Mixed causes
2020-01-01 Phoenix-Mesa-Scottsdale mixed-cause episode
Daily PM2.5 peaked at 149.1 µg/m³ near Phoenix across 1 covered metro home to 5.2 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 ≈ 6.2 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 32 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 local and ADEQ evidence supports a mixed New Year's episode involving residential fireplace and fire-pit smoke together with fireworks.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Phoenix-Mesa-Scottsdale, AZ | 149.1 µg/m³ | 6.8 | Jan 1, 2020 | #3 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 2
- Appendix C ADEQ's retrospective assessment identifies the West Phoenix 149.1 µg/m3 PM2.5 value on January 1, 2020 and describes New Year's Eve/Day conditions, including a midnight fireworks peak and persistent high concentrations into the morning.
- Hikers unfazed by poor air quality on New Year's Day Contemporaneous local reporting attributed poor Valley air to smoke from fireplaces and fire pits mixed with New Year's fireworks.
What remains uncertain
- The supplied evidence resolves cause but does not establish identity with another candidate episode.
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.