Daily PM2.5 peaked at 79.2 µg/m³ near Detroit across
6 covered metros home to 11 million people.
2 metros 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 ≈ 2.3 cigarettes.
Across everyone living in the affected metros, that is the collective equivalent of
≈ 25 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 “Other”
Qualified frozen evidence supports other documented PM source or accumulation mechanism as the broad root cause and supports grouping the contemporaneous affected events into one time-bounded episode. Qualified frozen evidence supports other documented PM source or accumulation mechanism as the broad root cause and supports grouping the contemporaneous affected events into one time-bounded episo
DocumentedAn agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
Journal of Geophysical Research: Atmospheres · Apr 15, 2021official
This retrospective scientific assessment identifies June 26–28, 2005 as a Midwest extreme aerosol event, with elevated PM2.5 at many EPA sites; its assessed regional-scale extreme events are described as dominated by anthropogenic emissions. It supports a regional anthropogenic-aerosol attribution, not a city-specific source apportionment.
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.
This retrospective scientific assessment identifies June 26–28, 2005 as a Midwest extreme aerosol event, with elevated PM2.5 at many EPA sites; its assessed regional-scale extreme events are described as dominated by anthropogenic emissions. It…
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
79.2 µg/m³ near Detroit
EPA monitors recorded the event across 6 metros.
The peak daily concentration is roughly 3.6 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 “Other” explanation; it does
not assign the cause by itself.
Observed context · not attribution
Akron, OH
Monitor comparison window 2005-06-24 to 2005-06-30 · PM2.5 target: Five Points
4 pollutant signals
Fine-particle pulse46.7 µg/m³
84% above nearby days
Carbon monoxide0.546 ppm
About the same as surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.546.7 µg/m³
84% higher than surrounding days
Before24.8 µg/m³ Event46.7 µg/m³ After25.4 µg/m³
Carbon monoxide0.546 ppm
About the same as surrounding days
Before0.480 ppm Event0.546 ppm After0.550 ppm
Sulfur dioxide7.87 ppb
About the same as surrounding days
Before12.7 ppb Event7.87 ppb After6.85 ppb
Ozone0.073 ppm
48% higher than surrounding days
Before0.068 ppm Event0.073 ppm After0.044 ppm
Cleveland-Elyria, OH
Monitor comparison window 2005-06-24 to 2005-06-30 · PM2.5 target: St Theodosius
6 pollutant signals
Fine-particle pulse50.6 µg/m³
90% above nearby days
PM1068 µg/m³
24% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.550.6 µg/m³
90% higher than surrounding days
Before26.7 µg/m³ Event50.6 µg/m³ After26.4 µg/m³
PM1068 µg/m³
24% higher than surrounding days
Before55 µg/m³ Event68 µg/m³ After47 µg/m³
Carbon monoxide0.564 ppm
34% higher than surrounding days
Before0.554 ppm Event0.564 ppm After0.400 ppm
Nitrogen dioxide21.6 ppb
5% lower than surrounding days
Before22.3 ppb Event21.6 ppb After24.6 ppb
Sulfur dioxide7 ppb
About the same as surrounding days
Before7.22 ppb Event7 ppb After5.75 ppb
Ozone0.075 ppm
44% higher than surrounding days
Before0.061 ppm Event0.075 ppm After0.043 ppm
Detroit-Warren-Dearborn, MI
Monitor comparison window 2005-06-24 to 2005-06-30 · PM2.5 target: New Haven
6 pollutant signals
Fine-particle pulse56.9 µg/m³
78% above nearby days
Air movement2.97 kt
13% lower than surrounding days
PM1095 µg/m³
44% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.556.9 µg/m³
78% higher than surrounding days
Before32 µg/m³ Event56.9 µg/m³ After29.4 µg/m³
PM1095 µg/m³
44% higher than surrounding days
Before66 µg/m³ Event95 µg/m³ After46 µg/m³
Carbon monoxide0.444 ppm
16% higher than surrounding days
Before0.244 ppm Event0.444 ppm After0.381 ppm
Nitrogen dioxide21.2 ppb
About the same as surrounding days
Before15.3 ppb Event21.2 ppb After29.6 ppb
Sulfur dioxide2.83 ppb
21% lower than surrounding days
Before6 ppb Event2.83 ppb After3.58 ppb
Ozone0.075 ppm
67% higher than surrounding days
Before0.045 ppm Event0.075 ppm After0.036 ppm
Atmospheric conditions
Nearby EPA weather observations
Humidity53.1 %
About the same as surrounding days
Pressure994 Millibars
About the same as surrounding days
Temperature83.6 °F
About the same as surrounding days
Wind2.97 kt
13% lower than surrounding days
Toledo, OH
Monitor comparison window 2005-06-24 to 2005-06-30 · PM2.5 target: Erie
4 pollutant signals
Fine-particle pulse52.7 µg/m³
97% above nearby days
PM1071 µg/m³
75% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.552.7 µg/m³
97% higher than surrounding days
Before26.7 µg/m³ Event52.7 µg/m³ After17.5 µg/m³
PM1071 µg/m³
75% higher than surrounding days
Before47 µg/m³ Event71 µg/m³ After34 µg/m³
Sulfur dioxide5.11 ppb
80% higher than surrounding days
Before2.94 ppb Event5.11 ppb After2.78 ppb
Ozone0.069 ppm
22% higher than surrounding days
Before0.064 ppm Event0.069 ppm After0.041 ppm
Grand Rapids-Wyoming, MI
Monitor comparison window 2005-06-24 to 2005-06-30 · PM2.5 target: Jenison
6 pollutant signals
Fine-particle pulse46.8 µg/m³
77% above nearby days
Air movement2.74 kt
About the same as surrounding days
PM1062 µg/m³
No adjacent-day comparison
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.546.8 µg/m³
77% higher than surrounding days
Before21.4 µg/m³ Event46.8 µg/m³ After28.6 µg/m³
PM1062 µg/m³
No adjacent-day comparison
Before— Event62 µg/m³ After—
Carbon monoxide0.317 ppm
About the same as surrounding days
Before0.242 ppm Event0.317 ppm After0.338 ppm
Nitrogen dioxide15.6 ppb
About the same as surrounding days
Before8.71 ppb Event15.6 ppb After17.9 ppb
Sulfur dioxide2.54 ppb
79% higher than surrounding days
Before0.625 ppb Event2.54 ppb After1.42 ppb
Ozone0.067 ppm
7% higher than surrounding days
Before0.056 ppm Event0.067 ppm After0.063 ppm
Atmospheric conditions
Nearby EPA weather observations
Pressure996 Millibars
About the same as surrounding days
Temperature81.9 °F
About the same as surrounding days
Wind2.74 kt
About the same as surrounding days
Milwaukee-Waukesha-West Allis, WI
Monitor comparison window 2005-06-24 to 2005-06-30 · PM2.5 target: MILWAUKEE - FIRE DEPT. HQ
6 pollutant signals
Fine-particle pulse46.8 µg/m³
79% above nearby days
PM1058 µg/m³
57% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors
PM2.546.8 µg/m³
79% higher than surrounding days
Before26.1 µg/m³ Event46.8 µg/m³ After8.90 µg/m³
PM1058 µg/m³
57% higher than surrounding days
Before21 µg/m³ Event58 µg/m³ After37 µg/m³
Carbon monoxide0.465 ppm
29% higher than surrounding days
Before0.360 ppm Event0.465 ppm After0.308 ppm
Nitrogen dioxide13.9 ppb
48% higher than surrounding days
Before6.13 ppb Event13.9 ppb After9.40 ppb
Sulfur dioxide5.67 ppb
134% higher than surrounding days
Before2 ppb Event5.67 ppb After2.42 ppb
Ozone0.071 ppm
59% higher than surrounding days
Before0.055 ppm Event0.071 ppm After0.041 ppm
Atmospheric conditions
Nearby EPA weather observations
Pressure1016 Millibars
About the same as surrounding days
Temperature79.9 °F
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.
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.
Journal of Geophysical Research: Atmospheres · Yafang Guo; Paola Crippa; Abhinav Thota; Sara C. Pryor · Apr 15, 2021official
This retrospective scientific assessment identifies June 26–28, 2005 as a Midwest extreme aerosol event, with elevated PM2.5 at many EPA sites; its assessed regional-scale extreme events are described as dominated by anthropogenic emissions. It supports a regional anthropogenic-aerosol attribution, not a city-specific source apportionment.
What remains uncertain
The retained evidence does not map the documented mechanism to a more specific catalog cause type.
Status and provenance
DocumentedAn agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
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.