AIR QUALITY MA

Air Quality in Boston, MA: Good (42 AQI)

AQI 42 · Good · PM2.5 · Updated 2026-05-03

Boston's air quality is good. Air pollution poses little or no risk.

Data: EPA AirNow, FEMA National Risk Index Last verified: 2026-05-03

Average AQI

Good

AQI Category

Wildfire Risk

Mold Score

ZIP Codes

What is AQI?

The Air Quality Index (AQI) is a standardized scale from 0 to 500 that measures air pollution levels. 0-50 is "Good," 51-100 is "Moderate," 101-150 is "Unhealthy for Sensitive Groups," and above 150 is "Unhealthy" for everyone. AQI tracks five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Boston's average AQI of 42 falls in the "Good" range.

How do wildfires affect air quality?

Wildfire smoke contains fine particulate matter (PM2.5) that can travel hundreds of miles and dramatically spike AQI readings. During fire season, even cities far from active fires can experience unhealthy air. HEPA air purifiers (rated for PM2.5) are the most effective indoor protection. Check AirNow.gov for real-time conditions during fire season.

Air Quality Map: Boston, MA

Each dot represents a ZIP code. Color indicates AQI level. Tap a dot for details.

Good (0-50) Moderate (51-100) USG (101-150) Unhealthy (151+)

Air Quality by ZIP Code in Boston

AQI varies across Boston's 38 ZIP codes based on proximity to pollution sources and local geography.

ZIP Code	AQI	Category	Wildfire	Mold
02108	42	Good	22	59	View report →
02109	42	Good	22	62	View report →
02110	42	Good	22	51	View report →
02111	42	Good	22	36	View report →
02112	42	Good	22	35	View report →
02113	42	Good	22	59	View report →
02114	42	Good	22	53	View report →
02115	42	Good	22	62	View report →
02116	42	Good	22	62	View report →
02117	42	Good	22	35	View report →
02118	42	Good	22	62	View report →
02123	42	Good	22	35	View report →
02127	42	Good	22	59	View report →
02128	42	Good	22	62	View report →
02133	42	Good	22	53	View report →

Showing 15 of 20 ZIP codes. View all.

Air Quality Overview

Boston, Massachusetts has good air quality with an average AQI of 42. This means air pollution poses little or no risk. The dominant pollutant measured is PM2.5.

The Air Quality Index (AQI) is an EPA-standardized scale from 0 to 500. Values below 50 are "Good," 51-100 "Moderate," 101-150 "Unhealthy for Sensitive Groups," 151-200 "Unhealthy," 201-300 "Very Unhealthy," and above 300 "Hazardous."

Dominant Pollutant: PM2.5

PM2.5 (fine particulate matter) consists of particles smaller than 2.5 micrometers — about 30 times thinner than a human hair. These particles can penetrate deep into the lungs and enter the bloodstream.

Health effects of PM2.5 exposure:

Short-term: coughing, shortness of breath, aggravated asthma
Long-term: reduced lung function, cardiovascular disease, premature death
Most vulnerable: children, elderly, people with heart or lung disease

Common sources in urban areas: vehicle exhaust, construction dust, industrial emissions, wildfire smoke, residential wood burning.

Air Quality by ZIP Code in Boston

AQI varies across Boston's 38 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:

ZIP Code	AQI	Category	Wildfire Risk	Mold Score
02108	42	Good	22	59
02109	42	Good	22	62
02110	42	Good	22	51
02111	42	Good	22	36
02112	42	Good	22	35
02113	42	Good	22	59
02114	42	Good	22	53
02115	42	Good	22	62
02116	42	Good	22	62
02117	42	Good	22	35
02118	42	Good	22	62
02123	42	Good	22	35
02127	42	Good	22	59
02128	42	Good	22	62
02133	42	Good	22	53

Showing 15 of 38 ZIP codes. Check your specific ZIP for detailed data.

Wildfire Smoke Risk

Boston has an elevated wildfire smoke risk with an average smoke risk score of 22 (scale 0-100). There have been 69 fires recorded within 100 km of city ZIP codes.

Metric	Value
Avg. smoke risk score	22
Max smoke risk score	22
Fires within 100 km	69
High-risk ZIP codes	0

Wildfire smoke contains PM2.5, carbon monoxide, and volatile organic compounds. Even short-term exposure can trigger asthma attacks and respiratory distress.

Indoor Mold Risk

Boston has an average mold risk score of 43 out of 100, with 9 ZIP codes in the high-risk category.

Factor	Value
Mold risk score	43/100
Average humidity	67% RH
High-risk ZIPs	9
Peak season	summer high

Mold risk is influenced by humidity levels, housing age (older homes have more moisture issues), flood history, and water infrastructure quality. Indoor humidity above 60% creates favorable conditions for mold growth.

Signs of mold problems: musty odors, visible growth on walls or ceilings, worsening allergies indoors, condensation on windows. Professional mold testing ($300-$600) can identify hidden issues.

Health Recommendations

With good air quality (AQI 42), Boston residents can enjoy outdoor activities without significant restrictions. General tips:

Monitor AQI during wildfire season for temporary spikes
Use HEPA air purifiers indoors if you have respiratory conditions
Maintain indoor humidity between 30-50% to prevent mold

Boston vs. Nearby Massachusetts Cities

How Boston's air quality compares to nearby cities:

City	AQI	Category	Population
Boston	42	Good	3,335,937
Chelsea	42	Good	2,698,319
Brookline Village	42	Good	2,660,000
Charlestown	42	Good	2,660,000

ZIP Codes in Boston

Boston covers 38 ZIP codes. Air quality can vary by neighborhood based on proximity to highways, industrial areas, and green spaces. Check your specific ZIP code for localized data.

Data Sources

Air quality: EPA AirNow — real-time and historical AQI data
Wildfire risk: FEMA National Risk Index
Mold risk: Derived from EPA, FEMA, Census ACS (humidity, housing age, flood history)
Monthly AQI: EPA Air Quality Statistics

Updated daily.

Frequently Asked Questions

Is the air safe to breathe in Boston?

Yes — Boston's average AQI is 42 (Good). Air pollution poses little or no risk for the general population.

How many unhealthy air days does Boston have?

Boston has zero recorded unhealthy air quality days, which is excellent. Air quality can still vary seasonally due to wildfire smoke, pollen, or industrial activity.

What is the AQI in Boston?

The average Air Quality Index (AQI) in Boston is 42, categorized as Good. The primary pollutant is PM2.5. AQI ranges from 0-500, where 0-50 is Good, 51-100 Moderate, 101-150 Unhealthy for Sensitive Groups, and 151+ Unhealthy.

What is the wildfire risk in Boston?

Boston has a wildfire risk score of 22 out of 100. Low wildfire risk means smoke events are uncommon, but regional fires can still temporarily affect air quality.

Is mold a concern in Boston?

Boston has a mold risk score of 43 out of 100, based on humidity, precipitation, and temperature data. Maintain good ventilation and address any water intrusion promptly to prevent mold growth.

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