Stagnant pollution mixture Possible
Daily PM2.5 peaked at 39.4 µg/m³ near Des Moines across 1 covered metro home to 753,913 people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 1.1 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
A contemporaneous Iowa report documents an exact-window particle alert across central and eastern Iowa and describes humid, hazy conditions with suspended particulate matter. It supports an accumulation episode but does not apportion the emissions, so confidence remains possible.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
Radio Iowa · Aug 15, 2003 corroborates
Iowa officials issued a particle-pollution alert for central and eastern Iowa during the event window; the report describes humid haze with suspended particulates typical of late-summer accumulation conditions.
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
Iowa officials issued a particle-pollution alert for central and eastern Iowa during the event window; the report describes humid haze with suspended particulates typical of late-summer accumulation conditions.
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 1 metro. The peak daily concentration is roughly 1.8 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 “Stagnant pollution mixture” explanation; it does not assign the cause by itself.
Des Moines-West Des Moines, IA
Monitor comparison window 2003-08-11 to 2003-08-17 · PM2.5 target: CARPENTER
168% above nearby days
56% higher than surrounding days
168% higher than surrounding days
56% higher than surrounding days
12% 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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Des Moines-West Des Moines, IA | 39.4 µg/m³ | 1.8 | Aug 14, 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.
Radio Iowa
Iowa officials issued a particle-pollution alert for central and eastern Iowa during the event window; the report describes humid haze with suspended particulates typical of late-summer accumulation conditions.
A retained source supports the attributed cause for the stated place and dates.
The report explains the haze and alert mechanism but does not identify or quantify the contributing emissions sources.
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.