Dust Likely
Daily PM2.5 peaked at 43.4 µg/m³ near Dallas across 1 covered metro home to 8.3 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.5 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
Satellite/AirNow analysis and airborne aerosol research independently document a long-range Saharan dust layer across Texas on August 8, with PM2.5 elevated beyond the pattern normally expected under Gulf inflow.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
Earthzine / NASA AirNow satellite evaluation · Apr 15, 2014 corroborates
The case study says Saharan dust crossed the Atlantic on August 8, 2013 and that PM2.5 in Texas and Louisiana reached Moderate to Unhealthy for Sensitive Groups levels beyond what is normally expected with clean Gulf inflow.
North Carolina State University repository corroborates
The repository text reports that on August 8 a transported Saharan-dust layer extended across Texas, Louisiana, and the Gulf of Mexico and was observed by airborne lidar and AQS measurements.
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 case study says Saharan dust crossed the Atlantic on August 8, 2013 and that PM2.5 in Texas and Louisiana reached Moderate to Unhealthy for Sensitive Groups levels beyond what is normally expected with clean Gulf inflow.
View supporting source ↗Air-mass movement
The case study says Saharan dust crossed the Atlantic on August 8, 2013 and that PM2.5 in Texas and Louisiana reached Moderate to Unhealthy for Sensitive Groups levels beyond what is normally expected with clean Gulf inflow.
View transport source ↗Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.0 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 “Dust” explanation; it does not assign the cause by itself.
Dallas-Fort Worth-Arlington, TX
Monitor comparison window 2013-08-05 to 2013-08-11 · PM2.5 target: Fort Worth Northwest
111% above nearby days
About the same as surrounding days
No adjacent-day comparison
111% higher than surrounding days
No adjacent-day comparison
7% lower than surrounding days
28% 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
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 |
|---|---|---|---|---|
| Dallas-Fort Worth-Arlington, TX | 43.4 µg/m³ | 2.0 | Aug 8, 2013 | #15 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.
Earthzine / NASA AirNow satellite evaluation
The case study says Saharan dust crossed the Atlantic on August 8, 2013 and that PM2.5 in Texas and Louisiana reached Moderate to Unhealthy for Sensitive Groups levels beyond what is normally expected with clean Gulf inflow.
A retained source supports the attributed cause for the stated place and dates.
The accessible narrative describes Texas and Louisiana broadly rather than reporting a Dallas-only source-apportionment value.
North Carolina State University repository
The repository text reports that on August 8 a transported Saharan-dust layer extended across Texas, Louisiana, and the Gulf of Mexico and was observed by airborne lidar and AQS measurements.
A retained source supports the attributed cause for the stated place and dates.
The flight analysis establishes the regional dust layer but does not isolate the Dallas monitor-day contribution.
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.