Stagnant pollution mixture Possible
Daily PM2.5 peaked at 107.8 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 ≈ 4.3 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 4.0 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 National Weather Service's January 2015 record describes persistent stagnant air degrading San Joaquin Valley air quality and a weak disturbance reaching Kern County on January 10. A California Air Resources Board study of the month reports nitrate accumulation in Bakersfield. Together they support a possible stagnant anthropogenic mixture, but neither source apportions the exact January 10 monitor value.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
National Weather Service Hanford hypothesis
NWS documented persistent stagnant air and degraded San Joaquin Valley air quality during January 2015 and a weak disturbance bringing only light precipitation to Kern County on January 10.
Inference, not direct attribution
monthly_speciation_stagnation_possible.v1: This inference is recorded in the catalog methodology.
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
monthly_speciation_stagnation_possible.v1. This inference is recorded in the catalog methodology.
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 1 metro. The peak daily concentration is roughly 4.9 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 “Stagnant pollution mixture” explanation; it does not assign the cause by itself.
Bakersfield, CA
Monitor comparison window 2015-01-07 to 2015-01-13 · PM2.5 target: Bakersfield-California
27% above nearby days
About the same as surrounding days
About the same as surrounding days
27% 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
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 | 107.8 µg/m³ | 4.9 | Jan 10, 2015 | #16 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.
California Air Resources Board
CARB's month-scale analysis reports that particulate nitrate accumulated in Bakersfield during January 2015 even though the month lacked a single consistent valley-wide stagnation episode.
Context for the event; this item does not establish the attributed cause by itself.
The analysis is month-scale and does not attribute the January 10 daily peak.
National Weather Service Hanford
NWS documented persistent stagnant air and degraded San Joaquin Valley air quality during January 2015 and a weak disturbance bringing only light precipitation to Kern County on January 10.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The report documents meteorology and regional air-quality context, not exact-day source apportionment.
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.