Interim Report of the Committee on Changes in New Source Review Programs for Stationary Sources of Air Pollutants (2005) / Chapter Skim
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3 Overview of Health Effects, Air Quality, and Emissions
3 Overview of Health Effects, Air Quality, and Emissions
Pages 49-83
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From page 49... ...
It also describes progress that has been made toward NAAQS attainment and where further work is needed. The chapter discusses the inventory of emission sources, including stationary sources subject to NSR and the emissions contributed by the various industrial sectors.
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. Pollutants for which there are NAAQS are known as criteria pollutants because EPA prepares "criteria documents" for them describing their sources and effect.
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OVERVIEW OF HEALTH EFFECTS, AIR QUALITY, AND EMISSIONS 51 TABLE 3-1 National Ambient Air Quality Standards Pollutant or Secondary Indicator Primary Standards Averaging Times Standards Carbon monoxide 9 ppm (10 mg/m3) 8-houra None (CO)
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· Attainment -- an area that meets the NAAQS and does not contribute to the violation of a NAAQS in a nearby area. · Unclassifiable -- an area that cannot be classified on the basis of available information as meeting or not meeting the NAAQS for a pollutant.3 HEALTH EFFECTS OF AIR POLLUTION This section provides brief descriptions of the status of health concerns associated with the criteria pollutants, excluding lead.4 In addition, summary information is given for VOCs, which are also regulatory targets but are managed differently from the criteria pollutants.5 A large and growing body of published epidemiologic and toxicologic research establishes that the criteria pollutants are associated with a variety of health effects, including increased occurrence of cardiopulmonary morbidity, cardiopulmonary and cancer mortality, effects on birth outcomes (low birth weight, small for gestation age)
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In the case of PM, the problem is compounded by the fact that PM is a complex physical-chemical mixture whose components likely interact with other criteria pollutants (e.g., O3) in a number of ways that may affect health outcomes.
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Ambient PM is produced by a variety of emission sources. Some particles are emitted directly into the atmosphere from sources (such as metals from industrial processes)
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OVERVIEW OF HEALTH EFFECTS, AIR QUALITY, AND EMISSIONS 55 Volatile Compounds Organic Particles Organic Semivolatile Compounds Compounds OH Secondary Organic Semivolatile and RO2 Particles Gaseous Compounds O3 O3 OH NO3 Inorganic N2O2 NO NO2 Nitrates O3 HNO3 h Ozone NH4NO3 NH3 OH H2O (NH4) 2SO4 SO2 H2SO4 Chemical Deposition O3, H2O2, O2 FIGURE 3-1 Chemical links between O3 and PM formation processes.
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56 CHANGES IN NEW SOURCE REVIEW PROGRAMS vigilance. Present data, however, suggest that ambient concentrations are unlikely to cause such effects unless ambient exposures are superimposed on exposures from other sources, such as heavy smoking or hot spots caused by extreme traffic emissions (EPA 2000)
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. Although unconfirmed, it is possible that NOx emissions may contribute to the associations between respiratory illness in children and proximity to heavily traveled roadways (Wjst et al.
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58 CHANGES IN NEW SOURCE REVIEW PROGRAMS potentially contributing to increased sensitivity to O3 (Mudway and Kelly 2000)
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PM can be solid, liquid, or composed of semivolatile species (partitioned between the PM and vapor phases depending on ambient conditions) , and it can be either directly emitted from sources (primary; e.g., fly ash)
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The quantitative relationship between PM exposure levels and health effects remains uncertain, as does the proportion of the criteria pollutant health effects attributable to PM versus co-pollutants. Despite the uncertainties and the attendant debates, it seems clear that current concentrations in some areas and at some times in the United States are associated with health burdens that warrant concern, with a causal interpretation of the epidemiologic evidence implying a public health burden from PM exceeding that of other criteria air pollutants (EPA 2004e)
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Volatile Organic Compounds In addition to the NAAQS pollutants, emissions addressed by the NSR program include a diverse group of air contaminants termed for regulatory purposes, volatile organic compounds (VOCs)
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62 CHANGES IN NEW SOURCE REVIEW PROGRAMS organic structure (primarily hydrocarbons, including oxidized and substituted hydrocarbons) , a presence primarily or entirely in the gas phase under ambient conditions (vapor pressure generally greater than 10-4 millimeters of mercury, below which most organic compounds typically are considered semivolatile)
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OVERVIEW OF HEALTH EFFECTS, AIR QUALITY, AND EMISSIONS 63 mosphere (secondary pollutants)
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Therefore, it is usually more important to reduce VOCs and NOx emissions in urban and rural areas, respectively. Indeed, NOx reductions in some urban areas may even increase O3 levels, as evidenced by weekend versus weekday comparisons, where weekend NOx emissions are lower, and the resulting O3 concentrations are higher (Fujita et al.
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OVERVIEW OF HEALTH EFFECTS, AIR QUALITY, AND EMISSIONS 65 FIGURE 3-2 Locations of ozone nonattainment areas for 2004 based on the 8hour ozone standard. Source: EPA 2004j.
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Even though SO2 and NO2 NAAQS are largely attained, SO2 and NOx emissions are relevant to PM2.5, and further reductions are needed to attain the PM2.5 NAAQS. Similarly, although VOCs and ammonia are not regulated by NAAQS,
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. EMISSION SOURCES AND TRENDS EPA prepares a national database of air emissions based on input from state and local air agencies, Indian tribes, and industry.
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. For example, a cement kiln might calculate its emissions by multiplying an emission factor for fuel oil by the amount of fuel consumed.
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The NEI database defines three classes of criteria air pollutant sources: -- Point Sources: large stationary sources of emissions, such as an elec tric power plant, that can be identified by name and location. A major source emits a threshold amount (or more)
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. A variety of regulations controlling emission sources of pollution have been implemented over the past several decades and have been associated with declining emissions for some pollutants in some source categories.
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that participate in the formation of secondary aerosols. For SO2, 75% of point source emissions are attributable to coal combustion by the electric utility industry, with the remaining contributions due to fuel combustion from other industrial sources (Figure 3-9)
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FIGURE 3-9 Top 10 SO2 point source emission categories (1999)
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FIGURE 3-11 Top 10 VOC point source emission categories (1999)
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and mirror the spatial pattern of SO2 emissions, although there are fewer counties with major point sources of NOx emissions in the west. For VOCs (Figure 3-13)
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VINTAGES OF EMISSION SOURCES Information on vintages of different facilities within most of the major NSR-affected industries is difficult to obtain.6 Linking these emissions data to information about vintage is difficult to do without access to the facility-level information from the U.S. Census.
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Table 3-3a and 3-3b provides summaries of NOx and SO2 emission rates, respectively, from coal-fired generators in 2002 by vintage of generating unit, where vintage is assigned based on the year that a power plant came into service. The table also provides information on how much each vintage class (with classes arranged by decade)
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Generators in this category typically have much higher SO2 and NOx emission rates (in units of pounds of pollutant per megawatt-hour of electricity generated) than generators that were permitted under the NSPS standards that
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came into effect in 1971. The generators in the post-1978-standard category have substantially lower SO2 emission rates than those subject to earlier standards but NOx emission rates virtually identical to the earlier group, reflecting the fact that new source standards for NOx did not change much in 1978 (Burtraw and Evans 2004)
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annual emissions of NOx across the different categories of NSPS status, which is consistent with the smaller differences in average NOx emission rates across these different classes of generating units. Most of the emitting units are in the east, but new units can have total annual emissions as high as older units, reflecting in part the higher capacity factors at the newer units.
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· Data presented from electricity-generating facilities (coal plants) show that older facilities have higher emission rates than newer facilities, and older facilities tend to contribute proportionately more to total emissions than they contribute to total electricity generation.
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NOx % of Emitted % of CoalNSPS Status Emission % Total Coal-Fired per % of Fired According to Rate NOx Electricity Electricity Electricity EIA 767 (lb/MWh) Emitted Generation Generateda Capacity Unknown 2.93 0.16 0.23 0.69 0.27 Not Affected 4.67 65.90 59.51 1.11 62.62 by NSPS Subject to 3.57 26.73 31.58 0.85 29.56 Aug.
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SO2 % of % of Emitted per Avg. Average Status Emission Total Coal-Fired % of Capacity Heat Rate According Rate SO2 Electricity Electricity Factorb (Btu/kWh to EIA 767 (lb/MWh)
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