards as well as benefits. The court concluded that EPA must consider the increased risk of skin cancers that could result from the new ozone standard. The court remanded to EPA "to formulate adequate decision criteria" for analysis of both health benefits and risks presented by the standard, and to use those decision criteria to determine whether tropospheric ozone has a beneficial effect on health, and if so, "assess ozone's net adverse health effect by whatever criteria it adopts."

The court found that PM10 was not an appropriate indicator for coarse particles because it includes fine particles in its measurement. In the court's view, this amounts to double regulation of PM2.5 and underregulation of coarse particles (i.e., particles between 2.5 and 10 micrometers in size). Accordingly, the PM10 standard was vacated and the judges directed the EPA to develop a new one.

The court did not vacate the EPA's ozone rule altogether, but said the standard "cannot be enforced." The court believes that the ozone standard is unlikely to engender costly compliance activities in light of the determination that it cannot be enforced by virtue of the Clean Air Act.

While the court process was playing out, EPA had indicated that the Agency was going to

proceed with its proposal for cleaner vehicles and cleaner gasoline; ensure the air quality monitoring program continues and the PM 2.5 monitors are put in place; continue support for voluntary "right-to-know" programs managed by states and coordinated through EPA, such as the Ozone Action Days and the air quality data submitted to EPA's Internet Ozone Mapping Site; and designate areas as attainment or nonattainment for the 8-hour ozone standard.

On October 29, 1999, the U.S. Court of Appeals for the D.C. Circuit rejected a request by the Environmental Protection Agency to reconsider a ruling that struck down the agency's new 8-hour and PM national air pollution standards. The court denied the EPA's appeal for a rehearing by all 11 judges of a ruling in May that the EPA had overstepped its constitutional authority in adopting the standards two years ago. Of the 11 judges on the appeals court, two did not participate and five voted to rehear the case. The appeals court requires six votes to review a case.

On January 28, 2000, the Justice Department, on behalf of the EPA, filed a petition for certiorari with the U.S. Supreme Court The EPA appealed the following three issues:

Whether Section 109 of the Clean Air Act, 42 U.S.C. 7409, as interpreted by the Environmental Protection Agency (EPA) in setting revised National Ambient Air Quality Standards (NAAQS) for ozone and particulate matter, effects an unconstitutional delegation of legislative power; Whether the court of appeals exceeded its jurisdiction by reviewing, as a final agency action that is ripe for review, EPA's preliminary preamble statements on the scope of the agency's authority to implement the revised "eight-hour" ozone NAAQS; and Whether provisions of the Clean Air Act Amendments of 1990 specifically aimed at achieving the long-delayed attainment of the then-existing ozone NAAQS restrict EPA's general authority under other provisions of the CAA to implement a new and more protective ozone NAAQS until the prior standard is attained.

EPA did not appeal the D.C. Circuit's finding that the Agency must consider all health effects, both negative and positive, in setting a standard.

On November 7, 2000, the Supreme Court heard the case about the D.C. Circuit's decision remanding the ozone and particulate matter national ambient air quality standards to the EPA. In addition, the Court also heard the cross-appeal by the U.S. Chamber of Commerce, the American Trucking Associations, and others. The challengers asked the justices to review those portions of the appeals court ruling that freed the EPA from taking costs into account and rejected the groups' contention that the air-quality standards were based on incomplete and poor science.

On February 27, 2001, the Supreme Court upheld the way the federal government sets clean-air standards, rejecting industry arguments that officials must balance compliance costs against the health benefits of cleaner air. The justices also ruled against industry arguments that the Environmental Protection Agency took too much lawmaking power from Congress when it set tougher standards for ozone and soot in 1997. However, the court ordered the EPA to reconsider the standards it set for ozone, saying the agency's interpretation of a section of the Clean Air Act was unreasonable. The justices ruled against the EPA's implementation of revised ozone standards in areas whose ozone levels exceed the maximum allowable amount. The justices held that the EPA had ignored the law, which in 1990, allowed many regions extra time to meet the air quality standards. The Court wrote that Congress would hardly have intended for the EPA to adopt the tougher 1997 rules and enforce them immediately.

The U. S. Supreme Court summarized the holdings of the complex cases of Whitman, Administrator of the U.S. EPA et al. versus American Trucking Associations, Inc. et al. that was argued on November 7, 2000.

(1) The EPA may not consider implementation costs in setting primary and secondary NAAQS under Section 109(b) of the Clean Air Act (CAA).

(2) Section 109(b)(1) of the CAA does not delegate legislative power to the EPA in contravention of Art. I, Sect. 1, of the Constitution.

(3) The Court of Appeals had jurisdiction to review the EPA's
interpretation of Part D of Title I of the CAA, relating to the
implementation of the revised ozone NAAQS.

(4) The EPA's interpretation of that Part is unreasonable.

In regard to (4) above, the Supreme Court found "the EPA's implementation policy to be unlawful, though not in the precise respect determined by the Court of Appeals. After remand, and the Court of Appeals final disposition of this case, it left to the EPA to develop a reasonable interpretation of the nonattainment implementation provisions insofar as they apply to revised ozone NAAQS.

The judgment of the Court of Appeals, therefore, is affirmed in part and reversed in part, and the cases are remanded for proceedings consistent with the opinion.

On December 22, 2006, the DC Circuit Court of Appeals announced its ruling on EPA’s April 2004 Phase 1 Rule to implement the 8-hour ozone National Ambient Air Quality Standard. The unanimous ruling vacated the rule. In EPA’s 2004 rule, 8-hour ozone nonattainment areas were classified into Subpart 1 or Subpart 2, EPA distinguished between the two classifications based on the area’s 1-hour ozone design value at the time of designation. If an area’s 1-hour ozone design value exceeded 0.121 ppm, the area was classified as Subpart 2. If an area only exceeded the 8-hour ozone design value of 0.085 ppm, but not the 0.121 ppm 1-hour design value, the area was designated as Subpart 1.

The court ruled that the Clean Air Act mandated that EPA should have applied the 8-hour design value equivalent in stringency to the old 1-hour standard, which EPA had calculated to be an 8-hour level of 0.09 ppm. The court ruled that for areas with 8-hour ozone design values between 0.08 and 0.09 ppm, where the Clean Air Act did not mandate a certain procedure, EPA did not adequately support classifying these areas under Subpart 1. If you care to read the DC Circuit Court of Appeals' decision, please click here.

On September 21, 2006, EPA announced with regard to primary standards for fine particles (generally referring to particles less than or equal to 2.5 micrometers (µm) in diameter, PM2.5) that it was revising the level of the 24-hour PM2.5 standard to 35 micrograms per cubic meter (µg/m3) and retaining the level of the annual PM2.5 standard at 15 µg/m3. With regard to primary standards for particles generally less than or equal to 10 µm in diameter (PM10), EPA is retaining the 24-hour PM10 and revoking the annual PM10 standard. With regard to secondary PM standards, EPA is making them identical in all respects to the primary PM standards, as revised. The issue of reliability of the epidemiological time-series methodologies continues to be of concern to the Administrator. The Administrator noted in his decision that there were many sources of uncertainty and variability inherent in the inputs to the assessment and that there was a high degree of uncertainty in the resulting PM2.5 risk estimates. Such uncertainties generally related to a lack of clear understanding of a number of important factors, including, for example, the shape of concentration-response functions, particularly when, as here, effect thresholds can neither be discerned nor determined not to exist; issues related to selection of appropriate statistical models for the analysis of the epidemiologic data; and the role of potentially confounding and modifying factors in the concentration-response relationships. For those interested in the possible violation areas for the revised 24-hour PM-2.5 standard based on 2004-2005 data, please click here.

On December 15, 2006, public health and environmental groups filed suit against the U.S. EPA for refusing to strengthen the PM-2.5 annual standard. On February 24, 2009, as a result of the suit filed against the U.S. EPA by public health and environmental groups, the U.S. Court of Appeals for the D.C. Circuit remanded the National Ambient Air Quality Standards (NAAQS) for fine particulate matter (PM2.5) to EPA for reconsideration of the annual level of the standard (which EPA left at 15 micrograms per cubic meter (µg/m3)) and reconsideration of the secondary PM2.5 NAAQS. With respect to the annual PM2.5 NAAQS, the court held that the agency “failed to explain adequately why an annual level of 15 µg/m3 is ‘requisite to protect the public health,’ including the health of vulnerable subpopulations, while providing ‘an adequate margin of safety.’ 42 U.S.C.§ 7409(b)(1).” For the secondary standards, the court held that EPA “unreasonably concluded that the NAAQS are adequate to protect the public welfare from adverse effects on visibility.” The court denied petitions for review of the primary daily standard for coarse PM and the petition for review of EPA’s revocation of the primary annual standard for coarse PM. The Court opinion can be read by clicking here.

In May 27, 2008, health and environmental organizations filed a lawsuit arguing that the EPA failed to protect public health and the environment when it issued in March 2008 new ozone standards. On March 10, 2009, the US EPA requested that the Court vacate the existing briefing schedule and hold the consolidated cases in abeyance. EPA requested the extension to allow time for appropriate EPA officials that are appointed by the new Administration to review the Ozone NAAQS Rule to determine whether the standards established in the Ozone NAAQS Rule should be maintained, modified, or otherwise reconsidered. EPA further requested that it be directed to notify the Court and the Parties within 180 days of the Court's order vacating the briefing schedule of the actions the Agency has taken or intends to take, if any, with regard to the Ozone NAAQS Rule, and the anticipated time frame for any such actions.

On September 16, 2009, the EPA announced it would reconsider the 2008 national ambient air quality standards (NAAQS) for ground-level ozone for both human health and environmental effects. The Agency planned to propose any needed revisions to the ozone standards by December 2009 and issue a final decision by August 2010. On January 7, 2010, the EPA announced on its web site its proposal to strengthen the national ambient air quality standards for ground-level ozone. The EPA's proposal decreased the 8-hour “primary” ozone standard level, designed to protect public health, to a level within the range of 0.060-0.070 parts per million (ppm). EPA also proposed to establish a distinct cumulative, seasonal “secondary” standard, referred to as the W126 index, which was designed to protect sensitive vegetation and ecosystems, including forests, parks, wildlife refuges, and wilderness areas. EPA proposed to set the level of the W126 secondary standard within the range of 7-15 ppm-hours. On August 20, the Agency announced that it would delay its final announcement to on or around the end of October. In early November, the EPA announced that it would reach a final decision on the ozone standards by December 31, 2010. On December 8, the EPA announced that it would delay its final decision on the ozone standards until July 2011. EPA announced on July 26 that it would not make a decision on the ozone standards by its previously announced deadline of July 29. On September 2, 2011, President Obama requested that the EPA withdraw its proposed revisions to the ozone standards. The proposed revisions result from a reconsideration of the identical primary and secondary ozone standards set at 0.075 ppm in March 2008.

In response to a series of lawsuits, on July 23, 2013, the D.C. Circuit issued its opinion in the 2008 ozone NAAQS litigation. The court denied the petitions for review of both industry and the states/environmental groups challenging the primary ozone NAAQS. In other words, the court upheld the 0.075 ppm primary standard and is not requiring EPA to lower the NAAQS further. The court remanded the secondary ozone NAAQS to EPA because it found that EPA had failed to justify setting the secondary standard at the same level as the primary. The decision makes interesting reading and is available by clicking here.

Following the promulgation of the 2008 ozone NAAQS, EPA undertook another comprehensive review of the ozone standards and scientific data. EPA consolidated its review on remand of the 2008 secondary standard with its then ongoing review for the 2015 ozone NAAQS. On October 1, 2015, the EPA announced its revisions to the primary and secondary ozone standards. On August 23, 2019, the D.C. Court of Appeals rendered its decision on the various challenges to the Environmental Protection Agency's 2015 revisions to the primary and secondary national ambient air quality standards for ozone. The Court denied the petitions, except with respect to the secondary ozone standard, which it remanded for reconsideration, and grandfathering provision, which the Court vacated.

Petitioners from the oil and gas industry ("Industry Petitioners") and from several states ("State Petitioners") claimed that the primary and secondary NAAQS were too protective. Conversely, petitioners from public health and environmental groups ("Environmental Petitioners") claimed that these NAAQS are not protective enough. Environmental Petitioners also contended that EPA's decision to allow limited grandfathering of certain permit applications was inconsistent with the Clean Air Act.

The Court found "In setting the secondary standard, EPA failed to justify its decision to use a three-year average benchmark without lowering the level to account for single-year spikes in ozone exposures, and it arbitrarily declined to set a level to protect against adverse welfare effects associated with visible leaf injury. EPA also impermissibly allowed sources that had completed applications for preconstruction permits before the 2015 Rule was adopted to demonstrate compliance with the previous NAAQS rather than the new, more stringent primary and secondary standards. Accordingly, we grant those portions of the Environmental Petitioners' petition, vacate the grandfathering provision, and remand to EPA for reconsideration of the secondary standard."