Other
1999-11-12 other documented PM source or accumulation mechanism episode affecting Bakersfield, CA, Fresno, CA
Daily PM2.5 peaked at 134.8 µg/m³ near Bakersfield 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 ≈ 9.2 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 19 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 other documented PM source or accumulation mechanism as the broad root cause.
Sequence: Bakersfield (Nov 12) → Fresno (Nov 14)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Bakersfield, CA | 134.8 µg/m³ | 16.9 | Nov 13, 1999 | #3 of its top days |
| Fresno, CA | 115 µg/m³ | 5.2 | Nov 14, 1999 | #24 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
Agency and publisher pages 1
- Historical Meteorological Analysis in Support of the 2003 San Joaquin Valley PM10 State Implementation Plan: Final Report The District's retrospective analysis identifies the November 14, 1999 San Joaquin Valley episode, including Bakersfield and Fresno PM2.5 observations. It concludes that worsening dispersion, strong atmospheric stability, humid/foggy conditions, and formation of nitrate and sulfate drove a short pollution buildup; agricultural burning was probably not a contributor because November 13–14 were district-wide no-burn days.
What remains uncertain
- The retained evidence does not map the documented mechanism to a more specific catalog cause type.
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.