Stagnant pollution mixture Likely
Daily PM2.5 peaked at 107.2 µg/m³ near Bakersfield across 1 covered metro home to 922,529 people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 8.3 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 7.7 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
Contemporaneous reporting quotes the air district attributing the exact episode to an unusually low inversion, extreme stagnation, drought, and warm November conditions that concentrated locally formed secondary PM2.5.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
San Joaquin Valley Air Pollution Control District news clipping archive · Nov 13, 2014 corroborates
Archived local coverage reports Bakersfield PM2.5 spiking over the weekend while a Pacific high-pressure ridge lowered the inversion and locked existing particulate pollution near the surface.
KQED · Nov 12, 2014 corroborates
KQED quotes San Joaquin Valley air officials blaming unusually warm November temperatures and drought; they describe a low overnight inversion and extreme stagnation that pressed pollution toward the ground and allowed secondary PM2.5 to form.
ABC30 Fresno · Nov 8, 2014 corroborates
Contemporaneous San Joaquin Valley reporting quotes Valley Air District staff describing unhealthy and unhealthy-for-sensitive-groups air conditions during the November 8 episode; it does not assign a specific PM2.5 source for Bakersfield.
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
Archived local coverage reports Bakersfield PM2.5 spiking over the weekend while a Pacific high-pressure ridge lowered the inversion and locked existing particulate pollution near the surface.
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
Contemporaneous San Joaquin Valley reporting quotes Valley Air District staff describing unhealthy and unhealthy-for-sensitive-groups air conditions during the November 8 episode; it does not assign a specific PM2.5 source for Bakersfield.
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.
Bakersfield, CA
Monitor comparison window 2014-11-05 to 2014-11-12 · PM2.5 target: Bakersfield-Golden / M St
54% above nearby days
About the same as surrounding days
8% lower than surrounding days
54% higher than surrounding days
8% lower than surrounding days
About the same as surrounding days
7% lower than surrounding days
36% higher than surrounding days
About the same as 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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Bakersfield, CA | 107.2 µg/m³ | 9.5 | Nov 8, 2014 | #17 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.
San Joaquin Valley Air Pollution Control District news clipping archive
Archived local coverage reports Bakersfield PM2.5 spiking over the weekend while a Pacific high-pressure ridge lowered the inversion and locked existing particulate pollution near the surface.
A retained source supports the attributed cause for the stated place and dates.
The archive compiles newspaper reporting and shares the air district as the principal causal source with KQED.
KQED
KQED quotes San Joaquin Valley air officials blaming unusually warm November temperatures and drought; they describe a low overnight inversion and extreme stagnation that pressed pollution toward the ground and allowed secondary PM2.5 to form.
A retained source supports the attributed cause for the stated place and dates.
The article is Valley-wide and does not apportion Bakersfield's mass among tailpipe and other precursor sources.
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.