Air Quality Management in the United States (2004) / Chapter Skim
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6 Measuring the Progress and Assessing the Benefits of AQM
6 Measuring the Progress and Assessing the Benefits of AQM
Pages 216-267
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From page 216... ...
In this chapter, the committee discusses how such estimates of the progress and benefits of AQM in the United States are made, the uncertainty of the estimates, and what can be done to reduce the uncertainty. MONITORING POLLUTANT EMISSIONS Direct Measurement The most direct way to confirm that specific emission-control technologies are working effectively is to measure the rate at which pollutants are released from relevant sources.
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From page 217... ...
Using Ambient Concentrations to Confirm Emission Trends EPA estimates that nationwide emissions of volatile organic compounds (VOCs) , SO2, PM, carbon monoxide (CO)
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From page 218... ...
Changes in Estimated Pollutant Emissions, %a NOx 15 12 VOC 40 25 SO2 33 31 PM10 b 34c 22 PM2.5 b No trend data available 17 CO 41 21 Pb 93 5 B Changes in Measured Ambient Pollutant Concentrations, % NO2 d 21 11 O3 1-hr 22 2 O3 8-hr 14 +4 SO2 54 39 PM10 No trend data available 13 PM2.5 No trend data available 8e CO 65 42 Pb 94 57 aNegative numbers indicate reductions in emissions and improvements in air quality.
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From page 219... ...
. More important, the nation's air quality monitoring network was not designed to track nationwide emission trends or evaluate emission inventories; instead, it was largely designed to monitor urban pollution levels and compliance with National Ambient Air Quality Standards (NAAQS)
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From page 220... ...
provides for air quaity monitoring stations in major urban areas and other appropriate areas throughout the United States to provide monitoring such as will supplement (but not duplicate) air quality monitoring carried out by the States required under any applicable implementation plan, (3)
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Atmospheric Composition Monitoring Networks National, State, and Local Air Monitoring Stations The CAA requires every state to establish a network of air monitoring stations for the criteria air pollutants. These networks are called the state and local air monitoring stations (SLAMS)
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Summary Environments and local assessment monitoring stations Monitoring 6-2 air and Visual Status (CASTNet)
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From page 223... ...
223 to , , + , y pH, some ,Na ,Cl 2+ deposition, 3 designed nongovern 4 data; NO/NO NADP/NTN ,Mg methylmercury wet deposition: ,PO deposition, particulate temporal ,and 2+ 2002; period of + ,CO, 4 2 wet ,Ca ;dry and tribal SO report of ,NH + 2 K greater ,Cl amounts 3 SO ;measurements at local, + 4 sampling sites + meteorological ,NO ,and 4 and NADP/MDN + and VOCs ,NH and some measurements 2 3 ,NH state, 3 continuous 4 O 3 ,Na 3 2002; SO HNO measurements ,NO ,precipitation and 2+ mercury ;NO information federal, 2 + K ,Mg 2 measure periodically 4 2+ 4 CASTNet Weekly SO and Total precipitation; Research including Ca including SO provide resolution Continuous sites and several 2002; in including 9 5 (multiple national AIRMoN ~250 ~80 Wet: Dry: ~30 parks stations some) support, 2002; a in-kind and IMPROVE Cooperators -- NOAA NPS 2002; monetary GPMN provide 1978 1996 1984 1986 that 2002; PAMS cooperators 2002; Research and (AIRMoN)
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From page 224... ...
Photochemical Assessment Monitoring Stations The CAA Amendments of 1990 required EPA, in partnership with state and local agencies, to carry out more extensive monitoring of O3 and its precursors in areas with persistent exceedances of the O3 NAAQS (those O3 nonattainment areas that are classified as severe or worse)
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From page 225... ...
MEASURING THE PROGRESS AND ASSESSING THE BENEFITS OF AQM 225 Operating PAMS Sites, 1998 Portsmouth Boston Milwaukee Springfield Providence Greater Connecticut New York Sacramento Baltimore Philadelphia Chicago Washington San Joaquin Valley Santa Barbara Southeast Desert Ventura County Los Angeles San Diego Phoenix-Mesa Atlanta Dallas - Ft. Worth El Paso Houston Baton Rouge 6-3 FIGURE 6-3 The PAMS network.
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From page 226... ...
is a monitoring system established to assess visibility levels and trends and to identify sources of visibility impairment primarily in national parks and wilderness areas. Through the IMPROVE program, annual and seasonal spatial patterns in PM and light extinction can be assessed (Box 6-1)
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From page 227... ...
Locations of the initial PM supersites are shown in Table 6-3. Hazardous Air Pollutants There is not as extensive a nationwide monitoring network for hazardous air pollutants (HAPs)
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Deposition Monitoring Networks National Atmospheric Deposition Program and National Trends Network Wet deposition of major solutes is monitored throughout the country by the interagency-supported National Atmospheric Deposition Program and National Trends Network (NADP/NTN) (see Figure 6-4)
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From page 229... ...
toring for current and future toxic air pollutants of concern in a consistent manner across the nation and in a way that provides data to support exposure and risk characterization is an important consideration, and research into methods to accurately estimate ambient concentrations and exposure to HAPs is needed. FIGURE 6-4 Locations of the National Atmospheric Deposition Program and National Trends Network (NADP/NTN)
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That reduction has occurred, as illustrated in Figure 6-6 and according to an analysis of data from the National Atmospheric Deposition Program and the National Trends Network (Stod dard et al.
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Clean Air Status and Trends Network The Clean Air Status and Trends Network (CASTNet) measures the components of atmospheric deposition that enter the environment in dry form, such as particles and gases.
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In this section, particular strengths, weaknesses, and other aspects of the air quality monitoring system are considered. EPA is developing a new national ambient air monitoring strategy, which includes a new network design called NCore, as well as a continuous monitoring implementation plan.
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Moreover, major urban areas were the only areas specifically identified in the congressional mandate that initially directed the EPA administrator to develop a national monitoring program. As a result, the nation's ambient air quality monitoring networks have been dominated by urban sites.
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From page 234... ...
Another shortcoming of the current monitoring networks for gaseous and aerosol pollutants is their strong emphasis on measuring ambient concentrations rather than concentrations in specific microenvironments that TABLE 6-4 Ozone Monitoring Sites in the United Statesa Number of Sites Number of Sites Measuring Ozone Number of Sites Designated Designated Vertical Profiles Using Urban or Suburbanb in AIRSc Ruralb in AIRSc Ozonesondes 1,071 504 4 aFor the 48 contiguous states. bAs noted in text, many of the sites designated rural are not truly rural in character.
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. The pollutant concentrations within hot spots can vary over time depending on various factors including the emission rates, activity levels of contributing sources, and meteorological conditions.
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Air Quality Trend Analysis Techniques A variety of techniques can be used to determine long-term trends in ambient pollutant concentrations. The method most commonly used by EPA is to compute yearly averages of concentrations at all stations within a metropolitan statistical area (MSA)
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From page 237... ...
Many states have begun to make their air quality monitoring data available in real time over the 4A trend analysis for CO in Fairbanks and an approach by Reddy (2000) for estimating the probabilities of future CO exceedances in Denver are described in earlier NRC reports (NRC 2002b, 2003b)
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From page 238... ...
As a result, subtle trends can be masked by the fluctuations of the extreme values. Several research groups have questioned EPA's reported O3 trends and car ried out independent studies using data from national monitoring networks.
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From page 239... ...
in a so-called four-dimensional data assimilation mode to predict future pollutant concentrations. This approach typically makes use of data from monitoring networks to specify current air pollutant concentrations and meteorological fields and detailed meteo rological forecasts from the National Weather Service to calculate pollutant con centrations in the future (McHenry et al.
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If air pollution forecasting is to reach a level of sophistication and use comparable to that of meteorological forecasting, a serious program of assess ment must be undertaken. Monitoring Vertical Profiles of Air Pollutants Vertical profiles of pollutants are only available from intensive, researchoriented field campaigns and thus are very limited in time and space.
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From page 241... ...
can be used to obtain vertical profiles of atmospheric constituents. Monitoring Long-Distance Transport of Air Pollutants As state and local emission controls have successfully reduced local pollution sources, long-range transport has become an increasingly important source of NAAQS violations, especially for O3 and PM2.5.
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From page 242... ...
This challenge is made even more daunting when one tries to track changes in multipollutant, multipathway exposures and the resulting changes in health. Because of the current inability to directly link observed population health trends with contemporaneous ambient air quality benefits, less direct approaches have been adopted to assess the health benefits of reductions in air pollution.
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From page 243... ...
. This risk function is then multiplied by the observed change in ambient air pollution over some span of time using data from air quality monitoring (or estimates of emission reductions)
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With respect to the second point, because the studies used to derive the risk functions can be the same as, or similar to, those used in the goal and standard setting process, this type of assessment does not provide an independent verification that the air quality improvements attained by an AQM system had the intended health benefits. Despite these limitations, the risk-function approach has the advantage of providing a relatively simple and straightforward method for translating observed changes in air quality into an associated health outcome and as such will likely continue to be used.
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From page 245... ...
The study includes tracking environmental factors, such as chemical exposures and nutrition, but does not monitor chronic diseases that may develop in the later years of life. In addition, Congress provided CDC with funding in fiscal year 2002 of over $17 million to begin developing a nationwide environmental public health tracking network and to further develop capabilities to track environmentally related health problems within state and local health departments.
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From page 246... ...
There are a number of ways that an improved national health database, when coupled with ambient air quality data, could be used to derive a metric for the effects of AQM on health outcomes. For example, periodic epidemiological studies could be carried out that independently test for the association between ambient pollutant concentrations and the incidence of adverse health effects (Burnett et al.
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From page 247... ...
These efforts are analogous in some ways to the baseline estimates for criteria pollutants used to justify regulatory action under the NAAQS and at least provide a start for future assessments as changes in HAP emissions are implemented. The largest of these efforts is EPA's National Air Toxics Assessment (NATA)
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From page 248... ...
Although the health risk data for the compounds vary in quality, the estimates of cancer and other risks continue to be limited by the lack of a robust human database that avoids some of the challenges of extrapolation from higher concentrations. In its urban air toxics strategy, EPA is funding work to improve both the health database and the NATA.
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Monitoring Actual Human Exposure AQM progress can be also be evaluated by directly tracking human exposure to air pollutants over time. Because concentrations measured by ambient monitors may not reflect human exposures, personal monitors worn by study participants have been used, and sampling of biomarkers in,
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Because exposure biomarkers are a specific indication of exposure and a primary step in the causal chain of a disease outcome, their appearance provides stronger evidence of an actual health outcome from exposure to a pollutant compared with measurements of ambient pollutant concentrations. As such, tracking the appearance and abundance of specific biomarkers within a population over time may be a useful and convincing way to document a public health benefit (or lack thereof)
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at U.S. monitoring sites from 1977 to 1996.
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Measuring such benefits relies on a multitiered approach that includes the following: · Long-term monitoring of ecosystem condition simultaneously with air pollutant exposure and meteorology to elucidate patterns and trends in exposure and response in time and space. · An enhanced network of meteorology and exposure measurements, including more measurement locations and variables (for example, incident diffuse and direct radiation)
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From page 253... ...
Tracking Ecosystem Exposure Evaluation of ecosystem exposure is conducted using data from the air quality and deposition monitoring networks. A major deficiency of the current network design for air pollutants is the scarcity of air quality monitors in rural and forested areas.
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Reduced uncertainty in these studies will depend on the effective use of new meteorological measurements, improvements in the models, and the use of remote-sensing observations in more advanced data assimilation in the models to adapt them to spatially and temporally relevant scales (Seaman 2003)
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From page 255... ...
. BOX 6-6 The Response of Sensitive Ecosystems to Acid Rain Emission Controls Despite marked decreases in SO2 emissions and sulfate deposition over the past decade, sensitive areas have not recovered from acid deposition at the rates anticipated at the time of the passage of the 1990 CAA Amendments.
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From page 256... ...
Although soil acidity is one of the variables being monitored in the FIA/FHM program, soil acidity can be influenced by a number of factors; atmospheric deposition may or may not have a major role, depending on location and soil type. Extractable soil sulfur measurements, which may be useful for quantifying sulfur deposition, were added to the program in 2001.
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From page 257... ...
A number of programs are in place to monitor aspects of this problem. The most comprehensive atmospheric deposition monitoring networks are NADP/NTN, NADP/MDN, CASTNet, and AIRMoN (for example, see Figure 6-6)
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From page 258... ...
These efforts are usually multidisciplinary and involve cooperative efforts between university researchers and state or federal scientists to look holistically at a system plagued by problems, such as coastal eutrophication, associated with atmospheric deposition. For example, Neuse River estuary modeling and monitoring program involves researchers from several North Carolina universities as well as cooperation from the North Carolina Department of Environment and Natural Resources and Weyerhauser Corporation.
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From page 259... ...
has the Air Quality-Plant Growth and Development Research Unit to carry out the following objectives: determine the separate and combined effects of O3 and elevated CO2 on growth and yield of selected agronomic species; determine whether plant, pest, and pathogen interactions are altered by exposure of plants to these pollutants; and develop techniques for mitigating the problems (USDA-ARS 2002)
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From page 260... ...
. Intensive ecosystem studies to understand the influence of air pollutants on ecosystem processes and community dynamics have been conducted by independent research programs at academic and research institutions but not as part of a larger
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Model development should be an integral part of ecosystem studies and modeling. The models should be appropriate for application across regions to estimate response at the scale of air pollutant impacts.
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. Progress in air quality and the resulting human health and welfare benefits were then estimated using the air quality data and methods described in the preceding sections of this chapter.
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Consequently, a wealth of information is provided to decision-makers about the probable future gains from better air quality. Aggregate analyses, such as those mandated in the 1990 CAA Amendments and carried out by EPA, also provide a sense of scale and can support assessments of the relative benefits of alternative regulatory policies (for example, focusing resources on reducing ambient concentrations of criteria pollutants versus hot-spot concentrations of HAPs)
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· The usefulness of economic assessments such as those carried out by EPA could be enhanced if the connection between specific air quality policies and the dollar values of discrete health and welfare benefits were more transparent (Hall 1996; Krupnick and Morgenstern 2002)
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SUMMARY Strengths of Techniques for Tracking Progress in AQM · Continuous emissions monitoring (CEM) systems on electric utilities regulated under the acid deposition program of the CAA have documented substantial reductions in SO2 emissions.
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· The air quality monitoring network for criteria pollutants is dominated by urban sites, limiting its ability to address a number of important issues. · Some of the instruments and methods used in the nation's air quality monitoring networks are inadequate to meet the objectives of the monitoring.
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From page 267... ...
While significant resources have been expended in the United States to identify air quality problems and to reduce the pollutant emissions be lieved to be fostering these problems, there appears to have been a far less con certed effort to track and document objectively and comprehensively the real-world benefits of AQM. Fortunately, a new paradigm appears to be emerging at EPA that recognizes the importance of such an effort.
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