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New England Experienced Fewer Unhealthy Air Quality Days During 2019 Ozone Season

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David Deegan (

BOSTON – The U.S. Environmental Protection Agency (EPA) today confirmed that New England states experienced fewer days with unhealthy air quality this year, compared to 2018. Based on preliminary data collected between March and September 2019, there were 24 days when ozone monitors in New England recorded ozone concentrations above levels considered healthy. In 2018 there were 28 unhealthy ozone days in New England.

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

  • 21 days in Connecticut (compared to 23 in 2018)
  • 5 days in Massachusetts (12 in 2018)
  • 2 days in Rhode Island (12 in 2018)
  • 1 day in New Hampshire (6 in 2018)
  • 1 day in Maine (3 in 2018)
  • 0 days in Vermont (1 in 2018).

"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. "There is still work to be done, as especially in some parts of southern New England, we continue to experience too many days with unhealthful air quality."

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 emit most of the pollution that makes ozone. Fossil fuels burning at electric power plants, which run at high capacities on hot days, 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 2019, a cool, wet spring lead into an average New England summer. 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 24 this year. This downward trend is due to a reduction in emissions that form ozone. Although the 2019 ozone season is ending, pollution from small particles in the air is a year-round concern.

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