Middlesex, Massachusetts Air Quality
Middlesex County, Massachusetts (MA)
↑ Worseningover 10 years
10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days). Air quality in this area has been declining over the past decade.
Air Quality Day Breakdown
Number of days per year in each EPA AQI category. Green = Good (AQI 0-50), Yellow = Moderate (51-100), Orange = Unhealthy for Sensitive Groups (101-150), Red = Unhealthy or worse (151+).
Year-by-Year Data
| Year | Median AQI | 90th Pct | Max AQI | Good Days | Moderate | Unhealthy+ | Pollutant |
|---|---|---|---|---|---|---|---|
| 2023 | 39 | 57 | 101 | 281 | 83 | 1 | Ozone |
| 2022 | 38 | 54 | 90 | 310 | 55 | 0 | Ozone |
| 2021 | 37 | 55 | 153 | 299 | 64 | 2 | PM2.5 |
| 2020 | 39 | 54 | 93 | 306 | 60 | 0 | PM2.5 |
| 2019 | 41 | 54 | 80 | 289 | 75 | 0 | PM2.5 |
| 2018 | 38 | 54 | 97 | 308 | 57 | 0 | Ozone |
| 2017 | 33 | 44 | 105 | 341 | 14 | 1 | Ozone |
| 2016 | 33 | 46 | 100 | 341 | 21 | 0 | Ozone |
| 2015 | 33 | 46 | 119 | 345 | 16 | 1 | Ozone |
| 2014 | 32 | 46 | 97 | 338 | 19 | 0 | Ozone |
What This Means for Middlesex County Residents
Middlesex, Massachusetts has received an Air Quality Grade of C (60/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 39 falls in the "Good" range.
Concerning trends show air quality has been declining, with the median AQI rising by 7 points over the monitoring period. This could be driven by increased development, wildfire smoke, or industrial activity.
The primary pollutant affecting this area is Ground-Level Ozone. Over the past 5 years, this area has averaged 1 unhealthy air quality days per year — days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity. The American Lung Association's State of the Air report provides additional context on long-term health risks from air pollution exposure.
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Frequently Asked Questions
Middlesex, Massachusetts has a current median AQI of 39, which falls in the "Good" range. The area has received an Air Quality Grade of C (60/100) based on 10 years of EPA monitoring data.
Air quality in Middlesex, Massachusetts is worsening over the past decade. The median AQI has changed by +7 points from 2014 to 2023.
Middlesex, Massachusetts averages 1 unhealthy air quality days per year over the past 5 years. On these days, sensitive groups including children, the elderly, and those with respiratory conditions should limit outdoor activity.
The primary pollutant affecting Middlesex, Massachusetts is Ground-Level Ozone. This is the dominant contributor to elevated AQI readings in the Middlesex County area.
Middlesex, Massachusetts averages 1 unhealthy air days per year. This is relatively low, making it a reasonable choice for asthma sufferers. The primary pollutant is Ground-Level Ozone, which is a known asthma trigger.
With a median AQI of 39 (Good), outdoor exercise in Middlesex, Massachusetts is generally safe year-round. Middlesex, Massachusetts averages 1 days per year when athletes should move workouts indoors.