Worcester, Massachusetts Air Quality
Worcester has a median AQI of 42, earning an air quality grade of A- — excellent air quality that ranks better than 44% of US cities. Air quality has remained relatively stable over the past decade. Ground-level ozone is the primary concern, typically peaking on warm sunny days due to vehicle and industrial emissions. In 2025, Worcester recorded 183 good air quality days (75% of monitored days).
Population: 496,386 • County: Worcester
Current AQI
Quick Facts
| Current AQI | 10 — Good |
| Air Quality Grade | A- |
| Median AQI (2025) | 42 |
| vs. U.S. Cities | Better than 44% |
| Primary Pollutant | Ozone |
| Unhealthy Days/Year | 0 |
| 10-Year Trend | → Stable |
| Data Source | EPA AQS (historical) · AirNow (live) |
Health Recommendation
Air quality is satisfactory, and air pollution poses little or no risk.
It's a great day to be active outside!
5-Day AQI Forecast
Last 90 Days
Current Pollutant Levels
Real-time data from EPA AirNow
Local Air Quality Context
Air quality data for Worcester is sourced from the Worcester - Summer St monitoring area, located approximately 1 miles from city center. This EPA-certified station continuously tracks ground-level ozone, the primary driver of air quality alerts in this area.
Major roadways in the area include I-290, I-90, I-190, MA-9, and US-20. Heavy vehicle traffic on these corridors is a primary source of nitrogen dioxide, carbon monoxide, and fine particulate matter (PM2.5).
Key local pollution sources include vehicle traffic, manufacturing legacy, upwind emissions transport, and winter wood-burning.
AQI Trend (10 Years)
Air Quality Days by Year
Worcester Median AQI by Year
Annual EPA air quality data for Worcester — median AQI, day-category breakdown, and primary pollutant per year.
| Year | Median AQI | Good Days | Unhealthy Days | Max AQI | Primary Pollutant |
|---|---|---|---|---|---|
| 2025 | 42 | 183 | — | 100 | Ozone |
| 2024 | 37 | 321 | — | 90 | Ozone |
| 2023 | 39 | 268 | 4 | 148 | Ozone |
| 2022 | 45 | 228 | — | 100 | PM2.5 |
| 2021 | 45 | 218 | 3 | 125 | PM2.5 |
| 2020 | 43 | 257 | — | 90 | PM2.5 |
| 2019 | 45 | 238 | — | 93 | PM2.5 |
| 2018 | 40 | 265 | 4 | 129 | Ozone |
| 2017 | 40 | 288 | 3 | 143 | Ozone |
| 2016 | 41 | 285 | 4 | 143 | Ozone |
Source: EPA Air Quality System (AQS) annual summaries. "Unhealthy Days" includes Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous categories.
2025 Air Quality Summary
Primary Pollutant Days (2025)
Days when each pollutant was the primary driver of AQI. Learn about pollutants →
Frequently Asked Questions About Worcester Air Quality
What is the air quality in Worcester today?
The current AQI in Worcester is 10, rated "Good". Air quality is good — outdoor activity is safe for everyone today. Air quality is satisfactory, and air pollution poses little or no risk.
Is air quality in Worcester getting better or worse?
Air quality in Worcester has been stable. The median AQI has risen 1 points (from 41 in 2016 to 42 in 2025).
What is the most common air pollutant in Worcester?
Ozone is the primary air pollutant in Worcester, responsible for 176 days (72% of monitored days) in 2025. Ground-level ozone forms when sunlight reacts with emissions from vehicles and industry, typically peaking on hot summer afternoons.
How many unhealthy air days does Worcester have per year?
In 2025, Worcester recorded 75% good air quality days (183 days) out of 244 monitored days. There were 0 Unhealthy for Sensitive Groups days and 0 Unhealthy days (AQI above 100). The highest single-day AQI recorded was 100.
What air quality grade does Worcester receive?
Worcester receives an air quality grade of A-, placing it better than 44% of US cities. This is based on a median AQI of 42 in 2025, with 183 good air quality days. The EPA monitors air quality in this area continuously using certified monitoring stations.
Air Quality Grade
Better than 44% of US cities
Nearby Cities
Get AQI Alerts
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National Rankings
See how Worcester compares to every other US city by air quality.
Best Air Quality Cities →All city rankingsRecommended Air Purifiers for Worcester
Ozone is Worcester's primary pollutant. Standard HEPA filters don't capture ozone molecules — you need activated carbon or PECO technology to chemically break them down. We highlight those units here.
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