Wildfire smoke
Late-October 2003 Southern California wildfire-smoke episode
Daily PM2.5 peaked at 239.2 µg/m³ near San Diego across 5 covered metros home to 24 million people. 2 metros recorded their worst day on record; 4 placed a top-ten day.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 11.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 266 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 wildfire smoke as the broad root cause and supports grouping the contemporaneous affected events into one time-bounded episode. Qualified frozen evidence supports wildfire smoke as the broad root cause and supports grouping the contemporaneous affected events into one time-bounded episode.
Sequence: San Diego (Oct 26) → Los Angeles (Oct 26) → Riverside (Oct 26) → Oxnard (Oct 27) → Las Vegas (Oct 29)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| San Diego-Carlsbad, CA | 239.2 µg/m³ | 15.6 | Oct 27, 2003 | Worst day on record |
| Oxnard-Thousand Oaks-Ventura, CA | 116 µg/m³ | 5.3 | Oct 27, 2003 | Worst day on record |
| Los Angeles-Long Beach-Anaheim, CA | 115.5 µg/m³ | 14.5 | Oct 26, 2003 | #3 of its top days |
| Riverside-San Bernardino-Ontario, CA | 104.3 µg/m³ | 12.8 | Oct 26, 2003 | #4 of its top days |
| Las Vegas-Henderson-Paradise, NV | 46.2 µg/m³ | 2.1 | Oct 29, 2003 | #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
Official records
- NOAA Storm Events Wildfire, CALIFORNIA, Oct 21, 2003 "Named the Grand Prix Fire, this fire was started by arsonist on October 21, 2003. It burned 59,448 acres before being fully contained on November 5, 2003. During the first seven days, the fire increased rapidly in size …" record →
- NOAA Storm Events Wildfire, CALIFORNIA, Oct 25, 2003 "Named the Old Fire, this fire was started by an arsonist on October 25. It consumed 91,200 acres before it was fully contained on November 5, 2003. During the month of October, it destroyed 850 houses, 10 commercial buil…" record →
- NOAA Storm Events Wildfire, CALIFORNIA, Oct 25, 2003 "Named the Cedar Fire, this fire was started around sunset on October 25 by a lost hunter. Wind gusts from the northeast over 30 mph began within 2 hours of the fire's start. Atmospheric conditions remained favorable for …" record →
- NOAA Storm Events Wildfire, CALIFORNIA, Oct 21, 2003 "Named the Grand Prix Fire, this fire was started by arsonist on October 21, 2003. It burned 59,448 acres before being fully contained on November 5, 2003. During the first seven days, the fire increased rapidly in size …" record →
- NOAA Storm Events Wildfire, CALIFORNIA, Oct 25, 2003 "Named the Old Fire, this fire was started by an arsonist on October 25. It consumed 91,200 acres before it was fully contained on November 5, 2003. During the month of October, it destroyed 850 houses, 10 commercial buil…" record →
EPA AQS monitor qualifier 3
- AQS PM2.5 qualifier E — Forest Fire. EPA AQS carries an agency-submitted request-exclusion qualifier (E, Forest Fire.) on 4 PM2.5 samples in the candidate CBSA on 2003-10-27, identifying wildfire smoke 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 E — Forest Fire. EPA AQS carries an agency-submitted request-exclusion qualifier (E, Forest Fire.) on 1 PM2.5 sample in the candidate CBSA on 2003-10-26, identifying wildfire smoke as affecting the sample. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
- AQS PM2.5 qualifier E — Forest Fire. EPA AQS carries an agency-submitted request-exclusion qualifier (E, Forest Fire.) on 2 PM2.5 samples in the candidate CBSA on 2003-10-27, identifying wildfire smoke as affecting the samples. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
Agency and publisher pages 2
- Air Quality and the Wildland Fires of Southern California: October 2003 CARB's contemporaneous preliminary review attributes the late-October regional PM2.5 episode to Southern California wildland-fire smoke. Its table reports October 26–28 PM2.5 elevations in the South Coast, San Diego, and Ventura basins, including 239 µg/m³ in San Diego on October 27.
- Southern California Wildfires NWS Service Assessment Report 2003 The NWS assessment documents the late-October Southern California fire outbreak, including the Cedar, Old, Paradise, and Simi fires, and the Santa Ana wind conditions that drove their rapid spread during the event period.
What remains uncertain
- AQS qualifiers are submitting-agency causal flags and 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.