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Making Progress on Ground-Level Ozone
Table of Contents
Ground-Level Ozone
Ground-level ozone is a gas that forms when emissions of NOX and VOCs react with other chemicals in the air in the presence of strong sunlight. NOX and VOCs are emitted by combustion sources (such as vehicles and power plants). VOCs are also given off by solvents, cleaners, and paints. Ground-level ozone can cause or exacerbate respiratory illnesses and is especially harmful to young children, the elderly, and those suffering from chronic asthma and/or bronchitis. Ground-level ozone can affect leaves and roots of plants, especially trees, which can make them more susceptible to attack from insects and diseases and can reduce their ability to withstand droughts, windstorms, and manmade stresses such as acid rain.
Key Commitments of the Ozone Annex
The commitments to reduce NOX and VOCs apply to a defined region in both countries known as the Pollutant Emission Management Area (PEMA), which includes central and southern Ontario, southern Quebec, 18 U.S. states, and the District of Columbia. The states and provinces within the PEMA are the areas where emission reductions are most critical for reducing transboundary ozone.
CANADA:
- The Ozone Annex commits Canada to new stringent NOX and VOC emission reduction standards for vehicles, engines, and fuels. By 2020, it is estimated that NOX and VOC emissions combined from on-road and off-road vehicles and engines in the Canadian portion of the PEMA will be reduced by 41 and 35 percent, respectively, compared to 2005 emissions.
- With regard to stationary sources, Canada is complying with its commitment to cap NOX emissions from large fossil fuelfired power plants in the Ontario and Quebec portions of the PEMA at 39 kt and 5 kt, respectively, for 2007.
- Canada has taken efforts to reduce VOC emissions by developing two regulations—one on dry cleaning and another on solvent degreasing—and using VOC emission limits for new stationary sources.
- The Canada-wide Standard (CWS) for ozone committed provincial jurisdictions to developing implementation plans outlining the comprehensive actions being taken within each jurisdiction to achieve the standards.
UNITED STATES:
- The Ozone Annex commits the United States to implementing the NOX transport emission reduction program, known as the NOX SIP Call, in the PEMA states that are subject to the rule.
- As of 2007, all affected states and the District of Columbia chose to meet the mandatory NOX SIP Call emission reductions primarily through participating in the NOX Budget Trading Program (NBP), a market-based cap and trade program.
- In the 2007 ozone season (May 1 to September 30), sources participating in the NBP emitted 506,312 tons of NOX (Figure 6).This is almost 5 percent below the 2007 allowable NOX emission level (total state trading budget).
Figure 6. Ozone Season NOX Emissions under the NOX Budget Trading Program
Source: EPA, 2008
- To help reduce emissions of NOX and VOCs from major new sources, EPA has promulgated New Source Performance Standards (NSPS) for the 36 categories of stationary sources identified in the Ozone Annex.
- To help reduce VOC emissions, EPA has promulgated regulations to control hazardous air pollutant emissions for the 40 categories of industrial sources listed in the Ozone Annex. Additionally, EPA has promulgated national rules for the control of VOCs in automobile repair coatings, consumer products, and architectural coatings.
- To address motor vehicle emissions, the United States committed to implementing regulations for reformulated gasoline, controls of emissions from new and in-use highway vehicles and engines, and controls and prohibitions on diesel fuel quality. EPA has applied engine standards for the five nonroad engine categories identified in the Ozone Annex.
Ambient Levels of Ozone
Under the Ozone Annex, the United States and Canada are required to report on the amount of ozone, NOX, and VOCs in the air we breathe (i.e., ambient concentrations) from all relevant monitors within 500 km of the border. Both countries have extensive networks to monitor ground-level ozone and its precursors, and both governments prepare routine reports summarizing measurement levels and trends. The latest reported data from both countries are for 2006.
Figure 7 illustrates that higher levels of ozone occurred in the Great Lakes and Ohio Valley regions, as well as downwind of urban areas.
Figure 7. Ozone Concentrations along the Canada–U.S. Border (Three-Year Average of the Fourth Highest Daily Maximum 8-Hour Average), 2004–2006
Note: Data contoured are the 2004–2006 averages of annual fourth highest daily values, where the daily value is the highest running 8-hour average for the day. Sites used had at least 75 percent of possible daily values for the period.
Source: Environment Canada National Air Pollution Surveillance (NAPS) Network Database, 2008 (www.etc-cte.ec.gc.ca/naps/index_e.html); EPA Aerometric Information Retrieval System (AIRS) Database (www.epa.gov/air/data/index.html)
Ambient Concentrations of Ozone, NOX, and VOCs
Figure 8 illustrates that ozone levels within the PEMA have decreased over time with a notable decline in ozone levels since 2002. Figures 9 and 10 depict the average ozone season levels of ozone precursors NOX and VOCs in the eastern United States and Canada. Although NOX and VOC concentrations have fluctuated over recent years, these fluctuations are most likely attributable to changes in weather conditions. Overall, the data indicate a downward trend in the ambient levels of both NOX and VOCs.
Figure 8. Annual Average Fourth Highest Maximum 8-Hour Ozone Concentration for Sites within 500 km of the Canada–U.S. Border, 1995–2006
Source: EPA and Environment Canada, 2008
Figure 9. Average Ozone Season 1-Hour NOX Concentration for Sites within 500 km of the Canada–U.S. Border, 1995–2006
Source: EPA and Environment Canada, 2008
Figure 10. Average Ozone Season 24-Hour VOC Concentration for Sites within 500 km of the Canada–U.S. Border, 1997–2006
Source: EPA and Environment Canada, 2008