Rethinking Health-based Environmental Standards

though only at too high a level of generality to provide regulators with the needed guidance.32 For example, Professor Mark Sagoff suggests agencies should regulate up to the “knee of the [cost] curve,”33 which is “the point at which the cost of controlling the next incremental unit of pollution begins to increase rapidly,” and returns to the environment rapidly diminish per dollar spent.34 But the slope of a cost curve typically increases continuously as the stringency of regulation increases.35 Determining what counts as the “knee of the curve” is therefore an inevitably arbitrary inquiry. And, ironically, these “knee of the curve” approaches themselves balance, in a poorly specified way, regulatory benefits and regulatory costs. Supporters of this line of criticism of cost-benefit analysis often favor feasibility standards, the second major approach to setting environmental regulation. Professor David Dreisen, a strong advocate of feasibility standards, defines them as requiring “stringent regulation” subject to constraints on “physically impossible environmental improvements” and standards “so costly that they cause widespread 29 See FRANK ACKERMAN & LISA HEINZERLING, PRICELESS: ON KNOWING THE PRICE OF EVERYTHING AND THE VALUE OF NOTHING 8–11 (2004) (“[F]ormal cost-benefit analysis often hurts more than it helps: it muddies rather than clarifies fundamental clashes about values.”). 30 KYSAR, supra note 7, at 20 (2010) (arguing that cost-benefit analysis “offers the implicit and misleading message that our needs consist only of better data and morerigorous techniques of valuation”). 31 See Jonathan S. Masur & Eric A. Posner, Against Feasibility Analysis, 77 U. CHI. L. REV. 657, 659–60 (2010) (“[C]ritics have never been very clear about what decision procedure they prefer to CBA.”). 32 See Sidney A. Shapiro & Christopher H. Schroeder, Beyond Cost-Benefit Analysis: A Pragmatic Reorientation, 32 HARV. ENVTL. L. REV. 433, 469–82 (2008) (suggesting a general “pragmatic alternative”). 33 MARK SAGOFF, PRICE, PRINCIPLE, AND THE ENVIRONMENT 25 (2004); accord Mark Sagoff, Ethical and Economic Principles, in LAW OF ENVIRONMENTAL PROTECTION 161, 209 (Sheldon M. Novick et al. eds., 2012). 34 SAGOFF, supra note 33, at 25; see Sidney A. Shapiro & Thomas O. McGarity, Not So Paradoxical: The Rationale for Technology-Based Regulation, 1991 DUKE L.J. 729, 743 n.7 (1991) (noting that the “knee-of-the-curve” analysis “may provide an attractive starting point” for determining how much to spend on risk-reduction). 35 Shapiro & Schroeder, supra note 32, at 481. \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 10 16-OCT-14 11:36 October 2014] RETHINKING ENVIRONMENTAL STANDARDS 1193 plant shutdowns.”36 Dreisen defends feasibility standards as appropriately accounting for the concentrated costs associated with job losses from plant closure while giving no weight to “even large costs . . . if regulated parties will disperse those costs widely,” as would be the case for a slight increase in the price of a widely used consumer good.37 Best available technology standards in the Clean Air Act38 and Clean Water Act39 are prominent examples of feasibility standards. Professors Eric Posner and Jonathan Masur offer a persuasive argument that feasibility standards are normatively undesirable.40 Drawing on detailed case studies of the regulation of chromium by the Occupational Safety and Health Administration and of paper mills by EPA, they argue that if welfare maximization is taken as the goal of regulatory policy, feasibility standards “create[ ] significant problems of overand underregulation.”41 Overregulation results “because feasibility analysis ignores the cost of regulations to consumers”42 and underregulation because “feasibility analysis tolerates dangerous industrial practices”43 in instances in which shutting down plants would be socially desirable. In these two ways, feasibility standards differ from, and are inferior to, cost-benefit standards. Furthermore, Posner and Masur argue that alternative understandings of well-being, such as the capabilities approach put forward by Martha Nussbaum, do not map onto the priorities expressed by feasibility standards, and that “[n]o attempt to reverse-engineer a theory of well-being that justifies feasibility analysis has been successful.”44 On the basis of this analysis, they conclude that feasibility standards “lack[ ] a normative justification and should have no place in government regulation.”45 Health-based standards, the subject of this Article, are the third principal approach to determining the stringency of environmental regulation. These standards seek either the entire elimination of a 36 David M. Driesen, Distributing the Costs of Environmental, Health, and Safety Protection: The Feasibility Principle, Cost-Benefit Analysis, and Regulatory Reform, 32 B.C. ENVTL. AFF. L. REV. 1, 9 (2005). 37 David M. Driesen, Two Cheers for Feasible Regulation: A Modest Response to Masur and Posner, 35 HARV. ENVTL. L. REV. 313, 323 (2011). 38 42 U.S.C. § 7412(d)(2) (2012); id. § 7475(a)(4) (requiring facilities to use “best available control technology”); id. § 7479(3) (defining “best available control technology”). 39 33 U.S.C. § 1311(b)(2)(A) (2012). 40 Masur & Posner, supra note 31. 41 Id. at 704. 42 Id. 43 Id. 44 Id. at 709. 45 Id. at 662. \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 11 16-OCT-14 11:36 1194 NEW YORK UNIVERSITY LAW REVIEW [Vol. 89:1184 public health risk or, failing that, the achievement of what is deemed to be an acceptable level of risk.46 They thus differ from cost-benefit standards because they do not (explicitly) trade off health improvements against competing social priorities such as costs. They differ from feasibility standards because they are not constrained by what a particular industry could achieve without going out of business. The balance of this Article addresses the desirability of health-based standards as an alternative to cost-benefit analysis and focuses on the NAAQS—the most prominent example of health-based standards in U.S. environmental law. B. Arguments for Health-Based Standards There have been several attempts by academic commentators and protection-oriented interest groups to justify the use of health-based over cost-benefit standards. This section summarizes the four leading arguments made by supporters of health-based standards. First, they argue that cost-benefit analysis tends to overemphasize costs and underemphasize health concerns.47 Much of this criticism stems from the manner in which the costs and benefits are evaluated in practice. Some contend that while costs are relatively easy to quantify, health risks are “difficult to quantify, statistical, and remote.”48 Second, they express the concern that cost-benefit analysis fails to address the power imbalance between regulated industries and the diffuse beneficiaries of environmental protection.49 They believe that, in contrast, health-based standards can counteract this imbalance by elevating environmental protection above the considerations of cost.50 For example, Professor Amy Sinden argues that “cost-blind” stan46 See David M. Driesen, Should Congress Direct the EPA to Allow Serious Harms to Public Health to Continue?: Cost-Benefit Tests and NAAQS Under the Clean Air Act, 11 TUL. ENVTL. L.J. 217, 220–21 (1998) (noting that in the context of setting the NAAQS, “we must either choose a zero level for pollutants or recognize some element of discretion in deciding what constitutes an adequate margin of safety”). 47 See John P. Dwyer, The Pathology of Symbolic Legislation, 17 ECOLOGY L.Q. 233, 248 (1990). 48 Id.; see also Driesen, supra note 46, at 222–23 (noting the difficulty of quantifying environmental and public health problems). 49 Cf. Sinden, supra note 5, at 1409; see also Dwyer, supra note 47, at 248 (“[I]ndustry generally has the best information about the costs and feasibility of pollution controls, and thus it is able to present data supporting predictions of dire economic consequences if strict standards are adopted.”). 50 See Sinden, supra note 5, at 1410–11 (advocating a “trumping approach” in environmental law by analogizing to constitutional rights jurisprudence, which is also concerned with combating disparities of power). \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 12 16-OCT-14 11:36 October 2014] RETHINKING ENVIRONMENTAL STANDARDS 1195 dards “place a thumb on the scale in favor” of environmental protection and serve a “crucially important power-shifting function.”51 A third argument offered in support of health-based standards is that they can serve as a “technology-forcing” device.52 According to this rationale, by directing the regulator to consider only healthrelated factors, industry may be forced to develop stronger control technologies.53 Attainment of a standard that appears to be prohibitively expensive at the time legislation is adopted may become affordable as new control technologies and pollution prevention strategies are developed.54 For example, the architects of the CAA believed that polluters would find effective ways to meet new requirements, even if the necessary technology did not exist at the time.55 Fourth, proponents of health-based standards also seek to justify them on nonwelfarist grounds.56 Under these types of justifications, regulation is necessary even when “the aggregate cost outweighs the aggregate harm” because “[s]trong ethical considerations support the notion that we all have an obligation to avoid seriously harming our neighbors’ health.”57 One version of this view is that human life and health, or a clean environment, should not be viewed as a commodity whose value can be compared with the economic costs of pollution 51 See id. at 1411. 52 Dwyer, supra note 47, at 248. 53 See id.; see also Driesen, supra note 46, at 234 (“Health-protective standards may help stimulate needed innovations, overcome failures to implement inexpensive and obvious measures, create jobs, and stimulate efficiency improvements, while greatly reducing the numerous harms dirty air causes.”); Thomas O. McGarity, Media-Quality, Technology, and Cost-Benefit Balancing Strategies for Health and Environmental Regulation, 46 LAW & CONTEMP. PROBS. 159, 221 (1983) (“Congress might, for example, decide to ‘force’ technology by prescribing requirements that are capable of being met only through the implementation of newly evolving or nonexistent technologies.”). 54 Joseph M. Feller, Non-Threshold Pollutants and Air Quality Standards, 24 ENVTL. L. 821, 885 (1994). 55 See Whitman v. Am. Trucking Ass’ns, 531 U.S. 457, 490 (2001) (Breyer, J., concurring) (“[L]egislative history shows that Congress intended the statute to be ‘technology forcing.’”); see also Union Elec. Co. v. EPA, 427 U.S. 246, 256–57 (1976) (stating that the 1970 Amendments to the CAA were “expressly designed to force regulated sources to develop pollution control devices that might at the time appear to be economically or technologically infeasible”); John E. Bonine, The Evolution of “Technology-Forcing” in the Clean Air Act, ENV’T REP. (BNA), MONOGRAPH NO. 21 (1975), as reprinted in JOHN E. BONINE & THOMAS O. MCGARITY, THE LAW OF ENVIRONMENTAL PROTECTION 280 (1984) (discussing the “technology-forcing” motivations of the Clean Air Act). 56 For a discussion of the ethical criticisms of cost-benefit analysis in environmental regulation, see Steven Kelman, Cost-Benefit Analysis and Environmental, Safety, and Health Regulation: Ethical and Philosophical Consideration, in COST-BENEFIT ANALYSIS AND ENVIRONMENTAL REGULATIONS: POLITICS, ETHICS, AND METHODS 137 (Daniel Swartzman et al. eds., 1982). 57 Driesen, supra note 46, at 223. \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 13 16-OCT-14 11:36 1196 NEW YORK UNIVERSITY LAW REVIEW [Vol. 89:1184 reduction.58 Others have argued that a “‘right’ to a healthy environment” trumps other considerations.59 Some supporters of healthbased standards emphasize their symbolic benefits. Under this view, Congress adopts health-based environmental controls “because they establish government priorities and public values promoting protection of public health.”60 C. Regulatory Programs Prohibiting the Consideration of Costs While the NAAQS are the highest profile and most important example of health-based standards, they are not the only one. This section briefly describes some other examples. When many environmental, public health, and safety statutes were adopted, “formal economic cost-benefit analysis remained largely confined to academic circles, and . . . Congress and the courts remained highly skeptical of the idea.”61 Since that time, attitudes toward cost-benefit analysis have undergone a major shift, as exemplified by the emergence of OIRA review as a major component of the administrative state.62 Statutes from an earlier era, however, remain on the books and prohibit the consideration of costs in determining the extent of protection to the environment or to health and safety. For example, section 182(a) of the Atomic Energy Act requires that the Nuclear Regulatory Commission (NRC) make a finding that “the utilization or production of special nuclear material will be in accord with the common defense and security and will provide adequate protection to the health and safety of the public.”63 In Union of Concerned Scientists v. U.S. Nuclear Regulatory Commission, the D.C. Circuit held that “[i]n setting or enforcing the standard of ‘adequate protection’ that this section [182] requires, the Commission may not consider the economic costs of safety measures.”64 The UCS court reasoned that “when Congress desired agencies to consider economic costs, it knew how to say so,” citing the Flood Control Act of 1936 as an example.65 Looking to the legislative history of the 1954 amendments, the court painted a picture of a Congress deeply concerned with the “grave threats” that nuclear power 58 See Feller, supra note 54, at 881 (discussing core criticisms of cost-benefit analysis). 59 McGarity, supra note 53, at 161. 60 Dwyer, supra note 47, at 249. 61 Amy Sinden, The Economics of Endangered Species: Why Less Is More in the Economic Analysis of Critical Habitat Designations, 28 HARV. ENVTL. L. REV. 129, 136 (2004). 62 See supra text accompanying notes 21–26. 63 42 U.S.C. § 2232(a) (2012). 64 824 F.2d 108, 114 (D.C. Cir. 1987). 65 Id. at 114–15. \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 14 16-OCT-14 11:36 October 2014] RETHINKING ENVIRONMENTAL STANDARDS 1197 presented “to the very existence of civilization,” and therefore construed the statute as implicitly prohibiting cost considerations.66 One of the most controversial prohibitions on cost consideration existed for many years in the context of food additives: the Delaney Clause of the Food, Drug, and Cosmetics Act.67 Courts interpreted the clause to prevent the Food and Drug Administration (FDA) from approving any food additive “if it is found to induce cancer when ingested by man or animal,”68 holding that costs could play no role in this determination.69 When an absolute prohibition on the approval of such additives proved to be unworkable, the FDA attempted to create an exception to the prohibition, which would allow approval of additives that produced lifetime cancer risk of less than one in one million.70 The D.C. Circuit, however, found this interpretation to be unacceptable, determining that even “trivial risks” were impermissible.71 66 Id. at 115. The UCS court held that the NRC could consider costs when “devising or administering requirements that offer protection beyond” those required by “adequate protection.” Id. at 114; see also Pub. Citizen v. Nuclear Regulatory Comm’n, 573 F.3d 916, 918 (9th Cir. 2009) (“The Commission is authorized to impose additional safety measures on licensees above those required by adequate protection, and in doing so may consider the economic costs of those extra measures.”). 67 21 U.S.C. § 348(c)(3)(A) (1994) (repealed 1996). 68 See Bell v. Goddard, 366 F.2d 177, 181 (7th Cir. 1966) (quoting 21 U.S.C. § 348(c)(3)(A)). 69 See Les v. Reilly, 968 F.2d 985, 989 (9th Cir. 1992) (holding that “Congress intended to ban all carcinogenic food additives, regardless of amount or significance of risk”); Frank B. Cross, The Consequences of Consensus: Dangerous Compromises of the Food Quality Protection Act, 75 WASH. U. L. Q. 1155, 1159 (1997) (noting that decisions under the Delaney Clause were taken “regardless of any cost-benefit balancing”); Richard A. Merrill, FDA’s Implementation of the Delaney Clause: Repudiation of Congressional Choice or Reasoned Adaptation to Scientific Progress?, 5 YALE J. ON REG. 1, 1 (1988) (noting that food ingredients shown to cause cancer are prohibited “regardless of the benefits the ingredients might provide or the magnitude of the risk”). 70 Pub. Citizen v. Young, 831 F.2d 1108, 1111 (D.C. Cir. 1987). 71 Id. at 1122. A similar pattern is present in the Endangered Species Act, an environmental program not involving the protection of public health. In TVA v. Hill, the Supreme Court enjoined the construction of the Tellico Dam because of its impact on the then-endangered snail darter, famously holding that the Endangered Species Act precluded cost consideration, at least in certain contexts. 437 U.S. 153, 184 (1978) (“The plain intent of Congress in enacting this statute was to halt and reverse the trend toward species extinction, whatever the cost.”). The Court’s holding was softened somewhat by a subsequent statutory amendment, which created an exemption process for government projects that jeopardize endangered or threatened species. See 16 U.S.C. § 1536(h)(1) (2012). See generally Holly Doremus, Listing Decisions Under the Endangered Species Act: Why Better Science Isn’t Always Better Policy, 75 WASH. U. L. Q. 1029 (1997) (discussing decisionmaking under the Endangered Species Act). \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 15 16-OCT-14 11:36 1198 NEW YORK UNIVERSITY LAW REVIEW [Vol. 89:1184 The Delaney Clause had many detractors,72 and in the years prior to its repeal the FDA consistently sought to reinterpret or ignore it in order to produce more palatable regulatory outcomes.73 The statute was ultimately amended in 1996.74 Although important, none of these health-based standards have the salience of the NAAQS, which are the cornerstone of the United States’ air pollution control efforts. We now turn to showing how the NAAQS came to be understood to bar the consideration of costs. D. NAAQS and American Trucking Under the Clean Air Act, EPA is directed to set both primary and secondary NAAQS based on a “criteria” document that analyzes the most current scientific information on the air pollutant.75 The primary NAAQS must be set at the level “requisite to protect the public health” with an “adequate margin of safety.”76 The secondary NAAQS must be set at the level “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.”77 NAAQS are set uniformly across the entire country.78 The prohibition on the consideration of costs in the setting of the NAAQS is longstanding, dating back to the D.C. Circuit’s 1980 decision in Lead Industries Association v. EPA.79 The court reasoned there that if Congress had intended for EPA “to be concerned about 72 See, e.g., Merrill, supra note 69, at 1 (calling the Delaney Clause an “extreme polic[y]” that was “increasingly difficult to administer”). 73 See id. at 2. 74 Thomas O. McGarity, Politics by Other Means: Law, Science, and Policy in EPA’s Implementation of the Food Quality Protection Act, 53 ADMIN. L. REV. 103, 116–17 (2001) (noting that consumer groups were able to extract concessions during the legislative process in the form of heightened protections for children). 75 42 U.S.C. §§ 7408(a)(2), 7409(a) (2012). See infra note 247 for the current form of the criteria document. 76 Id. § 7409(b)(1). 77 Id. § 7409(b)(2). “Welfare” is defined as including, inter alia, “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, whether caused by transformation, conversion, or combination with other air pollutants.” Id.§ 7602(h). 78 In particular, the NAAQS do not take into account local population concentrations or the ease with which ambient concentrations can be achieved. See James E. Krier, The Irrational National Air Quality Standards: Macroand Micro-Mistakes, 22 UCLA L. REV. 323, 323–25 (1974) (stating that NAAQS are uniform and describing a particularly costly application of that rule in Los Angeles). The State Implementation Plan process, by which states implement the NAAQS, may somewhat alleviate this problem. See Douglas R. Williams, Cooperative Federalism and the Clean Air Act: A Defense of Minimum Federal Standards, 20 ST. LOUIS U. PUB. L. REV. 67, 75 (2001) (discussing the SIP process). 79 647 F.2d 1130 (D.C. Cir. 1980). \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 16 16-OCT-14 11:36 October 2014] RETHINKING ENVIRONMENTAL STANDARDS 1199 economic and technological feasibility, it [would have] expressly so provided.”80 Further, the court relied on the statute’s legislative history to conclude that the omission of any discussion of “economic and technological feasibility” was “a deliberate decision by Congress to subordinate such concerns to the achievement of health goals.”81 In Whitman v. American Trucking Associations, the Supreme Court affirmed EPA’s practice of not considering costs when setting NAAQS.82 Justice Scalia, writing for the Court, noted that the language of section 109 was “absolute” and instructed EPA to use the information about health effects contained in the criteria documents to “identify the maximum airborne concentration of a pollutant that the public health can tolerate, decrease the concentration to provide an ‘adequate’ margin of safety, and set the standard at that level.”83 He added that “[n]owhere are the costs of achieving such a standard made part of that initial calculation.”84 The plaintiffs in American Trucking unsuccessfully argued that cost could be considered under various phrases in the statute. They first claimed that costs were included in the definition of “public health,” as the economic cost of implementing a too-stringent standard could produce health losses sufficient to offset the health gains achieved from decreased air pollution. The Court rejected this argument, finding that Congress was aware of this problem and had factored it into other provisions of the CAA that explicitly discussed compliance costs.85 The Court similarly dismissed arguments that cost could be considered in the context of determining the “adequate margin [of safety]” or what is “requisite” to protect public health.86 It “refused to find implicit in ambiguous sections of the CAA an authorization to consider costs that has elsewhere, and so often, been expressly granted.”87 The Court concluded that section 109(b), interpreted “in its statutory and historical context and with appreciation for its importance to the CAA as a whole, unambiguously bars cost considerations from the NAAQS-setting process.”88 80 Id. at 1148. 81 Id. at 1149. 82 531 U.S. 457 (2001). 83 Id. at 465. 84 Id. The Supreme Court also found that the NAAQS were not an unconstitutional delegation of legislative power, reversing the D.C. Circuit’s holding that EPA’s construction of the CAA effected an unconstitutional delegation of legislative power, because it was not guided by an intelligible principle. Id. at 475–76. 85 Id. at 466–67. 86 Id. at 468. 87 Id. at 467. 88 Id. at 471. \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 17 16-OCT-14 11:36 1200 NEW YORK UNIVERSITY LAW REVIEW [Vol. 89:1184 II STOPPING-POINT PROBLEM This Part examines the decisionmaking process used by EPA when setting the NAAQS and argues that the agency faces choices at several points along the way that it cannot resolve on health considerations alone. There are a host of judgments that the Administrator must make when setting the NAAQS. Scientific questions that the Administrator must confront include the ability (or inability) of central site monitors to accurately reflect regional pollution concentrations,89 the exposure levels for which specific health effects occur,90 and the role that individual behaviors may play in modifying exposures or risks.91 In spite of limited information, the Administrator must exercise considerable judgment to provide best-estimate answers to empirical questions concerning the state of the world. The current NAAQS process also requires the Administrator to confront questions that are not scientific in nature. These decisions require the agency to identify a stopping point for regulatory stringency given a set of state-of-the-world estimates (including uncertainty about those estimates). This second set of judgments includes deciding which negative health consequences will be deemed tolerable and what level of certainty concerning the link between exposure and health is sufficient to justify imposing controls. It also includes the determination of the percentage of the population to protect, which often translates into a question of how many people who are particularly susceptible to the negative consequences of the pollutant (for genetic reasons or otherwise92) to leave unprotected. To the extent that there are correct answers to such questions, they sound in morality or politics, not science.93 Most important for purposes of this 89 See infra notes 212, 353 (noting the impact that monitoring site location can have on pollution statistics). 90 See, e.g., infra text accompanying notes 115–17 (describing how EPA established the relationship between environmental exposure and critical effect with respect to the lead standard). 91 See Ozone Action Days, U.S. ENVTL. PROT. AGENCY, http://www.epa.gov/region04/ air/naaqs/ozoneday.htm (last updated Dec. 13, 2012) (suggesting behaviors to help reduce ozone formation). Our thanks to Kevin Cromar for his suggestions on this categorization. 92 See Gary E. Marchant, Genetic Susceptibilities: The Future Driver of Ambient Air Quality Standards?, 43 ARIZ. ST. L.J. 791, 795–98 (2011) (emphasizing the importance of addressing genetic predispositions). 93 See McGarity, supra note 10, at 734 (“Correct answers to [trans-scientific] questions may exist as a philosophical matter, but the ‘truth’ is ultimately unascertainable in either the scientific or the legal forum.”). Cf. RONALD DWORKIN, JUSTICE FOR HEDGEHOGS 152–56 (2011) (distinguishing scientific and moral inquiries and offering an “interpretive” account of moral truth). \\jciprod01\productn\N\NYU\89-4\NYU402.txt unknown Seq: 18 16-OCT-14 11:36 October 2014] RETHINKING ENVIRONMENTAL STANDARDS 1201 Article, this second type of question cannot be answered simply by weighing evidence to estimate the state of the physical world.94 As will be demonstrated in more detail below, health-based standards encourage the Administrator to conflate these two different types of inquiry under the rubric of “public health policy judgment[s].”95 The general point concerning inquiries of this sort has been made before.96 This Part moves the conversation forward through three basic contributions. First, it provides a fine-grained analysis of the Administrator’s reasoning in several recent NAAQS and shows where agency decisionmaking tends to shade from empirical to normative matters. Second, it distinguishes among several distinct sources of the stopping-point problem. Finally, it shows how a population-level threshold assumption turns out not to be a solution, because the stopping-point problem can be generated at multiple points in the NAAQS process. Even where the agency treats a pollutant as having such a threshold, the stopping-point problem continues