2000-02-24 Albany-Schenectady-Troy, NY, Bridgeport-Stamford-Norwalk, CT, and 2 other metros mixed-source pollution episode
February 24, 2000
Daily PM2.5 peaked at 49.6 µg/m³ near Albany across
4 covered metros home to 3.1 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the
average affected resident ≈ 1.7 cigarettes.
Across everyone living in the affected metros, that is the collective equivalent of
≈ 5.3 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
The basis for “Mixed causes”
Manual research connected 4 source events to one mixed-source pollution episode using the deterministic grouping rule.
PossibleThis is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
Casco Bay Estuary Partnership air-deposition field program corroborates
The regional field program identifies February 24, 2000 as a high-sulfur and organic-carbon aerosol sample at its Casco Bay site and presents exact-date HYSPLIT back trajectories. Its broader analysis says the site's fine aerosol was dominated by sulfate and organic material and identifies a secondary/transport factor containing organic carbon, elemental carbon, nitrate, and sulfate.
EPA records show median daily PM2.5 of 48.4 micrograms per cubic meter across 3 monitors, 3.565 times the adjacent-window level. Co-pollutants at least 10% above the adjacent-window comparison were carbon monoxide (2.099x), sulfur dioxide (1.879x).
National Weather Service surface observations via Iowa Environmental Mesonet · Feb 24, 2000hypothesis
ALBANY COUNTY ARPT recorded calm conditions during 48% of event hours and wind at or below three knots during 56%. Observations included 7 haze hours, 7 mist hours, minimum visibility 1.25 miles.
Inference, not direct attribution
exact_date_regional_field_sample_mixed_fingerprint_possible.v1: This inference is recorded in the catalog methodology.
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.
The regional field program identifies February 24, 2000 as a high-sulfur and organic-carbon aerosol sample at its Casco Bay site and presents exact-date HYSPLIT back trajectories. Its broader analysis says the site's fine aerosol was dominated by…
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.
Research gap
3
Local response
49.6 µg/m³ near Albany
EPA monitors recorded the event across 4 metros.
The peak daily concentration is roughly 2.3 cigarette-equivalents at the outdoor daily rate.
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.
Observed context · not attribution
Albany-Schenectady-Troy, NY
Monitor comparison window 2000-02-21 to 2000-02-27 · PM2.5 target: ALBANY COUNTY HEALTH DEPT
4 pollutant signals
Fine-particle pulse48.4 µg/m³
240% above nearby days
Air movement3 kt median wind
11 calm hours observed
What observers saw1.25 mi minimum visibility
Haze reported during 7 hours
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.548.4 µg/m³
240% higher than surrounding days
Before14.3 µg/m³ Event48.4 µg/m³ After12.9 µg/m³
Carbon monoxide1.48 ppm
88% higher than surrounding days
Before0.787 ppm Event1.48 ppm After0.625 ppm
Sulfur dioxide14.2 ppb
282% higher than surrounding days
Before12 ppb Event14.2 ppb After3.08 ppb
Ozone0.006 ppm
71% lower than surrounding days
Before0.019 ppm Event0.006 ppm After0.022 ppm
Atmospheric conditions
ALBANY COUNTY ARPT, 13.4 km from the PM2.5 target
Wind3 kt median
8 kt maximum · 11 of 23 observed hours calm
Visibility1.25 mi minimum
6 observed hours at or below 3 miles
Temperature42°F median
38°F to 49°F
Humidity73% median
97% maximum
New Haven-Milford, CT
Monitor comparison window 2000-02-21 to 2000-02-27 · PM2.5 target: State St-New Haven
Monitor comparison window 2000-02-21 to 2000-02-27 · PM2.5 target: DEC REGIONAL OFFICE
4 pollutant signals
Fine-particle pulse34 µg/m³
84% above nearby days
Air movement4 kt median wind
1 calm hour observed
What observers saw5 mi minimum visibility
Haze reported during 2 hours
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.534 µg/m³
84% higher than surrounding days
Before18.5 µg/m³ Event34 µg/m³ After15.8 µg/m³
Carbon monoxide1.59 ppm
223% higher than surrounding days
Before0.492 ppm Event1.59 ppm After0.438 ppm
Sulfur dioxide6.62 ppb
128% higher than surrounding days
Before8.44 ppb Event6.62 ppb After1.41 ppb
Ozone0.014 ppm
55% lower than surrounding days
Before0.033 ppm Event0.014 ppm After0.031 ppm
Atmospheric conditions
SYRACUSE/HANCOCK, 8.5 km from the PM2.5 target
Wind4 kt median
8 kt maximum · 1 of 24 observed hours calm
Visibility5 mi minimum
0 observed hours at or below 3 miles
Temperature42°F median
34°F to 49°F
Humidity78% median
97% maximum
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.
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.
"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.
6 retained sources
Official record
Albany-Schenectady-Troy, NY surface conditions, 2000-02-24
National Weather Service surface observations via Iowa Environmental Mesonet
ALBANY COUNTY ARPT recorded calm conditions during 48% of event hours and wind at or below three knots during 56%. Observations included 7 haze hours, 7 mist hours, minimum visibility 1.25 miles.
What it supports
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Limit
A single surface station documents weak ventilation and obscuration but not the full vertical profile or particle source mix.
Official record
Albany-Schenectady-Troy, NY joint pollution fingerprint, 2000-02-24
U.S. EPA AirData
EPA records show median daily PM2.5 of 48.4 micrograms per cubic meter across 3 monitors, 3.565 times the adjacent-window level. Co-pollutants at least 10% above the adjacent-window comparison were carbon monoxide (2.099x), sulfur dioxide (1.879x).
What it supports
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Limit
The broad multi-pollutant response does not apportion traffic, heating, industry, wood combustion, or secondary aerosol.
Scientific research
Air Deposition of Pollutants to Casco Bay: February 24, 2000 high-sulfur and organic-carbon sample
Casco Bay Estuary Partnership air-deposition field program
The regional field program identifies February 24, 2000 as a high-sulfur and organic-carbon aerosol sample at its Casco Bay site and presents exact-date HYSPLIT back trajectories. Its broader analysis says the site's fine aerosol was dominated by sulfate and organic material and identifies a secondary/transport factor containing organic carbon, elemental carbon, nitrate, and sulfate.
What it supports
A retained source supports the attributed cause for the stated place and dates.
Limit
The sampled site was near Casco Bay, Maine, not one of the affected metros; it is retained as same-day regional composition and transport evidence rather than a metro-specific source apportionment.
Scientific research
Air Deposition of Pollutants to Casco Bay: February 24, 2000 high-sulfur and organic-carbon sample
Casco Bay Estuary Partnership air-deposition field program
The regional field program identifies February 24, 2000 as a high-sulfur and organic-carbon aerosol sample at its Casco Bay site and presents exact-date HYSPLIT back trajectories. Its broader analysis says the site's fine aerosol was dominated by sulfate and organic material and identifies a secondary/transport factor containing organic carbon, elemental carbon, nitrate, and sulfate.
What it supports
A retained source supports the attributed cause for the stated place and dates.
Limit
The sampled site was near Casco Bay, Maine, not one of the affected metros; it is retained as same-day regional composition and transport evidence rather than a metro-specific source apportionment.
Scientific research
Air Deposition of Pollutants to Casco Bay: February 24, 2000 high-sulfur and organic-carbon sample
Casco Bay Estuary Partnership air-deposition field program
The regional field program identifies February 24, 2000 as a high-sulfur and organic-carbon aerosol sample at its Casco Bay site and presents exact-date HYSPLIT back trajectories. Its broader analysis says the site's fine aerosol was dominated by sulfate and organic material and identifies a secondary/transport factor containing organic carbon, elemental carbon, nitrate, and sulfate.
What it supports
A retained source supports the attributed cause for the stated place and dates.
Limit
The sampled site was near Casco Bay, Maine, not one of the affected metros; it is retained as same-day regional composition and transport evidence rather than a metro-specific source apportionment.
Scientific research
Air Deposition of Pollutants to Casco Bay: February 24, 2000 high-sulfur and organic-carbon sample
Casco Bay Estuary Partnership air-deposition field program
The regional field program identifies February 24, 2000 as a high-sulfur and organic-carbon aerosol sample at its Casco Bay site and presents exact-date HYSPLIT back trajectories. Its broader analysis says the site's fine aerosol was dominated by sulfate and organic material and identifies a secondary/transport factor containing organic carbon, elemental carbon, nitrate, and sulfate.
What it supports
A retained source supports the attributed cause for the stated place and dates.
Limit
The sampled site was near Casco Bay, Maine, not one of the affected metros; it is retained as same-day regional composition and transport evidence rather than a metro-specific source apportionment.
What remains uncertain
A single surface station documents weak ventilation and obscuration but not the full vertical profile or particle source mix.
No exact or same-window source with enough causal and geographic specificity was recovered from the accessible government, scientific, news, archive, community, and meteorological web record.
No exact or same-window source with enough causal and geographic specificity was recovered from the accessible web record.
The broad multi-pollutant response does not apportion traffic, heating, industry, wood combustion, or secondary aerosol.
The presentation does not prove that every Northeast metro received the identical air mass or quantify local source fractions.
The result is capped at possible because no official source apportions the event's local PM2.5 mass.
The same pattern also occurred in benchmark temperature-inversion and regional-secondary-PM episodes.
The sampled site was near Casco Bay, Maine, not one of the affected metros; it is retained as same-day regional composition and transport evidence rather than a metro-specific source apportionment.
The strict joint-fingerprint rule achieved 22.2% precision for stagnant mixed pollution on the 56-case labeled benchmark.
Status and provenance
PossibleThis 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.