Dust
Dust episode, 2018-07-08
Daily PM2.5 peaked at 63.5 µg/m³ near Phoenix across 1 covered metro home to 5.2 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.3 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.
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.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Phoenix-Mesa-Scottsdale, AZ | 63.5 µg/m³ | 2.9 | Jul 8, 2018 | #21 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 9, 2018 "Scattered thunderstorms developed across the south-central Arizona deserts, including the greater Phoenix area, during the afternoon and evening hours on July 9th. The storms generated strong and gusty outflow winds in e…" record →
NWS Air Quality Alert 1
- Air Quality Alert AQAPSR An archived NWS Air Quality Alert for Phoenix-Mesa-Scottsdale, AZ, issued 2018-07-07T21:52Z, explicitly identifies windblown or transported dust. IEM is the archive, not the official system of record.
Agency and publisher pages 2
- Times Matter, the Impact of Convective Dust Events on Air Quality in the Greater Phoenix Area, Arizona The study identifies July 8, 2018 as a Greater Phoenix convective dust event with exceptionally high daily PM10, supporting dust as the event driver; it does not separately quantify the PM2.5 share.
- Arizona Department of Environmental Quality issues high pollution advisories for July 9–10, 2018 The county relayed ADEQ's PM10 dust and PM2.5 smoke advisory immediately following the July 8 dust event.
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.