Dust EPA monitor flag
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
Qualified frozen evidence supports windblown-dust as the broad root cause of the 2010-04-11 PM2.5 episode affecting Bakersfield, CA.
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
U.S. EPA Air Quality System and the submitting air monitoring agency · Apr 11, 2010 official
EPA AQS carries an agency-submitted informational qualifier (IJ, High Winds.) on 12 PM2.5 samples in the candidate CBSA on 2010-04-11, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
U.S. EPA Air Quality System and the submitting air monitoring agency · Apr 11, 2010 official
EPA AQS carries an agency-submitted request-exclusion qualifier (RJ, High Winds.) on 1 PM2.5 sample in the candidate CBSA on 2010-04-11, identifying windblown or transported dust as affecting the sample. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
California Air Resources Board official
CARB staff concluded that the 107.8 µg/m³ reading at Bakersfield-Planz on April 11, 2010 was potentially caused by windblown fugitive dust during high winds, likely from disturbed airport-infield soils upwind of the monitor; it also found the value was not representative of Valley-wide ambient conditions.
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
EPA AQS carries an agency-submitted informational qualifier (IJ, High Winds.) on 12 PM2.5 samples in the candidate CBSA on 2010-04-11, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official…
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 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 “Dust” explanation; it does not assign the cause by itself.
Bakersfield, CA
Monitor comparison window 2010-04-08 to 2010-04-14 · PM2.5 target: Bakersfield-Airport (Planz)
656% above nearby days
146% higher than surrounding days
571% higher than surrounding days
656% higher than surrounding days
571% higher than surrounding days
45% lower 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
146% higher 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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Bakersfield, CA | 107.8 µg/m³ | 4.9 | Apr 11, 2010 | #15 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.
AQS PM2.5 qualifier IJ — High Winds.
EPA AQS carries an agency-submitted informational qualifier (IJ, High Winds.) on 12 PM2.5 samples in the candidate CBSA on 2010-04-11, identifying windblown or transported dust as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier RJ — High Winds.
EPA AQS carries an agency-submitted request-exclusion qualifier (RJ, High Winds.) on 1 PM2.5 sample in the candidate CBSA on 2010-04-11, identifying windblown or transported dust as affecting the sample. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
CARB staff concluded that the 107.8 µg/m³ reading at Bakersfield-Planz on April 11, 2010 was potentially caused by windblown fugitive dust during high winds, likely from disturbed airport-infield soils upwind of the monitor; it also found the value was not representative of Valley-wide ambient conditions.
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
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.