Wildfire smoke
2021-07-26 5-area wildfire-smoke episode
Daily PM2.5 peaked at 59 µg/m³ near Boston across 5 covered metros home to 9.4 million people. 3 metros placed a top-ten day in their record.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 19 million cigarettes. An awareness illustration of outdoor exposure at 22 µg/m³ per cigarette (Berkeley Earth), counting only the event's ranked days; not a medical dose.
Episode peak
-- cigarettes
The smoke map's scale, replayed over this event: the surface interpolates between covered metros' daily records, framed to the affected region. Hover for a reading, click a metro to pin it to the card. Days a monitor did not report draw nothing.
What happened, in the record
Supplied qualified evidence supports wildfire-smoke as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode.
Sequence: Boston (Jul 26) → New Haven (Jul 26) → Hartford (Jul 26) → Worcester (Jul 26) → Providence (Jul 26)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Boston-Cambridge-Newton, MA-NH | 59 µg/m³ | 2.7 | Jul 26, 2021 | #5 of its top days |
| New Haven-Milford, CT | 50.9 µg/m³ | 2.3 | Jul 26, 2021 | #17 of its top days |
| Hartford-West Hartford-East Hartford, CT | 49.8 µg/m³ | 2.3 | Jul 26, 2021 | #9 of its top days |
| Worcester, MA-CT | 45.3 µg/m³ | 2.1 | Jul 26, 2021 | #9 of its top days |
| Providence-Warwick, RI-MA | 43.7 µg/m³ | 2.0 | Jul 26, 2021 | #18 of its top days |
"Cigarettes, whole event" totals a metro's ranked event days at 22 µg/m³ per cigarette: what a person outdoors there breathed across the event, as the illustration. "All-time standing" is where this episode's days sit in each metro's ranked record (worst-area measure, since 1999). Full local context is on each metro's Air Records page.
The evidence
EPA AQS monitor qualifier 2
- AQS PM2.5 qualifier IT — Wildfire-U. S. EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 66 PM2.5 samples in the candidate CBSA on 2021-07-26, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
- AQS PM2.5 qualifier IT — Wildfire-U. S. EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 56 PM2.5 samples in the candidate CBSA on 2021-07-26, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
Agency and publisher pages 1
- Elevated Levels of Fine Particles in Air This Evening Due to Western Wildfires Connecticut DEEP reported that the western-wildfire smoke plume produced unhealthy PM2.5 across Connecticut on July 26, supporting wildfire-smoke attribution for this regional New England event.
What remains uncertain
- An AQS informational qualifier is an official submitting-agency flag, not an EPA-concurred exclusion determination.
- The supplied evidence resolves cause but does not establish identity with another candidate episode.
Status and provenance
Research preview: this record carries research-only status and its boundaries, cause, and name may change as evidence review completes. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula.