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Air quality alert extended for another day in 4 western Mass. counties due to Canadian wildfires

Haze dimmed the morning sun Tuesday in Boston. Air quality alerts from Canadian wildfires were continuing Wednesday.Joanne Rathe/Globe Staff

Western Massachusetts is in for another day of smoky skies and potential health risks on Thursday, prompting state officials to extend an air quality alert for another day in Berkshire, Franklin Hampshire, and Hampden counties.

The alert will remain in effect from midnight to 11:59 p.m. Thursday, the state Department of Environmental Protection said in an e-mail Wednesday night.

The DEP already had issued a statewide air quality alert, effective until midnight, and warned that sensitive groups and, in some areas everyone, should reconsider heavy outdoor exertion.

The levels of fine particulate pollution, or PM2.5, will on average be in the “Unhealthy for Sensitive Groups” range in much of the state Wednesday, the DEP said.


Western sections of the state were likely to be hit hardest, with the more dangerous “Unhealthy” level “likely at times,” the agency said.

See the smoke forecast through Friday morning
Smoke forecast through Friday morning. (NOAA)

PM2.5 pollution is fine particulate matter that is 2.5 microns or less in width, or about 30 times thinner than the width of a single hair. PM2.5 pollution is caused by power plants, motor vehicles, burning wood or heating oil, and some industrial processes. It can be produced indoors by smoking, cooking, burning candles, and operating fireplaces.

When levels are in the Unhealthy for Sensitive Groups range, people with “heart or lung disease such as asthma, older adults, children, teenagers, and people who are active outdoors ... should reduce prolonged or heavy outdoor exertion, take more breaks and do less intense activities, and follow asthma action plans and keep quick relief medicine handy. Watch for symptoms such as coughing or shortness of breath,” the DEP said.

When levels are in the Unhealthy range, “everyone may begin to experience health effects,” the agency said.

“People in sensitive groups should avoid prolonged or heavy outdoor exertion and consider moving indoors or rescheduling,” DEP said. “Those with asthma should keep quick relief medicine handy. Everyone else should reduce prolonged or heavy outdoor exertion and take more breaks and do less intense activities.”


The National Weather Service said in a online posting early Wednesday that according to the latest computer modeling, a plume of smoke from Canadian fires will enter western and central Massachusetts Wednesday afternoon and arrive in Rhode Island and eastern Massachusetts in the evening. Visibilities may drop due to the haze and people may smell smoke, forecasters said.

“As bad as the smoke and air pollution was on Tuesday, the air quality can be even worse at times across parts of the Northeast on Wednesday,” AccuWeather Chief Meteorologist Jonathan Porter said in a statement. The smoke outbreak was the worst in more than 20 years, the company said.

On Wednesday evening, a national map of air pollution levels showed Unhealthy levels had reached the western edge of the state, with Unhealthy for Sensitive Groups and moderate readings to the east. In Boston, the smoke appeared to have cleared, data show.

Data from citizen sensors collected by showed the same pattern. (Note: the Unhealthy range begins at a PM 2.5 reading of 151.)

Hundreds of wildfires have been burning in eastern Canada for weeks. The smoke arrived Tuesday over parts of the Northeast and Midwest. The National Weather Service said the smoke that arrived in Southern New England Wednesday came from wildfires in Quebec.


On Tuesday night, pollution reached levels typical in a smoggy, traffic-choked megacity like Jakarta or New Delhi but rare in New York City.

New York Gov. Kathy Hochul said 1 million N95 masks would be available at state facilities. New York City Mayor Eric Adams told residents of the United States’ most populous city to limit outdoor activities and parks officials closed beaches as smoke smudged out the skyline.

The Federal Aviation Administration paused some flights bound for LaGuardia Airport and slowed planes to Newark Liberty and Philadelphia because the smoke was limiting visibility. Flights were delayed from Boston Logan International to New York airports. It also contributed to delayed arrivals at Dulles International Airport outside Washington, where a heavy haze shrouded the Washington Monument and forced the cancellation of outdoor tours.

Major League Baseball put off games in New York and Philadelphia, and even an indoor WNBA game in Brooklyn was called off.

Pollution is expected to return to moderate levels in Massachusetts on Thursday.

Tonya Alanez of the Globe Staff contributed to this report. Material from Globe wire services and prior Globe stories was also used.

Martin Finucane can be reached at