Fireworks
2020-07-04 Los Angeles-Long Beach-Anaheim fireworks episode
Daily PM2.5 peaked at 175 µg/m³ near Los Angeles across 1 covered metro home to 13 million people. 1 metro recorded their worst day on record.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 10.7 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 138 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 fireworks as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Los Angeles-Long Beach-Anaheim, CA | 175 µg/m³ | 12.1 | Jul 5, 2020 | Worst day on record |
"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 IH — Fireworks. EPA AQS carries an agency-submitted informational qualifier (IH, Fireworks.) on 61 PM2.5 samples in the candidate CBSA on 2020-07-05, identifying fireworks 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 IH — Fireworks. EPA AQS carries an agency-submitted informational qualifier (IH, Fireworks.) on 46 PM2.5 samples in the candidate CBSA on 2020-07-04, identifying fireworks as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
Agency and publisher pages 2
- 4th of July Fireworks Celebrations Lead to Highest PM2.5 Levels in Over a Decade South Coast AQMD concluded that Independence Day fireworks led to the South Coast Air Basin's highest PM2.5 levels in more than a decade during the July 4–5, 2020 period.
- Impact of 4th of July Fireworks on Spatiotemporal PM2.5 Concentrations in California Based on the PurpleAir Sensor Network: Implications for Policy and Environmental Justice Scientific analysis of 2020 California sensor data found the July 4–5 PM2.5 impact was especially pronounced in Southern California, including Los Angeles County.
What remains uncertain
- An AQS informational qualifier is an official submitting-agency flag, not an EPA-concurred exclusion determination.
- 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.