Ozone Monitoring Season Ends with Lowest Number of Unhealthy Air Days since Monitoring Began

With the conclusion of the 2020 Ozone Monitoring Season, the Massachusetts Department of Environmental Protection (MassDEP) announced that Massachusetts recorded three unhealthy ozone days, the fewest since ozone monitoring began in the 1970s. Also known as “exceedance days,” all three unhealthy air days occurred in late July and affected areas along the SouthCoast, Cape Cod and the Islands. The rest of the state experienced no unhealthy air days during the ozone monitoring season, which runs from March through September. One of the monitoring stations is in Lynn.

“While we still have work to do, the continual decline in ozone levels and unhealthy days is welcome news, providing health benefits to citizens across the Commonwealth,” said Energy and Environmental Affairs Secretary Kathleen Theoharides. “The Baker-Polito Administration remains committed to building on this progress and continuing our efforts to reduce emissions to combat climate change while improving air quality and public health.”

“Massachusetts remains committed to improving our air quality because it helps those who are most sensitive to air pollution, including children, older adults, and those with respiratory ailments,”said MassDEP Commissioner Martin Suuberg. “Fewer emissions from vehicles, power plants and other emitters, as well as the implementation of cleaner and greener renewable energy sources, provide increasing environmental and health benefits to citizens across the state.”

An exceedance day is when any one of the Commonwealth’s 17 ozone monitoring locations record a maximum 8-hour average ozone concentration above 70 parts per billion (ppb), a level that was made more stringent in 2015. Exceedance days were recorded on July 27 at monitoring stations in Fall River (73), Fairhaven (76), Truro (73) and Aquinnah, Martha’s Vineyard (78); on July 28 at Fairhaven (72) and Truro (71); and on July 30 at Fall River (71).

This ozone season, Massachusetts did not experience its first exceedance day until July 27, the furthest into the ozone season without an exceedance since 2014. The Commonwealth also recorded 14 fewer exceedances days than neighboring Connecticut, five fewer than New York and one less than Rhode Island.

Overall, Massachusetts continues to see a downward trend in ozone exceedance days (see chart below) after recording five in 2019 and well-below the all-time high of 56 in 2002, based on an 8-hour average, which began to be used as a standard in 1998.

Ozone is produced when heat and sunlight react with air pollutants. Numerous scientific studies have linked ozone exposure to coughing and throat irritation; increased sensitivity to allergens; uncomfortable sensations in the chest; lung-lining inflammation; and reduced lung function. When ground-level ozone reaches unhealthy levels, children are at highest risk because they tend to spend a lot of time playing outdoors in warmer weather and are more likely to have asthma. People with respiratory diseases are also vulnerable, even at lower ozone levels.

MassDEP measures outdoor air quality at more than 20 monitoring stations across the state and measures ozone at 16 – Boston, Brockton, Chelmsford (two sites), Chicopee, East Milton-Blue Hills, Fairhaven, Fall River, Greenfield, Haverhill, Lynn, Pittsfield, Truro, Uxbridge, Ware, and Worcester. The Wampanoag Tribe of Gay Head also measures ozone at a station in Aquinnah on Martha’s Vineyard. To get daily air quality updates and forecasts or learn more about the statewide air monitoring network, visit MassDEP’s air monitoring website MassAirLive here. MassDEP is responsible for ensuring clean air and water, safe management and recycling of solid and hazardous wastes, timely cleanup of hazardous waste sites and spills and the preservation of wetlands and coastal resources.

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