Dust Agency determination
Daily PM2.5 peaked at 40.8 µg/m³ near Las Vegas across 1 covered metro home to 2.4 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.5 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 3.5 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 supplied evidence supports dust as the root cause of this event. The supplied record does not establish a coherent shared occurrence with neighboring candidates, so the episode remains event-specific.
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
U.S. EPA Air Quality System and the submitting air monitoring agency · Apr 11, 2022 official
EPA AQS carries an agency-submitted informational qualifier (IJ, High Winds.) on 672 PM2.5 samples in the candidate CBSA on 2022-04-11, 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.
NOAA/NCEI Storm Events Database · Apr 11, 2022 corroborates
Webcams showed dust storm conditions reducing visibility below 1/4 mile across parts of the Las Vegas Valley.
NOAA National Centers for Environmental Information corroborates
NOAA records a Dust Storm in the Las Vegas Valley on April 11, with webcam-observed visibility below one-quarter mile. This corroborates a dust episode but does not quantify its PM2.5 contribution.
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 672 PM2.5 samples in the candidate CBSA on 2022-04-11, 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
NOAA records a Dust Storm in the Las Vegas Valley on April 11, with webcam-observed visibility below one-quarter mile. This corroborates a dust episode but does not quantify its PM2.5 contribution.
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.
Las Vegas-Henderson-Paradise, NV
Monitor comparison window 2022-04-08 to 2022-04-14 · PM2.5 target: Sunrise Acres
445% above nearby days
80% higher than surrounding days
815% higher than surrounding days
445% higher than surrounding days
815% 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
36% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
80% 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.
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 |
|---|---|---|---|---|
| Las Vegas-Henderson-Paradise, NV | 40.8 µg/m³ | 1.9 | Apr 11, 2022 | #22 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 672 PM2.5 samples in the candidate CBSA on 2022-04-11, 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.
Storm Events Database event 1025186: Dust Storm in Las Vegas Valley
NOAA records a Dust Storm in the Las Vegas Valley on April 11, with webcam-observed visibility below one-quarter mile. This corroborates a dust episode but does not quantify its PM2.5 contribution.
NWS Dust Storm record, LAS VEGAS VALLEY, NEVADA (2022-04-11)
Webcams showed dust storm conditions reducing visibility below 1/4 mile across parts of the Las Vegas Valley.
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
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.