Regional secondary PM Likely
Daily PM2.5 peaked at 49.4 µg/m³ near Jackson across 1 covered metro home to 606,178 people. 1 metro recorded their worst day on record.
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 ≈ 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
EPA identified a widespread sulfate event across the Southeast on June 24, and NASA independently documented stable humid conditions trapping vehicle, power-plant, and fire aerosols across the Mississippi Valley and Deep South.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
U.S. Environmental Protection Agency official
EPA's review found a widespread sulfate event across the Southeast on June 24, 2005 and found the submitted Kentucky wildfire evidence insufficient.
U.S. Environmental Protection Agency official
EPA's review found a widespread sulfate event across the Southeast on June 24, 2005 and found the Kentucky wildfire evidence insufficient for causal attribution. The source supplies regional context only for Jackson.
NASA Earth Observatory · Jul 2, 2005 hypothesis
NASA reports haze across the Mississippi River Valley and Deep South beginning June 20, with stable humid air keeping aerosols from vehicles, power plants, and fires suspended over the region.
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
EPA's review found a widespread sulfate event across the Southeast on June 24, 2005 and found the submitted Kentucky wildfire evidence insufficient.
View supporting source ↗Air-mass movement
NASA reports haze across the Mississippi River Valley and Deep South beginning June 20, with stable humid air keeping aerosols from vehicles, power plants, and fires suspended over the region.
View transport source ↗Local response
EPA monitors recorded the event across 1 metro. 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.
Jackson, MS
Monitor comparison window 2005-06-21 to 2005-06-27
37% above nearby days
About the same as surrounding days
37% higher than surrounding days
About the same as surrounding days
55% 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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Jackson, MS | 49.4 µg/m³ | 2.2 | Jun 24, 2005 | Worst day on record |
"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.
NASA Earth Observatory
NASA reports haze across the Mississippi River Valley and Deep South beginning June 20, with stable humid air keeping aerosols from vehicles, power plants, and fires suspended over the region.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
NASA describes a mixture of sources and does not quantify Jackson's sulfate fraction.
U.S. Environmental Protection Agency
EPA's review found a widespread sulfate event across the Southeast on June 24, 2005 and found the submitted Kentucky wildfire evidence insufficient.
An official source supports the attributed cause for the stated place and dates.
The review is regional context for Jackson and was written for Kentucky designations rather than Jackson's monitor.
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.