Plymouth, Massachusetts Air Quality
Plymouth County, Massachusetts (MA)
→ Stableover 10 years
How Plymouth, Massachusetts Air Quality Compares
Plymouth, Massachusetts's median AQI of 40is 2% better than the national average of 41. Air quality has improved by 4 AQI points over the past decade. The area averages 1 unhealthy air days per year. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
Plymouth, Massachusetts Air Quality: The Full Picture
Plymouth, Massachusetts (Plymouth County) holds an AirHistory Air Quality Grade of C (fair, scoring 64 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 4 points between 2014 (44) and 2023 (40), and the five-year median now sits at 41 — inside the "Good" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Fine Particulate Matter (PM2.5). In 2023, it set the daily AQI on 155 of 365 monitored days (42% of the year), making it the controlling pollutant for the C grade. The single worst reading logged that year hit an AQI of 114 (Unhealthy for Sensitive Groups), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 58.
In 2023, Plymouth County recorded 278 "Good" air days (76% of the 365 days with valid AQI data), 83 "Moderate" days, and 4 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 6 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 1 per year.
The decade-long trend is essentially flat, with year-to-year median AQI shifting by less than 0.05 points per year on average. The cleanest year in the record was 2016 (median AQI 39), and the most polluted was 2022 (median AQI 45). Because the data come straight from federally certified EPA monitors, these figures track the Massachusetts county the monitors physically sit in rather than a city boundary.
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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 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 | 40 | 58 | 114 | 278 | 83 | 4 | Ozone |
| 2022 | 45 | 57 | 93 | 235 | 125 | 0 | PM2.5 |
| 2021 | 39 | 58 | 112 | 257 | 106 | 2 | PM2.5 |
| 2020 | 42 | 56 | 80 | 267 | 99 | 0 | PM2.5 |
| 2019 | 40 | 54 | 90 | 289 | 74 | 0 | Ozone |
| 2018 | 39 | 56 | 126 | 279 | 82 | 3 | Ozone |
| 2017 | 39 | 55 | 147 | 281 | 80 | 4 | Ozone |
| 2016 | 39 | 56 | 105 | 298 | 67 | 1 | Ozone |
| 2015 | 40 | 61 | 126 | 246 | 116 | 1 | PM2.5 |
| 2014 | 44 | 60 | 93 | 229 | 134 | 0 | PM2.5 |
What This Means for Plymouth County Residents
Plymouth, Massachusetts has received an Air Quality Grade of C (64/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 40 falls in the "Good" range.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). 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
Plymouth, Massachusetts has a current median AQI of 40, which falls in the "Good" range. The area has received an Air Quality Grade of C (64/100) based on 10 years of EPA monitoring data.
Air quality in Plymouth, Massachusetts is stable over the past decade. The median AQI has changed by -4 points from 2014 to 2023.
Plymouth, 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 Plymouth, Massachusetts is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the Plymouth County area.
Plymouth, Massachusetts averages 1 unhealthy air days per year. This is relatively low, making it a reasonable choice for asthma sufferers. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 40 (Good), outdoor exercise in Plymouth, Massachusetts is generally safe year-round. Plymouth, Massachusetts averages 1 days per year when athletes should move workouts indoors.