Worcester Air Quality in 2019
In 2019, Worcester's air quality (Worcester, MA-CT area) had a median daily AQI of 45 (Good) across 365 monitored days. 1 day (0.3%) reached Unhealthy for Sensitive Groups or worse, 237 were Good, and the year's peak AQI was 105 (Unhealthy for Sensitive Groups). Fine particulate matter (PM2.5) set the daily AQI on 223 of those days. The cleanest month of 2019 was October (median AQI 34, 0 days above 100) and the worst was August (median 46, 1 day above 100, peak 105).
- Good: 64.9%
- Moderate: 34.8%
- Unhealthy for Sensitive Groups: 0.3%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Worcester
Today's main pollutant in Worcester is ground-level ozone (AQI 31). 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 Worcester's air quality in 2019?
Good on a typical day: median AQI 45, with 1 day above AQI 100 out of 365 monitored — the 4th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2019: 105 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 223 days.
- ✓Cleanest month: October; worst: August.
Frequently asked questions
What was the average AQI in Worcester in 2019?▾
EPA's Air Quality System puts Worcester's (Worcester, MA-CT) median daily AQI for 2019 at 45, which is Good. 1 day were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 105.
Which month had the worst air quality in Worcester in 2019?▾
The cleanest month of 2019 was October (median AQI 34, 0 days above 100) and the worst was August (median 46, 1 day above 100, peak 105).
Was 2019 a good or bad year for Worcester's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 4th cleanest by days above AQI 100. 2019's median of 45 is in line with the area's typical annual median of 43.
Worcester month by month in 2019
Worcester air quality month by month, 2019 (Worcester, MA-CT, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 51 | 0 | 62 | PM2.5 |
| February | 28 | 50 | 0 | 80 | PM2.5 |
| March | 31 | 51 | 0 | 71 | PM2.5 |
| April | 30 | 44 | 0 | 58 | O3 |
| May | 31 | 42 | 0 | 61 | O3 |
| June | 30 | 46 | 0 | 84 | PM2.5 |
| July | 31 | 55 | 0 | 97 | PM2.5 |
| Augustworst | 31 | 46 | 1 | 105 | PM2.5 |
| September | 30 | 39 | 0 | 80 | PM2.5 |
| Octobercleanest | 31 | 34 | 0 | 56 | PM2.5 |
| November | 30 | 41 | 0 | 65 | PM2.5 |
| December | 31 | 44 | 0 | 69 | PM2.5 |
How 2019 compares
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 4th cleanest by days above AQI 100.
2019's median of 45 is in line with the area's typical annual median of 43.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Worcester
The latest EPA AirNow observation puts Worcester's AQI at 31 (O3). The figures above are multi-year annual statistics, not today's reading.
View current Worcester air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Worcester, MA-CT), 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.