Industrial Documented
Daily PM2.5 peaked at 57.5 µg/m³ near Houston across 4 covered metros home to 21 million people. 4 metros 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 ≈ 5.9 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 126 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
Qualified frozen evidence supports industrial emissions as the broad root cause and supports grouping the contemporaneous affected events into one time-bounded episode.
Documented An agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
Journal of the Air & Waste Management Association · Jan 1, 2004 official
Trajectory and potential-source analysis identifies long-range transport from the eastern United States and possible contributing emission regions including industrialized Texas and Louisiana, the Mississippi Valley, Tennessee, and lower Ohio River Valley during the South Texas September 11–14 haze event with elevated PM2.5.
NASA corroborates
NASA describes a September 2002 haze blanket formed by humid, hot, stagnant air and industrial emissions in the upper Midwest, then moved around the eastern United States and generated air-quality alerts as far away as Texas.
See every retained source and limitation ↓
Sequence: Houston (Sep 12) → Dallas (Sep 12) → Austin (Sep 12) → San Antonio (Sep 12)
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 catalog has a grouping hypothesis, but no retained source directly establishes the proposed cause.
Air-mass movement
Trajectory and potential-source analysis identifies long-range transport from the eastern United States and possible contributing emission regions including industrialized Texas and Louisiana, the Mississippi Valley, Tennessee, and lower Ohio River…
View transport source ↗Local response
EPA monitors recorded the event across 4 metros. The peak daily concentration is roughly 2.6 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 “Industrial” explanation; it does not assign the cause by itself.
Houston-The Woodlands-Sugar Land, TX
Monitor comparison window 2002-09-09 to 2002-09-18 · PM2.5 target: Clinton
110% above nearby days
26% lower than surrounding days
48% higher than surrounding days
110% higher than surrounding days
48% higher than surrounding days
37% higher than surrounding days
57% higher than surrounding days
109% higher than surrounding days
102% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
26% lower than surrounding days
Austin-Round Rock, TX
Monitor comparison window 2002-09-09 to 2002-09-17 · PM2.5 target: Austin Webberville Rd
130% above nearby days
29% lower than surrounding days
39% higher than surrounding days
130% higher than surrounding days
39% higher than surrounding days
31% higher than surrounding days
39% higher than surrounding days
About the same as surrounding days
29% lower than surrounding days
Dallas-Fort Worth-Arlington, TX
Monitor comparison window 2002-09-09 to 2002-09-17 · PM2.5 target: Convention Center
88% above nearby days
About the same as surrounding days
35% higher than surrounding days
88% higher than surrounding days
35% higher than surrounding days
60% higher than surrounding days
33% lower than surrounding days
25% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
San Antonio-New Braunfels, TX
Monitor comparison window 2002-09-09 to 2002-09-17 · PM2.5 target: Selma
140% above nearby days
7% lower than surrounding days
40% higher than surrounding days
140% higher than surrounding days
40% higher than surrounding days
91% higher than surrounding days
35% higher than surrounding days
About the same as surrounding days
7% lower than 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 |
|---|---|---|---|---|
| Houston-The Woodlands-Sugar Land, TX | 57.5 µg/m³ | 9.6 | Sep 13, 2002 | #5 of its top days |
| Dallas-Fort Worth-Arlington, TX | 53.1 µg/m³ | 6.6 | Sep 14, 2002 | #6 of its top days |
| Austin-Round Rock, TX | 53 µg/m³ | 6.9 | Sep 13, 2002 | #3 of its top days |
| San Antonio-New Braunfels, TX | 48 µg/m³ | 5.7 | Sep 14, 2002 | #6 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.
Identification of source regions affecting south Texas during the September 2002 haze event
Trajectory and potential-source analysis identifies long-range transport from the eastern United States and possible contributing emission regions including industrialized Texas and Louisiana, the Mississippi Valley, Tennessee, and lower Ohio River Valley during the South Texas September 11–14 haze event with elevated PM2.5.
A New IDEA in Air Quality Monitoring
NASA describes a September 2002 haze blanket formed by humid, hot, stagnant air and industrial emissions in the upper Midwest, then moved around the eastern United States and generated air-quality alerts as far away as Texas.
Documented An agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
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.