Regional secondary PM Likely
Daily PM2.5 peaked at 53.4 µg/m³ near Scranton across 3 covered metros home to 2.3 million people. 1 metro 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 ≈ 2.2 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 5.1 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 Pennsylvania DEP-supported NE-OPS report identifies June 30-July 4 as the first major regional summer pollution episode of 2002, distinguishes it from the Canadian wildfire-smoke episode that began July 6, and attributes the earlier episode to transported pollution typical of summer ozone and PM events.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
Pennsylvania Department of Environmental Protection / NE-OPS · Jan 1, 2003 corroborates
The report identifies June 30-July 4 as a major summer ozone and PM episode caused by transported pollution from the westward boundary. It separately identifies July 6-8 as the Canadian forest-fire-smoke event, excluding that later smoke episode as the cause of these July 1-2 observations.
See every retained source and limitation ↓
Sequence: Scranton (Jul 1) → Syracuse (Jul 1) → Rochester (Jul 1)
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 report identifies June 30-July 4 as a major summer ozone and PM episode caused by transported pollution from the westward boundary. It separately identifies July 6-8 as the Canadian forest-fire-smoke event, excluding that later smoke episode as…
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 3 metros. The peak daily concentration is roughly 2.4 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 “Regional secondary PM” explanation; it does not assign the cause by itself.
Rochester, NY
Monitor comparison window 2002-06-28 to 2002-07-05
50% above nearby days
8% lower than surrounding days
14% higher than surrounding days
50% higher than surrounding days
14% higher than surrounding days
20% lower than surrounding days
37% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
5% higher than surrounding days
8% lower than surrounding days
Scranton--Wilkes-Barre--Hazleton, PA
Monitor comparison window 2002-06-28 to 2002-07-05 · PM2.5 target: Scranton
121% above nearby days
76% higher than surrounding days
121% higher than surrounding days
76% higher than surrounding days
96% higher than surrounding days
58% higher than surrounding days
88% higher than surrounding days
64% higher than surrounding days
Syracuse, NY
Monitor comparison window 2002-06-28 to 2002-07-05 · PM2.5 target: EAST SYRACUSE
183% above nearby days
19% lower than surrounding days
About the same as surrounding days
183% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
36% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
5% higher than surrounding days
19% lower 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 |
|---|---|---|---|---|
| Scranton--Wilkes-Barre--Hazleton, PA | 53.4 µg/m³ | 4.5 | Jul 2, 2002 | #13 of its top days |
| Syracuse, NY | 45.1 µg/m³ | 2.1 | Jul 1, 2002 | #10 of its top days |
| Rochester, NY | 42.4 µg/m³ | 1.9 | Jul 1, 2002 | #12 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.
Pennsylvania Department of Environmental Protection / NE-OPS
The report identifies June 30-July 4 as a major summer ozone and PM episode caused by transported pollution from the westward boundary. It separately identifies July 6-8 as the Canadian forest-fire-smoke event, excluding that later smoke episode as the cause of these July 1-2 observations.
A retained source supports the attributed cause for the stated place and dates.
The measurement campaign centered on the Northeast regional episode and does not provide monitor-by-monitor source apportionment for every listed metro.
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.