NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 1992 Chapter 1: Executive Summary 1.1 Introduction This is the twentieth annual report 1-19 documenting air pollution trends in the United States. As in previous years, the primary emphasis is on those pollutants for which the U.S. Environmental Protection Agency (EPA) has established National Ambient Air Quality Standards (NAAQS). EPA set these standards to protect public health and welfare. Primary standards are designed to protect public health, while secondary standards protect public welfare, such as effects of air pollution on vegetation, materials and visibility. For the first time, this report discusses air toxics, another set of pollutants regulated under the Clean Air Act. Air toxics are those pollutants known to or suspected of causing cancer or other serious health effects, such as reproductive effects or birth defects. Because ambient data on air toxics is limited, this report simply provides an introduction to the subject and an overview of the types of air toxics information that future reports may provide as additional data becomes available. The analyses in this report focus on comparisons with the primary standards in effect in 1992 to examine changes in air pollution levels over time, and to summarize current air pollution status. The six pollutants with National Ambient Air Quality Standards are: carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), ozone (O3), particulate matter whose aerodynamic size is equal to or less than 10 microns (PM-10), and sulfur dioxide (SO2). It is important to note that the discussions of ozone in this report refer to ground level, or tropospheric, ozone and not to stratospheric ozone. Ozone in the stratosphere, miles above the earth, is a beneficial screen from the sun's ultraviolet rays. Ozone at ground level, in the air we breathe, is a health and environmental concern and is the primary ingredient of what is commonly called smog. The report tracks two kinds of trends: air concentrations, based on actual direct measurements of pollutant concentrations in the air at selected sites throughout the country; and emissions, which are estimates of the total tonnage of these pollutants released into the air annually based upon the best available engineering calculations. The estimates of emissions in this report differ from those reported last year. Emissions are now reported in units of short tons per year (2,000 pounds), rather than in metric tons (2,205 pounds) as used in earlier reports. Also, the report reflects a mixture of new estimation methodologies for fuel combustion, industrial, and transportation sources, and includes data obtained from a new model which was used to update mobile source emissions in response to concerns about possible underestimates of the mobile source contribution to total emissions. This is discussed in Chapter 3. The first three chapters of this report cover trends in the six pollutants with National Ambient Air Quality Standards. Chapter 4 presents the information on air toxics. Chapter 5 includes a detailed listing of selected 1992 air quality summary statistics for every metropolitan statistical area (MSA) in the nation. Chapter 6 presents 1983-92 trends for 23 cities throughout the U.S. Chapter 7 presents summary air pollution statistics from other countries to provide a broader range of air pollution information. 1.2 Major Findings CARBON MONOXIDE Air Concentrations 1983-92: 34 percent decrease (8-hour second high at 308 sites) 94 percent decrease (8-hour exceedances at 308 sites) 1991-92: 7 percent decrease (8-hour second high at 390 sites) Emissions 1983-92: 25 percent decrease 1991-92: 4 percent decrease Overview Trends. Improvements continued with the 1983-92 ten year period showing 34 percent improvement in air quality levels and a 25 percent reduction in total emissions. The air quality improvement agrees more closely with the estimated 30 percent reduction in highway vehicle emissions. This progress occurred despite continued growth in miles of travel in the U.S. Transportation sources account for approximately 80 percent of the nation's CO emissions. The 30 percent decrease in highway vehicle emissions during the 1983-92 period occurred despite a 37 percent increase in vehicle miles of travel. Estimated nationwide CO emissions decreased 4 percent between 1991 and 1992. Status. In November 1991, EPA designated 42 areas as nonattainment for CO. Based upon the magnitude of the CO concentrations, 41 of these areas were classified as moderate and 1 (Los Angeles) was classified as serious. In September 1993, Syracuse, NY became the first of these 42 nonattainment areas to be redesignated as an attainment area. Some Details. The first major clean fuel program under the 1990 Clean Air Act Amendments is the oxygenated fuel program implemented by state and local agencies following EPA guidelines. Increasing the oxygen content of gasoline reduces CO emissions by improving fuel combustion, which is typically less efficient at cold temperatures. On November 1, 1992, new oxygenated fuel programs began in 28 metropolitan areas. These programs generally run from November through February and preliminary results suggest greater CO air quality improvements, with peak CO levels declining 13 percent in areas with the new oxy-fuel program as compared to a 3 percent decline in non-program areas. CO EFFECTS Carbon monoxide enters the bloodstream and reduces the delivery of oxygen to the body's organs and tissues. The health threat from carbon monoxide is most serious for those who suffer from cardiovascular disease, particularly those with angina or peripheral vascular disease. Healthy individuals also are affected but only at higher levels. Exposure to elevated carbon monoxide levels is associated with impairment of visual perception, work capacity, manual dexterity, learning ability and performance of complex tasks. LEAD Air Concentrations 1983-92: 89 percent decrease (maximum quarterly average at 203 sites) 1991-92: 9 percent decrease (maximum quarterly average at 235 sites) Emissions 1983-92: 89 percent decrease in total lead emissions (96 percent decrease in lead emissions from transportation sources) 1991-92: 3 percent increase in total lead emissions (6 percent decrease in lead emissions from transportation sources) Overview Trends. Ambient lead (Pb) concentrations in urban areas throughout the country have decreased 89 percent since 1983. Total Pb emissions have also dropped 89 percent since 1983 due principally to reductions from automotive sources. The drop in Pb consumption and subsequent Pb emissions was brought about by the increased use of unleaded gasoline in catalyst-equipped cars (99 percent of the total gasoline market in 1992) and the reduced Pb content in leaded gasoline. Status. In 1991, EPA announced that 12 areas would be designated as nonattainment because of recorded violations of the National Ambient Air Quality Standard for lead. EPA also designated as "unclassifiable" 9 other areas for which existing air quality data are insufficient at his time to designate as either attainment or nonattainment. On April 22, 1993, EPA designated one of the unclassifiable areas as nonattainment. Some Details. The large reduction in lead emissions from transportation sources has changed the nature of the ambient lead problem in the U.S. In 1983, estimated lead emissions were 49,232 tons and 91 percent was due to transportation sources. In 1992, estimated lead emissions had dropped to 5,176 tons and transportation sources accounted for 31 percent, due to the remaining fraction of leaded gasoline sales. Remaining lead nonattainment problems are associated with point sources, such as smelters, battery plants, and solid waste disposal. Consequently, EPA's current monitoring and control strategies target these kinds of specific sources. PB EFFECTS Exposure to lead can occur through multiple pathways, including inhalation of air and ingestion of lead in food, water, soil or dust. Lead accumulates in the body in blood, bone and soft tissue. Because it is not readily excreted, lead also affects the kidneys, liver, nervous system and blood-forming organs. Excessive exposure to lead may cause neurological impairments such as seizures, mental retardation and/or behavioral disorders. Even at low doses, lead exposure is associated with changes in fundamental enzymatic, energy transfer and homeostatic mechanisms in the body. Fetuses, infants and children are especially susceptible to low doses of lead, often suffering central nervous system damage. Recent studies have also shown that lead may be a factor in high blood pressure and subsequent heart disease in middle-aged white males. NITROGEN DIOXIDE Air Concentrations 1983-92: 8 percent decrease (annual mean at 183 sites) 1991-92: 3 percent decrease (annual mean at 235 sites) Emissions: Nitrogen Oxides (NOx) 1983-92: 5 percent increase 1991-92: 1 percent decrease Overview Trends. Nitrogen oxide emissions are estimated to have increased 5 percent since 1983, with a 9 percent increase in fuel combustion emissions. Air quality improved 8 percent since 1983. The two primary source categories of nitrogen oxide emissions, and their contribution in 1992, are fuel combustion (51 percent) and transportation (45 percent). Since 1983, emissions from highway vehicles have remained relatively constant. Status. In November 1991, EPA designated Los Angeles as the only nonattainment area for NO2. Some Details. In recent years, Los Angeles was identified as the only location not meeting the National Ambient Air Quality Standard for nitrogen dioxide. In 1992, all monitoring locations in Los Angeles reported data meeting the federal standard. This is the first step towards Los Angeles being redesignated as an attainment area for nitrogen dioxide. The scientific community has expressed concerns that previous EPA emission estimates have underestimated the contribution of transportation sources. An extensive off-highway survey did indeed show marked increases in off-highway emissions from 1983 to 1992. However, highway emissions using a new model (MOBILE5) stayed relatively flat. The major increases, using new methodologies, are from electric utilities, industrial sources, and off-highway mobile sources. Last year's trend from 1982-1991 showed an 8 percent decrease in NOx, whereas this year's trend shows a 5 percent increase. As methodologies continue to improve, we expect to see variance in the estimates in future years as well. NO2 EFFECTS Nitrogen dioxide can irritate the lungs and lower resistance to respiratory infection (such as influenza). The effects of short-term exposure are still unclear but continued or frequent exposure to concentrations higher than those normally found in the ambient air may cause increased incidence of acute respiratory disease in children. Nitrogen oxides are an important precursor both to ozone and to acidic precipitation and may affect both terrestrial and aquatic ecosystems. Atmospheric deposition of NOx is a potentially significant contributor to ecosystem effects including algal blooms in certain estuaries such as the Chesapeake Bay. In some western areas, NOx is an important precursor to particulate matter concentrations. OZONE Air Concentrations 1983-92: 21 percent decrease (second highest daily max 1-hour at 509 sites) 65 percent decrease (exceedance days at 509 sites) 1991-92: 7 percent decrease (second highest daily max 1-hour at 672 sites) Emissions: Volatile Organic Compounds (VOC) 1983-92: 11 percent decrease (+5 percent for NOx) 1991-92: 3 percent decrease (-1 percent for NOx) Overview Trends. Ground level ozone, the primary constituent of smog, has been a pervasive pollution problem for the U.S. Ambient trends during the 1980s were influenced by varying meteorological conditions. Relatively high 1983 and 1988 ozone levels are likely attributable in part to hot, dry, stagnant conditions in some areas of the country. The 1992 levels were the lowest of the 1983-92 period. While the complexity of the ozone problem and the effects of meteorological conditions warrant caution in interpreting the data, there have been recent control measures, such as lower Reid Vapor Pressure for gasoline resulting in lower fuel volatility and lower NOx and VOC emissions from tailpipes. Emission estimates for volatile organic compounds (VOCs), which contribute to ozone formation, are estimated to have improved by 11 percent since 1983. However, these VOC emission estimates represent annual totals. NOx emissions, the other major precursor factor in ozone formation, increased 5 percent between 1983 and 1992. While these annual emission totals are the best national numbers now available, seasonal emission trends would be preferable. Status. In November 1991, EPA designated 98 nonattainment areas for O3. Based upon the O3 concentrations in these areas, EPA classified 43 areas as marginal, 31 as moderate, 14 as serious, 9 as severe, and 1 (Los Angeles) as extreme. In June 1992, Kansas City became the first of these 98 nonattainment areas to be redesignated as an attainment area. In December 1992, Cherokee County, SC became the second. In September 1993, Greensboro, NC and Knoxville, TN were also redesignated as attainment areas for ozone. Some Details. Year to year ozone trends are affected by changing meteorological conditions. The 21 percent improvement between 1983 and 1992 is in part due to 1983 being a relatively high year for ozone. New statistical techniques to account for meteorological influences suggest an improvement of 10 percent for the 10-year period. O3 EFFECTS The reactivity of ozone causes health problems because it damages lung tissue, reduces lung function and sensitizes the lungs to other irritants. Scientific evidence indicates that ambient levels of ozone not only affect people with impaired respiratory systems, such as asthmatics, but healthy adults and children, as well. Exposure to ozone for 6 - 7 hours at relatively low concentrations has been found to significantly reduce lung function in normal, healthy people during periods of moderate exercise. This decrease in lung function often is accompanied by such symptoms as chest pain, coughing, nausea and pulmonary congestion. Though less well established in humans, animal studies have demonstrated that repeated exposure to ozone for months to years can produce permanent structural damage in the lungs and accelerate the rate of lung function loss and aging of the lungs. Ozone is responsible each year for agricultural crop yield loss in the U.S. of several billion dollars and causes noticeable foliar damage in many crops and species of trees. Forest and ecosystem studies indicate that damage is resulting from current ambient ozone levels. PARTICULATE MATTER Air Concentrations: Particulate Matter (PM-10) 1988-92: 17 percent decrease (based on arithmetic mean at 652 sites) 1991-92: 9 percent decrease (based on arithmetic mean at 652 sites) Emissions: PM-10 1983-92: 3 percent decrease 1988-92: 8 percent decrease 1991-92: 2 percent increase Overview Trends. In 1987, EPA replaced the earlier total suspended particulate (TSP) standard with a PM-10 standard. PM-10 focuses on the smaller particles likely to be responsible for adverse health effects because of their ability to reach the lower regions of the respiratory tract. Ambient monitoring networks have been revised to measure PM-10 rather than TSP. Although PM-10 trends data are limited, ambient levels decreased 17 percent between 1988 and 1992. PM-10 emissions from sources historically included in inventories are estimated to have decreased 8 percent since 1988 and 3 percent since 1983. Nationally, fugitive sources (such as emissions from agricultural tilling, construction, and unpaved roads) provide 6-8 times more tonnage of PM-10 emissions than sources historically included in emission inventories. Status. In November 1991, EPA designated 70 areas as nonattainment for PM-10. Some Details. Because many PM-10 monitoring networks evolved from previously established Total Suspended Particulate networks, emphasis is being placed on evaluating current PM-10 monitoring networks to be certain that they adequately characterize problems from these finer particles. New monitoring techniques, such as low cost portable monitors, are being used as a tool in these evaluations. PM EFFECTS Based on studies of human populations exposed to high concentrations of particles (often in the presence of sulfur dioxide), and laboratory studies of animals and humans, the major effects of concern for human health include effects on breathing and respiratory symptoms, aggravation of existing respiratory and cardiovascular disease, alterations in the body's defense systems against foreign materials, damage to lung tissue, carcinogenesis and premature mortality. The major subgroups of the population that appear likely to be most sensitive to the effects of particulate matter include individuals with chronic obstructive pulmonary or cardiovascular disease, individuals with influenza, asthmatics, the elderly and children. Particulate matter causes damage to materials, soiling and is a major cause of substantial visibility impairment in many parts of the U.S. SULFUR DIOXIDE Air Concentrations 1983-92: 23 percent decrease (arithmetic mean at 476 sites) 31 percent decrease (24-hour second high at 476 sites) 1991-92: 7 percent decrease (arithmetic mean at 557 sites) Emissions: Sulfur Oxides (SOx) 1983-92: no change 1991-92: < 1 percent decrease Overview Trends. Since 1983, SOx emissions were unchanged while average air quality improved by 23 percent. This difference occurs because the historical ambient monitoring networks are population-oriented while the major emission sources tend to be in less populated areas. Status. Almost all monitors in U.S. urban areas meet EPA's ambient air quality standards for SO2. Dispersion models are commonly used to assess ambient SO2 problems around point sources because it is frequently impractical to operate enough monitors to provide a complete air quality assessment. Currently, there are 46 areas designated nonattainment for SO2. Current concerns focus on major emitterstotal atmospheric loadings and the possible need for a shorter-term standard. Seventy percent of all national SOx emissions are generated by electric utilities. Some Details. The Acid Rain provisions of the 1990 Clean Air Act Amendments include a goal of reducing SOx emissions by 10 million tons relative to 1980 levels. The focus of this control program is an innovative market-based emission allowances trading program which will provide affected sources flexibility in meeting the mandated emission reductions. This is EPA's first large-scale regulatory use of market-based incentives and the first allowance trade was announced in May 1992. This program is coordinated with the air quality standard program to ensure that public health is protected while allowing for cost effective reductions of SO2. SO2 EFFECTS The major health effects of concern associated with high exposures to sulfur dioxide include effects on breathing, respiratory illness and symptoms, alterations in the lung's defenses, and aggravation of existing respiratory and cardiovascular disease. The major subgroups of the population most sensitive to sulfur dioxide include asthmatics and individuals with chronic lung disease (such as bronchitis or emphysema) or cardiovascular disease. Children and the elderly may also be sensitive. Sulfur dioxide produces foliar damage on trees and agricultural crops. It and nitrogen oxides are major precursors to acidic deposition (acid rain), which is associated with a number of effects including acidification of lakes and streams, accelerated corrosion of buildings and monuments and visibility impairment. 1.3 Some Perspective It is important to realize that many of these air quality improvements during the past ten years occurred even in the face of growth of emissions sources. More detailed information on these emission trends and the updated estimation methodologies are contained in a companion report.20 While progress has been made, it is important not to lose sight of the magnitude of the air pollution problem that still remains. About 54 million people in the U.S. reside in counties which did not meet at least one air quality standard based upon data submitted to EPA's data base for the single year 1992. Ground level ozone is the most common contributor with 45 million people living in counties that exceeded the ozone standard in 1992. This is the first year that no areas had measured values exceeding the nitrogen dioxide standard; previous reports had identified Los Angeles with annual means not meeting the nitrogen dioxide standard. With respect to sulfur dioxide, it is important to note that while no measured data were submitted to EPA's data base showing exceedances in 1992, the current sulfur dioxide problems in the U.S. are associated with point sources and typically identified by modelling rather than by routine ambient monitoring. These statistics, and associated qualifiers and limitations, are discussed in Chapter 5. These population estimates are based only upon a single year of data, 1992, and only consider counties with monitoring data for that pollutant. As noted in Chapter 5, there are other approaches that would yield different numbers. In 1991, EPA issued a rule formally designating areas that did not meet air quality standards.21 Based upon these designations, EPA estimated that 140 million people live in ozone nonattainment areas. This difference between the 140 million and 54 million population figures is because the formal designations are based upon three years of data, rather than just one, to reflect a broader range of meteorological conditions. Also, the boundaries used for nonattainment areas may consider other air quality related information, such as emission inventories and modeling, and may extend beyond those counties with monitoring data to more fully characterize the ozone problem and to facilitate the development of an adequate control strategy. For the pollutant lead, EPA's aggressive effort to better characterize lead point sources has resulted in new monitors that have documented additional problem areas. Finally, it should be recognized that this report emphasizes those six pollutants that have National Ambient Air Quality Standards. As discussed in Chapter 4, there are other pollutants of concern. According to industry estimates, more than 2.0 billion pounds of toxic pollutants were emitted into the atmosphere in 1991, compared to 2.2 billion pounds for the previous year.22,23 They are chemicals known or suspected of causing cancer or other serious health effects (e.g., reproductive effects). Control programs for the pollutants discussed in this report can be expected to reduce these air toxic emissions by controlling particulates, volatile organic compounds and nitrogen oxides. However, Title III of the Clean Air Act Amendments of 1990 provided specific new tools to address routine and accidental releases of these toxic air pollutants. The statute established an initial list of 189 toxic air pollutants. Using this list, EPA published a list of the industry groups (or "source categories") for which EPA will develop emission standards. EPA will issue standards for each listed source category, requiring the maximum degree of emissions reduction that has been demonstrated to be achievable. These are commonly referred to as maximum achievable control technology (MACT) standards. EPA is also implementing other programs to reduce emissions of chlorofluorocarbons, halons, and other pollutants that are depleting the stratospheric ozone layer, and pollutants contributing to acid deposition. 1.4 References 1. The National Air Monitoring Program: Air Quality and Emissions Trends - Annual Report, EPA-450/1-73-001a and b, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, July 1973. 2. Monitoring and Air Quality Trends Report, 1972, EPA-450/1-73-004, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, December 1973. 3. Monitoring and Air Quality Trends Report, 1973, EPA-450/1-74-007, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, October 1974. 4. Monitoring and Air Quality Trends Report, 1974, EPA-450/1-76-001, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, February 1976. 5. National Air Quality and Emissions Trends Report, 1975, EPA-450/1-76-002, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, November 1976. 6. National Air Quality and Emissions Trends Report, 1976, EPA-450/1-77-002, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, December 1977. 7. National Air Quality and Emissions Trends Report, 1977, EPA-450/2-78-052, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, December 1978. 8. 1980 Ambient Assessment - Air Portion, EPA-450/4-81-014, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, February 1981. 9. National Air Quality and Emissions Trends Report, 1981, EPA-450/4-83-011, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, April 1983. 10. National Air Quality and Emissions Trends Report, 1982, EPA-450/4-84-002, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, March 1984. 11. National Air Quality and Emissions Trends Report, 1983, EPA-450/4-84-029, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, April 1985. 12. National Air Quality and Emissions Trends Report, 1984, EPA-450/4-86-001, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, April 1986. 13. National Air Quality and Emissions Trends Report, 1985, EPA-450/4-87-001, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, February 1987. 14. National Air Quality and Emissions Trends Report, 1986, EPA-450/4-88-001, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, February 1988. 15. National Air Quality and Emissions Trends Report, 1987, EPA-450/4-89-001, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, March 1989. 16. National Air Quality and Emissions Trends Report, 1988, EPA-450/4-90-002, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, March 1990. 17. National Air Quality and Emissions Trends Report, 1989, EPA-450/4-91-003, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, February 1991. 18. National Air Quality and Emissions Trends Report, 1990, EPA-450/4-91-023, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, November 1991. 19. National Air Quality and Emissions Trends Report, 1991, EPA-450/R-92-001, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, October 1992. 20. National Air Pollutant Emission Estimates, 1900-1992, EPA-454/R-93-032, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, October 1992. 21. Federal Register, November 6, 1991. 22. 1991 Toxics Release Inventory, EPA-745-R-93-003, U. S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, D.C. 20460, May 1993. 23. 1990 Toxics Release Inventory, EPA 700-S-92-002, U. S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, D.C. 20460, May 1992.