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 to 2003-07-05 Bridgeport-Stamford-Norwalk, CT, Hartford-West Hartford-East Hartford, CT, and 2 other metros fireworks episode
Daily PM2.5 peaked at 69.6 µg/m³ near Scranton across 4 covered metros home to 3.3 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 ≈ 1.9 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 6.4 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.
See every retained source and limitation ↓
Sequence: Scranton (Jul 4) → New Haven (Jul 5) → Bridgeport (Jul 5) → Hartford (Jul 5)
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
69.6 µg/m³ near Scranton
EPA monitors recorded the event across 4 metros. The peak daily concentration is roughly 3.2 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.
Scranton--Wilkes-Barre--Hazleton, PA
Monitor comparison window 2003-07-01 to 2003-07-08 · PM2.5 target: Wilkes-Barre
85% above nearby days
66% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 43.8 µg/m³
85% higher than surrounding days
Before22.6 µg/m³ Event43.8 µg/m³ After22 µg/m³
PM10 56 µg/m³
66% higher than surrounding days
Before34.5 µg/m³ Event56 µg/m³ After33 µg/m³
Carbon monoxide 0.254 ppm
58% higher than surrounding days
Before0.150 ppm Event0.254 ppm After0.171 ppm
Nitrogen dioxide 9.03 ppb
22% lower than surrounding days
Before14.1 ppb Event9.03 ppb After11.5 ppb
Sulfur dioxide 8.59 ppb
28% higher than surrounding days
Before4.98 ppb Event8.59 ppb After5.94 ppb
Ozone 0.048 ppm
20% higher than surrounding days
Before0.043 ppm Event0.048 ppm After0.034 ppm
Bridgeport-Stamford-Norwalk, CT
Monitor comparison window 2003-07-01 to 2003-07-08 · PM2.5 target: Health Dept
79% above nearby days
14% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 44 µg/m³
79% higher than surrounding days
Before18.1 µg/m³ Event44 µg/m³ After24.6 µg/m³
Carbon monoxide 0.878 ppm
14% higher than surrounding days
Before0.710 ppm Event0.878 ppm After0.754 ppm
Nitrogen dioxide 18.4 ppb
10% higher than surrounding days
Before16.7 ppb Event18.4 ppb After15.3 ppb
Sulfur dioxide 3.49 ppb
167% higher than surrounding days
Before0.536 ppb Event3.49 ppb After1.13 ppb
Ozone 0.059 ppm
21% higher than surrounding days
Before0.049 ppm Event0.059 ppm After0.046 ppm
Atmospheric conditions
Nearby EPA weather observationsAbout the same as surrounding days
About the same as surrounding days
Hartford-West Hartford-East Hartford, CT
Monitor comparison window 2003-07-01 to 2003-07-08
105% above nearby days
About the same as surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 35.1 µg/m³
105% higher than surrounding days
Before12.3 µg/m³ Event35.1 µg/m³ After17.7 µg/m³
Carbon monoxide 1.02 ppm
About the same as surrounding days
Before1.11 ppm Event1.02 ppm After1 ppm
Nitrogen dioxide 12.8 ppb
8% lower than surrounding days
Before15.2 ppb Event12.8 ppb After13.5 ppb
Sulfur dioxide 1.73 ppb
66% higher than surrounding days
Before1.13 ppb Event1.73 ppb After0.708 ppb
Ozone 0.058 ppm
23% higher than surrounding days
Before0.047 ppm Event0.058 ppm After0.048 ppm
Atmospheric conditions
Nearby EPA weather observations5% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
New Haven-Milford, CT
Monitor comparison window 2003-07-01 to 2003-07-08
66% above nearby days
45% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 38.7 µg/m³
66% higher than surrounding days
Before11.6 µg/m³ Event38.7 µg/m³ After24.5 µg/m³
PM10 59.5 µg/m³
45% higher than surrounding days
Before36 µg/m³ Event59.5 µg/m³ After40 µg/m³
Carbon monoxide 0.771 ppm
6% higher than surrounding days
Before0.600 ppm Event0.771 ppm After0.742 ppm
Nitrogen dioxide 19 ppb
About the same as surrounding days
Before22.5 ppb Event19 ppb After16.8 ppb
Sulfur dioxide 2.42 ppb
54% higher than surrounding days
Before1.81 ppb Event2.42 ppb After0.979 ppb
Ozone 0.066 ppm
38% higher than surrounding days
Before0.040 ppm Event0.066 ppm After0.036 ppm
Atmospheric conditions
Nearby EPA weather observationsAbout the same as 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.
Views from the selected metro
Camera views near
Select a metro on the map to see nearby cameras. Where an operator archive reaches the event, drag the divider to compare two moments, adjust either date and time, or play the available event-day frames. Camera imagery is visual context, not an air-quality measurement or proof of smoke.
No useful public camera views are currently available within 80 km of this metro.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Scranton--Wilkes-Barre--Hazleton, PA | 69.6 µg/m³ | 3.2 | Jul 4, 2003 | #7 of its top days |
| New Haven-Milford, CT | 51.6 µg/m³ | 2.3 | Jul 5, 2003 | #15 of its top days |
| Bridgeport-Stamford-Norwalk, CT | 46.1 µg/m³ | 2.1 | Jul 5, 2003 | #18 of its top days |
| Hartford-West Hartford-East Hartford, CT | 45.3 µg/m³ | 2.1 | Jul 5, 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.
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.
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.