Mixed causes Possible
Daily PM2.5 peaked at 52.5 µg/m³ near Atlanta across 1 covered metro home to 6.4 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.8 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 12 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
NOAA's same-day satellite narrative places a broad smoke-and-haze area over western Georgia, thickest over Georgia and Alabama, and attributes the smoke to western wildfires plus agricultural and controlled burns in the lower Mississippi Valley. The same-day NWS Atlanta discussion forecast clear but hazy skies, two-to-four-mile visibility overnight, and three-to-five-mile visibility in haze the next morning. The date, place, and stated limitations support possible confidence only.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
NOAA Satellite Services Division · Sep 13, 2005 corroborates
NOAA's same-day satellite narrative places a broad smoke-and-haze area over western Georgia, thickest over Georgia and Alabama, and attributes the smoke to western wildfires plus agricultural and controlled burns in the lower Mississippi Valley.
U.S. EPA AirData Chemical Speciation Network · Sep 13, 2005 hypothesis
EPA's exact-date CSN sample reconstructed 32.1 µg/m³ of PM2.5. Ammonium sulfate and ammonium nitrate contributed 20.7 µg/m³, or 64.5% of reconstructed mass.
National Weather Service Atlanta via Iowa Environmental Mesonet · Sep 13, 2005 hypothesis
The same-day NWS Atlanta discussion forecast clear but hazy skies, two-to-four-mile visibility overnight, and three-to-five-mile visibility in haze the next morning.
Inference, not direct attribution
Same-day particle composition: EPA speciation observations on the peak date show a majority secondary-inorganic aerosol signature. This supports a regional secondary-particle mechanism, not a single emitting source.
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
NOAA's same-day satellite narrative places a broad smoke-and-haze area over western Georgia, thickest over Georgia and Alabama, and attributes the smoke to western wildfires plus agricultural and controlled burns in the lower Mississippi Valley.
View supporting source ↗Air-mass movement
NOAA's same-day satellite narrative places a broad smoke-and-haze area over western Georgia, thickest over Georgia and Alabama, and attributes the smoke to western wildfires plus agricultural and controlled burns in the lower Mississippi Valley.
View transport source ↗Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.4 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 “Mixed causes” explanation; it does not assign the cause by itself.
Atlanta-Sandy Springs-Roswell, GA
Monitor comparison window 2005-09-10 to 2005-09-16 · PM2.5 target: E. Rivers School
13% above nearby days
39% higher than surrounding days
13% higher than surrounding days
39% higher than surrounding days
10% higher than surrounding days
21% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
5% 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 |
|---|---|---|---|---|
| Atlanta-Sandy Springs-Roswell, GA | 52.5 µg/m³ | 2.4 | Sep 13, 2005 | #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.
NOAA Satellite Services Division
NOAA's same-day satellite narrative places a broad smoke-and-haze area over western Georgia, thickest over Georgia and Alabama, and attributes the smoke to western wildfires plus agricultural and controlled burns in the lower Mississippi Valley.
A retained source supports the attributed cause for the stated place and dates.
Satellite analysis does not establish how much of Atlanta's surface PM2.5 came from smoke versus the co-located regional haze.
U.S. EPA AirData Chemical Speciation Network
EPA's exact-date CSN sample reconstructed 32.1 µg/m³ of PM2.5. Ammonium sulfate and ammonium nitrate contributed 20.7 µg/m³, or 64.5% of reconstructed mass.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Chemical composition identifies the measured aerosol mechanism, not a particular emitting facility or source region.
National Weather Service Atlanta via Iowa Environmental Mesonet
The same-day NWS Atlanta discussion forecast clear but hazy skies, two-to-four-mile visibility overnight, and three-to-five-mile visibility in haze the next morning.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The forecast discussion confirms local surface haze but does not identify its source.
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.