FASTNET community / CAPITA corroborates
July 4 aerosol pulse event report
FASTNET's AirNow analysis reports a nationally discernible July 4-5 fireworks PM2.5 pulse and says a pulse of the same magnitude occurred on July 4, 2003.
Fireworks Possible
2003-07-04 Louisville/Jefferson County, KY-IN fireworks episode
Daily PM2.5 peaked at 55.7 µg/m³ near Louisville/Jefferson County across 1 covered metro home to 1.4 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 ≈ 2.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 2.7 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.
Why we think this happened
The basis for “Fireworks”
The event falls exactly on July 4-5, a source analysis identifies a national fireworks aerosol pulse on those exact 2003 dates, and the versioned holiday rule applies. The evidence is not local enough to exceed possible.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
Inference, not direct attribution
Holiday timing: The event falls in the July 3–5 or December 31–January 1 fireworks window. That makes fireworks a reasonable hypothesis, but no retained source directly attributes this event.
Evidence path
From source to city
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
- 1Documented
Source or mechanism
Fireworks
FASTNET's AirNow analysis reports a nationally discernible July 4-5 fireworks PM2.5 pulse and says a pulse of the same magnitude occurred on July 4, 2003.
View supporting source ↗ - 2Research gap
Air-mass movement
The transport path has not been reconstructed
The retained record does not yet show how air traveled from the proposed source to these metros. A trajectory replay or dated plume analysis belongs here.
- 3Documented
Local response
55.7 µg/m³ near Louisville/Jefferson County
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.5 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓
Event autopsy
What the instruments saw
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Fireworks” explanation; it does not assign the cause by itself.
Louisville/Jefferson County, KY-IN
Monitor comparison window 2003-07-01 to 2003-07-07 · PM2.5 target: Southwick
174% above nearby days
90% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 54.6 µg/m³
174% higher than surrounding days
Before19.9 µg/m³ Event54.6 µg/m³ After19.9 µg/m³
PM10 74 µg/m³
90% higher than surrounding days
Before39 µg/m³ Event74 µg/m³ After37 µg/m³
Carbon monoxide 0.596 ppm
About the same as surrounding days
Before0.865 ppm Event0.596 ppm After0.546 ppm
Nitrogen dioxide 12.2 ppb
22% higher than surrounding days
Before14.4 ppb Event12.2 ppb After6.32 ppb
Sulfur dioxide 2 ppb
25% lower than surrounding days
Before2.96 ppb Event2 ppb After2.67 ppb
Ozone 0.040 ppm
39% higher than surrounding days
Before0.026 ppm Event0.040 ppm After0.029 ppm
Atmospheric conditions
Nearby EPA weather observations8% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
Measured daily PM2.5 at EPA monitors, as cigarette-equivalents
EPA monitors sit in metro areas, so the colour clusters there. Land between and beyond
them is unmeasured, not clean: this map shows where IAQng has readings, not the extent
of the smoke.
—
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.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Louisville/Jefferson County, KY-IN | 55.7 µg/m³ | 2.5 | Jul 4, 2003 | #10 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.
Public evidence library
What supports this account
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
Effects of Independence Day fireworks on atmospheric concentrations of fine particulate matter in the United States
NOAA Air Resources Laboratory
A peer-reviewed analysis of 315 U.S. monitors from 1999-2013 found Independence Day PM2.5 elevated by 42 percent on average, with the largest hourly increase late July 4.
What it supports
Context for the event; this item does not establish the attributed cause by itself.
Limit
The national multi-year pattern does not independently prove fireworks caused any supplied metro's 2003 value.
July 4 aerosol pulse event report
FASTNET community / CAPITA
FASTNET's AirNow analysis reports a nationally discernible July 4-5 fireworks PM2.5 pulse and says a pulse of the same magnitude occurred on July 4, 2003.
What it supports
A retained source supports the attributed cause for the stated place and dates.
Limit
The published page shows a national aggregate, not a city-specific attribution.
July Fourth Fireworks Cause Brief Spike In Louisville Air Pollution
Louisville Public Media
Local reporting says Louisville fireworks caused a brief 2019 pollution spike and that July 4 displays exceeded the federal 24-hour particle standard in 2014 and 2015.
What it supports
Context for the event; this item does not establish the attributed cause by itself.
Limit
This establishes a recurring Louisville pattern, not direct attribution for 2003.
Holiday timing pattern
IAQng deterministic inference policy
The event peak falls on 2003-07-04 and the event lasts no more than two days. Under holiday_fireworks_possible.v1, that timing is consistent with a possible fireworks contribution.
What it supports
A possible fireworks contribution; this is a reproducible inference, not direct occurrence or causal evidence.
Limit
Pre-event and post-event temporal-shape data were not supplied.
What remains uncertain
- No exact local 2003 agency or newspaper attribution was recovered.
Status and provenance
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.