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EPA's End-of-Season Ozone Data Show Decrease in Bad Air Days

Release Date: 10/04/2000
Contact Information: Amy Miller (617) 918-1042

BOSTON -- The U.S. Environmental Protection Agency announced this week that unseasonably cool weather this summer resulted in a decrease in the number of unhealthy air days experienced throughout New England.

Based on preliminary data, there were 20 days when ozone monitors in New England recorded concentrations above the level considered healthy. Last summer, there were a total of 35 unhealthy days. Ground level ozone, the main ingredient of smog, is unhealthy when average concentrations exceed .08 parts per million over an eight-hour period.

The number of unhealthy days in each state this summer were as follows: 15 days in Connecticut (compared to 33 in 1999); 5 days in Massachusetts (22 in 1999); 8 days in Rhode Island (13 in 1999); 3 days in Maine (10 in 1999); 1 day in New Hampshire (9 in 1999); and 1 day in Vermont (2 in 1999).

The long term trend in the number of unhealthy days in New England also continues downward. Historical charts of unhealthy air days are available for each state on EPA New England's web site at A table of ozone exceedances for the summer of 2000 by date and monitor location is also available at

Progress in reducing the number of unhealthy days has been made as a result of air pollution control programs, such as vehicle inspection and maintenance, that have been implemented in the region. The fact that New England still experiences unhealthy days during a relatively cool summer, however, indicates that there is still work to be done in curbing air pollution.

"When we look back to the air quality conditions a generation ago, we can feel proud of the advances we've made in reducing pollution," said Mindy Lubber, EPA's New England Administrator. "The fact that we still see unhealthy days during cool summers, however, reminds us that our efforts for cleaner cars and fuels and our commitment to controlling power plants in the east and midwest must continue."

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

Ground-level ozone (smog) is formed when volatile organic compounds and oxides of nitrogen interact 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, particularly on hot days, give off a lot of smog-making pollution. Gas stations, print shops, household products like paints and cleaners, as well as lawn and garden equipment, also contribute to smog formation.

Further air quality improvements are expected from tougher tailpipe emission standards for cars and light-duty trucks, including sport utility vehicles (SUVs), and limits on the amount of sulfur in gasoline scheduled to begin in 2004. In addition, EPA has taken aggressive steps to reduce pollution from power plants upwind of New England. These actions will result in an additional reduction of approximately 900,000 tons of nitrogen oxides from power plants in the eastern United States by 2004.

To inform New Englanders about ozone levels, EPA maintains an ozone mapping system that shows "real-time" images and daily forecasts of ground-level ozone levels. The daily ozone forecast is available from May through September on the EPA's Wide Web air pollution information page at Citizens can also sign up at this web address to receive free smog alerts from EPA's New England office.