Boston Air Quality in 2024
In 2024, Boston's air quality (Boston-Cambridge-Newton, MA-NH area) had a median daily AQI of 43 (Good) across 366 monitored days. 5 days (1.4%) reached Unhealthy for Sensitive Groups or worse, 256 were Good, and the year's peak AQI was 1513 (Hazardous). Ground-level ozone set the daily AQI on 222 of those days. The cleanest month of 2024 was September (median AQI 39, 0 days above 100) and the worst was November (median 43, 3 days above 100, peak 1513).
- Good: 69.9%
- Moderate: 28.7%
- Unhealthy for Sensitive Groups: 0.3%
- Unhealthy or worse: 1.1%
Reduce Indoor Ozone in Boston
Today's main pollutant in Boston is ground-level ozone (AQI 33). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
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How was Boston's air quality in 2024?
Good on a typical day: median AQI 43, with 5 days above AQI 100 out of 366 monitored — the 3rd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2024: 1513 (Hazardous).
- ✓Ground-level ozone was the main pollutant on 222 days.
- ✓Cleanest month: September; worst: November.
Frequently asked questions
What was the average AQI in Boston in 2024?▾
EPA's Air Quality System puts Boston's (Boston-Cambridge-Newton, MA-NH) median daily AQI for 2024 at 43, which is Good. 5 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 1513.
Which month had the worst air quality in Boston in 2024?▾
The cleanest month of 2024 was September (median AQI 39, 0 days above 100) and the worst was November (median 43, 3 days above 100, peak 1513).
Was 2024 a good or bad year for Boston's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 3rd cleanest by days above AQI 100. 2024's median of 43 is below the area's typical annual median of 48.
Boston month by month in 2024
Boston air quality month by month, 2024 (Boston-Cambridge-Newton, MA-NH, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 43 | 0 | 63 | PM2.5 |
| February | 29 | 42 | 0 | 63 | O3 |
| March | 31 | 41 | 0 | 60 | O3 |
| April | 30 | 45 | 0 | 58 | O3 |
| May | 31 | 43 | 0 | 93 | O3 |
| June | 30 | 49 | 1 | 122 | O3 |
| July | 31 | 54 | 0 | 97 | O3 |
| August | 31 | 52 | 0 | 87 | PM2.5 |
| Septembercleanest | 30 | 39 | 0 | 87 | O3 |
| October | 31 | 40 | 1 | 162 | O3 |
| Novemberworst | 30 | 43 | 3 | 1513 | PM2.5 |
| December | 31 | 39 | 0 | 73 | PM2.5 |
How 2024 compares
Among the 7 years EPA has published for the area (2019–2025), 2024 ranks 3rd cleanest by days above AQI 100.
2024's median of 43 is below the area's typical annual median of 48.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Boston
The latest EPA AirNow observation puts Boston's AQI at 33 (O3). The figures above are multi-year annual statistics, not today's reading.
View current Boston air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Boston-Cambridge-Newton, MA-NH), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.