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News Releases from Region 01

New England Experienced Fewer Unhealthy Air Quality Days During 2020 Ozone Season

Contact Information: 
David Deegan (
(617) 918-1017

BOSTON – The U.S. Environmental Protection Agency (EPA) New England Regional office today confirmed that New Englanders experienced a decrease number of unhealthy air quality days this past summer, compared to 2019. Based on preliminary data collected between March and September 2020, there were 18 days when ozone monitors in New England recorded ozone concentrations above levels considered healthy. By contrast, in 2019 there were 23 unhealthy ozone days in New England.

The number of unhealthy ozone days in each state this summer, and for last summer are as follows:

  • 17 days in Connecticut (compared to 20 in 2019)
  • 3 days in Massachusetts (5 in 2019)
  • 4 days in Rhode Island (2 in 2019)
  • 0 day in New Hampshire (1 in 2019)
  • 1 day in Maine (1 in 2019)
  • 0 days in Vermont (0 in 2019).

"We can all feel proud of the progress we have made in reducing ozone pollution over the past several decades," said Dennis Deziel, Regional Administrator of EPA's Region 1 office. "Unfortunately, portions of New England, especially coastal Connecticut, continue to experience too many days with unhealthful air quality. EPA is taking steps to improve ozone air quality, such as implementing rules to reduce air pollution from passenger cars and trucks and power plants."


Ground-level ozone is formed when volatile organic compounds and oxides of nitrogen chemically react in the presence of sunlight. In New England, cars and trucks give off the majority of the pollution that makes ozone. Emissions from power plants, which run at high capacities on hot days generating electricity, also emit substantial amounts of ozone-making pollution. Gasoline refilling stations, print shops, household products like paints and cleaners, as well as gasoline-powered lawn and garden equipment, also contribute to ozone formation.

The number of unhealthy days (when ozone concentrations exceed the 0.070 parts per million standard) vary from year to year due to weather conditions. Hot, sunny, summery weather is conducive to ozone formation. For 2020, a cool, wet spring contributed to the record low number of exceedance days.

Since 1983, New England has experienced a decrease in the number of unhealthy ozone days. In 1983, New England had 118 unhealthy days compared with only 18 this year. This downward trend is due to a reduction in emissions that form ozone. Although the 2020 ozone season is ending, pollution from small particles in the air is a year-round concern.

More information:

EPA provides a free daily air quality forecast throughout the year 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 small particles are predicted to occur, in their area.

Historical charts of unhealthy air days from 1983 through 2020 are available for each New England 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: