Citations
- 902 F.2d 962
Full opinion text
Opinion for the Court filed PER CURIAM.
Separate opinion filed by Chief Judge WALD.
Concurring and dissenting opinion filed by Circuit Judge HARRY T. EDWARDS.
Concurring and dissenting opinion filed by Circuit Judge SILBERMAN.
PER CURIAM:
In these consolidated cases, petitioners seek review of several aspects of the Revisions to the National Ambient Air Quality Standards for Particulate Matter, 52 Fed. Reg. 24,634 (1987) (“Revisions”), issued on July 1, 1987 by the Environmental Protection Agency (“EPA” or “agency”). For various reasons, we dismiss all of the challenges to the Revisions raised by the American Iron and Steel Institute and by the American Mining Congress; in addition, while we dismiss the challenge raised by the Natural Resources Defense Council and affiliated petitioners vis-a-vis a secondary ambient air quality standard protecting against visibility impairment, we order EPA to submit a statement of reasons within sixty days of the issuance of the mandate of this opinion explaining its decision not to initiate a rulemaking on a secondary standard protecting against acid deposition.
I. STATUTORY AND REGULATORY OVERVIEW
A. The Regulated Pollutant
Before presenting a brief overview of the relevant portions of the Clean Air Act (“CAA” or “Act”), 42 U.S.C. §§ 7401-7626 (1982), and of the regulatory developments culminating in the 1987 rulemaking, we describe the regulated pollutant — particulate matter. The term “particulate matter” includes the discrete particles captured and filtered by an air-sampling device meeting certain specifications. Particulate matter originates from stationary and mobile sources, both natural and man-made, such as the earth’s crust, sea salt, tires and various industrial and agricultural processes.
The 1987 Revisions focus on particles with an aerodynamic diameter of 10 microns or less. “PMio” is the abbreviation used to describe this group of particulate matter. Prior to the Revisions, particulate matter standards applied to a more inclusive subset of particulate matter, known as “total suspended particulates,” or “TSP.”
B. Statutory Framework
The Clean Air Act provides a comprehensive program for control of air pollution through a system of shared state and federal responsibility. Under § 108 of the Act, EPA identifies air pollutants that are emitted from “numerous or diverse” sources and whose presence in the ambient air “may reasonably be anticipated to endanger public health or welfare.” Id. § 7408(a)(1). For each pollutant, EPA is required to issue a “criteria” document reflecting its health and welfare effects and a “control techniques” document discussing the costs and benefits of different types of emission controls. Id. § 7408(a)(2), (b)(1).
Under § 109, EPA must issue “primary” and “secondary” national ambient air quality standards (“NAAQS”) for each pollutant identified under § 108. See id. § 7409(a)(2). The primary standards must protect the public health while allowing an adequate margin for safety; the secondary standards must protect the public welfare from any known or anticipated adverse effects. See id. § 7409(b). The EPA Administrator is required to complete a thorough review of the standards, and revise them as appropriate, by December 31, 1980 and at five-year intervals thereafter. See id. § 7409(d). Within nine months of the promulgation or revision of an NAAQS, each state must adopt or revise a plan for the attainment and maintenance of the standard. The state plan must be submitted for EPA’s approval. See id. § 7410(a).
In the 1977 Amendments to the Clean Air Act, Congress ordered the states to classify each of their air quality regions as in attainment, nonattainment, or unclassifiable with regard to the NAAQS then in effect. See id. § 7407(d). For areas in attainment or unclassifiable, Congress prescribed measures to prevent significant deterioration (PSD) of air quality. See id. §§ 7470-79. To this end, Congress specified the “maximum allowable increase” in concentrations of particulate matter. Id. § 7473(b). States were required to ensure that new or modified emissions sources would not exceed these allowable increments. The 1977 Amendments also included the review and revision timetable of § 109(d)(1), see id. § 7409(d)(1), and directed the EPA Administrator to appoint an independent scientific review committee, see id. § 7409(d)(2).
C. Regulatory Evolution of 1987 Revisions
The 1987 Revisions to the ambient air quality standards for particulate matter were a long time coming. Drawing from a 1969 air quality Criteria Document for particulate matter, EPA first promulgated primary and secondary standards for particulate matter in April 1971. See National Primary and Secondary Ambient Air Quality Standards, 36 Fed.Reg. 8186 (1971). In the late 1970s, EPA began to revise the 1969 particulate matter Criteria Document to correct its scientific shortcomings. This process was completed when the Revised Criteria Document for particulate matter was published in December 1982. See Air Quality Criteria for Particulate Matter and Sulfur Oxides (1982).
On March 20, 1984, EPA proposed revisions to the particulate matter ambient air quality standards. See Proposed Revisions to the National Ambient Air Quality Standards for Particulate Matter, 49 Fed.Reg. 10,408 (1984). In the main, EPA proposed to replace the TSP indicator with PMi0 for the primary standard, while retaining TSP for secondary standard, see id. at 10,412, 10,418-19; to select the levels of the revised 24-hour and annual primary standards from specified ranges, see id. at 10,-415-17; to issue a secondary (welfare) standard aimed at the soiling and nuisance effects, while deferring a decision on a separate fine particle standard addressing visibility impairment and continuing to evaluate alternative approaches to reduce acid deposition, see id. 10,418-19; and to alter the form of the secondary standard, see id.
After a lengthy notice and comment period and the issuance of several supplemental proposals, EPA issued the final rule revising the particulate matter standards on July 1, 1987. See 52 Fed.Reg. 24,634. EPA replaced TSP with PMi0 as the indicator for the primary standards, see id. at 24,638-39; selected annual and 24-hour primary standards from the specified ranges, see id. at 24,641-45; set a PM10 secondary standard for soiling and nuisance identical to the primary standard; and continued to defer on a fine particle standard to address visibility impairment while research proceeded on controlling acid deposition, see id. at 24,645-47.
Relevant details of the Revisions are discussed in the appropriate sections of this opinion.
In December 1988, EPA denied petitions for reconsideration of various aspects of the Revisions. See 53 Fed.Reg. 52,698, 52,-705 (1988). This court then consolidated those petitions for review purposes in March 1989. After a joint motion by two parties to stay proceedings in one of the consolidated cases, we substituted No. 87-1438 as lead docket in August 1989.
II. The AMERICAN Iron and Steel Institute’s Claims
In this Part, we consider the petition from the American Iron and Steel Institute (“AISI”), challenging as arbitrary and capricious the Administrator’s selection of 150 fig/m and 50 ¡ig/m as, respectively, the twenty-four hour and annual national primary ambient air quality standards for particulate matter, measured in PMi0s. In addition, AISI claims that the Administrator violated § 109(b)(1) of the Clean Air Act, 42 U.S.C. § 7409(b)(1) (1982), when he failed to discuss the degree of “safety” provided by the levels selected for the primary standards, that the Administrator erred in failing to consider the health consequences of unemployment in his assessment of the appropriate level for the primary standard, and that the control techniques information issued by EPA for particulate matter does not meet the requirements of § 108(b)(1) and (c), 42 U.S.C. § 7408(b)(1), (c) (1982). On the record before us, we find no basis to overturn or defer EPA’s final rule instituting annual and twenty-four hour national primary ambient air quality standards for particulate matter, measured in PMi0s. We further conclude that AISI lacks standing to challenge the adequacy of the control techniques information issued by EPA. Accordingly, we deny AISI’s petition for review of these matters.
A. Background
In revising the primary standards for particulate matter pursuant to 42 U.S.C. § 7409(d), the Administrator must set the primary standards at levels which in his judgment are “requisite to protect the public health.” CAA § 109(b)(1), (d), 42 U.S.C. § 7409(b)(1), (d) (1982). Primary standards must be based on the air quality criteria issued under § 108, and they also must “allow[] an adequate margin of safety.” Id. The criteria document, which serves as the basis for establishing the pollutant levels, must “accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health ... which may be expected from the presence” of particulate matter “in the ambient air, in varying quantities.” CAA § 108(a)(2), 42 U.S.C. § 7408(a)(2) (1982).
EPA completed a revised criteria document for particulate matter in 1982 (“Revised Criteria Document”). In order to “bridge the gap” between the scientific review in the Revised Criteria Document and the judgments required by the Administrator in setting ambient air quality standards for particulate matter, EPA’s Office of Air Quality Planning and Standards drafted a “Staff Paper.” The Staff Paper recommended that the Administrator select a value from a range of concentrations from 150 to 350 micrograms per cubic meter (pg/m) as PM10 for the twenty-four hour partieu-late matter primary standard and a range from 55 to 110 ¿ig/m as PMi0 for the annual particulate matter primary standard.
In 1986, the Environmental Criteria and Assessment Office reviewed scientific studies on the health effects of particulate matter that had emerged since its review of relevant information in the 1982 Revised Criteria Document. On the basis of this updated analysis, EPA’s Office of Air Quality Planning and Standards recommended that the Administrator consider twenty-four hour standards at levels from 140 to 250 jug/m and annual standards at levels from 40 to 65 ^g/m. The Administrator set the twenty-four hour particulate matter standard at 150 jag/m and the annual standard at 50 jug/m. See 52 Fed.Reg. at 24,643, 24,645. AISI contends that these levels are needlessly stringent. AISI asks this court to set aside the levels as arbitrary and contrary to law, and seeks remand to the Agency for further reconsideration and explanation.
B. EPA’s Basis for the Twenty-Four Hour and Annual Particulate Matter Primary Standard Levels
AISI does not contest EPA’s retention of both a short-term (twenty-four hour) and a long-term (annual) standard for particulate matter; nor does AISI contest the particle size fraction (PMio) used as an indicator. What AISI disputes are the numerical levels for the twenty-four hour and annual standards. AISI contends that the Administrator acted arbitrarily in setting the twenty-four hour and annual PMjo standards at 150 and 50 ¡i.g/m respectively because he provided no basis for distinguishing the health effects associated with the levels selected from those associated with the levels rejected. AISI claims that the “only reliable scientific evidence shows that standards at the highest levels proposed would still protect the public health, including sensitive subgroups of the population, with an adequate margin of safety.” Brief of the American Iron and Steel Institute at 20.
1. Standard of Review
In reviewing the primary standards for particulate matter, and the “adequacy” of the margin of safety, we are reviewing “predictions within an agency’s area of special expertise, at the frontiers of science,” New York v. EPA, 852 F.2d 574, 580 (D.C.Cir.1988), cert. denied, — U.S. -, 109 S.Ct. 1338, 103 L.Ed.2d 809 (1989). In such circumstances, we must defer to the agency’s interpretation of equivocal evidence, so long as it is reasonable. See id. And where, as here, the statute is “precautionary ” in nature, the evidence “uncertain or conflicting” and the “regulations designed to protect the public health,” the court “will not demand rigorous step-by-step proof of cause and effect.” Ethyl Corp. v. EPA, 541 F.2d 1, 28 (D.C.Cir.) (en banc), cert. denied, 426 U.S. 941, 96 S.Ct. 2662, 49 L.Ed.2d 394 (1976). “The Administrator may apply his expertise to draw conclusions from suspected, but not completely substantiated, relationships between facts, from trends among facts, from theoretical projections from imperfect data, from probative preliminary data not yet certifiable as ‘fact,’ and the like.” Id. But we must, nevertheless, carefully review the record to ascertain that the agency has made a reasoned decision based on “reasonable extrapolations from some reliable evidence.” Natural Resources Defense Council v. Thomas, 805 F.2d 410, 432 (D.C.Cir.1986); see also Marsh v. Oregon Natural Resources Council, — U.S. -, 109 S.Ct. 1851, 1861, 104 L.Ed.2d 377 (1989) (noting that courts must carefully review record and “satisfy[] themselves that the agency has made a reasoned decision based on its evaluation of the significance ... of the ... information”). It is against this standard of review that the court must consider EPA’s adoption of the twenty-four hour and annual national primary ambient air quality standards for particulate matter.
2. Twenty-Four Hour Standard
AISI challenges the twenty-four hour standard on several grounds. First, AISI claims that “EPA has no reason for rejecting a standard at 250 /xg/m3 that would not apply with equal force to a standard at 150 /xg/m3, and no reason for settling on a standard at 150 /xg/m3 that would not firmly justify a standard at 250 /xg/m3.” Brief of AISI at 20. According to AISI, “[t]he format of EPA’s calculation gives the Agency so much latitude that it could, with artful assumptions, ‘justify’ virtually any number on the same basis as it did 150 /xg/m3” and EPA’s selection of 150 /xg/m3 for the twenty-four hour standard is, therefore, “inherently arbitrary and must be set aside.” Id. at 23. Second, and more specifically, AISI claims that EPA rested too little on the Lawther and London mortality studies. According to AISI, the Lawther study, taken alone, would support setting the twenty-four hour standard at 250 /xg/m3. See id. at 21. According to AISI, the London mortality data also indicate that a standard of 250 /xg/m3 would be “well below” the levels where a “ ‘scientific consensus’ accepts ‘pollution’ as responsible for some unknown amount of ‘life shortening’ among ‘the elderly and persons with pre-existing respiratory or cardiac disease.’ ” Id. (quoting 52 Fed.Reg. at 24,-642-43. Third, AISI claims that EPA relied too much on the Six Cities Study, which is comprised of the Dockery study and the Ware study. See Brief of AISI at 10-15. AISI describes the Six Cities Study as the “linchpin” for setting the standards at the lower end of the proposed ranges: the Dockery study for the twenty-four hour standard and the Ware study for the annual standard.
We do not agree that the Administrator’s selection of the twenty-four hour standard lacks the necessary reasoned analysis and supportive evidence. The Administrator concluded that a twenty-four hour PMio standard greater than 150 /xg/m3 would “present an unacceptable risk of premature mortality” and allow the possibility of significant lung function changes. After carefully reviewing the record, we find EPA’s selection of the twenty-four hour standard reasonable in light of the divergent results in the studies and the agency’s mandate to provide an adequate margin of safety. Studies contained in the record provided evidence of adverse health effects at levels below 250 /xg/m3.
As an initial matter, the Administrator noted that the data do not provide evidence of clear thresholds in exposed populations and, hence, the Administrator needed to select a level along a continuum of responses. See 52 Fed.Reg. at 24,642, 24,643 (citing studies by Mazumdar et al., 1982; Os-tro, 1984; Shumway et al, 1983). In seeking the point along the continuum that would provide the requisite adequate margin of safety, EPA “was required to take into account all the relevant studies revealed in the record.” American Petroleum Inst. v. Costle, 665 F.2d 1176, 1187 (D.C.Cir.1981), cert. denied, 455 U.S. 1034, 102 S.Ct. 1737, 72 L.Ed.2d 152 (1982).
The Administrator acknowledged that the Lawther study indicates that a PMio standard of 250 ¡ig/m3 might contain some margin of safety and that the London mortality studies indicate that the upper portion of the proposed twenty-four hour range would be “well below” the pollution levels that produced “excess mortality” in London. But results from other studies indicating adverse health effects at lower concentrations of particulate matter, differences between the United States and London in particulate composition and difficulties in converting from British Smoke — the indicator for particulate matter used in the London and Lawther studies — to PMio measurements, discouraged exclusive reliance on these results. The Administrator explained that more recent reanalyses of the London mortality data suggest that the risk of premature mortality to sensitive individuals extends to concentrations substantially lower than the 500 to 1000 jug/m3 British Smoke levels of the historical London episodes in which the scientific consensus indicates that pollution was responsible for excess mortality. Indeed, the Administrator noted that one of the more recent studies, Ozkaynak & Spengler (1985), provides qualitative support for an association of daily mortality and particle concentrations in nearly contemporary United States atmospheres. These studies prompted the Administrator to consider levels that extended from 250 /xg/m down to the lower bound of the original staff range of interest — 150 /xg/m — and even lower. In light of these explanations and the results in other studies, the Administrator’s decision not to rely more heavily on the Lawther and London mortality studies cannot be said to be arbitrary and capricious.
Nor can we conclude that the EPA’s reliance on the Dockery study was unreasonable. The Dockery study reported statistically significant decreases in lung function in a group of children exposed to peak PMio levels of 140-250 /xg/m3. These decrements persisted for two to three weeks following the exposure and the study suggested the possibility of larger responses in a subset of the children. But EPA did not rely on the results of that study alone in selecting a standard at the low end of the range. A study by Dassen recorded similar effects in children exposed to PMio levels of 200 to 250 /xg/m3 in the Netherlands, but no observable effects two days after exposure to PMio levels estimated at 125 /ixg/m3. EPA also considered several reanalyses of the London mortality data by Mazumdar et al. (1982), Ostro (1984) and Shumway et al. (1983), and qualitative data that suggested increased risks for sensitive groups, risks of potential effects not demonstrated in the quantitative epidemiological literature and “interactive responses” due to the presence of other pollutants.
EPA explained that “[i]t is reasonable to expect that the effects observed (small reversible reductions in lung function in children) are, in most cases, more sensitive to air pollution than those observed in the London studies.” “The staff assessment ... suggests that short-term lung function effects in children are possible across a range of 140-250 fxg/m3 or more as PMio.” EPA noted that “[t]he standard is in the lower portion of the range where sensitive, reversible physiological responses of uncertain health significance are possibly, but not definitely, observed in children.” And it concluded that a “substantial margin of safety below the levels at which there is a scientific consensus that particulate matter causes premature mortality and aggravation of bronchitis” is warranted “because of the seriousness of these effects and because of the recent analyses of daily mortality that suggest adverse effects may occur at particulate matter levels well below the consensus levels.”
In setting a standard under § 109, the Administrator must “take into account all the relevant studies revealed in the record” and “make an informed judgment based on available evidence.” American Petroleum Inst. v. Costle, 665 F.2d at 1187. The record shows that the Administrator did so. The Administrator relied on studies which showed adverse effects at and below the 250 yg/m3 level. AISI essentially asks this court to give different weight to the studies than did the Administrator. We must decline. It is simply not the court’s role to “second-guess the scientific judgments of the EPA.” See New York v. EPA, 852 F.2d at 580. The Administrator articulated a satisfactory explanation, which is supported by the record evidence, that levels at the top end of the range might not adequately protect against adverse health effects. While there was some evidence that levels even at the low end of the range might produce adverse reactions in sensitive portions of the population, the Administrator did not act arbitrarily in drawing conclusions from the uncertain and conflicting data. The Administrator may reasonably apply his expertise to draw conclusions from “imperfect data,” Ethyl Corp., 541 F.2d at 28, as he did here.
3. Annual Standard
AISI next claims that the annual standard established by the Administrator at 50 yg/m3 lacks a coherent scientific basis. See Brief of AISI at 24. In addition, AISI contends that there is no basis for distinguishing the level rejected from the level selected. AISI cites EPA’s explanation that it would not set the annual level below 50 yg/m3 on the ground that even if “some small risk of increased respiratory symptoms may exist at this concentration, the available data are currently inconclusive.” See 52 Fed.Reg. at 24,645. According to AISI, EPA’s rationale could as easily justify setting the annual standard at the top end of the range because the data do not show that people will suffer health risks at the top end of the range any more conclusively than that they will suffer from pollution levels at the bottom of the range. See Brief of AISI at 25. We cannot agree. The record is replete with support for the final standard.
The Administrator selected a standard near the middle of the “range of interest” of 40 yg/m3 to 65 yg/m3 recommended by the Office of Air Quality Planning and Standards. In support of this standard, the agency cites studies by Bouhuys, Haus-man, Ostro and Ware. The Ware study “indicates the possibility of increased respiratory symptoms and illnesses in children at multi-year levels across a range of 40 to over 58 yg/m3 as PMio.” The Bouhuys study suggests some possibility of symptomatic responses in adults at long-term median levels at or below about 50 to 55 yg/m3 as PM10. Studies by Ostro (1987) and Hausman et al. (1984) suggest the possibility of respiratory effects in adults at comparable levels. Other studies provided evidence of no observed effects at or below 60 to 65 /xg/m3. The Administrator also noted that “the information available to support the existence of significant adverse effects at annual PMio levels below 50 ¡xg/m3 — especially when 24-hour levels are maintained below 150 /xg/m3 — is quite limited and uncertain.”
The Administrator acknowledged that these data are uncertain and limited in scope. Consequently, the Administrator considered it “particularly important to examine the results of qualitative data from a number of epidemiological, animal, and ambient particle composition studies when evaluating what constitutes an adequate margin of safety for an annual standard.” In deciding to set the standard at the lower bound of the original proposed range, the Administrator reasoned that “[t]his standard provides a reasonable margin of safety against the serious effect of long-term degradation in lung function, which has been judged likely at estimated PMio levels above 80-90 /xg/m3 and for which there is some evidence at PMio levels above 60 to 65 /xg/m3.”
The Administrator admits that the 50 /xg/m3 did not spring from a bounty of definitive research as the clear and sole appropriate standard. But such is not required. The Administrator is required to provide an adequate margin of safety. And “[i]n setting margins of safety the Administrator need not regulate only the known dangers to health, but may ‘err’ on the side of overprotection by setting a fully adequate margin of safety.” American Petroleum Inst. v. Costle, 665 F.2d at 1186. The level selected might not be the only one that would have been reasonable based on the Revised Criteria Document and the Revised Criteria Document Addendum. But we certainly cannot conclude that the level selected resulted from an unreasonable interpretation of the equivocal evidence, where some studies indicated threats to health even at the low end of the range. Cf. Public Citizen Health Research Group v. Tyson, 796 F.2d 1479, 1505 (D.C.Cir.1986) (“as long as Congress delegates power to an agency to regulate on the borders of the unknown, courts cannot interfere with reasonable interpretations of equivocal evidence”); New York v. EPA, 852 F.2d at 580 (upholding EPA’s rejection of a particular air pollution model); American Petroleum Inst. v. Costle, 665 F.2d at 1186 (upholding EPA’s standards for photochemical oxidants as reasonable “given the uncertain information”). “That the evidence in the record may also support other conclusions, even those that are inconsistent with the Administrator’s, does not prevent us from concluding that his decisions were rational and supported by the record.” Lead Indus. Ass’n v. EPA, 647 F.2d 1130, 1160 (D.C.Cir.), cert. denied, 449 U.S. 1042, 101 S.Ct. 621, 66 L.Ed.2d 503 (1980).
As to AISI’s challenge to the Administrator’s use of the Ware study, EPA agrees with AISI that the Ware study showed no evidence of reduced lung function in children at concentrations of 40 to 58 /xg/m3. See 52 Fed.Reg. at 24,644; Brief of AISI at 24. And EPA also noted that the study did not find gradients in symptoms and illness within some of the cities in the study that had somewhat smaller localized pollution gradients. See 52 Fed.Reg. at 24,644. But EPA also noted that the study did indicate the possibility of increased respiratory symptoms and illnesses in children at mul-ti-year levels across a range of 40 to 58 /xg/m3 as PMio, a finding AISI concedes. AISI and EPA differ only in the inferences drawn from the study “on balance.” See Brief of AISI at 24. We cannot say, however, that the Administrator was unreasonable in his interpretation of the Ware results, especially in light of the other studies suggesting respiratory effects at these levels.
C. Consideration of the Effects of Unemployment
AISI next contends that EPA erred in refusing to consider the health consequences of unemployment in determining the primary standards for particulate matter. This claim is entirely without merit. In three previous cases this court has emphatically stated that § 109 does not permit EPA to consider such costs in promulgating national ambient air quality standards. See Natural Resources Defense Council v. EPA (“Vinyl Chloride”), 824 F.2d 1146, 1157, 1159 (D.C.Cir.1987) (en banc); American Petroleum Inst. v. Costle, 665 F.2d at 1185; Lead Indus. Ass’n v. EPA, 647 F.2d at 1148-49. It is only health effects relating to pollutants in the air that EPA may consider. See 42 U.S.C. § 7408(a)(2) (“Air quality criteria for an air pollutant shall accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare which may be expected from the presence of such pollutant in the ambient air, in varying quantities.”) (emphasis added). Consideration of costs associated with alleged health risks from unemployment would be flatly inconsistent with the statute, legislative history and case law on this point.
D. Identifying a Safe Level
AISI also challenges the agency's selection of the primary standard levels for particulate matter on the ground that EPA did not identify a “safe level” indicating what “ ‘risks are acceptable in the world in which we live.’ ” Brief of AISI at 26 (quoting Vinyl Chloride, 824 F.2d at 1165). AISI contends that both § 109 and this court’s decision in Vinyl Chloride require EPA to identify the risk to health it considers acceptable.
Neither the holding in Vinyl Chloride, nor the decision’s rationale, is apposite to actions involving § 109. The challenge in Vinyl Chloride related to the appropriate use of cost and technological feasibility factors in establishing an emission standard for a “hazardous air pollutant,” pursuant to § 112 of the Clean Air Act, 42 U.S.C. § 7412 (1982). Under § 112, the agency may consider cost and technological feasibility in selecting levels for hazardous pollutant standards. However, this court rejected the agency’s argument that the Administrator “need only find that the costs of control are greater than the reduction in risk to health.” Vinyl Chloride, 824 F.2d at 1164. In setting national emission standards for hazardous air pollutants pursuant to § 112 of the Clean Air Act, “the congressional mandate to provide ‘an ample margin of safety’ ‘to protect the public health’ requires the Administrator to make an initial determination of what is ‘safe.’ ” Id. This court held that the Administrator may not consider cost and technological feasibility in determining what is “safe”; such a determination “must be based solely upon the risk to health.” Id. at 1166. Once EPA has determined a “safe” level of exposure, it may then consider cost and feasibility in providing for the “ample margin of safety” required by § 112.
The two-step methodological requirement endorsed by Vinyl Chloride was necessary because of the need under § 112 to sever determinations that must be based solely on health considerations from those that may include economic and technological considerations. Under § 109, however, the Administrator may not consider cost and technological feasibility. Hence, the rationale for parsing the Administrator’s determination into two steps is inapposite to actions under § 109.
The foreclosure from consideration of cost and technological feasibility also persuades us that § 109 itself does not mandate the methodological requirement we found necessary under § 112. In facing substantive challenges to national ambient air quality standards, the Agency may sometimes need to articulate the level of threat to the population it considers tolerable; but there is no separate methodological requirement under § 109 that the Administrator establish a measure of the risk to safety it considers adequate to protect public health every time it establishes a standard pursuant to § 109.
Indeed, this court has previously declined to impose specific requirements on the Administrator’s methodological approach to selecting an adequate margin of safety under § 109. In Lead Industries, one petitioner argued that EPA must separately determine the maximum level of a pollutant that is protective of human health and the adequate margin of safety by which the level that is protective of health must be reduced. See 647 F.2d at 1161. The court ruled that the choice of approach to determining the margin of safety “is a policy choice of the type that Congress specifically left to the Administrator’s judgment. This court must allow him the discretion to determine which approach will best fulfill the goals of the Act.” Id. at 1162.
In the instant case, the Administrator determined the primary standards for particulate matter based solely upon the risk to health. Methodologically, that is all that is required under § 109. We recognize that pursuant to a substantive challenge of the “safety” of the selected levels, EPA might be required to explain the risk it considered tolerable in meeting the requirements of providing a reasoned explanation for an administrative decision. But, partly because of the uncertainty of the data upon which the Administrator needed to rest his assessment, we do not find such further articulation necessary here. Consequently, AISI’s complaint provides no basis for reversal or remand.
E. Motion to Hold the Decision in Abeyance
On December 7, 1989, AISI filed with the court a motion to hold the decision in abeyance pending final action by EPA on AISI’s “Petition for Investigation and, If Appropriate, Reconsideration of the PMio NAAQS,” filed with EPA on the same date. AISI’s Petition for Investigation asked EPA to commence an investigation of the “Six Cities” study. The motion and petition were prompted by a Wall Street Journal article reporting that the National Institutes of Health’s Office of Scientific Integrity “is reviewing ‘a claim that there could be serious errors in the data base’ of the so-called Six Cities study.” Wall Street Journal, Nov. 30, 1989, at B-5.
This court faced a similar request in Lead Industries Association v. EPA, 647 F.2d 1184 (D.C.Cir.), cert. denied, 449 U.S. 1042, 101 S.Ct. 621, 66 L.Ed.2d 503 (1980). In that ease, EPA denied the petition for reconsideration before the court handed down its decision in the lead standards case. See id. at 1186. But the petitioner sought the court’s deferral of action on the appeal of the lead standards until it could obtain judicial review of EPA’s decision denying its petition for reconsideration. See id. The court ruled that in order to conclude that such a delay is justified, “the court must be convinced that the ‘new information’ which provides the basis for the reconsideration petition raises substantial questions about the validity of the Agency’s analysis.” Id. at 1187.
We do not believe that the alleged “new information” cited in the petition for reconsideration warrants delay of our review of the standards. First, even if we assume that there are serious errors in the Six Cities studies, these studies were only part of the evidence on which EPA relied in selecting the twenty-four hour and annual particulate matter standards. Other studies support the selection of the PMio standards at the levels promulgated in the final rule. Second, there is considerable doubt about whether the Six Cities data are actually infected with error. All that the “new information” indicates is that the National Institutes of Health (“NIH”) is investigating charges that one of the authors of the studies suppressed evidence of errors. Both the outcome and the duration of NIH’s investigation, and any investigation EPA might undertake, are completely beyond our ken. In short, the significance of the opening of the investigation is too speculative to provide grounds for delaying our decision on AISI's petition for review of the PMio standards. Thus we deny AISI’s motion to hold this appeal in abeyance.
F. Compliance with Control Techniques Requirements
Finally, AISI claims that EPA has unlawfully failed to issue up-to-date PMio control techniques information to the states, in violation of 42 U.S.C. § 7408(b)(1) and (c). EPA argues that since the rules under review here involve the revision of particulate matter criteria and ambient air quality standards, EPA’s duty to revise and reissue control techniques information is controlled by 42 U.S.C. § 7408(c) — not by § 7408(b)(1) — and that it has met the statutory requirements.
Under either provision, it is to “the States and appropriate air pollution control agencies” that EPA has a duty to provide cited information. See 42 U.S.C. § 7408(b)(1). On this record, we conclude that AISI lacks standing to challenge EPA’s alleged failure to furnish adequate control techniques information to the states. Article III of the Constitution limits the exercise of the “Judicial Power” of the United States to the resolution of “Cases” and “Controversies.” U.S. CONST, art. Ill, § 2. The Supreme Court has defined the essential elements of a case or contro very as follows:
[A]t an irreducible minimum, Art. Ill requires the party who invokes the court’s authority to “show that he personally has suffered some actual or threatened injury as a result of the putatively illegal conduct of the defendant,” and that the injury “fairly can be traced to the challenged action” and “is likely to be redressed by a favorable decision.”
Valley Forge Christian College v. Americans United for Separation of Church and State, 454 U.S. 464, 472, 102 S.Ct. 752, 758, 70 L.Ed.2d 700 (1982) (citations omitted).
We find here that the “injury” asserted by the petitioner is too speculative and the causation and redressability too attenuated and uncertain for AISI to meet the constitutional requirements for standing. AISI’s petition does not identify “concrete organizational interests detrimentally affected by the particular” agency action it challenges. See Action Alliance of Senior Citizens v. Heckler, 789 F.2d 931, 937 (D.C.Cir.1986). The injury AISI appears to allege is that — in giving effect to the new PMio primary standards — states might adopt implementation plans that are needlessly stringent or EPA might approve needlessly stringent state implementation plans, by relying on “out-dated” control techniques information.
But, as counsel for AISI conceded at oral argument, it is clear that the control techniques information does not have a regulatory effect on AISI. Indeed, it is not even clear that the states are bound to use the information. Although EPA must provide control techniques information to the states, the choice of control techniques is within the state’s discretion. See, e.g., Train v. Natural Resources Defense Council, 421 U.S. 60, 79, 80, 95 S.Ct. 1470, 1481, 1482, 43 L.Ed.2d 731 (1975); Union Elec. Co. v. EPA, 427 U.S. 246, 250, 96 S.Ct. 2518, 2522, 49 L.Ed.2d 474 (1976); Florida Power & Light Co. v. Costle, 650 F.2d 579, 586-87 (5th Cir.1981). EPA has only a “secondary role in the process of determining and enforcing the specific, source-by-source emission limitations.” Train, 421 U.S. at 79, 95 S.Ct. at 1481; see also 42 U.S.C. §§ 7401(a)(3), 7407(a) (1982). So long as the technique employed by the state is “adequate to achieve compliance with national air quality standards, the Administrator is not authorized to reject it in favor of another technique.” Mission Indus. v. EPA, 547 F.2d 123, 129 (1st Cir.1976). Thus, it appears that the causal relationship between the Administrator’s issuance of control techniques information and the control techniques implemented by the states is very attenuated.
Moreover, we assume that affected parties will contribute to the states’ consideration of suitable control techniques in the development of state implementation plans. See, e.g., United States v. Ford Motor Co., 814 F.2d 1099, 1104 (6th Cir.) (noting that emission sources are “offered the opportunity to have significant input on the setting of emission limits,” for example, in the state’s promulgation of the state implementation plan and EPA’s approval of it), cert. denied, 484 U.S. 822, 108 S.Ct. 83, 98 L.Ed.2d 45 (1987); see also United States v. Alcan Foil Products, 889 F.2d 1513, 1516 (6th Cir.1989) (company’s proposed revision to Kentucky state implementation plan approved by air pollution control region), petition for cert. filed, 58 U.S.L.W. 3480 (U.S. Jan. 17, 1990) (No. 89-1104). We further assume that a state implementation plan founded on poor control-techniques information would be open to challenge by affected parties.
The Senate Report accompanying the Clean Air Amendments of 1970 “recognize[d] that the States will continue to need this information to develop meaningful programs for implementation of ambient air quality standards on a regional basis.” See S.Rep. No. 1196, 91st Cong., 2d Sess. 9 (1970). The legislative history shows that Congress intended the control-techniques information to “serve as guidance to States, not as limitations on control technology innovation.” Id. AISI has not persuaded us that the “guidance” EPA has made available to the states has or will wreak injury on it. We do not determine here that it would be impossible under all circumstances for AISI, or another organization, to establish standing to challenge EPA’s failure to comply with its obligation to release control-techniques information. We conclude only that AISI lacks standing in the case before us to challenge EPA’s compliance with the requirements of 42 U.S.C. § 7408(b)(1) and (c).
G. Conclusion
We conclude that each of AISI’s challenges to EPA’s final rule must fail.
III. The American Mining Congress’ Claims
Congress amended the Clean Air Act in 1977 in response to the widespread failure of states to attain the NAAQS promulgated in 1971. Under a new § 107(d) of the Act, every state must classify each of its air quality regions for each air quality standard as “attainment,” “nonattainment,” or, in the event that insufficient information exists, “unclassifiable.” For regions identified as attainment or unclassifiable, Congress adopted a Prevention of Significant Deterioration (“PSD”) program in a new Part C of the Act, 42 U.S.C. §§ 7470-7479. The PSD provisions are designed to preserve air quality, in regions that have already satisfied the NAAQS, by imposing “maximum allowable increases” in the emission of pollutants from new and existing sources. See 42 U.S.C. § 7473. The program requires each state to adopt pre-construction review of any “major emitting facility” to ensure that emissions in the region where the facility is located will not exceed allowable PSD increments. See 42 U.S.C. § 7475. Congress delegated to EPA the authority to promulgate PSD increments for hydrocarbons, carbon monoxide, photochemical oxidants, nitrogen oxides, and other “pollutants for which national ambient air quality standards are promulgated after August 7, 1977.” 42 U.S.C. § 7476. But Congress specified in § 163(b) the exact numerical increments for particulate matter and sulfur dioxide. See 42 U.S.C. § 7473(b). Although § 163(b) does not explicitly mention what size indicator (Total Suspended Particulates (“TSP”) or PM10) would be the standard of measurement, EPA has consistently interpreted the statute as mandating the use of the TSP standard.
Petitioner American Mining Congress (“AMC”), an industry association representing the coal mining industry, challenges EPA’s decision to retain the TSP indicator for purposes of the PSD program once the agency adopted the PMio indicator, the successor measuring device, for the particulate matter NAAQS, see 52 Fed. Reg. 24,685, 24,699-702 (1987). EPA did announce that the agency would promulgate new PSD increments for particulate matter using the PM10 reference through a rulemaking proceeding pursuant to § 166. See 52 Fed.Reg. 24,672, 24,685 (1987). The AMC contends, however, that EPA should have kept the same numbers specified in § 163(b) but “administratively redefined” them as referring to a PMi0 indicator rather than TSP. The PSD program expressed in TSP terms, the AMC believes, severely disrupts coal mining because such operations release large-particle “fugitive dust” into the air. AMC maintains that as long as the TSP standard is retained for the PSD provisions, coal mines will likely exceed the maximum particulate matter increments. Petitioner argues that EPA’s refusal to modify the PSD increment calculations contravenes congressional intent and our circuit’s precedent. Furthermore, AMC believes that the retention of the admittedly flawed TSP standard constitutes arbitrary and capricious decisionmak-ing. We find none of the petitioner’s arguments persuasive.
Although § 163(b) does not define “particulate matter” by size, both EPA and the AMC agree that Congress intended to apply the TSP indicator when it enacted the PSD increments in 1977. The numbers Congress specified in § 163(b) reflect percentages of the then-existing NAAQS for particulate matter — which was measured only in TSP terms — and indicate Congress’ judgment on what constitutes a significant deterioration of air quality. See H.R.Rep. No. 294, 95th Cong., 1st Sess. 153 (1977); S.Rep. No. 127, 95th Cong., 1st Sess. 11 (1977) U.S.Code Cong. & Admin.News 1977, pp. 1077, 1232. Consequently, the only issue is whether EPA was authorized to alter the TSP measurement embedded in the statute when the agency adopted a new indicator for NAAQS purposes.
It hardly bears noting that EPA’s discretion cannot include the power to rewrite a statute and reshape a policy judgment Congress itself has made. See, e.g., Louisiana Public Serv. Comm’n v. FCC, 476 U.S. 355, 376, 106 S.Ct. 1890, 1902, 90 L.Ed.2d 369 (1986); MCI Telecommunications Corp. v. FCC, 765 F.2d 1186, 1195 (D.C.Cir.1985). The AMC argues that the legislative history of the 1977 Amendments to the Clean Air Act demonstrates a congressional intent to authorize EPA to modify the TSP reference in the § 163(b) PSD increments if and when the agency adopts a new size cutoff for measurement purposes. The petitioner directs us to a short passage in the 1977 Senate Committee report suggesting that EPA use “administrative good sense” in responding to imprecisions in the TSP measurement. See S. Rep. No. 127, 95th Cong., 1st Sess. 98 (1977). And according to the AMC, the absence of any specific standard of measurement in § 163(b) indicates that Congress meant to give EPA flexibility to change the standard even though the numbers were to be constant.
The AMC’s position would require us to rely on this snippet of legislative history to set aside what appears to us to be a specific and unambiguous congressional policy judgment. By establishing PSD increments numbers expressed in what could only have been TSP terms, Congress determined the permissible amount of increases in emissions of particulate matter. Congress arrived at those § 163(b) numbers based on its estimate of the particulate matter emissions that would normally accompany moderate and intensive economic growth. See H.R.Rep. No. 294, 95th Cong., 1st Sess. 152-53 (1977). Simply changing the measurement reference from TSP to PMio while maintaining the same numbers, as AMC urges EPA to do, would dramatically relax the PSD restrictions on particulate matter since the TSP indicator is a much more inclusive measure of pollutants. The absence of a specific indicator in § 163(b) hardly suggests the flexibility that AMC reads into the statute; only the TSP indicator existed at the time of the 1977 Amendments and Congress could have thought it superfluous and excessively technical to mention it. If Congress had intended to delegate the power to alter the § 163(b) increments, it could have done so explicitly — as it did for other pollutants in § 166. It would be wholly irrational for Congress to set forth specific numbers for particulate matter increments and yet authorize a choice of indicators which radically alters the numbers’ significance and therefore ultimately how much particulate matter may be emitted. Congress has plainly expressed an intent to allow a certain quantum of particulate matter emissions, and we must give that intent effect. See Chevron U.S.A. Inc. v. Natural Resources Defense Council, 467 U.S. 837, 842-43, 104 S.Ct. 2778, 2780-81, 81 L.Ed.2d 694 (1984).
The AMC also contends that in Alabama Power v. Costle, 636 F.2d 323 (D.C.Cir.1980), we previously authorized EPA to redefine particulate matter to exclude the larger particle fugitive dust from the PSD provisions. In a footnote in Alabama Power, we did suggest, in dicta, that EPA could define particulate matter to exclude those of a size or composition believed to be harmless. See id. at 370 n. 134. That footnote in Alabama Power, however, did not directly confront Congress’ explicit direction in § 163(b) detailing the permissible particulate matter increment and is thus hardly binding on either EPA or this court.
Finally, the AMC urges us to reverse as arbitrary and capricious EPA’s decision to retain the TSP indicator. Petitioner presented a welter of scientific evidence demonstrating that the TSP measure is flawed, large particle fugitive dust is harmless, and therefore the TSP standard fails a cost benefit analysis. Unfortunately for the AMC, however, its real dispute is not with EPA but with Congress, which decided for itself what increases in particulate matter emissions were acceptable. EPA may not be faulted for following Congress’ clear direction in § 163(b) and deciding that the agency possessed no discretion to consider the costs and benefits of maintaining the TSP indicator.
The AMC also challenges, in a most cursory fashion, three highly technical and minor features of the particulate matter NAAQS: the shift from a geometric to arithmetic mean in expressing the annual particulate matter standard, the continued adjustment of particulate matter concentrations to standard temperature and pressure, and the refusal to modify the technique for adjusting particulate matter concentrations due to high wind speeds. These challenges are nothing more than an invitation to second-guess an expert agency’s resolution of scientific and technical issues of its rulemaking — the paradigm instance of agency discretion — and we will defer to EPA as long as its explanation is rational. See American Petroleum Inst. v. Costle, 665 F.2d 1176, 1184 (D.C.Cir.1981), cert. denied, 455 U.S. 1034, 102 S.Ct. 1737, 72 L.Ed.2d 152 (1982); Lead Indus. Ass’n v. EPA, 647 F.2d 1130, 1162 (D.C.Cir.), cert. denied, 449 U.S. 1042, 101 S.Ct. 621, 66 L.Ed.2d 503 (1980).
EPA changed the form of its annual particulate matter standard from an anmial geometric mean to an expected arithmetic mean. See 52 Fed.Reg. 24,634, 24,640 (1987). The AMC complains, with virtually no explanation, that the arithmetic mean is too sensitive to aberrationally high values and is therefore unjustified. According to EPA, because the arithmetic mean is proportional to the sum of the daily means, it may better reflect health data based on total exposure. Indeed, the public health studies underlying the annual standard applied the arithmetic mean. The geometric mean, moreover, may be too sensitive to aberrationally low data points since it would multiply the terms together and find their Nth root. Thus, EPA noted that a single day of zero concentration would result in a geometric mean calculation of zero for the entire year, regardless of the concentrations present in the 364 other days. The “choice of statistical methods is committed to the sound discretion of the Administrator,” Chemical Mfrs. Ass’n v. EPA, 870 F.2d 177, 227 (5th Cir.1989), and we find no basis for questioning the rationality of EPA’s decision to shift the method of calculation.
EPA also continued its longstanding requirement that samples of ambient air be corrected to standard temperature (298 degrees K) and pressure (101.3 kPa). See 40 C.F.R. Part 50, Appendix J, § 11. The AMC objects, again with very little elaboration, that this adjustment exaggerates particulate matter concentration when sampling ambient air at higher altitudes. The agency explained that even at moderate altitudes exercise can stimulate significant differences in ventilation between residents at those altitudes and comparable conditions at sea level. The decreased oxygen pressure, moreover, could adversely affect sensitive individuals. The AMC made no attempt to rebut this explanation, and we conclude that EPA’s retention of this adjustment is reasonable.
Finally, the AMC asserts that EPA’s measurement techniques do not adequately account for high wind speeds that might skew the particulate matter concentration results. See 40 C.F.R. Parts 53 and 55. EPA denied the AMC’s petition because the AMC did not raise this issue during the rulemaking. The AMC has not offered any explanation why it might have been impractical to raise the wind speed issue during rulemaking or special circumstances that might justify consideration of its petition. Therefore, we find that EPA properly denied the AMC’s petition. See 42 U.S.C. § 7607(d)(7)(B); see also Northside Sanitary Landfill, Inc. v. Thomas, 849 F.2d 1516, 1519 (D.C.Cir.1988), cert. denied, — U.S. -, 109 S.Ct. 1528, 103 L.Ed.2d 833 (1989).
IV. The Natural Resources Defense Council’s Claims
The following opinions by Chief Judge Wald and Circuit Judges Edwards and Silberman consider the claims of the Natural Resources Defense Council (“NRDC”) concerning EPA’s conduct vis-avis a secondary national ambient air quality standard for particulate matter to protect the public welfare from visibility impairment and acid deposition. Although Chief Judge Wald’s opinion lays out the statutory and regulatory framework of the issue, the three opinions differ in their analyses and, to some degree, in their conclusions. In sum, the judgment of the court is as follows. We hold that EPA has not taken final action with regard to the appropriateness of a fine particle standard protecting the public welfare against visibility impairment; accordingly, we do not have jurisdiction under § 307 of the CAA over NRDC’s petition to order that such action be taken. The portion of NRDC’s petition concerning a visibility impairment standard is, consequently, dismissed. We also conclude that EPA has taken final action, for purposes of this rulemaking, not to issue a fine particle standard protecting the public from acid deposition; accordingly, we do have jurisdiction over the section of NRDC’s petition concerning an acid deposition standard. We remand this portion of the case to the agency and order it to provide, within sixty days of the issuance of the mandate of this opinion, a statement of reasons for its decision not to initiate a rulemaking on a secondary standard protecting against acid deposition.
WALD, Chief Judge:
This Part considers a suit by the Natural Resources Defense Council (“NRDC”) and affiliated petitioners claiming that the Environmental Protection Agency (“EPA” or “agency”) improperly failed to set a secondary national ambient air quality standard (“NAAQS”) for particulate matter to protect the public welfare from visibility impairment and acid depositions. NRDC asks us to establish a one-year timetable for EPA to implement this aspect of its secondary standard. Our reading of the Clean Air Act leads us to conclude (1) that we do not have jurisdiction to consider NRDC’s contention as to visibility impairment, and (2) that while we do have jurisdiction to consider NRDC’s contention as to acid deposition, the thinness of the record requires us to remand for a more adequate explanation by EPA of its decision not to initiate rulemaking on a particulate matter standard dealing with acid deposition.
I. Statutory and Regulatory Framework
A. The Clean Air Act
I begin by briefly setting out the statutory context in which NRDC’s suit arises. Section 109 of the Clean Air Act (“CAA” or “Act”), 42 U.S.C. § 7409 (1982), instructs the EPA Administrator to publish a primary and secondary NAAQS for each air pollutant for which air quality criteria have been issued. Primary standards are designed to protect the public health. Secondary standards, at issue here,
shall specify a level of air quality the attainment and maintenance of which in the judgment of the Administrator, based on such criteria, is requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of such air pollutant in the ambient air.
Id. § 7409(b)(2). The Act elsewhere explains that
[a]ll language referring to effects on welfare includes, but is not limited to, effects on soils, water, crops, vegetation, manmade 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.
Id. § 7602(h).
In 1977, after nearly ten years of review and evaluation of the ambient air quality standards, see H.R.Rep. No. 294, 95th Cong., 1st Sess. 179-82 (1977), Congress enacted § 109(d) of the Act, 42 U.S.C. § 7409(d). It states in relevant part:
Not later than December 31, 1980, and at five-year intervals thereafter, the Administrator shall complete a thorough review of the criteria published under section 7408 of this title and the national ambient air quality standards promulgated under this section and shall make such revisions in such criteria and standards and promulgate such new standards as may be appropriate in accordance with section 7408 of this title and subsection (b) of this section. The Administrator may review and revise criteria or promulgate new standards earlier or more frequently than required under this paragraph.
Id. § 7409(d)(1).
Thus, EPA bears continuing regulatory responsibilities for updating secondary standards. The CAA's complex scheme for judicial review of EPA’s performance, however, has given rise to conflicting interpretations as to which court has jurisdiction over claims that EPA has not fulfilled its obligations in this regard. Section 307(b)(1), id. § 7607(b)(1), provides in relevant part that
[a] petition for review of action of the Administrator in promulgating any national primary or secondary ambient air quality standard, ... any other nationally applicable regulations promulgated, or final action taken, by the Administrator under this chapter may be filed only in the United States Court of Appeals for the District of Columbia.
At the same time, § 304 of the Act, id. § 7604, the “citizen suit” provision, provides that district courts have jurisdiction over suits alleging the EPA Administrator’s failure to perform a non-discretionary act or duty. In appropriate cases, the district court may order the Administrator to perform such an act or duty. Id. § 7604(a)(2).
B. Regulatory Evolution
In March 1984, the Administrator proposed secondary standards protecting the public welfare against soiling and nuisance caused by airborne particulate matter. Proposed Revisions to the National Ambient Air Quality Standards for Particulate Matter, 49 Fed.Reg. 10,408, 10,418-19 (1984). In the same document, the Administrator explained that three other principal welfare effects — visibility impairment, climatic effects, and acid deposition — “are most strongly related to regional scale fine particle levels and any standards and controls would likely involve regional sulfur oxide emissions.” Id. at 10,419. Thus, the Administrator made a preliminary determination that EPA can best protect the public welfare from these effects through a separate standard involving only “fine” particulate matter. Id. To that end, the Administrator noted “the advantages of recognizing the interrelated aspects of the known and potential effects of fine particles on visibility and climate together with the acidic deposition phenomenon when considering a possible fine particle standard.” Id. As a result, the Administrator “decided to defer a decision on a possible fine particle secondary standard until it is possible to link such a standard with a coherent, scientifically based strategy for these related regional air quality problems.” Id. “In parallel with” its evaluations of various approaches to acidic deposition, EPA would continue to examine “the implications of acidic deposition control strategies on visibility and other air quality values.” Id. The information gathered by EPA would be used “in preparing an advance notice of proposed rulemaking soliciting public comment regarding a possible fine particle secondary sta