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Air Trends

National Air Quality -
Status and Trends through 2007 -
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The table below contains links to graphics (gif format) used in the Air Trends Report. The data used in the graphics are also available below in Excel format. Note that the data file is password protected. When the file opens and asks for a password, click on "Read Only" to view the data.

Figure Description
Highlights
  Number of people living in counties with air quality concentrations above the level of the primary (health-based) National Ambient Air Quality Standards (NAAQS) in 2007.
  Population density (2005 population per square mile) in counties with air quality concentrations above the level of any of the primary NAAQS in 2007.
Air Pollution
Fig 1 Distribution of national total emissions by source category for specific pollutants, 2007.
Fig 2 Distribution of national total emissions by source category for individual urban toxic air pollutants and diesel particle pollution, 2005.
Fig 3 Comparison of growth measures and emissions, 1990-2007.
Six Common Pollutants
Fig 4 Comparison of national levels of the six common pollutants to national ambient air quality standards, 1990-2007. National levels are averages across all sites with complete data for the time period.
  EPA’s Air Quality Index
Fig 5 Number of days reaching Unhealthy for Sensitive Groups on the Air Quality Index for 2001-2007 at selected cities.

Fig 6a

Fig 6b

Status of original nonattainment areas for one or more standards (i.e., 8-hour ozone, maximum quarterly lead, annual PM2.5, 24-hour PM10, annual NO2, 8-hour CO, and annual SO2) as of 2007.
Ground-Level Ozone
Fig 7 National 8-hour ozone air quality trend, 2001-2007 (average of annual fourth highest daily maximum 8-hour concentrations).
Fig 8 Change in ozone concentrations in ppm, 2001-2003 vs. 2005-2007 (3-year average of annual fourth highest daily maximum 8-hour concentrations).
Fig 9 Ozone concentrations in ppm, 2007 (fourth highest daily maximum 8-hour concentration).
  Required Ozone Monitoring Time Periods
Fig 10 Difference between 2007 observed and adjusted ozone concentrations (average daily maximum 8-hour ozone for May-September). The map shows areas where weather contributed to higher or lower ozone concentrations than expected. Estimated changes for locations farther from monitoring sites (dots on map) have the largest uncertainty.
Fig 11 Trends in average summertime daily maximum 8-hour ozone concentrations (May-September), before and after adjusting for weather nationally, in California and in eastern states; and the location of urban and rural monitoring sites used in the averages.
Particle Pollution

Fig 12a

Fig 12b

National PM2.5 air quality trends, 2001-2007 (annual and 24-hour average).
  The Great American Woodstove Changeout

Fig 13a

Fig 13b

Change in PM2.5 concentrations in µg/m3, 2001-2003 vs. 2005-2007 (3-year average of annual and 24-hour average concentrations).

Fig 14a

Fig 14b

Annual average and 24-hour (98th percentile 24-hour concentrations) PM2.5 concentrations in µg/m3, 2007.
Fig 15 Trends in annual, cool months (October–April), and warm months (May–September) average PM2.5 concentrations, before and after adjusting for weather, and the location of urban monitoring sites used in the average.
Fig 16 Regional and seasonal trends in annual PM2.5 composition in µg/m3, 2002-2007.
Fig 17 National PM10 air quality trend, 2001-2007 (second maximum 24-hour concentration).
Fig 18 Change in PM10 concentrations in µg/m3, 2001-2003 vs. 2005-2007 (3-year average of annual average concentrations).
Fig 19 PM10 concentrations in µg/m3, 2007 (second maximum 24-hour concentration).
Lead
Fig 20 National lead air quality trend, 2001-2007 (maximum 3-month average).
Fig 21 Lead concentrations in µg/m3, 2007 (maximum 3-month averages).
NO2, CO, AND SO2
Fig 22 National NO2 air quality trend, 2001-2007 (annual average).
Fig 23 National CO air quality trend, 2001-2007 (second maximum 8-hour average).
Fig 24 National SO2 air quality trend, 2001-2007 (annual average).
Toxic Air Pollutants
Fig 25 Estimated county-level cancer risk from the 2002 National Air Toxics Assessment (NATA2002). Darker colors show greater cancer risk associated with toxic air pollutants.
Fig 26 Distribution of changes in ambient concentrations at U.S. toxic air pollutant monitoring sites, 2000-2005 (percent change in annual average concentrations). (Source: McCarthy M.C., Hafner H.R., Chinkin L.R., and Charrier J.G. [2007] Temporal variability of selected air toxics in the United States. Atmos. Environ. 41 [34], 7180-7194)
Fig 27 Toxic air pollutant monitoring sites operating in 2007 (by monitoring program).
Atmospheric Deposition

Fig 28a

Fig 28b

Fig 28c

Fig 28d

Three-year average deposition of sulfate (wet SO42-) and nitrate (wet NO3-) in 1989-1991 and 2005-2007. Dots show monitoring locations. (Data source: National Atmospheric Deposition Program, http://nadp.sws.uiuc.edu/)
  National Atmospheric Deposition Program/Mercury Deposition Network, 2006
Visibility in Scenic Areas
Fig 29 Trends in visibility on the 20 percent worst and best visibility days, 1996-2006. (Source: htt p://www.nature.nps.gov/air/)
Fig 30 Glide path to natural conditions in 2064 for Shenandoah (deciviews). (Source: Visibility Improvement State and Tribal Association of the Southeast—VISTAS)

Visibility Bar Chart

Visibility Images

Visibility at Great Smoky Mountains National Park. (Source: Images from WinHaze Visual Air Quality Model, Air Resource Specialists, Inc. and Jim Renfro, Great Smoky Mountains National Park)
Climate Change and Air Quality
Fig 31 Domestic greenhouse gas emissions in teragrams of carbon dioxide equivalents (Tg CO2 eq), 1990-2006. (Source: http://epa.gov/climatechange/emissions/usinventoryreport.html)
Fig 32 Estimated changes in 1-hour daily maximum ozone concentrations (ppm) in the 2050s compared with those in the 1990s for the New York metropolitan area, under scenario M1 in which climate change alone drives changes in air quality. (Source: Knowlton K., et al. [2004] Assessing ozonerelated health impacts under a changing climate. Environ. Health. Perspect., 112: 1557-1563)
Fig 33 Frequency of Western U.S. forest wildfires compared to spring-summer temperature. (Source: Westerling A.L., et al. [2006] Warming and earlier spring increase western U.S. forest wildfire activity. Science, 313: 940-943)
International Transport of Air Pollution
Fig 34 Major intercontinental transport pathways of CO emissions in the Northern Hemisphere. The colored boxes indicate the four source and receptor regions used in the Task Force on Hemispheric Transport of Air Pollution’s (HTAP) on-going model intercomparison study. The arrows approximate the magnitude of main transport pathways in summer (June, July, August) and winter (December, January, February), based on modelled average CO transport over 8–10 day periods. Light arrows indicate transport generally near ground level (less than 3 km above the surface) and dark arrows indicate transport higher in the atmosphere (more than 3 km above the surface). (Source: Figure E-1, HTAP 2007. Adapted from Figure 2 of Stohl and Eckhardt [2004], with kind permission of Springer Science and Business Media)

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