Keeping Pace with Science and Engineering Case Studies in Environmental Regulation (1993) / Chapter Skim
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Tropospheric Ozone
Tropospheric Ozone
Pages 39-90
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From page 39... ...
The governing atmospheric chemistry is exceedingly complex. This complexity, which involves numerous interactions among pollutants, has hindered the development of an understanding of the most effective paths to reducing ambient ozone concentrations.
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From page 40... ...
A BRIEF HISTORY OF OZONE LEGISLATION AND REGULATION In 1963 the Clean Air Act was enacted "to protect the Nation's air resources to promote the public health and welfare." It established "the prevention and control of air pollution at its source as the primary responsibility of the State and local governments." Federal leadership and financial assistance was requested to initiate research and development programs and to assist state and local air pollution control planning. Although the Department of Health, Education, and Welfare was authorized to execute the provisions of the act and to "recommend" air pollution control criteria, only limited enforcement authority was given to government agencies.
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From page 41... ...
New major stationary sources were defined as having the potential to emit 100 or more tons per year of a criteria air pollutant, or hydrocarbons in the case of ozone, and were required to apply the NSPSs. "Hazardous air pollutants," that is, pollutants not included in the NAAQS criteria but deemed by the EPA to cause irreversible harmful health effects, were also authorized for regulation under the 1970 amendments.
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From page 42... ...
It included guidance on air quality modeling and, for the first time, it addressed the potential need to reduce NOX emissions as well as, or in lieu of, VOC emissions. However, the EPA never finalized the policy.
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From page 43... ...
, followed by 3 percent per year thereafter. However, the post-1996 reduction could be satisfied by substituting a reduction of NOx emissions for some or all of the VOC reductions after demonstrating that reducing NOx would be as effective as reducing VOC emissions.
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Also, NOX reductions required by Title IV, Acid Deposition, may aid in reducing ozone. Regulations controlling NOX emissions from stationary sources were enacted for the first time.
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From page 47... ...
What is an appropriate air quality standard for ozone, in terms of concentration and averaging time? Setting the Original Standard The 1970 amendments to the Clean Air Act mandated that the EPA set primary and secondary air quality standards for the concentrations of oxidants in ambient air.
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, resulting in a range of ozone concentrations at which adverse health effects occur, rather than a threshold (Landy et al., 1990~. The EPA noted this fundamental point of confusion: "the adverse health effect threshold concentration cannot be identified with certainty" (FR, Vol.
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From page 49... ...
The controversy reflected concerns about uncertainties in defining the standard, skepticism about its scientific basis, and the health and economic implications of the policy decision. Although the EPA wrote, "the Clean Air Act does not permit any factors other than health to be taken into account in setting the primary standards" (FR, Vol.
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From page 50... ...
Ultimately, the EPA did not incorporate the opinion of the SAB into its suggested ozone standard. In 1978 the EPA's Office of Research and Development (ORD)
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From page 51... ...
In the end, as Douglas Costle, the administrator, later stated, selection of the concentration level "was a value judgement" (Landy et al., 19901. The role of scientific information in the selection process was further put into perspective when, during the 1988 review of the standard, the EPA wrote: Although scientific literature supports the conclusion that particular ozone concentrations and exposure patterns may pose risks to human health, scientific data can only identify the limits of a range within which a standard should be set.
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From page 52... ...
In 1988 only half of the members of the CASAC believed the current ozone standard was adequate to protect human health (Lippmann, 1989~. The significant existing concerns relate to averaging time.
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From page 53... ...
and estimated that the benefits of attaining the ozone standard would be $1.2 billion to $5.8 billion annually, with a best estimate of $2.7 billion. In presenting the implications of the study, the authors discuss the state of the methodology relative to policy decision making.
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From page 54... ...
This information is incorporated into legislation after policy deliberations that take into account socioeconomic factors and values, as well as knowledge. Emission Control Strategies · Should reductions in VOC or NOX emissions or both be favored in pursuing attainment of the ozone standard?
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From page 55... ...
to conclude in 1970 that reduction of VOC emissions would be the appropriate mechanism for effecting reductions in ambient ozone concentrations. Los Angeles officials believed that NOX controls should be implemented as well, on the basis of smog chamber studies carried out locally.
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The "Appendix J" curve was a nonlinear envelope that confined all plotted points below it; it thus was intended to represent an upper bound on feasible combinations of maximum VOC and ozone concentrations. The plot suffered from several deficiencies.
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From page 57... ...
indicate that decreases in VOC emissions will reduce peak ozone concentrations, but decreases in NOX emissions will have the opposite result. Urban Airshed Model simulations, using the same chemical mechanisms and taking into account full three-dimensional flow patterns as well, produced similar findings.
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From page 58... ...
diagram. Once "EKMA diagrams" were generally accepted as being schematically representative of the VOC-NOx-ozone system, they were used to demonstrate the potential merits of NOx control in areas where the "operating point" characteristic of the area was located "below the ridge," that is, at a location on the diagram (see Figure 2)
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From page 59... ...
(1988) found that when biogenic emissions were included in the inventory, the magnitude of VOC reductions needed to attain the ozone standard increased to a level surpassing the estimated NOX control requirement.
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Continuing work during the 1980s confirmed the inhibitory effect of NOX emissions controls in subregions near major source centers. Such findings merely heightened the dilemma: NOX controls appear to be beneficial in some conditions, detrimental in others.
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11) , the authors state that "to substantially reduce ozone concentrations in many urban, suburban, and rural areas of the United States, the control of NOX emissions will probably be necessary in addition to, or instead of, the control of VOCs." Considering the findings of past studies, areas likely to benefit from NOX control include rural areas (very low NOX concentrations)
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From page 62... ...
Studies conducted or reported beginning in the mid-1980s appear to have had the greatest influence in promoting the inclusion of NOX emissions reductions in the 1990 amendments. Until that time, evidence supporting NOX controls appears to have been viewed as either weak or unreliable.
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From page 63... ...
The OTA notes that ''NOX emissions affect more than just nonattainment area ozone concentrations, further complicating the decision about whether to mandate controls. NOX emissions contribute to acid deposition." Title IX directs that the administrator of the EPA "shall conduct a program of research, testing, and development of methods for sampling, measurement, monitoring, ~ ~ ~ ~ of air pollutants.
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From page 64... ...
Spatial Scales Pollutant processes at the regional and urban scales can be highly interactive: emissions and air quality in surrounding regions can contribute significantly to ozone formation in urban areas, and ozone formed in urban areas can contribute significantly to regional ambient ozone concentrations. Accounting for the transport of ozone and its precursors to downwind nonattainment areas is a problem that plagues the development of strategies .,,
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From page 65... ...
In this section, we briefly review the understanding of ozone transport and discuss the extent to which legislation, regulation, and guidance have addressed the issue. Two "transport-related" questions are central to developing effective regional ozone strategies: · At what spatial scales is effective planning for pursuing attainment of the ozone standard best achieved?
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As noted, the Clean Air Act amendments adopted through 1970 did not specifically address transport nor did they give much attention to nonattainment planning. With the passage of the 1977 amendments, two changes occurred.
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From page 67... ...
The 1988 California Clean Air Act specifically recognized the need to assess the impacts of transport from upwind areas in planning and to minimize its impacts over the longer term. Both the act and subsequent regulations require that upwind nonattainment areas develop control strategies that will attain the state and federal ozone standards and also mitigate (to the extent possible)
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From page 68... ...
The findings of these studies should provide valuable information for planning regional ozone attainment strategies. The basic issues facing policymakers today who are concerned with air quality planning on a regional scale include determining: · If a mixed or hybrid strategy" for example, VOC control in the urban area and NOX control in the surrounding rural areas is likely to be preferred over more traditional uniform strategies, .
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From page 69... ...
Technological Improvements and Modifications to the Motor Vehicle Congress, in amending the Clean Air Act in 1970, established emission standards that required a 90 percent reduction of hydrocarbons, CO, and NOX from the base year of 1970 for light duty vehicles (1971 for NOX)
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From page 70... ...
Congress, through the 1977 Clean Air Act Amendments, extended the implementation dates in a two-step process to 1981; the standards put in place at that time will remain operative until the 1990 Clean Air Act Amendments are implemented in the midl990s. The present standards, given in grams (g)
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The certification standards cover fleet emissions reductions, and the I/M program is intended to capture those vehicles whose emissions performance has degraded through age, neglect in maintenance, or tampering with the control system.
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Calculations made using the revised CARB mobile source emissions estimation model, EMFAC-7EP, suggest that emissions reductions of 18 percent for CO and hydrocarbons will provide appropriate credits for the present I/M program.
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One very important part of this new program, which is missing from the present I/M program, is the ability to detect failure of the evaporative emissions control system. Evaporative emissions have been identified by both EPA and CARB as a significant portion of the overall mobile source emissions inventory, but these emissions were properly taken into account only in the most recent versions of EPA's MOBILE emissions model.
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From page 74... ...
Motor Vehicles: Reducing Use · To what extent should measures that directly or indirectly limit vehicle use be considered in formulating regulations for reducing ambient ozone concentrations? During the past two decades, the public's consciousness of the adverse impacts of urban growth has increased in proportion to the diminution in quality of life, on a day-to-day basis, that the public confronts.
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In 1974 Congress made minor amendments to the Clean Air Act in the Energy Supply and Environmental Coordination Act. This act specifically prohibited the EPA from promulgating or requiring the states to promulgate an indirect source review program and left the program to the discretion of the states.
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However, the 1988 California Clean Air Act contains requirements for reducing VMT similar to those of the 1990 amendments. As part of the 1991 Clean Air Plan, the Bay Area Air Quality Management District (BAAQMD)
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From page 77... ...
Assessment of Progress Toward Attainment of the Standard The ozone monitoring network in the United States provides an adequate, although not fully satisfactory, sampling of ozone concentrations in and immediately downwind of urban areas. Rural monitoring is more sparse, and the network would certainly benefit from bolstering.
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From page 78... ...
Introduction of "Cleaner" Fuels Title II of the CAAAs of 1990 requires the eventual sale of only reformulated gasoline in the nine urban areas having the highest peak ozone concentrations, institutes two clean-fueled vehicle programs, including a pilot program in California, and mandates maximum fuel volatility. While volatility reductions have led to reduced VOC emissions, the impact of introducing "cleaner" fuels is less clear.
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Earlier we discussed issues that exemplify this pattern: · Revisiting specification of the ambient standard for ozone. The Clean Air Act provides for review of the ozone standard at five-year intervals.
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From page 80... ...
regulation - SIPs regulation - Federal ISC authority transferred to states - Federal TOM (discretionary) Clean Air Act Amendments of 1977 - Ozone standard revised to 0.12 ppm - SIP, NSR regulations revised - Vehicle emission standard guidance · Post-1987 attainment guidance proposed for Sips, including NOX reductions if necessary and use of UAM FIGURE 3 Timeline of significant scientific and technical, legislative, and regulatory events for ozone control.
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From page 81... ...
Putting in new standards doesn't mean you improve the air. It's the regulations we're issuing under the Clean Air Act that will improve air quality." · Emphasizing reduction in emissions of both precursors to ozone.
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From page 82... ...
As was discussed earlier, for much of the 1980s EPA's attention was diverted from the study of biogenic emissions in the belief that they were not a significant contributor to ozone formation. Although this view was disputed by some members of the scientific community, progress in this field was effectively limited by the paucity of funding for research to develop methods for sampling and analyzing naturally emitted and highly reactive VOCs, determine the rates of emissions from biota, and estimate total biomass for different species.
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From page 83... ...
111. As a result, the EPA and other agencies are giving intensive attention to evaluating the merits of NOX emissions reductions.
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Where circumstances require action, such as smog conditions in the South Coast Air Basin, the waiting time for research results exceeds the time practically available for taking the actions. Resolution of this dilemma is exceedingly difficult.
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determining if NOx control is an appropriate strategy, (3) addressing interpollutant issues, and (4)
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From page 86... ...
He noted that the California Air Resources Board "has pretty much had its own way and has been what the E.P.A. would probably like to be: tough, well funded and backed by a strong political consensus for cleaner air....
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From page 87... ...
In this case, science led, and regulation followed. In some instances, notably in determining the health effects and threshold concentrations of pollutants, the regulators have sought assistance and advice, have promoted the need for further scientific advances, and have prodded the scientific community to take positions on issues exhibiting significant uncertainties.
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From page 88... ...
1987. State Implementation Plans; Approval of Post-1987 Ozone and Carbon Monoxide Plan Revisions for Areas Not Attaining the National Ambient Air Quality Standards; Notice.
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1983. Regulation and the courts: The case of the Clean Air Act.
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From page 90... ...
. Report of the Clean Air Scientific Advisory Committee (CASAC)
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