Jump to main content.

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

Top of page

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.

Top of page

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  18. 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.
  19. 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 southern California children: results from a second cohort. American Journal of Respiratory and Critical Care Medicine 166 (1):76-84.
  20. 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.
  21. 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.
  22. 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.
  23. 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 and atopy in children. European Respiratory Journal 14 (3):669-77.
  24. 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.
  25. J. Schwartz. 1989. Lung function and chronic exposure to air pollution: a cross-sectional analysis of NHANES II. Environmental Research 50 (2):309-21.
  26. R. Schmitzberger, K. Rhomberg, H. Büchele, R. Puchegger, D. Schmitzberger-Natzmer, G. Kemmler and B. Panosch. 1993. Effects of air pollution on the respiratory tract of children. Pediatric Pulmonology 15 (2):68-74.
  27. 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. I. Prevalence of respiratory morbidity. American Journal of Respiratory and Critical Care Medicine 159 (3):760-7.
  28. M. Studnicka, E. Hackl, J. Pischinger, C. 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 Respiratory Journal 10 (10):2275-8.
  29. S. Walters, M. Phupinyokul and J. Ayres. 1995. Hospital admission rates for asthma and respiratory disease in the West Midlands: their relationship to air pollution levels. Thorax 50 (9):948-54.

Top of page

Environmental Contaminants

Measures:

Outdoor Air Pollutants

Indoor Air Pollutants

Drinking Water Contaminants

Pesticide Residues

Land Contaminants

 

Local Navigation

Jump to main content.