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New England Experienced More Smog Days During Recent Summer, But Long-Term Trend is Still Toward Cleaner Air

Release Date: 10/01/2007
Contact Information: David Deegan, (617) 918-1017

(Boston, Mass. – Oct. 1, 2007) – As the 2007 summer ozone season comes to an end, EPA today confirmed that New Englanders experienced a modest increase in the number of poor air quality days this year, compared to 2006. The increase in number of days with reduced air quality is related to hot weather experienced throughout the region during the summer.

Based on preliminary data collected between May and September, there were 26 days when ozone monitors in New England recorded concentrations above levels considered healthy. By contrast, in 2006 there were a total of 16 unhealthy ozone days. Over the longer term, however, the air quality in New England continues to improve.

The number of unhealthy ozone days in each state this summer were as follows: 17 days in Connecticut (compared to 13 in 2006); 20 days in Massachusetts (11 in 2006); 8 days in Rhode Island (3 in 2006); 8 days in Maine (2 in 2006); 6 days in New Hampshire (2 in 2006); and 1 day in Vermont (none in 2006). Ground-level ozone, the main ingredient of smog, is unhealthy when average concentrations exceed 0.08 parts per million over an 8-hour period.

The increase in the number of days with unhealthy air this year was directly related to the increase in the number of hot days this year. Sunlight and high temperatures speed the formation of ground-level ozone smog; many areas of New England had more days exceeding 90 degrees this summer than during last summer. August and September were especially hot, dry and sunny for much of New England.

Although warm temperatures this summer led to an increase in unhealthy days, over the long-term New England has experienced a decreasing number of unhealthy ozone days. Also, peak ozone concentrations have decreased significantly over the last 30 years. In 1983, New England had 90 unhealthy days, compared with 26 this summer. Overall, peak ozone concentrations in New England have decreased by more than 20 percent since 1980.

Another measure of air quality in New England is the geographic extent of the unhealthy air quality. This is determined by counting the number of air quality monitors that recorded exceedances of EPA’s health-protective 8-hour ozone standard. A higher number of monitor exceedances means a more extensive area of unhealthy air quality. When comparing the 2007 ozone season to the 2001 ozone season, a New England summer with temperature data similar to this summer, the total number of monitored exceedances dropped from 349 in 2001 to 175 this past summer. This is an approximately 50 percent decrease in the number of areas exceeding the standard over this six year period.

“When we look back to the air quality conditions a generation ago, we can feel proud of the advances we have made in reducing pollution,” said Robert Varney, regional administrator of EPA’s New England regional office. “The unhealthy days we experienced this summer, however, remind us that our efforts to use cleaner cars and our commitment to reducing industrial emissions and conserving energy in our own daily lives, all measures that lower air pollution, must continue.”

Ground-level ozone (smog) is formed when volatile organic compounds (VOC) and oxides of nitrogen (NOx) chemically react in the presence of sunlight. Cars, trucks and buses give off the majority of the pollution that makes smog. Fossil fuel burning at electric power plants, which run at high capacities on hot days, gives off significant amounts of smog-making pollution. Gas stations, print shops, household products like paints and cleaners, as well as gasoline-powered lawn and garden equipment, also contribute to smog formation.

Exposure to elevated ozone levels can cause serious breathing problems, and aggravate asthma and other pre-existing lung diseases. It can also make people who are vulnerable more susceptible to respiratory infection.

EPA has taken a number of steps to further reduce air pollution. Since model year 2004, new cars, sport utility vehicles, pickup trucks, and minivans are meeting stringent new emission standards. The requirements are being phased in between 2004 and 2009 resulting in vehicles that are 77 to 95 percent cleaner than older models. The program also requires a 90 percent reduction in the sulfur content of gasoline, which is helping reduce emissions from all vehicles new and old. Also, beginning in 2007, EPA’s standards for new diesel engines for trucks and buses will reduce NOx and particulate matter emissions by 90 percent.

In addition, EPA has issued the Clean Air Interstate Rule to help reduce the transport of air pollution from power plants across state boundaries. When fully implemented, this rule will reduce power plant NOx emissions by over 60 percent and sulfur dioxide by over 70 percent from 2003 levels.

Although the 2007 ozone season is ending, pollution from small particles in the air is a year-round concern. The daily air quality index forecast will continue to be available at New Englanders can also sign up at this address to receive air quality alerts. These alerts are issued by e-mail, whenever necessary, to notify program participants when high concentrations of ground-level ozone or fine particles are predicted to occur, in their area.

Historical charts of unhealthy air days from 1983 through 2007 are available for each state on EPA New England’s web site at: A preliminary list of the unhealthy readings recorded this summer by date and monitor location, and corresponding air quality maps for each day, can be found at:

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