Has the Case Been Made for New Air Quality Standards?
by Dr. Kenneth W. Chilton
Testimony Before the Senate Subcommittee on Clean Air, Wetlands, Private Property and Nuclear Safety
Washington, DC, April 24, 1997

I wish to thank the Senate Subcommittee on Clean Air and Wetlands for the opportunity to testify on the proposed national ambient air quality standards for ozone and particulate matter.

I have researched clean air issues for over a decade and a half. I am the director of the Center for the Study of American Business, a 501(c)(3) non-partisan, not-for-profit public policy research organization at Washington University in St. Louis. These are my personal comments and do not necessarily reflect the views of the Center for the Study of American Business or Washington University.

I would like to address several of the most important public health questions in the NAAQS debate. I will also speak about some very basic issues regarding the primary objective of the Clean Air Act.

The Science on Ozone

The scientific evidence on the health effects of ozone is rather extensive. Ozone has been demonstrated to cause undesirable physical effects in some individuals. The effects include coughing, wheezing, tightness in the chest and reduced lung function - less volume of air exchanged with each breath. Based on EPA's estimate of the relationship between changes in forced expiratory volume (FEV) and various combinations of exercise levels and ozone concentrations, typical subjects experience less than a 5 percent loss in lung function even at the highest ozone levels recorded in the United States in 1996 (about twice the current standard).\1\ (See Figure 1.) Medical experts do not consider lung function decrements of 10 percent, or less, an adverse health effect. The primary concern, however, is for ozone's effects on asthmatics or others especially sensitive to a combination of high ozone levels and moderate to heavy exercise.

Figure 1

Lung Function Decline for Varying Ozone and Exercise Levels\*\
(Exposures are for one to two hours)

\*\Lung function is measured as the volume of air a subject can force from his/her lungs in one second.

Source: Review of the National Air Quality Standard for Ozone Assessment of Scientific and Technical Information (Washington, D.C.: U.S. EPA, Office of Air Quality Planning and Standards, June 1996), p. 31.

No one should minimize the trauma that a severe attack of asthma causes the asthmatic or his or her loved ones. The EPA staff report, however, estimates that for each one million persons exposed, we can expect just one to three more summertime respiratory hospital admissions a day for each 100 parts per billion increase in ozone levels.\2\ This is a very low incidence rate and a very high elevation in ozone levels. In a city of one million people, one to three added respiratory hospital admissions would be virtually undetectable. Such days would also be very rare even in cities with persistent ozone air quality problems.

EPA has recently modified its risk assessments for ozone, resulting in less public health benefits expected from the proposed NAAQS. For example, the new risk assessment projects that attainment of the proposed standard would lower New York City asthmatic hospital admissions caused by ozone to 109 per year, from 139 under the current standard.\3\ That is a reduction of 30 hospital admissions, or one tenth of one percent of the 28,000 yearly asthmatic admissions. The previous estimate, contained in the Staff Paper, was that the standard would reduce yearly admissions by about 90.\4\

The revised risk assessments, which were conducted for nine urban areas, lower the expected benefit of the proposed standard in terms of other health effects, as well, especially for children playing out of doors. For example, EPA had previously expected 600,000 fewer occurrences of decreased lung function (instances where the amount of air that can be rapidly exhaled in one second decline by more than 15 percent) in children, but now projects just 282,000 such incidences. Anticipated improvements in episodes of moderate to severe chest pain in children were revised downward from 101,000 to 53,000, and the estimate for prevented cases of moderate to severe cough in children was lowered from 31,000 to 10,000.\5\

EPA's NAAQS proposal is based on the previous risk assessments. Because the revisions are large (reducing the expected benefit by half or more for several health effects), the wisdom of the proposed tighter standard is further called into question.

It is important to point out that, thus far, ozone has not been shown to cause premature mortality. The upper bound benefit estimate of $1.5 billion in EPA's Regulatory Impact Analysis of ozone, however, results almost entirely from the assumption that the proposed standard would save lives. This claim is unsubstantiated.

I also would like to note that a separate secondary standard to protect plants and buildings hardly seems justified. First, ozone concentration data for rural areas is very limited. Second, incremental cost and benefit estimates for meeting the proposed SUM06 secondary standard versus meeting the current 0.12 ppm goal have not been included in the agency's Regulatory Impact Analysis. Surely, we do not need to focus substantial financial and human resources preparing implementation plans to protect primarily commercial crops with no idea whether the hypothetical benefits outweigh the costs.

The Science on Fine Particulates

Unlike the science on ozone's health effects, the science for fine particulates is not very developed and, thus, is plagued with uncertainties. EPA makes the claim that full attainment of the new fine particulate standard would result in between $69 billion and $144 billion worth of health benefits.6 These predictions of extraordinary health benefits derive from estimates of reduced mortality from meeting a new fine particle standard. Whether the expected number of lives prolonged is 20,000, as stated by Administrator Browner when she testified before this subcommittee in February, or 15,000 as most recently predicted, or zero is hard to say given the paucity of scientific data supporting these projections.

The mortality improvements expected from reduced levels of fine particles are based not on thousands or even hundreds of studies, as the agency casually infers, but, in essence, from just two studies. These studies purport to show an association between PM-2.5 levels and death due to cardiovascular and pulmonary causes together and also a link between PM-2.5 and death.7 It is curious, to say the least, that the statistical link that has been demonstrated is between fine particles and cardiopulmonary deaths, and not deaths due to respiratory disease or lung cancer alone.8

Perhaps it shouldn't be totally surprising that a fine particle-mortality link has not been demonstrated where one might expect, because medical science has not yet discovered a biologically plausible mechanism to explain how fine particulates cause any deaths. Without knowing more about the mechanism through which particulates might affect human health, the observed association between premature mortality and fine particles cannot be considered tantamount to a cause-and-effect relationship.

An additional scientific uncertainty with regard to these studies results from the problem of confounding. Confounding is a situation in which an observed association between an exposure and a health effect is influenced by other variables that also are associated with the exposure and affect the onset of the health effect. A variety of factors such as temperature, humidity, or the existence of other air pollutants may cause mortality rates to rise and fall with, and thus appear to be caused by, fine particulate concentrations.\9\

Also, before regulating air pollutants simply on a basis of size, more research is needed to try to identify which components, if any, of fine particulate matter are producing the observed association - ultrafine particles, nitrates, sulfates, metals, volatile (or "transient") particles, and so forth. We know very little about transient particles, which form and disappear quickly, and, therefore, go undetected by filter monitors.

Lack of air quality data for PM-2.5 is another serious problem. EPA Administrator Browner testified that there are 51 PM-2.5 monitors collecting air quality data at present.\10\ The inference was that this is a large number; it is not. For example, in 1995 there were 972 monitors measuring ozone levels and 1,737 that collected data on PM-10.\11\ For EPA to derive mortality estimates, PM-2.5 concentrations had to be projected for many cities where monitoring data do not exist.

Administrator Browner says the scientific evidence establishing the need for a fine-particle standard is "compelling." I respectfully disagree. A convincing case for a new fine-particle standard has not been made.

Epidemiological evidence is scant and indicates an association, not a cause-and-effect relationship. A toxicological explanation for the observed mortality and fine particle link has not been established. Exposure data are lacking due to the small number of monitors and this lack of data raises questions about the epidemiological studies. Setting a separate PM-2.5 standard at this time could be another case of "ready, fire, aim," as former EPA Administrator William Reilly once described past quick responses to perceived environmental problems.

Let me shift gears and raise a more fundamental issue that thus far has been missing in the debate over the proposed ozone and particulate air quality standards. The Clean Air Scientific Advisory Committee hinted at this problem but perhaps its language was a bit too obtuse.

The Clean Air Act's Flawed Goal

As the members of this subcommittee are well aware, the Clean Air Act calls on the Environmental Protection Agency to establish and enforce air quality standards that protect public health with an adequate margin of safety. It proscribes the consideration of economic factors in this process. Economics may come into play only at the implementation phase.

This is a very high-minded objective. Who but a Philistine could disagree with it?

Well, nearly any economist might. In a world of scarce resources (the real world), people have to be concerned about balancing incremental benefits with incremental costs. Spending more on one activity than it brings about in added benefits means that resources aren't available to spend on other desirable activities that could produce more benefits than their costs.

Theoretically, it might still be possible to protect public health with an adequate margin of safety and spend resources wisely, provided that the health-based standard can be set at a level where added health benefits equal or exceed added costs. Unfortunately, two factors are conspiring against this happy state.

First of all, all health effects from air pollution can't be eliminated, at least not for ozone. Physical responses to ozone can be demonstrated at background levels - levels produced by natural processes. This is what the Clean Air Scientific Advisory Committee (CASAC) was trying to get across in its closure letter to Administrator Browner when it wrote:

The Panel felt that the weight of the health effects evidence indicates that there is no threshold concentration for the onset of biological responses due to exposure to ozone above background concentrations. Based on information now available, it appears that ozone may elicit a continuum of biological responses down to background concentrations. This means that the paradigm of selecting a standard at the lowest-observable-effects-level and then providing an "adequate margin of safety" is no longer possible.\12\

In plain English, the prime directive of the Clean Air Act is "mission impossible," at least for ozone. Taken literally, the standard would have to be set at a level produced by natural emissions of ozone precursors. The cost of such an effort is incalculable and the goal unattainable.

Secondly, the point where incremental costs equal benefits was crossed with respect to ozone with the passage of the 1990 Clean Air Act Amendments. The standard we are currently trying to meet is costing between $4 and $28 to produce $1 worth of benefits.13 A more restrictive standard, such as the one proposed, has to be an even worse tradeoff. Cost estimates from private economists and at the Council of Economic Advisers confirm this expectation.

The Agency has presented some very modest figures for both benefits and costs in its Regulatory Impact Analysis (RIA). While the ozone standard being proposed was not specifically addressed in the RIA, its benefits should be bounded between $0 and $1.5 billion and its costs between $600 million and $2.5 billion, according to the impact analysis.\14\ This figure most likely represents only a small fraction of the real cost of full attainment, for a variety of reasons. For example, full costs of attainment were calculated for only one to three cities.

Other estimates of costs and benefits are quite different, particularly on the cost side. Economist Susan Dudley predicts that full attainment of the current ozone standard will cost between $22 billion and $53 billion a year. The proposed standard would add an additional $54 billion to $328 billion to the price tag, according to Dr. Dudley.\15\ Council of Economic Advisers member Alicia Munnell has projected added costs for meeting the new ozone standard of $60 billion a year.\16\

EPA's Regulatory Impact Analysis for the fine particulate standard estimates an annual cost of $6 billion for partial attainment. Like EPA's cost estimate for the ozone standard, this figure is most likely far too low.\17\ EPA truncates costs at $1 billion per microgram (g) of fine particle reduction, although most areas would incur costs to lower particulates that are much higher than this cutoff figure.

A sensitivity analysis performed for two cities, Denver and Philadelphia, demonstrates how quickly marginal cost rises above EPA's $1 billion/g cutoff. In Philadelphia, the $1 billion/g cutoff would result in a 20 percent reduction in PM-2.5 concentration from the 2007 baseline. An additional one percent reduction would result from a $2 billion/g cutoff, but the cost would double. The RIA reports similar results for Denver.\18\


EPA is not required to tighten the ozone standard or to create a new PM-2.5 NAAQS. In the case of ozone, there is little evidence that a tighter standard will be more protective of those who are considered the sensitive population. For particulates, the science is not adequate to warrant a new PM-2.5 standard. Certainly, CASAC members were of quite divergent opinions on how to set a PM-2.5 standard. In her testimony, Administrator Browner made much ado about the fact that there was a consensus among CASAC members that a new PM-2.5 NAAQS be established. It is also true, however, that there was "no consensus on the level, averaging time, or form" of the standard.\19\

Indeed, on February 5, the chair of CASAC shared with this subcommittee just how tepid the support for the proposed fine particle standard was. Only two members of the 21-member CASAC endorsed a range for an annual PM-2.5 standard as strict as 15 g/m3to 20 g/m3, yet EPA has proposed an annual limit of 15 g/m3. Eight of the members did not support any annual PM-2.5 standard.20 (See Table 1.)

Given the rather poor state of atmospheric and medical scientific knowledge of fine particles, it is difficult to see how setting a standard at this time will produce meaningful health benefits. Rather than press forward with a tighter air quality standard for ozone and a new standard for fine particles, EPA should appeal to Congress and The White House to revisit the Clean Air Act.

Two basic reforms are required. First the fundamental objective of the Act needs to be changed from "protecting the public health with an adequate margin of safety" to "protecting the public against unreasonable risk of important adverse health effects." Secondly, benefit-cost analyses should be required, not proscribed, when setting air quality standards.

The American people expect their elected officials to protect them from air pollution that might significantly impair their health. They do not expect, however, that the costs of this protection will be so out of proportion to benefits that other desirable outcomes are forgone because economic resources have been applied too generously to this task.

Table 1

Summary of CASAC Panel Members Recommendations for an Annual PM-2.5 Standard (all units g/m3)

Name Discipline PM-2.5 Annual
Ayres M.D. yes2
Hopke Atmospheric Scientist 20-30
Jacobson Plant Biologist yes2
Koutrakis Atmospheric Scientist yes2, 3, 4
Larntz Statistician 25-305
Legge Plant Biologist no
Lippmann Health Expert 15-20
Mauderly Toxicologist 20
McClellan Toxicologist no 6
Menzel Toxicologist no
Middleton Atmospheric Scientist yes2, 3
Pierson Atmospheric Scientist yes2, 7
Price Atmospheric Scientist/State Official yes 8
Shy Epidemiologist 15-20
Samet1 Epidemiologist no
Seigneur Atmospheric Scientist no
Speizer 1 Epidemiologist no
Stolwijk Epidemiologist 25-305
Utell M.D. no
White Atmospheric Scientist 20
Wolff Atmospheric Scientist no
EPA Staff 12.5-20


1. Not present at meeting; recommendations based on written comments

2. Declined to select a value or range

3. Concerned upper range is too low based on national PM-2.5/PM-10 ratio

4. Leans toward high end of staff recommended range

5. Desires equivalent stringency as present PM-10 standards

6. If EPA decides a PM-2.5 NAAQS is required, the 24-hour and annual standards should be 75 and 25 g/m3, respectively with a robust form

7. Yes, but decision not based on epidemiological studies

8. Low end of EPA's proposed range is inappropriate; desires levels selected to include areas for which there is broad public and technical agreement that they have PM-2.5 pollution problems

Source: CASAC Closure Letter on the Staff Paper for Particulate Matter, June 13, 1996, docketed as EPA-SAB-CASAC-LTR-96-008, Table 1.


( Dr. Kenneth W. Chilton is director of the Center for the Study of American Business at Washington University in St. Louis. His views do not necessarily reflect those of the Center or Washington University.

1. Review of National Ambient Air Quality Standards for Ozone Assessment of Scientific and Technical Information OAQPS Staff Paper (Research Triangle Park, N.C.: U.S. EPA Office of Air Quality Planning and Standards, June 1996), p. 31.

2. Ibid., p. 40.

3. R.G. Whitfield, A Probabilistic Assessment of Health Risks Associated with Short-Term Exposure to Tropospheric Ozone: A Supplement (Argonne, Illinois: Argonne National Laboratory, contracted for U.S. Environmental Protection Agency, January 1997), Table 6.

4. Ozone Staff Paper, p. 130.

5. Memorandum, "Supplemental Ozone Exposure and Health Risk Analyses," Harvey M. Richmond, EPA Risk and Exposure Assessment Group, to Karen Martin, EPA Health Effects and Standards Group, February 11, 1997.

6. Draft Document Regulatory Impact Analysis for Proposed Particulate Matter National Ambient Air Quality Standard (Research Triangle Park, N.C.: U.S. EPA Office of Air Quality Planning and Standards, December 1996), p. ES-20.

7. Douglas Dockery, C. Arden Pope III, Xiping Xu, John D. Spengler, James H. Ware, Martha E. Fay, Benjamin G. Ferris, Jr., Frank E. Speizer, "An Association Between Air Pollution and Mortality in Six U.S. Cities," New England Journal of Medicine, vol. 329, no. 24, December 9, 1993, pp. 1753-1759; C. Arden Pope III, Michael J. Thun, Mohan M. Namboodiri, Douglas W. Dockery, John S. Evans, Frank E. Speizer, Clark W. Heath, Jr., "Particulate Air Pollution as a Predictor of Mortality in a Prospective Study of U.S. Adults," American Journal of Respiratory Critical Care Medicine, vol. 151, 1995, pp. 669-674. Technically, while both Dockery et al. and Pope et al. show a link between increased mortality and fine particle concentrations, Pope et al. is the basis for EPA projections of lives prolonged by attaining the proposed PM-2.5 NAAQS.

8. William M. Landau, Gregory Evans, Raymond Slavin, letter to EPA Docket A-95-54, commenting on the proposed PM-2.5 NAAQS, March 7, 1997.

9. Suresh H. Moolgavkar and E. Georg Luebeck, "A Critical Review of the Evidence on Particulate Air Pollution and Mortality," Epidemiology, v. 7, n. 4, July 1996, pp. 420-428.

10. Testimony of EPA Administrator Carol Browner before U.S. Senate Committee on Environment and Public Works, February 12, 1997.

11. National Air Quality and Emissions Trends Report, 1995 (Research Triangle Park, N.C.: U.S. EPA Office of Air Quality Planning and Standards, October 1996), p. 163.

12. Clean Air Scientific Advisory Committee closure letter to EPA Administrator Carol Browner on the primary standard portion of the OAQPS Staff Paper for ozone (November 31, 1995), p. 2.

13. Kenneth Chilton and Stephen Huebner, Has the Battle Against Urban Smog Become "Mission Impossible?" (St. Louis: Center for the Study of American Business, Policy Study 136, November 1996), p. 14.

14. Regulatory Impact Analysis for Proposed Ozone National Ambient Air Quality Standard (Research Triangle Park, N.C.: U.S. EPA Office of Air Quality Planning and Standards Innovative Strategies and Economics Group, December 1996), p. ES-22.

15. Susan E. Dudley, Comments on the U.S. Environmental Protection Agency's Proposed National Ambient Air Quality Standard for Ozone (prepared for the Regulatory Analysis Program, Center for the Study of Public Choice, George Mason University, March 12, 1997), p. ES-3.

16. Memorandum from Alicia Munnell, Council of Economic Advisers, to Art Fraas, Office of Management and Budget, December 13, 1996.

17. Thomas Hopkins, Can New Air Standards for Fine Particles Live Up to EPA Hopes? (St. Louis: Center for the Study of American Business, Policy Brief 180, April 1997), pp. 10-17.

18. Regulatory Impact Analysis, p. 7.6.

19. Clean Air Scientific Advisory Committee closure letter to EPA Administrator Carol Browner on the Staff Paper for Particulate Matter (June 13, 1996), p. 2.

20. Ibid., Table 1.