Mixed causes
2024-08-01 mixed causes episode affecting Little Rock-North Little Rock-Conway, AR, Memphis, TN-MS-AR
Daily PM2.5 peaked at 46.2 µg/m³ near Memphis across 2 covered metros home to 2.1 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 ≈ 1.5 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 3.2 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
The supplied retained evidence explicitly supports multiple material causes (dust and wildfire smoke) for this episode, so it is retained as mixed.
Sequence: Memphis (Aug 1) → Little Rock (Aug 1)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Memphis, TN-MS-AR | 46.2 µg/m³ | 2.1 | Aug 1, 2024 | #9 of its top days |
| Little Rock-North Little Rock-Conway, AR | 39.5 µg/m³ | 1.8 | Aug 1, 2024 | #17 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 2
- AQS PM2.5 qualifier IA — African Dust. EPA AQS carries an agency-submitted informational qualifier (IA, African Dust.) on 2 PM2.5 samples in the candidate CBSA on 2024-08-01, 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 IF — Fire - Canadian. EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 24 PM2.5 samples in the candidate CBSA on 2024-08-01, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
News discovery (GDELT) 1
- Saharan dust is causing hazy skies in the Southeast The inaccessible local Memphis result explicitly attributes contemporaneous Southeast haze to Saharan dust; it directly concerns the Memphis member but does not independently establish Little Rock surface PM2.5.
What remains uncertain
- The supplied evidence does not quantify the relative contribution of each supported cause.
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.