This chapter covers conditions and trends through calendar year 1998 using data and information available as of December 31, 2000.
Much has been done in the last several decades to improve air quality in the United States. Since 1970, there have been significant reductions in emissions of criteria pollutants on the national level. As a result, there has been a downward trend in ambient concentrations of criteria pollutant in many metropolitan areas, some improvement in visibility in the West, and reduction in acid precipitation. Data on ambient air toxics, while more limited in geographic and temporal scope, generally reveal downward trends for most of the hazardous air pollutants monitored.
Not all indicators are encouraging, however. Trends in some areas, including rural locations, have worsened. Ozone concentrations, for example, have increased at 17 of the 24 National Park Service sites with trend data, and fine particulate concentrations have increased in some areas of the rural East. Over the last ten-year period (1989-1998), the number of "unhealthy" days, as assessed using the Air Quality Index, rose by 57 percent in southern California and by 10 percent in the remaining major cities across the United States. During this period, also, visibility in the eastern part of the country showed no signs of improving and U.S. emissions of greenhouse gases continued to increase.
An overview of these and other air quality trends is presented in this chapter.
CRITERIA POLLUTANTS
Carbon Monoxide
Total carbon monoxide (CO) emissions peaked in 1970 at 129.4 million tons and decreased rather steadily thereafter. A significant decrease in CO emissions occurred between 1973 and 1975 as a result of disruptions in world oil markets and a subsequent recession in the United States. (Emissions of nitrogen oxides and volatile organic compounds showed similar decreases during these years for the same reasons.) CO emissions fluctuated in the late 1980s, primarily due to year-to-year variation in wildfire activity, but have generally declined to 89.5 million tons in 1998 (Figure 5.1).
More than half of total CO emissions are from on-road vehicles. Since 1970, CO emissions from this category have significantly due to automotive emission limits set by EPA. Over the past decade (1989-1998), CO emissions from on-road vehicles decreased 24 percent, despite a 23-percent increase in vehicle miles traveled over the period.
Unlike emissions trends for on-road vehicles, emissions of CO from non-road engines and vehicles increased steadily from 1940 to 1996, with a slight reduction over the past 2 years. Non-road sources include non-road gasoline engines (e.g., industrial, lawn and garden, light commercial, and recreational marine vessels), non-road diesel (e.g., construction and farm), aircraft, and railroads. In 1940, emissions from this category accounted for 9 percent of total CO emissions, with emissions from railroad locomotives accounting for approximately 51 percent of this amount. CO emissions from non-road engines and vehicles have increased 90 percent since 1940 and now account for 22 percent of the national total. Gasoline equipment engines are now the predominant sources of non-road CO emissions.
Fires, including forest wildfires, agricultural fires, and slash/prescribed burning, are an unpredictable but occasionally significant source of carbon monoxide emissions. In 1940, CO emissions in this category accounted for 27 percent of the national total; since then, emissions have declined erratically to only 3 percent of total national CO emissions in 1998.
Historically, residential wood combustion has contributed the largest quantity of CO emissions in the fuel combustion category. In 1940, it accounted for 74 percent of CO emissions in this category; since then, there has been a substantial decline, particularly since 1985. For trends in other sources, see Table 5.1.
Long-term reductions in ambient atmospheric concentrations of CO have been measured across all monitoring environments — urban, suburban, and rural -- indicating that long-term improvements in air quality. On average, urban monitoring sites record higher CO concentrations than suburban sites, with lowest levels at rural sites. Using data from two separate 10-year trends databases, Figure 5.2 shows a consistent decline in national CO concentrations during the past 20 years.
Nitrogen Oxides
Over the period from 1940 to 1998, national emissions of nitrogen oxides (NOx) rose 233 percent from 7.37 million to 24.45 million tons. Changes in emissions over this period are shown in Figure 5.3. From 1970 to 1997, NOx emissions increased by approximately 19 percent, followed by a slight decline in 1998. In 1998, the principal sources of NOx emissions are fuel combustion from electric utilities and industrial processes (10.19 million tons), on-road vehicles (7.77 million tons), and non-road sources, which include non-road gasoline engines, non-road diesel (e.g., construction and farm), aircraft, marine vessels, and railroads (5.28 million tons). Historically, NOx emissions from fuel combustion sources peaked in 1977, and remained approximately constant at their peak level through the mid 1990s. Slight reductions in this category since 1994 are mainly due to emission controls on coal-fired electric utilities required by Title IV (Acid Deposition Control) of the Clean Air Act.
The increasing popularity of motorized vehicles during the first half of the 20th century led to a corresponding increase in emissions of NOx, CO, and volatile organic compounds (VOC). In general, automotive emissions limits set by EPA have resulted in significant decreases in CO and VOC emissions by on-road vehicles, but not NOx emissions. NOx emissions peaked around 1980 and have declined only slightly since then. New federal tailpipe emissions standards for NOx have been proposed.
Similarly to on-road vehicle NOx emissions trends, emissions from non-raod engines and vehicles increased over the period 1940 to 1998. To help slow this growth in emissions, EPA established emission control measures for new non-road diesel engines in certain horsepower categories. These standards began to take effect in 1996, with full phase-in for all horsepower categories scheduled for 2000.
NOx emissions from industrial processes peaked in 1960. Historically, NOx emissions from this category have accounted for only a small percentage of the national total. For emissions by source and other sources, see Part III, Table 5.2.
Nationally, ambient atmospheric concentrations of NOx have declined approximately 25 percent since 1980 (Figure 5.4), coincident with the decline in NOx emissions. Because most of the NOx monitoring sites are mobile-source oriented sites in urban areas, the 20-year decline in NOx concentrations more closely tracks the 19 percent reduction in NOx emissions from on-road vehicles since 1980.
VOCs and Ozone
National emissions of volatile organic compounds (VOCs), which along with NOx are precursors to ground level ozone formation, rose significantly from 1940 to a 1970 peak of 30.6 million tons, and then declined almost as significantly from the 1970 level to a low of 17.92 million tons in 1998 (Figure 5.5). (When calculating VOC emissions, EPA includes those VOC species that primarily contribute to ozone formation, but excludes emissions of methane, a nonreactive compound, and makes no adjustments to include chlorofluorocarbons (CFCs) or to exclude ethane and other VOCs with negligible photochemical reactivity.)
In 1900, emissions from all fuel combustion sources represented 68 percent of total national VOC emissions, with residential wood consumption accounting for 90 percent of those emissions. From 1940 to 1970, residential wood consumption declined steadily as many households switched to fossil fuels for home heating, cooking, and hot water; trends in VOC emissions from this source followed suite. Disruptions in crude oil deliveries in the mid 1970sand concomitant increases in fossils fuel prices led to a resurgence in the use of wood for home heating and a corresponding increase in emissions from residential wood combustion. By 1980, prices in fossil fuel products once again began to decline, as did corresponding VOC (and CO) emissions.
Industrial processes accounted for an increasing share of total national VOC emissions between 1900 and 1970. Although VOC emissions from industrial sources declined by 41 percent from 1970 to 1998, they still account for 41 percent of total national VOC emissions.
At the turn of the 20th century, VOC emissions from non-road engines and vehicles accounted for 4 percent of national total emissions, of which railroad locomotives accounted for 99 percent. The railroad contribution peaked in 1920 at 20 percent of national total VOC emissions, but has decreased since then to less than 1 percent currently. Although railroad emissions decreased, emissions from the entire non-road engine and vehicle category (which also includes lawn and garden equipment, recreational marine vessels, other non-road gasoline engines, non-road diesel construction and farm equipment, and aircraft) increased 216 percent during the 1940 to 1998 period. Today, emissions from this category represent approximately 14 percent of national total VOC emissions.
In general, the automotive emission limits set by EPA resulted in significant decreases since 1970. For emissions by this and other sources, see Table 5.3.
Ground-level ozone -- the prime ingredient of smog -- remains a pervasive pollution problem in the United States. Ozone is readily formed in the atmosphere by the reaction of VOCs and NOx in the presence of heat and sunlight. Hot, dry meteorological conditions, such as occurred in 1983, 1988 and 1995, are highly conducive to ozone formation. Despite increases in these years, the 20-year trend shows a 17-percent decline in annual 2nd-highest daily maximum 1-hour ozone concentrations (Figure 5.6). The highest concentration levels are typically found at suburban sites, consistent with the downwind transport of emissions from the urban center.
In 1998, approximately 51 million people lived in 92 counties where ozone concentrations were above the level of the 1-hour ozone NAAQS. Higher concentrations are typically found in Southern California, the Gulf Coast, and the Northeast and North Central states. Using the proposed new 8-hour ozone standard (See Box 5.1), the number of people living in counties exceeding the standard increases to 130 million and the affected area is more widespread, covering much of the eastern half of the county, isolated counties in the West, and almost the entire state of California.
----------------------------------------------------------------------------------------------------------------------------------------------
Box 5.1
Revised Primary and Secondary 8-hour Ozone Standards Challenged
In mid-1997, EPA announced new primary and secondary 8-hour ozone standards standard to protect against longer exposure periods that are of concern for both human health and vegetation . The new standards would be met when the 3-year average of the annual fourth-highest daily maximum 8-hour ozone concentration is less than or equal to 0.08 ppm. However, due to legal challenges concerning the new standards, EPA proposes to reinstate the original 1-hour primary and secondary standards (0.12 ppm daily maximum 1-hour concentration not to be exceeded more than once per year on average) until the matter is resolved.
-------------------------------------------------------------------------------------------------------------------------------------------------
Sulfur Dioxide
Sulfur dioxide (SO2) belongs to a family of sulfur oxide gases which are formed when fuel containing sulfur (mainly coal and oil) is burned, and during metal smelting and other industrial processes. The highest monitored concentrations of SO2 have been recorded in vicinity of large industrial facilities. Progress toward reducing SO2 concentrations during the past 20 years has been accomplished by installing flue-gas control equipment in coal-fired electric utilities, reducing emissions from industrial processing facilities, and switching to cleaner, lower-sulfur coal and other fuels in residential, commercial, and industrial burners. The national 1998 composite average SO2 annual mean concentration was 53 percent lower than the 1979 level (Figure 5.7).
National SO2 emissions rose 56 percent between 1940 and 1970 and have declined since (Figure 5.8), primarily because of regulatory actions, especially those that targeted utility sources. For example, SO2 emissions from electric utilities using all types of energy sources decreased approximately 24 percent from 1970 to 1998 (See Box 5.2).
-----------------------------------------------------------------------------------------------------------------------------------------------
Box 5.2
The Acid Rain Program
Established by EPA under Title IV of the Clean Air Act Amendments, the Acid Rain Program’s principal goal is to achieve significant reductions in SO2 and NOx emissions. Phase I compliance for SO2 began in 1995 and significantly reduced emissions from the participating electric utilities. Since 1995, however, total SO2 emissions from electric utilities have increased. The majority of the increase is attributed to those units not yet participating in the acid rain program. Most of these units will be included in Phase II of the Program, which begins in 2000. The rest of the increase came from some Phase I plants which over-complied in 1995 and were able to use their banked emission allowances in 1996 -1998. When fully implemented, total SO2 emissions from electric utilities will be capped at 8.9 million tons per year.
-----------------------------------------------------------------------------------------------------------------------------------------------
Industrial process SO2 emissions peaked in 1970, when they contributed approximately 23 percent of the national total SO2 emissions. From 1970 to 1998, emissions decreased by 79 percent, and by 1998 industrial processes only contributed 8 percent of the national total SO2 emissions. A major reason for the decline is the large reduction in SO2 emissions from metal processing industries. SO2 emissions from chemical and allied manufacturing, petroleum and related industries, and other industrial processes have also declined since 1970.
SO2 emissions from non-road engines and vehicles declined by 97 percent from 1940 to 1970, primarily due to the obsolescence of coal-fired railroad locomotives. Emissions in this category have risen again, to about one third of the 1940 levels. For emissions by other sources, see Table 5.4.
PM10 Particulate Matter
Nationally, PM10 emissions peaked around 1950, steadily declined until the mid-1980s, and since then have remained relatively stable. EPA divides PM10 sources into two categories: fugitive dust sources and nonfugitive dust sources. Fugitive dust sources include a combination of natural sources (wind erosion ) and some miscellaneous sources (agriculture and forestry, wildfires and managed burning, construction, and roads). These sources actually account for about 90 percent of the total PM10 emissions nationwide, although they can be difficult to quantify compared to the traditionally inventoried sources. Since 1990, emissions from fugitive dust sources have increased slightly, primarily as a result of increases in unpaved roads and construction emissions. PM10 emissions from wildfires varies annually depending on the incidence of wildfires and prevailing weather conditions.
The second group of PM10 emissions includes the more traditionally inventoried sources -- fuel combustion, industrial processes, transportation, and non-road engines and vehicles (Figure 5.9). PM10 emissions from fuel combustion increased between 1940 and 1970, which corresponds mainly to an increase in coal combustion by electric utilities. PM10 emissions from residential wood burning increased between 1970 and 1980, but total PM10 emissions from all fuel combustion sources combined have declined from 1970 levels.
Nonfugitive dust PM10 emissions from industrial processes increased from 1940 to 1960, primarily as a result of increased industrial production. From 1960 to 1970, industrial output continued to grow, but PM10 emissions began to decline due to the installation of pollution control equipment. Since 1970, significant progress has been achieved in reducing PM10 emissions in this category.
Nonfugitive dust PM10 emissions from on-road vehicles comes mainly from heavy-duty diesel trucks. Emissions in this category increased between 1940 and 1960 and have since declined. PM10 emissions from non-road engines and vehicles comes mainly from diesel equipment on farms and construction sites and from railroad locomotives. PM10 emissions in this category declined significantly from 1940 to 1960 (as railroads switched to non-coal energy sources), rose slightly in the period 1960 to 1990, and have declined slightly since 1990 (primarily due to emissions reductions in the farming sector). See Table 5.5 for emissions by source and Table 5.6 for miscellaneous sources.
Mean annual PM10 concentrations have decreased 25 percent since 1989, which was the second year of PM10 trends data for most monitors (Figure 5.10). Urban, suburban, and rural areas have similar trends, although concentrations in rural areas are significantly lower. Several factors have played a role in reducing PM10 concentrations since 1989. Where appropriate, states required emissions from industrial sources and construction activities to be reduced to meet the PM10 standards. Measures were also adopted to reduce street dust emissions, including the use of clean anti-skid materials like washed sand, better control of the amount of material used, and removal of the material from the street as soon as the ice and snow melted. In addition, cleaner burning fuels like natural gas and fuel oil have replaced wood and coal as fuels for residential heating and industrial and electric utility furnaces.
-----------------------------------------------------------------------------------------------------------------------------------------------
BOX 5.3
Revised Primary and Secondary PM Standards Challenged
The original standards for PM, established in 1971, were for total suspended particulate (TSP) matter. In 1987, EPA replaced the TSP standards with PM10 standards to focus on smaller particles of aerodynamic diameter less than or equal to 10 micrometers. These smaller particles caused the greatest health concern because of their ability to penetrate into sensitive regions of the respiratory tract. The most recent review of the PM standards concluded that still more protection from adverse health effects was needed. In July 1997, the primary (health-based) PM standards were revised to add two new PM2.5 standards, set at 15mg/m3 for the annual standard and 65 mg/m3 for the 24-hour standard, and to change the form of the 24-hour PM10 standard. The secondary (welfare-based) standards were revised by making them identical to the primary standards. Like the new ozone NAAQS, the revised PM standards have been challenged .
------------------------------------------------------------------------------------------------------------------------------------------------
PM2.5 Particulate Matter
PM2.5 — those particles whose aerodynamic size is less than or equal to 2.5 micrometers -- is mainly associated with residential wood burning, natural sources (wind erosion), and miscellaneous fugitive dust sources. Overall PM2.5 emissions remained relatively constant from 1990 to 1998, while emissions from residential wood burning declined significantly and emissions from natural sources fluctuate.
From 1989 through 1998, data from the IMPROVE program was used to indicate PM2.5 concentrations and composition over broad regions of the country. The IMPROVE network was established in 1987 to track visibility impairment in the nation’s most pristine areas, like national parks and wilderness areas. (Visibility trends are discussed later in this chapter.) For this reason, the data primarily represent rural areas.
Rural PM2.5 concentrations vary regionally, with sites in the east typically having higher annual mean concentrations. The chemical composition of PM2.5 also varies regionally. Sites in the east have a higher percentage of sulfate concentrations while sites in the west have higher percentages of organic carbon and crushed material. Concentrations of nitrate and elemental carbon are nearly split between the east and the west.
Lead
Annual national emissions of lead have declined spectacularly, dropping from the 1970 level of 221,000 tons to the 1998 level of 3,973 tons (Figure 5.11). Emissions from on-road vehicles, estimated at 172,000 tons in 1970, dropped to about 19 tons in 1998 as a result of the federal phaseout of lead in gasoline. Emissions from metals processing also have dropped sharply, from the 1970 level of 24,000 tons to 2,098 tons in 1998
Over the past 10-year period, atmospheric lead concentrations decreased 56 percent at population-oriented monitoring sites (Figure 5.12). Air quality trends segregated by location (urban, suburban, and rural) show similar declines over the period.
OTHER AIR QUALITY TRENDS
Greenhouse Gas Emissions
U.S. emissions of greenhouse gases (GHG) continue to increase, generally following the trends in U.S. energy consumption. In 1998, for example, 83 percent of U.S. GHG emissions consisted of carbon dioxide (CO2) released by the combustion of energy fuels — coal, petroleum, and natural gas. In recent years, national energy consumption has grown relatively slowly, with year-to-year fluctuations in the growth rate of energy consumption largely caused by variations in weather patterns, business cycles, fuel use for electricity generation, and domestic and international energy markets. Figure 5.13 shows U.S. energy-related CO2 emissions by residential, commercial, industrial, and transportation sectors. (Emissions from electric utility sector are prorated across these end-user sectors.)
Other GHG comprise only a fraction of U.S. total GHG emissions. These include CO2 from non-combustion sources (2 percent), methane (9 percent), nitrous oxide (6 percent), and other gases (2 percent). Methane and nitrous oxide emissions are caused by the biological decomposition of various waste streams and fertilizers, fugitive emissions from chemical processes, fossil fuel production and consumption, and many smaller sources. The other gases include hydrofluorocarbons (HFCs), used primarily as refrigerants, perfluorocarbons (PFCs), released as fugitive emissions from aluminum smelting and also used in semiconductor manufacture, and sulfur hexafluoride (SF6), used as an insulator in electrical transmission and distribution equipment and as a cover gas in magnesium production and processing. (Also see Chapter 11, Global Environment.)
Atmospheric Deposition
Total atmospheric deposition of sulfate, nitrate, and other ions is determined using both wet and dry deposition measurements. Wet deposition (or acid rain) is the portion dissolved in cloud droplets and is deposited on land and water surfaces in precipitation. Dry deposition is the portion deposited on dry surfaces during periods of no precipitation as particles or in a gaseous form and accounts for 20-60 of total deposition.
The National Acid Deposition Program (NADP) monitors wet deposition at over 220 National Trends Network (NTN) sites throughout the United States. The program is a partnership between the U.S. Geological Survey (USGS) and over 100 other federal, state, local and private organizations. A new subnetwork of the NADP, the Mercury Deposition Network (MDN), measures mercury in precipitation.
Trend analyses for sulfate and nitrate concentrations in precipitation indicate that sulfur concentrations have decreased over the past two decades while current nitrate concentrations are not appreciably different from historical levels. Recent studies support the conclusion that the Acid Deposition Control Program (Title IV) mandated by the Clean Air Act Amendments of 1990 has, wholly or in part, reduced acid deposition, particularly in the eastern United States. The largest reductions in sulfate concentrations have occurred in the Ohio River Valley (where many of the largest emitters of sulfur dioxide targeted by Phase I of Title IV are located) and in eastern states immediately downwind of this region. For example, the average reduction in sulfate concentrations in Ohio was approximately 21 percent, in Maryland, 27 percent, and in Pennsylvania, 15 percent. The largest decrease (32 percent) occurred in the northern portion of West Virginia. Also noteworthy are reductions in sulfate deposition in three sensitive ecoregions in the eastern United States: Adirondacks, Mid-Appalachians, and Southern Blue Ridge (Text Table 5.1).
The Clean Air Status and Trends Network (CASTNet) monitors dry deposition as well as ground-level ozone and other forms of atmospheric pollution. Established in 1987, CASTNet now comprises 79 monitoring stations across the United States. The majority of the monitoring sites are operated by EPA; however, 27 sites are operated by the National Park Service in cooperation with EPA. The longest data records are primarily at eastern sites.
During the 10-year period, 1989-1998, data from 34 eastern CASTNet sites with the most complete historical record show that both ambient SO2 concentrations and dry sulfate deposition decreased 38 percent and 22 percent, respectively. An average 10-percent increase in sulfates between 1997 and 1998 is noted, but not explained. The trend for total nitrate concentrations (nitrates plus nitric acid) was essentially flat, corresponding to the relatively small change in NOx emissions during the period.
Visibility
Visibility impairment, as measured by the amount of haze during summer months at 280 monitoring stations located at airports across the country, increased greatly between 1970 and 1980 and then decreased slightly between 1980 and 1990. These trends follow overall trends in emissions of sulfur oxides during these periods. Recent aerosol and light extinction data (1989-1998) from 34 sites in the Interagency Monitoring of Protected Environments (IMPROVE) network show that the haziest visibility days in eastern sites do not appear to be getting any better. In fact, a 4-percent degradation has occurred since 1992. In contrast, there appears to be steady improvement in visibility in the West.
Air Toxics
According to the most recent National Toxics Inventory, 4.6 million tons of hazardous air pollutants (HAPs) were emitted to the atmosphere in 1996. HAPs are emitted from all types of manmade sources: large point sources such as industrial facilities and utilities; smaller stationary sources such as neighborhood dry cleaners; area sources facilities such as wildfires and prescribed burnings; and mobile sources such as automobiles and trucks. In 1996, stationary point sources that emit more than 10 tons per year of an individual HAP or 25 tons per year of aggregate emissions of HAPs accounted for approximately 24 percent of the total HAP emissions nationally, while on-road mobile sources contributed 30 percent and non-road engines and mobile sources contributed 20 percent. Area and other sources, which are often too small or ubiquitous in nature to be inventoried as individual sources, accounted for another 26 percent (Figure 5.14).
In 1996, emissions of the 33 Urban Air Toxics Strategy HAPs totaled 1.1 million tons per year. Among the 33 HAPs on the urban strategy list, 25 pollutants have sufficient historical data for trends assessment of ambient concentrations. The results generally reveal downward trends for most monitored HAPs on the list. The most consistent improvements are apparent for benzene, which is predominantly emitted by mobile sources, and for total suspended (lead emissions are discussed earlier in this chapter). From 1993-1998, annual average concentrations for these two HAPs declined 37 and 41 percent, respectively. Similar to benzene, annual average toluene concentrations dropped 44 percent. The reduction in benzene and toluene is attributed to the use of reformulated gas in many areas of the country.
People can be exposed to air toxics by breathing contaminated air or ingesting food from contaminated waters where air toxics are deposited. Potential health effects resulting from exposure to hazardous air pollutants include leukemia and other cancers; reproductive and developmental effects such as impaired development in newborns and young children, miscarriage, decreased fertility; and damage to the pulmonary system. The extent to which these effects actually occur in the population depends on a number of factors, including the level and duration of exposure. Air toxics can also adversely impact ecosystems; in some cases, deposited air pollutants can be significant contributors to overall pollutant loadings to waterbodies. As of December 1998, over 2,506 U.S. waterbodies are under fish consumption advisories (for particular species of fish), representing approximately 15.8 percent of the nation’s total lake acreage and 6.8 percent of the nation’s total river miles. (See Chapter 6, Aquatic Resources).
Air Quality Index
EPA’s Air Quality Index (AQI) (formerly the Pollution Standards Index) is used to assess trends in air quality in metropolitan statistical areas (MSAs). The AQI provides information on pollutant concentrations from ground-level O3, PM, CO, SO4, and NO2. It is normalized across pollutants so that an AQI value of 100 represents the level of health protection associated with the national health-based standard for each pollutant and an AQI value of 500 represents the level at which the pollutant causes significant harm. The AQI is reported daily in all MSAs with populations exceeding 350,000. (See Table 5.11 for definitions and changes in reporting categories)
Analysis of AQI trends in the nation’s 94 largest metropolitan areas over the period 1989- 1998 show an improvement in air quality in southern California MSAs -- an overall 57-percent decrease in AQI values greater than 100 -- but just the opposite in the remaining major cities -- an overall 10-percent increase decrease in AQI values greater than 100. Ground-level O3 increasingly accounts for the worsening air quality conditions.
Nonattainment Areas
When an area does not meet the air quality standard for one of the criteria pollutants it may be subject to EPA’s formal rule-making process which designates the area as nonattainment. As of September 1998, there were a total of 130 nonattainment areas on EPA’s condensed nonattainment list. The list is updated as new areas are designated or existing areas are redesignated.
There are approximately 113 million people living in areas currently designated as nonattainment.
Indoor Air Quality
Research indicates that air in homes, schools, and workplaces can have higher levels of pollution than outdoor air. Since many Americans spend about 90 percent of their time indoors, health risks from indoor pollutants can be substantial and may include asthma, cancer, reproductive and developmental problems, and other health effects.
Asthma and Indoor Environments
Asthma is one of the most common chronic diseases in the United States, and it has increased in importance during the preceding 20 years, especially among children. In 1998, asthma affected an estimated 17.3 million people in the United States in 1998 and was the underlying cause of death for 5,438 people. The Centers for Disease Control and Prevention reports that the prevalence rate for asthma has nearly tripled since 1980 while the estimated annual number of visits to office-based physicians more than doubled (Figure 5.15). Overall rates of death with asthma as the underlying cause decreased from 1960 through 1977 and have gradually increased since then. The increasing trends are evident among all race strata, both sexes, and all age groups; however young, poor inner city dwellers are disproportionately affected by asthma and more people in the South have had asthma than in any other region.
Recent studies suggest that indoor air exposures — to dust mites, cockroaches, mold, pet dander, environmental tobacco smoke (ETS), and other biological and chemical pollutants — may influence the disease course of asthma. In a recent report, the National Academy of Sciences/Institute of Medicine concludes that there is sufficient scientific evidence of a causal relationship between:
The report also presents evidence of an association between ETS exposure and the development of asthma in younger children as well as an association between indoor exposure to dog allergen, fungi, rhinovirus, and high-level NO2 and the exacerbation of asthma in sensitized asthmatics. Cancer and Indoor Exposures
A number of indoor pollutants, such as asbestos, radon, ETS, and benzene, are known human carcinogens. Several others — chlorinated solvents, polycyclic aromatic hydrocarbons, aldehydes, and pesticides — are considered likely to cause cancer in humans.
Asbestos causes several diseases, including asbestosis, a disabling disease of the lungs; lung cancer; and mesothelioma, a usually fatal cancer of the chest or abominal cavity lining. Asbestos is often in old fireproofing, roofing, vinyl flooring, pipe and boiler insulation, and some roads, cement pipe, and cement-sheet products. Construction workers have had some of the largest exposures to asbestos, installing it between 1940 and the mid-1970s and removing it since then.
Asbestos-related cancers usually do not appear until 20 to 30 years after exposure, while asbestosis is usually associated with higher exposures and can occur much sooner. Asbestosis deaths have increased from fewer than 100 in 1968 to nearly 1,200 annually in the mid-1990s, with no apparent leveling off through 1996, the most recent year for which data are available (Figure 5.16). Asbestos-related cancer deaths are not expected to decline among construction workers until after the year 2000.
Radon, a naturally occurring gas, is the country’s second leading cause of lung cancer. The National Academy of Sciences estimates that about 12 percent of lung cancer deaths in the United States are linked to radon. They calculate the number of lung cancer cases attributable to radon exposure to range from 15,000 to 22,000 annually. Radon can be managed with readily available technology.
ETS is responsible for approximately 3,000 lung cancer deaths in nonsmokers annually, as well as 150,000 to 300,000 lower respiratory tract infections in infants, resulting in up to 15,000 hospitalizations per year. ETS is also associated with bladder cancer.
References
Lynch, J.A., V.C. Bowersox, and J.W. Grimm, Trends in Precipitation Chemistry in the United States, 1983-94: An Analysis of the Effects in 1995 of Phase I of the Clean Air Act Amendments of 1990, Title IV, U.S.Department of the Interior, Geological Survey Open-File Report 96-0346 (DOI, USGS, 1996).
--. "Changes in Sulfate Deposition in the Eastern USA Following Enactment of Title IV of the Clean Air Act Amendments of 1990," Atmospheric Environment (Elsevier Science, 1999).
National Academy of Sciences (NAS), Biological Effects of Ionizing Radiation (BEIR) VI Report: "The Health Effects of Exposure to Indoor Radon" (National Academy Press, Washington, DC, 1998). (http://www.epa.gov/iaq/radon/beirvi.html)
--, Clearing the Air: Asthma and Indoor air Exposures (National Academy Press, Washington, DC, 2000) http://books.nap.edu/catalog/9610.html)
U.S. Department of Energy, Energy Information Administration, Emissions of Greenhouse Gases in the United States, 1999, EIA/DOE-0573(99) (DOE, EIA, Washington, DC, 2000). (http://www.eia.doe.gov/oiaf/1605/ggrpt/index.html)
U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, Work-Related Lung Disease Surveillance Report, 1999, DHHS (NIOSH) 2000-105 (HHS, PHS, CDC, Washington, DC, 1999). (http://www.cdc.gov/niosh/W99front.html)
--, "Surveillance for Asthma — United States, 1960-1995," Morbidity and Mortality Weekly Report 47(SS-1):1-28 (1998). (http://www.cdc.gov/mmwr/preview/mmwrhtml/00052262.htm)
--, "Forecasted State-Specific Estimates of Self-Reported Asthma Prevalence — United States, 1998," Morbidity and Mortality Weekly Report 47(47):1022-1025 (1998). http://www.cdc.gov/mmwr/preview/mmwrhtml/00055803.htm
U.S. Environmental Protection Agency, Office of Air and Radiation, Healthy Buildings, Healthy People: A Vision for the 21st Century, 402-K-00-002 (EPA, Washington, DC, 2000). (http://www.epa.gov/iaq/hbhp/index.html)
--, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-1998, EPA 236-R-00-001 (EPA, Washington, DC, 2000). (http://www.epa.gov/globalwarming/publications/emissions/us2000/index.html)
--, National Air Pollutant Emission Trends Report, 1900 - 1998, EPA 454/R-00-002 (EPA, Washington, DC, 2000). (http://www.epa.gov/ttn/chief/trends/trends98/index.html)
--, National Air Quality and Emissions Trends Report, 1998, EPA 454/R-00-003 (EPA, Washington, DC, 2000). (http://www.epa.gov/oar/aqtrnd98/)
--, National-Scale Air Toxics Assessment Results: Emissions, EPA Air Toxics Website (http://www.epa.gov/ttn/atw/nata/natsa1.html)
