Regional Differences in Sources for Ozone and Particle Pollution
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Table of Contents
◊ Region 1: Maine, Vermont, New Hampshire, Massachusetts, Rhode Island, and Connecticut
◊Region 2: New York, New Jersey, and Puerto Rico
◊Region 3: Pennsylvania, Delaware, Maryland, Washington, D.C., West Virginia, and Virginia
◊Region 4: Kentucky, North Carolina, South Carolina, Georgia, Tennessee, Alabama, Mississippi, and Florida
◊Region 5: Ohio, Indiana, Michigan, Illinois, Wisconsin, and Minnesota
◊Region 6: Texas, Oklahoma, Arkansas, Louisiana, and New Mexico
◊Region 7: Nebraska, Kansas, Iowa, and Missouri
◊Region 8: Montana, North Dakota, South Dakota, Wyoming, Utah, and Colorado
◊Region 9: California, Nevada, Arizona, and Hawaii
◊Region 10: Washington, Oregon, Idaho, and Alaska
The Full Report
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Introduction
Ozone requires the right mix of two essential groups of gases: volatile organic compounds (VOCs) and nitrogen oxides (NOx). When those gases are combined in sunlight with the right amount of heat, ozone forms. Particle pollution (PM2.5) can be formed directly by mechanical processes, such as dust is formed by wind action on soil and rocks, but it is frequently formed by chemical reactions in the atmosphere. For more discussion on the formation of these two pollutants, see the chapter "Health Effects of Ozone and Particle Pollution."
However, the sources of these pollutants, the success at reducing them and the complications of pollution transported by the winds vary from region to region. The following analysis looks at the sources, trends and transport of ozone and particle pollution in each of the ten regions that EPA uses to group the states.
National Sources of Ozone and Particle Pollution
All the data on emissions of VOCs, NOxand PM2.5 in this appendix were obtained from the U.S. EPA's National Emissions Trends Tier reports for 1999 inventoried data. Those data include emissions not only from individual facilities (called point sources), but also from so-called area sources that include many small, individual sources (like cars or residences) and sources that cover a large geographic area, such as wildfires. The data are estimated annually, but the sources are inventoried only every three years. The 1999 data are the most current based on inventories of sources. The data are available here.
The National Emissions Trend Tier data were sorted by region, by major source category, and by pollutant for this discussion. A brief description from EPA follows to explain each of the major source categories. Omitted from this discussion are those sources that are not anthropogenic, or not generated by human activity, 1 including fugitive dust in the discussion of particle pollution and isoprenes from vegetation in the discussion of VOC sources.
What do the categories in these pie charts mean?
| Category |
Includes these activities or sources
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| Electric Utility Fuel Combustion |
Power plants that produce electricity
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| Industrial Fuel Combustion |
Boilers and other processes that burn fuel at industrial plants
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| Other Fuel Combustion |
Residential woodstoves and fireplaces; other processes burning fuel in residential, commercial and institutional settings
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| Chemicals and Allied Products |
Industries that produce chemicals and related products
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| Metals Production |
Industries that produce metals and metal products
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| Petroleum and Related Products |
Rubber and plastics production; oil and gas production; petroleum refining
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| Other Industrial Production |
Agriculture, food, and related products; wood, pulp, and paper; machinery, mineral products
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| Solvent Use |
Graphic arts, dry cleaning, surface coating, degreasing processes, pesticide applications
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| Storage and Transport |
Storage and transport of petroleum and petroleum products, including service stations and bulk terminals and plants and organic chemicals, rail and tank car cleaning
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| Waste Disposal and Recycling |
Wastewater treatment; treatment, storage and disposal facilities; incineration, open burning; scrap and waste materials; landfills
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| Highway Vehicles |
Cars, buses, trucks
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| Off Highway Vehicles |
Recreational vehicles, construction equipment, marine, rail
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| Miscellaneous |
Cooling towers, firefighter training, engine testing, forest fires, slash/prescribed burning
| Source: EPA, Handbook for Criteria Pollutant Inventory Development: A Beginners Guide for Point and Area Sources, 1999.
Ozone Trends
Nationally, we have seen a significant improvement in the past 20 years in monitored ozone levels with a decline of 14 percent between 1983 and 2002.2 The EPA map below shows that the success has varied greatly by region. The most successful improvement is Region 9, with the steepest drop of 29 percent led by California's stringent controls. The most surprising trend is the increase of 2 percent in the Northwest in Region 10. More ominously, if this map depicted trends for the period 1990-1999 only, EPA reports a 4 percent increase in ozone levels between 1993 and 2002 across the nation, though they report that this increase is not statistically significant. Even accepting EPA's determination that this is not a significant change, the stagnation in the ozone trend is clear. Furthermore, when EPA analyzed the 1983 to 2002 trend for 53 metropolitan areas and adjusted the data for the influences of local weather patterns, the trend remained flat.3
The trend data by region covers 1991-2000, which is the latest made available by EPA in its annual Trends report. The largest decline in ozone concentrations between 1991 and 2000 came in Region 1, with a decline of nearly 22 percent, followed by Region 2 with a 17.4 percent drop, and Region 9 with 14.4 percent decline. Region 6 had the largest increase in that decade, with 8.9 percent increase in monitored ozone levels, while two other regions (7 and 8) also increased monitored 8-hour ozone emissions. Compared to the trend findings reported in the American Lung Association State of the Air: 2003, several regions showed a positive turn-around: for example, Region 4 which had increased by 9 percent between 1990-1999, showed a drop of 12 percent between 1991 and 2000. Region 5 had increased ozone levels by 7 percent between 1990-1999, showed a drop of 11.5 percent between 1991 and 2000. Some of this monitored volatility is likely due to meteorological changes.4 For more discussion of the differences in 8-hour ozone trends, see the descriptions below for each region.
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Note on Regional Trends
Because air quality monitors are concentrated in urban locations, it is not possible, strictly speaking, to describe accurately average ozone or PM 2.5 concentrations across as large an area as an EPA Region. EPA includes this reminder in its discussion of the trend data: "These trends are influenced by the distribution of monitoring locations in a given region and, therefore, can be driven largely by urban concentrations. For this reason, they are not indicative of background regional concentrations". 5 For more discussion on regional trends, see EPA's annual National Air Quality and Emissions Trends Report, 2003. |
The Transport of Pollution
By their nature, ozone and much of the particle pollution are created in the atmospheric mixing bowl and carried by prevailing winds to areas often far beyond their sources. Section 110 of the Clean Air Act recognizes the impact of pollution transported across political boundaries, by requiring communities to prevent sources from "contributing significantly" to downwind areas. When that doesn't work, Section 126 of the Act allows downwind states to petition EPA to step in and act to reduce industrial pollution from upwind sources.
The most comprehensive effort to reduce transported ozone is currently in progress. Years of study in the 1990s had identified significant sources of NOx, largely from electric power plants, which were contributing to the ozone levels in much of the Northeast. At the request of 8 Northeastern states, EPA issued a rule in September 1998 targeting most of the eastern United States, a requirement commonly referred to as the NOx SIP call.6 This rule required 22 states and the District of Columbia to significantly reduce NOx emissions by May 1, 2003, a date that was later extended to May 31, 2004 by court action for most of the states.7 The states included in the requirement are: Alabama, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Massachusetts, Maryland, Michigan, Missouri, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, Wisconsin, and West Virginia.
Pollution is also transported across national borders. For example, ozone is produced south and west of the New England states in the Ohio Valley and in the Canadian "Windsor-Quebec Corridor." In those two areas, heavy concentrations of power plants and transportation corridors produce ozone, which is carried into New England and the Mid-Atlantic states (EPA Regions 2 & 3), as well as into New Brunswick and other Canadian provinces.8
Not only does pollution move into a state from the outside, it also moves within the state. For example, some air pollution episodes have been followed hour-by-hour as they move up downwind from city to city within Pennsylvania.9 In many cases, the highest levels of ozone will show up in suburban areas downwind of larger communities. For example, even though an area such as San Francisco County in California may not be experiencing high ozone readings, it may be contributing to poor air quality in outlying areas such as the Sacramento and San Joaquin Valley areas to the East and other parts of the Bay Area to the south.10
There are some regions that are notable as sources of transported pollutants affecting cities and states within the region and outside it. The Southeast (EPA Region 4) and the Midwest (EPA Region 5) are two. The Southeast is home to some of the most polluting power plants in the nation11 and to cities with extremely high driving rates. Atlanta residents average 37.6 miles per day; Birmingham, 35.6; and Asheville, North Carolina, 47.5 -- all of them much higher than the traditionally car-dependent Los Angeles, whose residents average only 22.2 miles each day.12 As a result, the Southeast produces more NOx emissions (5.4 million short tons in 1999), VOC emissions (4.15 million short tons) and particle pollution (830,992 short tons) than any other section of the country.
The Midwest (EPA Region 5) is another region with many of the nation's most polluting coal-fired power plants, including 8 of the top 20 NOx emitting facilities in the nation in 1999.13 This region produces the second highest NOx emissions, 4.98 million short tons, the second highest VOC emissions, 3.5 million short tons, and the second highest particle pollution emissions, 679,792 short tons, in 1999. 14
National Sources of VOC Emissions
According to the 1999 inventory of emissions, which is the latest inventory data available, transportation sources accounted for the bulk of emissions of VOCs, totaling nearly half (47%) of the emissions between the highway vehicles and the off-highway vehicles. Solvent use accounted for over one-quarter (27%) of VOC emissions. All other categories made up the remaining quarter, led by storage and transportation uses at 7 percent.
National Sources of NOx
Transportation also comprised over half the sources of NOx emissions in the 1999 inventory as well, with highway vehicles producing 33 percent and offhighway generating another 22 percent. However, electric utilities generated nearly one-quarter of the total, at 23 percent. The remaining quarter was led by industrial fuel combustion at 12 percent.
National Sources of Particle Pollution (PM 2.5)
Not including fugitive dust sources, over 4.5 million short tons of particle pollution were produced nationwide in 1999. Categorized as miscellaneous, together, other combustion, and agriculture and forestry comprised 47 percent of all particle pollution or nearly 2.2 million short tons, the largest source of particle pollution emissions in the nation. Nationwide, the next largest categories of particle pollution emissions sources are other fuel combustion (12%), waste disposal and recycling (10%), off-highway vehicles (7%), and industrial fuel combustion (6%).
State of the Air: 2004 Home
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