Regional secondary PM Likely
Daily PM2.5 peaked at 60.3 µg/m³ near Columbus across 2 covered metros home to 3.0 million people. 1 metro 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 ≈ 2.1 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 6.3 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 2 source events to one regional secondary-particle pollution episode using the deterministic grouping rule.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
Geophysical Research Letters corroborates
Airborne measurements during the August 14-15, 2003 blackout found large reductions in sulfur dioxide and particle light scattering and concluded that transported upwind power-plant emissions played a dominant role in regional sulfate haze.
See every retained source and limitation ↓
Sequence: Columbus (Aug 14) → Dayton (Aug 14)
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
Airborne measurements during the August 14-15, 2003 blackout found large reductions in sulfur dioxide and particle light scattering and concluded that transported upwind power-plant emissions played a dominant role in regional sulfate haze.
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 2 metros. The peak daily concentration is roughly 2.7 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.
Columbus, OH
Monitor comparison window 2003-08-11 to 2003-08-17 · PM2.5 target: Fairgrounds Garage
97% above nearby days
77% higher than surrounding days
97% higher than surrounding days
77% higher than surrounding days
23% higher than surrounding days
54% higher than surrounding days
9% higher than surrounding days
Dayton, OH
Monitor comparison window 2003-08-11 to 2003-08-17 · PM2.5 target: LIBRARY (DAYTON PUBLIC
81% above nearby days
36% higher than surrounding days
81% higher than surrounding days
36% higher than surrounding days
64% higher than 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 |
|---|---|---|---|---|
| Columbus, OH | 60.3 µg/m³ | 2.7 | Aug 14, 2003 | #7 of its top days |
| Dayton, OH | 45.3 µg/m³ | 2.1 | Aug 14, 2003 | #24 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.
Geophysical Research Letters
Airborne measurements during the August 14-15, 2003 blackout found large reductions in sulfur dioxide and particle light scattering and concluded that transported upwind power-plant emissions played a dominant role in regional sulfate haze.
A retained source supports the attributed cause for the stated place and dates.
The aircraft measurements establish a regional mechanism; they do not apportion the Columbus or Dayton daily monitor independently.
Geophysical Research Letters
Airborne measurements during the August 14-15, 2003 blackout found large reductions in sulfur dioxide and particle light scattering and concluded that transported upwind power-plant emissions played a dominant role in regional sulfate haze.
A retained source supports the attributed cause for the stated place and dates.
The aircraft measurements establish a regional mechanism; they do not apportion the Columbus or Dayton daily monitor independently.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
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.