Stagnant pollution mixture Possible
Daily PM2.5 peaked at 54.2 µg/m³ near New York across 1 covered metro home to 20 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 ≈ 38 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
An exact-date EPA chemical-speciation sample reconstructed 37.6 micrograms per cubic meter of PM2.5, close enough to the 54.2 event peak to describe the episode. Secondary inorganic aerosol contributed about 48% and organic plus elemental carbon about 43%, while the metro fingerprint showed simultaneous PM2.5 and combustion-tracer increases. Nearby surface observations recorded haze or mist during ten hours and calm or light wind during nine hours. Together these data support accumulation of a mixed anthropogenic aerosol, but they do not identify a dominant source sector.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
U.S. EPA AirData Chemical Speciation Network corroborates
EPA's exact-date CSN sample at site 36-005-0110 reconstructed 37.6 µg/m³ of PM2.5. Sulfate plus nitrate contributed 48%; organic matter plus elemental carbon contributed 43%.
U.S. EPA AirData hypothesis
EPA observations show event-day PM2.5 elevated across 26 FRM monitoring series and 25 hourly series. Carbon monoxide and nitrogen dioxide also rose sharply relative to the surrounding comparison windows, with PM10 and sulfur dioxide elevated where available.
NOAA/NWS surface observations via Iowa Environmental Mesonet · Nov 9, 2009 hypothesis
New York/LaGuardia, 7.1 km from the target monitor, reported 3 haze hour(s) and 7 mist hour(s). Winds were calm for 8 hours and at or below 3 knots for 9 hours.
Inference, not direct attribution
exact_composition_haze_multimonitor_mixture_possible.v1: This inference is recorded in the catalog methodology.
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's exact-date CSN sample at site 36-005-0110 reconstructed 37.6 µg/m³ of PM2.5. Sulfate plus nitrate contributed 48%; organic matter plus elemental carbon contributed 43%.
View supporting source ↗Air-mass movement
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.
Local response
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
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Stagnant pollution mixture” explanation; it does not assign the cause by itself.
New York-Newark-Jersey City, NY-NJ-PA
Monitor comparison window 2009-11-06 to 2009-11-12 · PM2.5 target: MORRISANIA
410% above nearby days
About the same as surrounding days
No adjacent-day comparison
410% higher than surrounding days
No adjacent-day comparison
146% higher than surrounding days
115% higher than surrounding days
32% higher than surrounding days
60% higher than surrounding days
19% higher than surrounding days
About 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.
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 | 54.2 µg/m³ | 2.5 | Nov 9, 2009 | #23 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
New York/LaGuardia, 7.1 km from the target monitor, reported 3 haze hour(s) and 7 mist hour(s). Winds were calm for 8 hours and at or below 3 knots for 9 hours.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The airport and regulatory pollution monitors are nearby but not co-located.
U.S. EPA AirData
EPA observations show event-day PM2.5 elevated across 26 FRM monitoring series and 25 hourly series. Carbon monoxide and nitrogen dioxide also rose sharply relative to the surrounding comparison windows, with PM10 and sulfur dioxide elevated where available.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The pollutant products were not necessarily measured at the same sites, so the fingerprint describes the metro episode rather than a single collocated source profile.
U.S. EPA AirData Chemical Speciation Network
EPA's exact-date CSN sample at site 36-005-0110 reconstructed 37.6 µg/m³ of PM2.5. Sulfate plus nitrate contributed 48%; organic matter plus elemental carbon contributed 43%.
A retained source supports the attributed cause for the stated place and dates.
Chemical composition describes the sampled aerosol mixture but does not identify a named source, facility, or origin region.
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.