Right now
The most recent data we hold from World Air Quality Index arrived 17 minutes ago, and this point is not in it. We record detections, not passes: an absence is not proof that nothing is there.
Nothing else has been detected within 20 km in the last 24 hours.
Reported by World Air Quality Index today.
It is the only one we have recorded within 20 km of this point since 30 April 2026. The last comparable one was on 30 April 2026.
What the source measured
World Air Quality Index reported: AQI 351 (Hazardous) at Ishikawa, Mito, Ibaraki, Japan (水戸石川水戸市)
The air quality index read 351 (Hazardous) at the Ishikawa, Mito, Ibaraki, Japan (水戸石川水戸市) station.
Urban PEI: 7,554 within a heuristic 5 km radius; not unique people.
How we know
One source: World Air Quality Index. Not yet confirmed by a second, independent source.
Our own score for this event is 50 out of 100.
This is our versioned heuristic index, not source severity or a calibrated probability. Urban PEI does not count unique people.
Computed under scoring rules v5. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Air Quality |
| Severity | Critical |
| Calamity Score (ours) | 50 / 100 |
| Legacy data-support index | 0.62/1 |
| Coordinates | 36.3924, 140.4259 |
| Nearest City | Mito (5 km) |
| Urban exposure index (PEI) | 7.6K within 5 km |
| Impact Tier | significant |
| Timestamp | 2026-09-25T06:00:00.000Z |
| Source | https://aqicn.org/city/@2275 |
Physical priority index · v5. Heuristic priority, not calibrated probability, predictive accuracy or damage. The legacy data-support index combines assigned source support and field availability. Urban PEI is distance-weighted and does not count unique people; zero does not establish that nobody is present. Model cards.
Source and revision timeline
Source: waqi. Occurrence: 2026-09-25T06:00:00.000Z.
First archived: 2026-09-25T07:57:51.737Z. Material modification: not recorded.
Retained revisions are prospective; earlier versions may be unavailable. No revision entry does not prove that a record never changed.
Score Breakdown
Technical Details
| Aqi | 351 |
| AqiCategory | Hazardous |
| StationName | Ishikawa, Mito, Ibaraki, Japan (水戸石川水戸市) |
| StationUid | 2275 |
Safety Information
When air quality is hazardous: stay indoors with windows closed, and run a filtered air purifier if you have one. Avoid outdoor exercise. Children, older adults and anyone with heart or lung conditions are affected first and worst — an N95 respirator helps outdoors, a cloth mask does not.
Series begins 8 March 2026. Comparisons refer to that period only. Collection gap: 14-26 August 2026.
This data is aggregated algorithmically from scientific sources. Not a replacement for official emergency warnings.
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