Mixed causes Possible
Daily PM2.5 peaked at 49 µg/m³ near Akron across 3 covered metros home to 3.7 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.1 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 7.8 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 3 source events to one mixed-source pollution episode using the deterministic grouping rule.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
U.S. Environmental Protection Agency archive · Jul 15, 2004 corroborates
The archived regional analysis concludes that the unusually widespread June 25 ozone episode was dominated by transported pollution, supported by back trajectories showing the affected air mass moving through the region.
U.S. EPA AirData hypothesis
EPA records show median daily PM2.5 of 45.575 micrograms per cubic meter across 3 monitors, 2.45 times the adjacent-window level. Co-pollutants at least 10% above the adjacent-window comparison were carbon monoxide (1.451x), sulfur dioxide (2.661x).
National Weather Service surface observations via Iowa Environmental Mesonet · Jun 24, 2003 hypothesis
WRIGHT PATERSON recorded calm conditions during 0% of event hours and wind at or below three knots during 60%. Observations included 9 haze hours, 9 mist hours, minimum visibility 2 miles.
Inference, not direct attribution
documented_regional_polluted_airmass_overlap_possible.v1: This inference is recorded in the catalog methodology.
See every retained source and limitation ↓
Sequence: Dayton (Jun 24) → Akron (Jun 25) → Columbus (Jun 25)
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
The archived regional analysis concludes that the unusually widespread June 25 ozone episode was dominated by transported pollution, supported by back trajectories showing the affected air mass moving through the region.
View supporting source ↗Air-mass movement
The archived regional analysis concludes that the unusually widespread June 25 ozone episode was dominated by transported pollution, supported by back trajectories showing the affected air mass moving through the region.
View transport source ↗Local response
EPA monitors recorded the event across 3 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.
Akron, OH
Monitor comparison window 2003-06-22 to 2003-06-28 · PM2.5 target: East HS
96% above nearby days
8 calm hours observed
Haze reported during 9 hours
96% higher than surrounding days
44% higher than surrounding days
About the same as surrounding days
201% higher than surrounding days
30% higher than surrounding days
10 kt maximum · 8 of 24 observed hours calm
0 observed hours at or below 3 miles
64°F to 87°F
90% maximum
Columbus, OH
Monitor comparison window 2003-06-22 to 2003-06-28 · PM2.5 target: ANN ST.
165% above nearby days
6 calm hours observed
Haze reported during 13 hours
165% higher than surrounding days
97% higher than surrounding days
11% higher than surrounding days
96% higher than surrounding days
31% higher than surrounding days
10 kt maximum · 6 of 24 observed hours calm
0 observed hours at or below 3 miles
64°F to 88°F
93% maximum
Dayton, OH
Monitor comparison window 2003-06-21 to 2003-06-28 · PM2.5 target: LIBRARY (DAYTON PUBLIC
112% above nearby days
9 kt maximum
Haze reported during 9 hours
112% higher than surrounding days
20% higher than surrounding days
149% higher than surrounding days
52% higher than surrounding days
9 kt maximum · No calm observed hours
3 observed hours at or below 3 miles
59°F to 89.6°F
100% 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.
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 |
|---|---|---|---|---|
| Akron, OH | 49 µg/m³ | 2.2 | Jun 25, 2003 | #15 of its top days |
| Columbus, OH | 48.9 µg/m³ | 2.2 | Jun 25, 2003 | #19 of its top days |
| Dayton, OH | 48.6 µg/m³ | 4.3 | Jun 25, 2003 | #13 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.
U.S. Environmental Protection Agency archive
The archived regional analysis concludes that the unusually widespread June 25 ozone episode was dominated by transported pollution, supported by back trajectories showing the affected air mass moving through the region.
A retained source supports the attributed cause for the stated place and dates.
The analysis addresses ozone and Southeast Michigan; it supports regional transport on the exact date but cannot apportion Ohio PM2.5.
U.S. Environmental Protection Agency archive
The archived regional analysis concludes that the unusually widespread June 25 ozone episode was dominated by transported pollution, supported by back trajectories showing the affected air mass moving through the region.
A retained source supports the attributed cause for the stated place and dates.
The analysis addresses ozone and Southeast Michigan; it supports regional transport on the exact date but cannot apportion Ohio PM2.5.
U.S. Environmental Protection Agency archive
The archived regional analysis concludes that the unusually widespread June 25 ozone episode was dominated by transported pollution, supported by back trajectories showing the affected air mass moving through the region.
A retained source supports the attributed cause for the stated place and dates.
The analysis addresses ozone and Southeast Michigan; it supports regional transport on the exact date but cannot apportion Ohio PM2.5.
NASA Earth Observatory
NASA reported that SeaWiFS observed thick haze along the U.S. eastern seaboard on June 24, concentrated around an offshore low, and described Canadian-fire smoke as a possible contributor.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
NASA used tentative language about smoke and did not attribute ground-level PM2.5 at any of the catalog metros.
National Weather Service surface observations via Iowa Environmental Mesonet
WRIGHT PATERSON recorded calm conditions during 0% of event hours and wind at or below three knots during 60%. Observations included 9 haze hours, 9 mist hours, minimum visibility 2 miles.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
A single surface station documents weak ventilation and obscuration but not the full vertical profile or particle source mix.
U.S. EPA AirData
EPA records show median daily PM2.5 of 45.575 micrograms per cubic meter across 3 monitors, 2.45 times the adjacent-window level. Co-pollutants at least 10% above the adjacent-window comparison were carbon monoxide (1.451x), sulfur dioxide (2.661x).
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The broad multi-pollutant response does not apportion traffic, heating, industry, wood combustion, or secondary aerosol.
U.S. Environmental Protection Agency AirNow
EPA's teaching case preserves the hour-by-hour Midwest ozone maps for June 25, 2003, including Dayton and Columbus in the mapped regional air-quality progression.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The maps are for ozone, not PM2.5, and establish a regional polluted-air episode rather than a particulate source allocation.
U.S. Environmental Protection Agency AirNow
EPA's teaching case preserves the hour-by-hour Midwest ozone maps for June 25, 2003, including Dayton and Columbus in the mapped regional air-quality progression.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The maps are for ozone, not PM2.5, and establish a regional polluted-air episode rather than a particulate source allocation.
Northeast Ohio Areawide Coordinating Agency
NOACA's historical trend table records widespread eight-hour ozone exceedances across Northeast Ohio on June 23, 24, and 25, with seven to ten monitors exceeding the standard on each day.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
Ozone documents a regional photochemical-pollution episode but does not determine the composition or source fractions of the simultaneous PM2.5.
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.