Regional secondary PM Possible
Daily PM2.5 peaked at 47.7 µg/m³ near Bridgeport across 4 covered metros home to 8.2 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.5 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 13 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.
Why we think this happened
Manual research connected 5 source events to one regional secondary-particle pollution episode using the deterministic grouping rule.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
Journal of Geophysical Research: Atmospheres / AIRMAP · Jan 31, 2007 corroborates
The peer-reviewed AIRMAP study isolates August 20-22, 2003 as an elevated sulfate event with westerly transport from Whiteface Mountain toward Mount Washington. It reports measured sulfate and sulfur dioxide at both sites, sulfur-dioxide oxidation during transit, and haze during the event.
Inference, not direct attribution
exact_window_regional_secondary_aerosol_study_possible.v1: This inference is recorded in the catalog methodology.
See every retained source and limitation ↓
Sequence: Bridgeport (Aug 22) → Springfield (Aug 22) → Boston (Aug 22) → Providence (Aug 22)
Evidence path
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
Source or mechanism
The peer-reviewed AIRMAP study isolates August 20-22, 2003 as an elevated sulfate event with westerly transport from Whiteface Mountain toward Mount Washington. It reports measured sulfate and sulfur dioxide at both sites, sulfur-dioxide oxidation…
View supporting source ↗Air-mass movement
The retained record does not yet show how air traveled from the proposed source to these metros. A trajectory replay or dated plume analysis belongs here.
Local response
EPA monitors recorded the event across 4 metros. The peak daily concentration is roughly 2.2 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓Event autopsy
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Regional secondary PM” explanation; it does not assign the cause by itself.
Bridgeport-Stamford-Norwalk, CT
Monitor comparison window 2003-08-19 to 2003-08-25 · PM2.5 target: Health Dept
143% above nearby days
15% higher than surrounding days
143% higher than surrounding days
15% higher than surrounding days
31% higher than surrounding days
160% higher than surrounding days
37% higher than surrounding days
12% higher than surrounding days
7% higher than surrounding days
Springfield, MA
Monitor comparison window 2003-08-19 to 2003-08-25 · PM2.5 target: LIBERTY ST PARKING LOT
156% above nearby days
44% higher than surrounding days
156% higher than surrounding days
44% higher than surrounding days
About the same as surrounding days
54% higher than surrounding days
38% higher than surrounding days
24% higher than surrounding days
About the same as surrounding days
6% higher than surrounding days
Boston-Cambridge-Newton, MA-NH
Monitor comparison window 2003-08-19 to 2003-08-25 · PM2.5 target: NORTH END SITE CENTRAL ARTERY
226% above nearby days
About the same as surrounding days
226% higher than surrounding days
About the same as surrounding days
10% lower than surrounding days
About the same as surrounding days
38% higher than surrounding days
11% higher than surrounding days
About the same as surrounding days
7% higher than surrounding days
Providence-Warwick, RI-MA
Monitor comparison window 2003-08-19 to 2003-08-25 · PM2.5 target: CCRI Liston Campus ROOFTOP
188% above nearby days
16% higher than surrounding days
188% higher than surrounding days
16% higher than surrounding days
20% higher than surrounding days
209% higher than surrounding days
About the same as surrounding days
11% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
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.
Views from the selected metro
Select a metro on the map to see nearby cameras. Where an operator archive reaches the event, drag the divider to compare two moments, adjust either date and time, or play the available event-day frames. Camera imagery is visual context, not an air-quality measurement or proof of smoke.
No useful public camera views are currently available within 80 km of this metro.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Bridgeport-Stamford-Norwalk, CT | 47.7 µg/m³ | 2.2 | Aug 22, 2003 | #17 of its top days |
| Springfield, MA | 46.3 µg/m³ | 2.1 | Aug 22, 2003 | #20 of its top days |
| Boston-Cambridge-Newton, MA-NH | 42.5 µg/m³ | 1.9 | Aug 22, 2003 | #22 of its top days |
| Providence-Warwick, RI-MA | 41.3 µg/m³ | 1.9 | Aug 22, 2003 | #21 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.
Public evidence library
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
Journal of Geophysical Research: Atmospheres / AIRMAP
The peer-reviewed AIRMAP study isolates August 20-22, 2003 as an elevated sulfate event with westerly transport from Whiteface Mountain toward Mount Washington. It reports measured sulfate and sulfur dioxide at both sites, sulfur-dioxide oxidation during transit, and haze during the event.
A retained source supports the attributed cause for the stated place and dates.
The chemical samples were collected at Whiteface Mountain and Mount Washington rather than at each listed urban monitor.
Journal of Geophysical Research: Atmospheres / AIRMAP
The peer-reviewed AIRMAP study isolates August 20-22, 2003 as an elevated sulfate event with westerly transport from Whiteface Mountain toward Mount Washington. It reports measured sulfate and sulfur dioxide at both sites, sulfur-dioxide oxidation during transit, and haze during the event.
A retained source supports the attributed cause for the stated place and dates.
The chemical samples were collected at Whiteface Mountain and Mount Washington rather than at each listed urban monitor.
Journal of Geophysical Research: Atmospheres / AIRMAP
The peer-reviewed AIRMAP study isolates August 20-22, 2003 as an elevated sulfate event with westerly transport from Whiteface Mountain toward Mount Washington. It reports measured sulfate and sulfur dioxide at both sites, sulfur-dioxide oxidation during transit, and haze during the event.
A retained source supports the attributed cause for the stated place and dates.
The chemical samples were collected at Whiteface Mountain and Mount Washington rather than at each listed urban monitor.
Journal of Geophysical Research: Atmospheres / AIRMAP
The peer-reviewed AIRMAP study isolates August 20-22, 2003 as an elevated sulfate event with westerly transport from Whiteface Mountain toward Mount Washington. It reports measured sulfate and sulfur dioxide at both sites, sulfur-dioxide oxidation during transit, and haze during the event.
A retained source supports the attributed cause for the stated place and dates.
The chemical samples were collected at Whiteface Mountain and Mount Washington rather than at each listed urban monitor.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.