Dust
Dust episode, 2018-07-16 through 2018-07-17
Daily PM2.5 peaked at 56.9 µg/m³ near Dallas across 2 covered metros home to 11 million people. 1 metro 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 ≈ 3.5 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 38 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.
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.
What happened, in the record
Qualified frozen evidence supports dust as the broad cause for this time-bounded episode.
Sequence: Dallas (Jul 16) → Austin (Jul 16)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Dallas-Fort Worth-Arlington, TX | 56.9 µg/m³ | 5.1 | Jul 17, 2018 | #2 of its top days |
| Austin-Round Rock, TX | 38.3 µg/m³ | 1.7 | Jul 16, 2018 | #13 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.
The evidence
News discovery (GDELT) 1
- Austin's air quality drops as more Saharan dust blows in Contemporaneous reporting states that a Saharan dust cloud arrived in Austin and that TCEQ categorized local air quality as unhealthy for sensitive groups on July 16. This supports dust attribution for the Austin member but does not independently establish the Dallas member or quantify the dust share of measured PM2.5.
What remains uncertain
- The evidence resolves the broad cause but does not require a named fire, facility, or incident.
Status and provenance
Research preview: this record carries research-only status and its boundaries, cause, and name may change as evidence review completes. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula.