Dust Possible
Daily PM2.5 peaked at 40.1 µg/m³ near Jackson across 1 covered metro home to 606,178 people. 1 metro placed a top-ten day in their record.
Why we think this happened
An exact-date EPA chemical-speciation sample reconstructed 23.35 micrograms per cubic meter of PM2.5, of which 15.39 micrograms per cubic meter—about 66%—was the reconstructed soil component. PM10 and PM2.5 were both elevated on the event date. This supports dust-like mineral aerosol as the broad mechanism, but one speciation site cannot distinguish transported dust, local resuspension, construction, or another mineral source.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
U.S. EPA AirData Chemical Speciation Network corroborates
EPA's exact-date CSN sample at site 28-049-0020 reconstructed 23.35 µg/m³ of PM2.5. The reconstructed soil component was 15.39 µg/m³, or 66% of reconstructed mass.
eastoregonian.com · Aug 14, 2018 corroborates
ijpr.org · Aug 14, 2018 corroborates
Inference, not direct attribution
csn_soil_majority_on_peak_date_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
EPA's exact-date CSN sample at site 28-049-0020 reconstructed 23.35 µg/m³ of PM2.5. The reconstructed soil component was 15.39 µg/m³, or 66% of reconstructed mass.
View supporting source ↗Air-mass movement
NOAA HYSPLIT modeled 12 backward paths across multiple arrival times and heights. They show where the air traveled, not which source polluted it.
Explore the modeled paths ↓Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 1.8 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.
Jackson, MS
Monitor comparison window 2018-08-12 to 2018-08-18 · PM2.5 target: Hinds CC
75% above nearby days
12% lower than surrounding days
105% higher than surrounding days
75% higher than surrounding days
105% higher than surrounding days
452% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
14% lower than surrounding days
About the same as surrounding days
12% 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.
Air-mass reconstruction
NOAA HYSPLIT traces the air arriving at each metro backward for 72 hours. Multiple arrival times and heights show whether the broad path is stable—or sensitive to assumptions about when and where the polluted layer arrived.
Air arriving near Jackson
Peak-date arrivals · 2018-08-15
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
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 |
|---|---|---|---|---|
| Jackson, MS | 40.1 µg/m³ | 1.8 | Aug 15, 2018 | #8 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.
NOAA/NWS surface observations via Iowa Environmental Mesonet
JACKSON/HAWKINS FIELD, 1.4 km from the target monitor, reported 0 haze hour(s) and 1 mist hour(s). Winds were calm for 14 hours and at or below 3 knots for 18 hours.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The airport and regulatory pollution monitors are nearby but not co-located.
U.S. EPA AirData Chemical Speciation Network
EPA's exact-date CSN sample at site 28-049-0020 reconstructed 23.35 µg/m³ of PM2.5. The reconstructed soil component was 15.39 µg/m³, or 66% of reconstructed mass.
A retained source supports the attributed cause for the stated place and dates.
Chemical composition describes the sampled aerosol mixture but does not identify a named source, facility, or origin region.
U.S. EPA AirData
EPA observations show elevated PM2.5 across two monitoring series and PM10 of 78 micrograms per cubic meter at the available PM10 site on August 15. The exact-date speciation sample was dominated by reconstructed soil mass rather than sulfate, nitrate, or carbon.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
PM10 coverage is limited to one monitoring series, and the PM10 and speciation measurements need not be collocated.
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.