Wildfire smoke EPA monitor flag
Daily PM2.5 peaked at 56.4 µg/m³ near New York across 10 covered metros home to 34 million people.
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 ≈ 65 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
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-bo
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
U.S. EPA Air Quality System and the submitting air monitoring agency · Jul 22, 2004 official
EPA AQS carries an agency-submitted request-exclusion qualifier (E, Forest Fire.) on 1 PM2.5 sample in the candidate CBSA on 2004-07-22, 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.
U.S. EPA Air Quality System and the submitting air monitoring agency · Jul 21, 2004 official
EPA AQS carries an agency-submitted request-exclusion qualifier (E, Forest Fire.) on 2 PM2.5 samples in the candidate CBSA on 2004-07-21, 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.
U.S. EPA Air Quality System and the submitting air monitoring agency · Jul 21, 2004 official
EPA AQS carries an agency-submitted request-exclusion qualifier (E, Forest Fire.) on 1 PM2.5 sample in the candidate CBSA on 2004-07-21, 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.
See every retained source and limitation ↓
Sequence: Durham (Jul 21) → New York (Jul 22) → Allentown (Jul 22) → Scranton (Jul 22) → Charlotte (Jul 22) → Columbia (Jul 22) → Boston (Jul 23) → Springfield (Jul 23) → Jacksonville (Jul 23) → Worcester (Jul 23)
Evidence path
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.
Source or mechanism
EPA AQS carries an agency-submitted request-exclusion qualifier (E, Forest Fire.) on 1 PM2.5 sample in the candidate CBSA on 2004-07-22, identifying wildfire smoke as affecting the sample. A request-exclusion qualifier is an official…
View supporting source ↗Air-mass movement
Analysis of measured and modeled PM2.5 attributed a 24–42% median enhancement across the eastern United States during 19–23 July 2004 to transported particulate pollution from Alaskan forest fires; Jacksonville's event falls on the final day of that…
View transport source ↗Local response
EPA monitors recorded the event across 10 metros. The peak daily concentration is roughly 2.6 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓Event autopsy
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Wildfire smoke” explanation; it does not assign the cause by itself.
Allentown-Bethlehem-Easton, PA-NJ
Monitor comparison window 2004-07-19 to 2004-07-26 · PM2.5 target: Freemansburg
116% above nearby days
78% higher than surrounding days
116% higher than surrounding days
78% higher than surrounding days
26% higher than surrounding days
24% higher than surrounding days
56% higher than surrounding days
66% higher than surrounding days
New York-Newark-Jersey City, NY-NJ-PA
Monitor comparison window 2004-07-19 to 2004-07-26 · PM2.5 target: Elizabeth Lab
122% above nearby days
35% higher than surrounding days
13% higher than surrounding days
122% higher than surrounding days
13% higher than surrounding days
21% higher than surrounding days
41% higher than surrounding days
51% higher than surrounding days
12% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
35% higher than surrounding days
Scranton--Wilkes-Barre--Hazleton, PA
Monitor comparison window 2004-07-19 to 2004-07-26 · PM2.5 target: Scranton
111% above nearby days
96% higher than surrounding days
111% higher than surrounding days
96% higher than surrounding days
21% higher than surrounding days
6% higher than surrounding days
45% higher than surrounding days
34% higher than surrounding days
Springfield, MA
Monitor comparison window 2004-07-19 to 2004-07-26 · PM2.5 target: LIBERTY ST PARKING LOT
210% above nearby days
22% higher than surrounding days
210% higher than surrounding days
22% higher than surrounding days
67% higher than surrounding days
65% higher than surrounding days
72% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Boston-Cambridge-Newton, MA-NH
Monitor comparison window 2004-07-20 to 2004-07-26 · PM2.5 target: DUDLEY SQUARE ROXBURY
120% above nearby days
20% higher than surrounding days
120% higher than surrounding days
20% higher than surrounding days
35% lower than surrounding days
About the same as surrounding days
44% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Worcester, MA-CT
Monitor comparison window 2004-07-20 to 2004-07-26 · PM2.5 target: WORCESTER SUMMER STREET
109% above nearby days
5% higher than surrounding days
109% higher than surrounding days
5% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
17% higher than surrounding days
About the same as surrounding days
Durham-Chapel Hill, NC
Monitor comparison window 2004-07-18 to 2004-07-25
70% above nearby days
29% higher than surrounding days
70% higher than surrounding days
29% higher than surrounding days
33% lower than surrounding days
14% higher than surrounding days
Charlotte-Concord-Gastonia, NC-SC
Monitor comparison window 2004-07-18 to 2004-07-25
53% above nearby days
7% lower than surrounding days
42% higher than surrounding days
53% higher than surrounding days
42% higher than surrounding days
67% higher than surrounding days
32% higher than surrounding days
13% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
7% lower than surrounding days
Columbia, SC
Monitor comparison window 2004-07-18 to 2004-07-25 · PM2.5 target: BATES HOUSE
21% above nearby days
About the same as surrounding days
52% higher than surrounding days
21% higher than surrounding days
52% higher than surrounding days
11% higher than surrounding days
26% higher than surrounding days
About the same as surrounding days
6% higher than surrounding days
About the same as surrounding days
Jacksonville, FL
Monitor comparison window 2004-07-20 to 2004-07-27 · PM2.5 target: Mandarin
64% above nearby days
25% higher than surrounding days
64% higher than surrounding days
25% higher than surrounding days
12% higher than surrounding days
About the same as surrounding days
23% higher than surrounding days
11% higher than 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.
Air-mass reconstruction
NOAA HYSPLIT traces the air arriving at each metro backward for 72 hours. Multiple arrival times and heights show whether the broad path is stable—or sensitive to assumptions about when and where the polluted layer arrived.
Air arriving near Charlotte-Concord-Gastonia
Peak-date arrivals · 2004-07-22
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Columbia
Peak-date arrivals · 2004-07-22
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Durham-Chapel Hill
Peak-date arrivals · 2004-07-21
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Allentown-Bethlehem-Easton
Peak-date arrivals · 2004-07-22
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near New York-Newark-Jersey City
Peak-date arrivals · 2004-07-22
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Scranton--Wilkes-Barre--Hazleton
Peak-date arrivals · 2004-07-22
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Springfield
Peak-date arrivals · 2004-07-23
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Jacksonville
Peak-date arrivals · 2004-07-23
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Boston-Cambridge-Newton
Peak-date arrivals · 2004-07-23
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Worcester
Peak-date arrivals · 2004-07-23
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
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
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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| New York-Newark-Jersey City, NY-NJ-PA | 56.4 µg/m³ | 2.6 | Jul 22, 2004 | #15 of its top days |
| Allentown-Bethlehem-Easton, PA-NJ | 54.5 µg/m³ | 2.5 | Jul 22, 2004 | #24 of its top days |
| Scranton--Wilkes-Barre--Hazleton, PA | 47.2 µg/m³ | 2.1 | Jul 22, 2004 | #21 of its top days |
| Boston-Cambridge-Newton, MA-NH | 46.4 µg/m³ | 2.1 | Jul 23, 2004 | #18 of its top days |
| Springfield, MA | 44.7 µg/m³ | 2.0 | Jul 23, 2004 | #24 of its top days |
| Charlotte-Concord-Gastonia, NC-SC | 43.9 µg/m³ | 2.0 | Jul 22, 2004 | #14 of its top days |
| Jacksonville, FL | 40.4 µg/m³ | 3.6 | Jul 23, 2004 | #17 of its top days |
| Worcester, MA-CT | 39.9 µg/m³ | 1.8 | Jul 23, 2004 | #17 of its top days |
| Columbia, SC | 37.6 µg/m³ | 1.7 | Jul 22, 2004 | #22 of its top days |
| Durham-Chapel Hill, NC | 37.5 µg/m³ | 1.7 | Jul 21, 2004 | #16 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
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.
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 2004-07-22, 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 2004-07-21, 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 2004-07-21, 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 2004-07-22, 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.
Analysis of measured and modeled PM2.5 attributed a 24–42% median enhancement across the eastern United States during 19–23 July 2004 to transported particulate pollution from Alaskan forest fires; Jacksonville's event falls on the final day of that assessed period.
Smoke from Alaska Fires off U.S. East Coast
NASA reported widespread intense Alaskan-fire smoke crossing North America and being swept over the East Coast on 21 July 2004, corroborating the regional transport context shortly before the event.
A NASA workshop analysis identifies a July 18–22 PM2.5 AQI episode, a plume from Alaskan forest fires, and merger of smoke and sulfate plumes over the Eastern Seaboard on July 22. It supports regional smoke transport as a hypothesis, but does not quantify or specifically attribute the listed metro-area observations.
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
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.