Measure E1: Exceedances of Air Quality Standards
Common Air Pollutants
Air pollution contributes to a wide variety of adverse health effects. Six of the most common air pollutants—carbon monoxide, lead, ground-level ozone, particulate matter, nitrogen dioxide, and sulfur dioxide—are known as “criteria” pollutants because EPA uses health-based criteria as the basis for setting permissible levels of these pollutants in the atmosphere.
EPA periodically conducts comprehensive reviews of the scientific literature on health effects associated with exposure to the criteria air pollutants. The resulting “criteria documents” critically assess the scientific literature and serve as the basis for making regulatory decisions about whether to retain or revise the National Ambient Air Quality Standards (NAAQS) that specify the allowable concentrations of each of these pollutants in the air. The standards are set at a level that protects public health with an adequate margin of safety. However, the standards are not “risk free.” Even in areas that meet the standards, there may be days when unusually sensitive individuals, including children, experience health effects related to air pollution. This is especially the case for pollutants such as ozone and particulate matter that do not have discernible thresholds below which health effects are absent.
Some of the standards are designed to protect the public from adverse health effects that can occur after being exposed for a short time, such as one hour or one day. Other standards are designed to protect people from health effects that can occur after being exposed for a much longer time, such as a year. For example, current standards for carbon monoxide are for short-term periods of one hour and eight hours. By contrast, the current standard for nitrogen dioxide is for one year. The standards and the varying time periods for which they apply are shown in Table 1 in the Full Methods Description for Measure E1 (PDF) (12pp, 336K, About PDF). Some pollutants have both short-term and long-term standards.
Health effects that have been associated with each of these pollutants are summarized below. This information is drawn from EPA’s criteria documents as well as more recent studies.
Ground-level Ozone
Short-term (also known as “acute”) exposure
to ground-level ozone can cause a variety of respiratory health
effects, including inflammation of the lung, reduced lung function,
and respiratory symptoms such as cough, chest pain, and shortness
of breath. It also can decrease the capacity to perform exercise.1 Exposure to ambient concentrations of ozone also has been associated
with the exacerbation of asthma, bronchitis, and respiratory effects
serious enough to require emergency room visits and hospital admissions.1 Some evidence suggests that high ozone concentrations may contribute
to increased mortality.1
Health effects associated with long-term (also known as “chronic”) exposure to ozone are not as well established and documented as health effects associated with short-term exposure, but long-term exposures also are of concern. In 1996, EPA’s criteria document for ozone concluded that there was insufficient evidence to determine whether health effects resulted directly from long-term exposure, although the evidence suggested that long-term ozone exposure, along with other environmental factors, could be responsible for health effects.1 Since 1996, a few studies suggest that long-term exposure to ozone is associated with decreases in lung function in humans,2 increased prevalence of asthma,3 increased development of asthma in children who exercise outdoors,4 and exacerbation of existing asthma.5
Particulate Matter
Particulate matter in the air (often called PM-10 or PM-2.5) has
been found to cause increased risk of mortality (death), hospital
admissions and emergency room visits for heart and lung diseases,
respiratory effects, and decreases in lung function.6 Such health effects have been associated with both short-term
and long-term exposure to particulate matter. Children and adults
with asthma are considered to be among the groups most sensitive
to respiratory effects.6-10 Studies published since the release of EPA’s criteria document
for particulate matter have found further evidence of an association
between particulate matter and increased respiratory disease and
symptoms in children with asthma11 and increased hospitalizations or emergency room visits for persons
with asthma.5, 12, 13 Studies also have confirmed
that chronic exposure to particulate matter is associated with
mortality in adults14-16 and suggest that it may be associated with mortality in infants.17 Also, recent studies suggest that chronic exposure to particulate
matter may affect lung function and growth.18, 19 Prior to 1997, the National
Ambient Air Quality Standard for particulate matter was based
on particulate matter measuring 10 microns or less (PM-10). In
1997, the standard was revised to address the health risks from
particulate matter measuring 2.5 microns or less (PM-2.5).
Lead
Lead accumulates in bones, blood, and soft tissues of the body.
Exposure to lead can affect development of the central nervous
system in young children, resulting in neurobehavioral effects
such as lowered IQ.20
Sulfur Dioxide
Sulfur dioxide poses particular concerns for those with asthma,
who are considered to be especially susceptible to its effects.21 Short-term exposures of asthmatic individuals to elevated levels
of sulfur dioxide while exercising at a moderate level may result
in breathing difficulties accompanied by symptoms such as wheezing,
chest tightness, or shortness of breath. Effects that have been
associated with longer-term exposures to high concentrations of
sulfur dioxide, in conjunction with high levels of particulate
matter include respiratory illness, alterations in the lung’s
defenses, and aggravation of existing cardiovascular diseases.
Carbon Monoxide
Exposure to carbon monoxide reduces the capacity of the blood
to carry oxygen, thereby decreasing the supply of oxygen to tissues
and organs such as the heart. Short-term exposure can cause effects
such as reduced time to onset of angina pain, neurobehavioral
effects, and a reduction in exercise performance.22 Long-term exposure has not been studied adequately in humans to
draw conclusions regarding possible chronic effects, though a
recent study reported an association between long-term exposure
to carbon monoxide and other traffic-related pollutants and respiratory
symptoms in children.23
Nitrogen Dioxide
Exposure to nitrogen dioxide has been associated with a variety
of health effects.24 Effects include decreased lung function,23, 25, 26 increased respiratory symptoms or illness,7, 23, 27-29 and increased symptoms in children with asthma.11 Nitrogen dioxide also is a major contributor to the formation
of ground-level ozone.1
Measure E1: Exceedances of Air Quality Standards
State agencies that monitor air quality report their findings to EPA. In turn, EPA compares the measured values reported by states to the National Ambient Air Quality Standards in order to determine whether pollutants exceed the established standards. EPA uses the term “exceedance” to refer to a case in which a reported measurement of a pollutant is higher than the standard. Table 1 in the Full Methods Description for Measure E1 (PDF) (12pp, 336K, About PDF) includes a description of the methods used to determine whether an exceedance has occurred.
This measure uses EPA data on exceedances of short-term air quality standards in counties in the United States. This data source simply indicates whether each standard was exceeded at any time during a year. This measure shows the percentage of children living in areas with any such exceedances, who thus may be exposed to poor daily air quality at some point during a year. This analysis differs from the analysis utilized by the U.S. Environmental Protection Agency for the designation of “nonattainment areas” for regulatory compliance purposes.
This measure does not differentiate between areas in which standards are exceeded frequently or by a large margin, and areas in which standards are exceeded only rarely or by a small margin. The measure is based on exceedances of individual standards and does not reflect any combined effect of multiple pollutants. Also, because the nature of health effects varies significantly and the averaging times associated with different standards vary widely, exceedances for different standards are not comparable. For example, the ozone standard considers measured levels of ozone within an eight-hour period and health effects such as lung function decrements, respiratory symptoms, and hospital admissions. In contrast, the averaging time for the lead standard is three months and is based on health effects such as IQ decrements and hypertension.
The graph shows the percentage of children who live in counties with exceedances for any of the criteria pollutants. Nitrogen dioxide is not included, as there is no short-term standard for this compound. Sulfur dioxide also is not shown, since few exceedances have been reported since 1993.
- U.S. Environmental Protection Agency. 1996. Air Quality Criteria for Ozone and Related Photochemical Oxidants. Washington, DC: National Center for Environmental Assessment,
Office of Research and Development. EPA/600/P-93/004aF. http://www.epa.gov/ttn/oarpg/t1cd.html.
- N. Kunzli, F. Lurmann, M. Segal, L. Ngo, J.
Balmes and I. B. Tager. 1997. Association between lifetime ambient
ozone exposure and pulmonary function in college freshmen—results
of a pilot study. Environmental Research 72 (1):8-23.
- M. Ramadour, C. Burel, A. Lanteaume, D. Vervloet,
D. Charpin, F. Brisse and H. Dutau. 2000. Prevalence of asthma
and rhinitis in relation to long-term exposure to gaseous air
pollutants. Allergy 55 (12):1163-9.
- R. McConnell, K. Berhane, F. Gilliland, S.
J. London, T. Islam, W. J. Gauderman, E. Avol, H. G. Margolis
and J. M. Peters. 2002. Asthma in exercising children exposed
to ozone: a cohort study. Lancet 359 (9304):386-91.
- P. E. Tolbert, J. A. Mulholland, D. L. MacIntosh,
F. Xu, D. Daniels, O. J. Devine, B. P. Carlin, M. Klein, J. Dorley,
A. J. Butler, D. F. Nordenberg, H. Frumkin, P. B. Ryan and M.
C. White. 2000. Air quality and pediatric emergency room visits
for asthma in Atlanta, Georgia, USA. American Journal of Epidemiology 151 (8):798-810.
- U.S. Environmental Protection Agency. 1996. Air Quality Criteria for Particulate Matter. Washington,
DC: National Center for Environmental Assessment, Office of Research
and Development. EPA/600/P-95/001aF.
- C. Braun-Fahrländer, U. Ackermann-Liebrich,
J. Schwartz, H. P. Gnehm, M. Rutishauser and H. U. Wanner. 1992.
Air pollution and respiratory symptoms in preschool children. American Review of Respiratory Disease 145 (1):42-7.
- J. H. Ware, B. G. Ferris, Jr., D. W. Dockery,
J. D. Spengler, D. O. Stram and F. E. Speizer. 1986. Effects of
ambient sulfur oxides and suspended particles on respiratory health
of preadolescent children. American Review of Respiratory
Disease 133 (5):834-42.
- D. W. Dockery, F. E. Speizer, D. O. Stram,
J. H. Ware, J. D. Spengler and B. G. Ferris, Jr. 1989. Effects
of inhalable particles on respiratory health of children. American
Review of Respiratory Disease 139 (3):587-94.
- D. W. Dockery, J. Cunningham, A. I. Damokosh,
L. M. Neas, J. D. Spengler, P. Koutrakis, J. H. Ware, M. Raizenne
and F. E. Speizer. 1996. Health effects of acid aerosols on North
American children: respiratory symptoms. Environmental Health
Perspectives 104 (5):500-5.
- R. McConnell, K. Berhane, F. Gilliland, S.
J. London, H. Vora, E. Avol, W. J. Gauderman, H. G. Margolis,
F. Lurmann, D. C. Thomas and J. M. Peters. 1999. Air pollution
and bronchitic symptoms in Southern California children with asthma. Environmental Health Perspectives 107 (9):757-60.
- G. Norris, S. N. YoungPong, J. Q. Koenig,
T. V. Larson, L. Sheppard and J. W. Stout. 1999. An association
between fine particles and asthma emergency department visits
for children in Seattle. Environmental Health Perspectives 107 (6):489-93.
- M. Lipsett, S. Hurley and B. Ostro. 1997.
Air pollution and emergency room visits for asthma in Santa Clara
County, California. Environmental Health Perspectives 105 (2):216-22.
- C. A. Pope 3rd, M. J. Thun, M. M. Namboodiri,
D. W. Dockery, J. S. Evans, F. E. Speizer and C. W. Heath, Jr.
1995. Particulate air pollution as a predictor of mortality in
a prospective study of U.S. adults. American Journal of Respiratory
and Critical Care Medicine 151 (3 Pt 1):669-74.
- C. A. Pope 3rd, R. T. Burnett, M. J. Thun,
E. E. Calle, D. Krewski, K. Ito and G. D. Thurston. 2002. Lung
cancer, cardiopulmonary mortality, and long-term exposure to fine
particulate air pollution. Journal of the American Medical
Association 287 (9):1132-41.
- D. E. Abbey, N. Nishino, W. F. McDonnell,
R. J. Burchette, S. F. Knutsen, W. Lawrence Beeson and J. X. Yang.
1999. Long-term inhalable particles and other air pollutants related
to mortality in nonsmokers. American Journal of Respiratory
and Critical Care Medicine 159 (2):373-82.
- T. J. Woodruff, J. Grillo and K. C. Schoendorf.
1997. The relationship between selected causes of postneonatal
infant mortality and particulate air pollution in the United States. Environmental Health Perspectives 105 (6):608-12.
- E. L. Avol, W. J. Gauderman, S. M. Tan, S.
J. London and J. M. Peters. 2001. Respiratory effects of relocating
to areas of differing air pollution levels. American Journal
of Respiratory and Critical Care Medicine 164 (11):2067-72.
- W. J. Gauderman, G. F. Gilliland, H. Vora,
E. Avol, D. Stram, R. McConnell, D. Thomas, F. Lurmann, H. G.
Margolis, E. B. Rappaport, K. Berhane and J. M. Peters. 2002.
Association between air pollution and lung function growth in
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- U.S. Environmental Protection Agency. 1990. Air Quality Criteria for Lead: Supplement to the 1986 Addendum. Washington, DC: Office of Research and Development. EPA 6000/8-89/049F.
- U.S. Environmental Protection Agency. 1994. Supplement to the Second Addendum (1986) to Air Quality Criteria
for Particulate Matter and Sulfur Oxides: Assessment of New Findings
on Sulfur Dioxide Acute Exposure Health Effects in Asthmatic Individuals. Research Triangle Park, NC: Office of Research and Development.
EPA 600/FP-93/002.
- U.S. Environmental Protection Agency. 2000. Air Quality Criteria for Carbon Monoxide. Washington, DC:
National Center for Environmental Assessment, Office of Research
and Development. EPA/600/P-99/001F. http://www.epa.gov/ncea/coabstract.htm.
- T. Hirsch, S. K. Weiland, E. von Mutius, A.
F. Safeca, H. Gräfe, E. Csaplovics, H. Duhme, U. Keil and
W. Leupold. 1999. Inner city air pollution and respiratory health
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- U.S. Environmental Protection Agency. 1993. Air Quality Criteria for Oxides of Nitrogen. Research
Triangle Park, NC: Environmental Criteria and Assessment Office,
Office of Health and Environmental Assessment. EPA-600/8-91/049aF. http://www.epa.gov/iris/subst/0080.htm.
- J. Schwartz. 1989. Lung function and chronic
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- R. Schmitzberger, K. Rhomberg, H. Büchele,
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1993. Effects of air pollution on the respiratory tract of children. Pediatric Pulmonology 15 (2):68-74.
- J. M. Peters, E. Avol, W. Navidi, S. J. London,
W. J. Gauderman, F. Lurmann, W. S. Linn, H. Margolis, E. Rappaport,
H. Gong and D. C. Thomas. 1999. A study of twelve Southern California
communities with differing levels and types of air pollution.
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Fangmeyer, N. Haschke, J. Kühr, R. Urbanek, M. Neumann and
T. Frischer. 1997. Traffic-related nitrogen dioxide and the prevalence
of asthma and respiratory symptoms in seven year olds. European
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Hospital admission rates for asthma and respiratory disease in
the West Midlands: their relationship to air pollution levels. Thorax 50 (9):948-54.
Environmental Contaminants
Measures:
Outdoor Air Pollutants
- Measure E1
- Measure E2
- Measure E3
- Measure E4
Indoor Air Pollutants
Drinking Water Contaminants
Pesticide Residues
Land Contaminants