Mixed causes Likely
Daily PM2.5 peaked at 48.2 µg/m³ near Bridgeport across 5 covered metros home to 4.7 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.6 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 7.3 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
Manual research connected 5 source events to one mixed-source pollution episode using the deterministic grouping rule.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
NOAA Satellite Analysis Branch · Sep 13, 2005 corroborates
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana fires and lower-Mississippi agricultural or control burns, overlapping the Rochester, NY event.
NOAA Satellite Analysis Branch · Sep 12, 2005 hypothesis
The preceding NOAA analysis traced smoke from Idaho and Montana fires across southeastern Ontario and Lake Ontario into New York and New England, establishing continuity into the September 13 plume.
NOAA/NWS surface observations via Iowa Environmental Mesonet · Sep 13, 2005 hypothesis
ROCHESTER/MONROE CO, 10.9 km from the target PM2.5 monitor, reported haze during 12 observed hours on the event date.
See every retained source and limitation ↓
Sequence: Bridgeport (Sep 13) → New Haven (Sep 13) → Hartford (Sep 13) → Rochester (Sep 13) → Worcester (Sep 13)
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
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana…
View supporting source ↗Air-mass movement
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana…
View transport source ↗Local response
EPA monitors recorded the event across 5 metros. The peak daily concentration is roughly 2.2 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 “Mixed causes” explanation; it does not assign the cause by itself.
Bridgeport-Stamford-Norwalk, CT
Monitor comparison window 2005-09-10 to 2005-09-16 · PM2.5 target: Roosevelt School-Bridgeport
468% above nearby days
No adjacent-day comparison
468% higher than surrounding days
No adjacent-day comparison
35% higher than surrounding days
99% higher than surrounding days
130% higher than surrounding days
93% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
New Haven-Milford, CT
Monitor comparison window 2005-09-10 to 2005-09-16
416% above nearby days
No adjacent-day comparison
416% higher than surrounding days
No adjacent-day comparison
89% higher than surrounding days
221% higher than surrounding days
86% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Hartford-West Hartford-East Hartford, CT
Monitor comparison window 2005-09-10 to 2005-09-16 · PM2.5 target: McAuliffe Park
365% above nearby days
No adjacent-day comparison
365% higher than surrounding days
No adjacent-day comparison
17% higher than surrounding days
60% higher than surrounding days
143% higher than surrounding days
128% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Rochester, NY
Monitor comparison window 2005-09-10 to 2005-09-16 · PM2.5 target: ROCHESTER 2
472% above nearby days
60% higher than surrounding days
16% higher than surrounding days
472% higher than surrounding days
16% higher than surrounding days
42% higher than surrounding days
52% higher than surrounding days
8% lower than surrounding days
About the same as surrounding days
8% higher than surrounding days
60% higher than surrounding days
Worcester, MA-CT
Monitor comparison window 2005-09-10 to 2005-09-16 · PM2.5 target: WORCESTER SUMMER STREET
487% above nearby days
No adjacent-day comparison
487% higher than surrounding days
No adjacent-day comparison
16% higher than surrounding days
75% higher than surrounding days
58% higher than surrounding days
63% higher than surrounding days
5% 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.
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 |
|---|---|---|---|---|
| Bridgeport-Stamford-Norwalk, CT | 48.2 µg/m³ | 2.2 | Sep 13, 2005 | #15 of its top days |
| New Haven-Milford, CT | 47 µg/m³ | 2.1 | Sep 13, 2005 | #24 of its top days |
| Hartford-West Hartford-East Hartford, CT | 42.3 µg/m³ | 1.9 | Sep 13, 2005 | #21 of its top days |
| Rochester, NY | 38.3 µg/m³ | 1.7 | Sep 13, 2005 | #23 of its top days |
| Worcester, MA-CT | 36.3 µg/m³ | 1.6 | Sep 13, 2005 | #24 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.
NOAA/NWS surface observations via Iowa Environmental Mesonet
ROCHESTER/MONROE CO, 10.9 km from the target PM2.5 monitor, reported haze during 12 observed hours on the event date.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The airport observation and regulatory PM2.5 monitor are nearby but not co-located.
NOAA Satellite Analysis Branch
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana fires and lower-Mississippi agricultural or control burns, overlapping the Rochester, NY event.
A retained source supports the attributed cause for the stated place and dates.
The satellite narrative describes the regional plume and its mixed origins; it does not quantify ground-level PM2.5 or apportion the contribution from each source class at this metro.
NOAA/NWS surface observations via Iowa Environmental Mesonet
Bridgeport/Sikorsky, 5.7 km from the target PM2.5 monitor, reported haze during 21 observed hours on the event date.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The airport observation and regulatory PM2.5 monitor are nearby but not co-located.
NOAA Satellite Analysis Branch
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana fires and lower-Mississippi agricultural or control burns, overlapping the Bridgeport, CT event.
A retained source supports the attributed cause for the stated place and dates.
The satellite narrative describes the regional plume and its mixed origins; it does not quantify ground-level PM2.5 or apportion the contribution from each source class at this metro.
NOAA Satellite Analysis Branch
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana fires and lower-Mississippi agricultural or control burns, overlapping the New Haven, CT event.
A retained source supports the attributed cause for the stated place and dates.
The satellite narrative describes the regional plume and its mixed origins; it does not quantify ground-level PM2.5 or apportion the contribution from each source class at this metro.
NOAA/NWS surface observations via Iowa Environmental Mesonet
NEW HAVEN/TWEED, 3.6 km from the target PM2.5 monitor, reported haze during 11 observed hours on the event date.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The airport observation and regulatory PM2.5 monitor are nearby but not co-located.
NOAA/NWS surface observations via Iowa Environmental Mesonet
HARTFORD/BRAINARD, 5.5 km from the target PM2.5 monitor, reported haze during 17 observed hours on the event date.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The airport observation and regulatory PM2.5 monitor are nearby but not co-located.
NOAA Satellite Analysis Branch
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana fires and lower-Mississippi agricultural or control burns, overlapping the Hartford, CT event.
A retained source supports the attributed cause for the stated place and dates.
The satellite narrative describes the regional plume and its mixed origins; it does not quantify ground-level PM2.5 or apportion the contribution from each source class at this metro.
NOAA/NWS surface observations via Iowa Environmental Mesonet
Worcester, 6.7 km from the target PM2.5 monitor, reported haze during 12 observed hours on the event date.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The airport observation and regulatory PM2.5 monitor are nearby but not co-located.
NOAA Satellite Analysis Branch
NOAA satellite analysts mapped a broad smoke/haze area through the eastern Great Lakes and southern Ontario/Quebec, with thin smoke extending southeast off New England and Long Island. They attributed the plume to a combination of Idaho/Montana fires and lower-Mississippi agricultural or control burns, overlapping the Worcester, MA event.
A retained source supports the attributed cause for the stated place and dates.
The satellite narrative describes the regional plume and its mixed origins; it does not quantify ground-level PM2.5 or apportion the contribution from each source class at this metro.
NOAA Satellite Analysis Branch
The preceding NOAA analysis traced smoke from Idaho and Montana fires across southeastern Ontario and Lake Ontario into New York and New England, establishing continuity into the September 13 plume.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Satellite-observed smoke may be aloft and the narrative does not quantify surface contribution.
NOAA Satellite Analysis Branch
The preceding NOAA analysis traced smoke from Idaho and Montana fires across southeastern Ontario and Lake Ontario into New York and New England, establishing continuity into the September 13 plume.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Satellite-observed smoke may be aloft and the narrative does not quantify surface contribution.
NOAA Satellite Analysis Branch
The preceding NOAA analysis traced smoke from Idaho and Montana fires across southeastern Ontario and Lake Ontario into New York and New England, establishing continuity into the September 13 plume.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Satellite-observed smoke may be aloft and the narrative does not quantify surface contribution.
NOAA Satellite Analysis Branch
The preceding NOAA analysis traced smoke from Idaho and Montana fires across southeastern Ontario and Lake Ontario into New York and New England, establishing continuity into the September 13 plume.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Satellite-observed smoke may be aloft and the narrative does not quantify surface contribution.
NOAA Satellite Analysis Branch
The preceding NOAA analysis traced smoke from Idaho and Montana fires across southeastern Ontario and Lake Ontario into New York and New England, establishing continuity into the September 13 plume.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Satellite-observed smoke may be aloft and the narrative does not quantify surface contribution.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
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.