Air quality in Massachusetts

Air quality index (AQI) and PM2.5 air pollution in Massachusetts

Last update at (local time)


Real-time Massachusetts
Most polluted city ranking

#cityUS AQI
1 Medfield


2 Attleboro


3 Hanson


4 Pepperell


5 Maynard


6 Oxford


7 Sherborn


8 Springfield


9 Greenfield


10 Uxbridge


(local time)



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Real-time Massachusetts
Cleanest city ranking

#cityUS AQI
1 Braintree


2 Chatham


3 Lawrence


4 Dracut


5 Nantucket


6 Stow


7 Townsend


8 Freetown


9 Harvard


10 Marblehead


(local time)


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Is Massachusetts a state with polluted air?

Massachusetts is a state located within the New England region of America, bordering on other states such as Connecticut, Rhode Island, New Hampshire and Vermont, as well as facing onto the Atlantic Ocean on its eastern side. It has a long history extending back to an era when the state was heavily dependent on the agricultural industry, as well as trade and fishing. Moving forward in time the state made a switch over to having a more industrialized based economy, and this has continued on until today, albeit with changes in the industries associated with Massachusetts.

In modern times the state sees itself having a prominent role in industries such as finance, maritime trade, engineering and biotechnology, as well as having a large amount of higher education facilities that attract students from all over the country, as well as abroad. The state is home to some 6.89 million people, with many new business startups constantly moving into the various cities across the state, causing consistent growth and further implementation of infrastructure, making Massachusetts to be considered as one of the best states in the entire country to live in (as well as one of the most expensive).

Whilst citizens can enjoy a good quality of life, with an ever growing population, coupled with large amounts of tourists and increases in areas of business and industry, there is an associated depreciation in the level of air quality, with the extra anthropogenic activity leading to widespread emissions of pollution, from a multitude of sources which will be discussed in short.

In 2020, to cite some of the cities with air pollution in Massachusetts, ones such as Townsend and Amesbury stood out. These came in with PM2.5 readings of 10.3 μg/m³ and 8.5 μg/m³ as their yearly averages respectively, placing Amesbury within the World Health Organizations (WHO's) target goal of 10 μg/m³ or less for the most optimal quality of air (with the closest to 0 of course being the end goal for perfect air quality), and Townsend in the 'good' ratings bracket (10 to 12 μg/m³ required).

Whilst these cities still came in within the two lowest target goals for the best quality of air, they had many months in which the PM2.5 count rose way higher, indicating that there are some prominent pollutive issues occurring within the state, particularly during certain months of the year. As such, Massachusetts could do much to improve the quality of its air, with the main emphasis being on seeing reductions in the big spikes of PM2.5 present at certain times of the year.

Why is there air pollution in Massachusetts?

As with many states throughout America, Massachusetts is subject to many of the same pollutive causes that are prevalent no matter what part of the country you may find yourself in. With its population of nearly 7 million people, it would mean that at any given time, there would be hundreds of thousands of vehicles on the road, with the number climbing up even higher during certain times of the day, in particular during rush hours or certain holidays.

This mass movement of people in their personal vehicles would put out large clouds of smoke and polluting haze, which can coalesce on the ground level as well as in the lower atmosphere, causing elevated PM2.5 readings and all manner of related health issues, due to the myriad of dangerous chemicals and hazardous particulate matter found in these areas. Another compounding factor is that of heavy duty vehicle use, namely trucks, lorries and buses.

With any amount of industry present within the city, there will always be a large amount of import and exportation happening, which requires the use of the aforementioned large vehicles. These typically run on diesel fuel, putting out far more pollution and particulate matter than regular vehicles do, with the different array of chemical pollutants being delved into in further detail in the following questions. Even the tire treads of vehicles can release tons of microscopic rubber particles into the air, showing just how prevalent the use of vehicles are on the air pollution levels present in Massachusetts and many other locations across the U.S.

Other prominent sources of pollution present in Massachusetts would be emissions from factories, power plants and other similar industrial zones. These areas often rely on fossil fuels such as coal or natural gas for their power, which in turn can release even more pollution into the atmosphere. The use of firewood, as well as the burning of charcoal can also add to the PM2.5 count, as well as forest fires occurring throughout the state, although these are not a constant occurrence, fortunately.

Lastly, construction sites, road repairs and any other similar excavation site that moves large amounts of earth can also release a huge amount of harmful particulate matter (PM2.5 and PM10) into the air, oftentimes far more than people are cognizant of. These are some of the main or most prominent causes of air pollution present in Massachusetts, with other ones being secondary sources of pollution whereby pollution already present in the air undergoes chemical reactions (under the right conditions) to form novel chemical pollutants.

When is the air quality at its worst in Massachusetts?

Observing the data taken over the course of 2020, Massachusetts came in with a PM2.5 reading of 7.2 μg/m³ and then again 7.2 μg/m³, recorded in the city of Townsend over the months of September and October. This city is being used as a prime example due to its high position amongst the most polluted cities found in the state. After these respectable readings of PM2.5 passed, the following month of November saw a sudden rise up to 11.3 μg/m³, and then a further reading of 11.8 μg/m³ in December, indicating that at the end of the year the pollution levels went up considerably, moving out of the WHO's target rating and into the ‘good’ air quality bracket. This requires a PM2.5 reading of anywhere between 10 to 12 μg/m³ to be classed as such.

Other months that came in with heightened readings were present in the earlier months of the year, with February and April coming in with readings of 13.6 μg/m³ and 12.7 μg/m³ in Townsend. Of significant note is that the months of February, July and November had the highest levels of pollution present throughout the state, seeing several large rises in the PM2.5 count across nearly every city. Townsend presented with a reading of 13.6 μg/m³ in February, whilst Amesbury came in with a PM2.5 reading of 11.5 μg/m³ in the same month. The most polluted month over the course of 2020 in Massachusetts was 24 μg/m³, recorded in Medfield city in November, a reading that placed it into the higher end of the ‘moderate’ pollution ratings bracket, which requires a PM2.5 reading of anywhere between 12.1 to 35.4 μg/m³ to be classed as such.

In closing, the late and early months of the year (namely, during wintertime) came in with higher readings of PM2.5. After this period was over, July also came in with a higher level of pollution, making all of the aforementioned time periods ones in which the air would be at its most permeated with smoke, haze and other polluting elements.

When is the air at its cleanest in Massachusetts?

In contrast to the previous question, the period of time between April and June, as well as August through to October was when the state saw its best readings of PM2.5 across all cities. To give some contrast, the city of Natick came in with a PM2.5 reading of 5.7 μg/m³ in April, and 4.5 μg/m³ in May, despite its July reading coming in at a much heftier 10.7 μg/m³, over two times higher than its cleanest months. During the aforementioned months, a large majority of the PM2.5 readings came in at 5 μg/m³ or below, indicating that these months are when the air quality would be at its best, and most free from smoke and contaminants.

What are the main pollutants found in the air in Massachusetts?

With much of its pollution arising from combustion sources, derived from both industry and anthropogenic movement, there would subsequently be a large amount of related pollutants found in the air. Some of the more common ones would be carbon monoxide (CO) and carbon dioxide (CO2), as well as ones released in extremely high quantities by vehicles, which include nitrogen dioxide (NO2) and sulfur dioxide (SO2).

Both of the last two pollutants can cause irritation to the respiratory tract, as well as inflammation to the lining of the lungs, triggering off asthma attacks and reducing full lung function, as well as a myriad of other health problems typically related to a person’s age or physical background. Other pollutants would be ones such as black carbon and volatile organic compounds (VOC's), both of which find their release from the incomplete combustion of fossil fuels, as well as organic material.

As such, they can find release from nearly all combustion sites, ranging from bonfires, to car engines and factory boilers. Black carbon is a potent carcinogen, making it an extremely harmful type of particulate matter to respire, along with other ones such as finely ground silica dust, often released from construction (or demolition) sites, along with dangerous metals such as mercury, lead and cadmium. Some examples of the previously mentioned VOC's include chemicals such as benzene, toluene, xylene, methylene chloride and formaldehyde.

Massachusetts air quality data attribution


Which is the most polluted city in Massachusetts?

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