Dust
2011-07-05 windblown-dust episode affecting Phoenix-Mesa-Scottsdale, AZ
Daily PM2.5 peaked at 102.3 µg/m³ near Phoenix across 1 covered metro home to 5.2 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 ≈ 4.1 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 21 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
National Weather Service, ADEQ, and monitor-qualifier evidence consistently support windblown dust as the broad cause of the July 5 Phoenix PM2.5 episode.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Phoenix-Mesa-Scottsdale, AZ | 102.3 µg/m³ | 4.6 | Jul 5, 2011 | #8 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
Official records
- NOAA Storm Events Dust Storm, ARIZONA, Jul 5, 2011 "Strong to severe thunderstorm development had occured in the early afternoon hours of July 5th near the Tucson, AZ area and east of Tucson. As thunderstorms dissipated and began moving northwest, outflows from these stor…" record →
EPA AQS monitor qualifier 2
- AQS PM2.5 qualifier RJ — High Winds. EPA AQS carries an agency-submitted request-exclusion qualifier (RJ, High Winds.) on 101 PM2.5 samples in the candidate CBSA on 2011-07-05, identifying windblown or transported dust as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier IJ — High Winds. EPA AQS carries an agency-submitted informational qualifier (IJ, High Winds.) on 1 PM2.5 sample in the candidate CBSA on 2011-07-05, identifying windblown or transported dust as affecting the sample. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
Agency and publisher pages 2
- July 5, 2011 - Historic Dust Storm across south-central Arizona The National Weather Service documented a large dust storm driven by thunderstorm outflow winds that entered and passed through the Phoenix metropolitan area during the evening of July 5.
- Monthly Air Quality Report for July 2011 Arizona DEQ's July 2011 report documents the major July 5 dust storm and PM2.5 exceedances in the Phoenix metropolitan area.
What remains uncertain
- Agency-submitted AQS qualifiers are causal flags but do not by themselves establish EPA concurrence.
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.