Dust
Late-June 2020 Saharan dust plume
Daily PM2.5 peaked at 64.9 µg/m³ near San Antonio across 13 covered metros home to 31 million people. 2 metros recorded their worst day on record; 9 placed a top-ten day.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 62 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
Supplied qualified evidence supports dust as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode. Supplied qualified evidence supports dust as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode. Supplied qualified evidence supports dust as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode. Supplied qualified evidence supports dust as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode. Supplied qualified evidence supports dust as the root ca
Sequence: McAllen (Jun 26) → Houston (Jun 26) → Jackson (Jun 26) → San Antonio (Jun 27) → Austin (Jun 27) → Dallas (Jun 27) → Little Rock (Jun 27) → Tulsa (Jun 27) → Nashville (Jun 27) → Oklahoma City (Jun 27) → +3 more metros
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| San Antonio-New Braunfels, TX | 64.9 µg/m³ | 3.0 | Jun 27, 2020 | #3 of its top days |
| McAllen-Edinburg-Mission, TX | 64 µg/m³ | 5.5 | Jun 27, 2020 | Worst day on record |
| Austin-Round Rock, TX | 60.3 µg/m³ | 2.7 | Jun 27, 2020 | Worst day on record |
| Dallas-Fort Worth-Arlington, TX | 53.2 µg/m³ | 2.4 | Jun 27, 2020 | #5 of its top days |
| Houston-The Woodlands-Sugar Land, TX | 50.9 µg/m³ | 2.3 | Jun 26, 2020 | #8 of its top days |
| Little Rock-North Little Rock-Conway, AR | 48.1 µg/m³ | 2.2 | Jun 27, 2020 | #4 of its top days |
| Tulsa, OK | 46.2 µg/m³ | 2.1 | Jun 27, 2020 | #5 of its top days |
| Nashville-Davidson--Murfreesboro--Franklin, TN | 43.7 µg/m³ | 2.0 | Jun 27, 2020 | #12 of its top days |
| Oklahoma City, OK | 43.7 µg/m³ | 3.6 | Jun 27, 2020 | #6 of its top days |
| Wichita, KS | 42 µg/m³ | 1.9 | Jun 28, 2020 | #13 of its top days |
| Jackson, MS | 40.7 µg/m³ | 1.9 | Jun 26, 2020 | #6 of its top days |
| Charleston-North Charleston, SC | 40.5 µg/m³ | 1.8 | Jun 27, 2020 | #22 of its top days |
| Columbia, SC | 39.4 µg/m³ | 1.8 | Jun 27, 2020 | #16 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
EPA AQS monitor qualifier 10
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 1 PM2.5 sample in the candidate CBSA on 2020-06-26, 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.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 96 PM2.5 samples in the candidate CBSA on 2020-06-26, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 1 PM2.5 sample in the candidate CBSA on 2020-06-27, 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.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 5 PM2.5 samples in the candidate CBSA on 2020-06-26, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 92 PM2.5 samples in the candidate CBSA on 2020-06-27, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 41 PM2.5 samples in the candidate CBSA on 2020-06-27, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 72 PM2.5 samples in the candidate CBSA on 2020-06-27, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 1 PM2.5 sample in the candidate CBSA on 2020-06-27, 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.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 50 PM2.5 samples in the candidate CBSA on 2020-06-28, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 22 PM2.5 samples in the candidate CBSA on 2020-06-27, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
NWS Air Quality Alert 2
- Air Quality Alert AQACAE An archived NWS Air Quality Alert for Columbia, SC, issued 2020-06-27T18:01Z, explicitly identifies windblown or transported dust. IEM is the archive, not the official system of record.
- Air Quality Alert AQACHS An archived NWS Air Quality Alert for Charleston-North Charleston, SC, issued 2020-06-27T17:24Z, explicitly identifies windblown or transported dust. IEM is the archive, not the official system of record.
Agency and publisher pages 5
- A Dust Plume to Remember NASA documented the June 2020 Saharan plume reaching the United States and reported unhealthy fine-particle AQI levels in Texas on June 27. This supports regional dust transport, not unique apportionment of the McAllen monitor value.
- Atmospheric heating in the US from Saharan dust: Tracking the June 2020 event with surface and satellite observations NOAA's analysis tracked the June 2020 Saharan dust event through Houston, identifying the event period at the Houston-area site as June 26–27 and using surface PM2.5 observations to track transport.
- Photos: KSAT viewers send in photos of San Antonio skies as Saharan dust arrives Contemporaneous San Antonio reporting stated that the visible haze was Saharan dust arriving that weekend.
- Saharan dust plume to reach highest levels in San Antonio on Saturday Contemporaneous San Antonio reporting said TCEQ expected a heavy African dust plume to reach its highest local levels on Saturday, June 27, with particle pollution unhealthy for sensitive groups.
- Saharan Dust Cloud Causes North Texas Air To Be Deemed 'Unhealthy' CBS Texas reported that a historic Saharan dust cloud reached North Texas on June 27 and caused unhealthy air conditions in Dallas-area counties.
News discovery (GDELT) 2
- Historic Saharan dust event fouls air along Gulf Coast The opened report uses satellite imagery and surface-air-quality data to describe Saharan dust over Mississippi and specifically forecasts impacts in Jackson on June 26. It supports regional dust transport and air-quality influence but does not quantify dust-attributable PM2.5 at the candidate monitor.
- Saharan dust plume could be dangerous for those with a respiratory illness The opened Nashville report says a Saharan dust plume was expected to produce a weekend air-quality alert in Middle Tennessee and that a significant amount would approach the surface. This supports dust transport for the June 27 candidate but remains partly forecast-based and does not quantify dust-attributable PM2.5.
Cited authorities: Saharan dust plume
What remains uncertain
- An AQS informational qualifier is an official submitting-agency flag, not an EPA-concurred exclusion determination.
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.