City report · South Korea
Sejong Air quality today
Air quality in Sejong currently reads AQI 117 (Unhealthy for sensitive groups): Sensitive groups should limit long or intense outdoor activity.
Air quality right now
AQI 117
Unhealthy for sensitive groups
- PM2.5, fine particles (µg/m³)
- 42.0
- tree cover
- 17.3%
- trees in this area
- 54.2K
- more trees needed
- 55.4K
Measured across a 2 km radius around Guncheong-ro, Jochiwon-eup, Sejong-si, South Korea (12.57 km²), from a satellite image of Sep 23, 2026. Lower AQI is better: 0–50 is Good, above 300 is Hazardous.
Sejong · AQI 117 (Unhealthy for sensitive groups)
Sejong's tree count comes to 54,187 trees across 12.53 km² of land, 18 points below the 35% tree-cover level considered healthy for this area, so roughly 55,439 more trees would close the gap.
Air quality detail
Air quality in Sejong today: AQI 117, Unhealthy for sensitive groups
Main pollutant: PM2.5 · Observed Nov 12, 00:00 local time via OpenAQ ground stations, US EPA index. Values in µg/m³.
Ground station · 조치원읍, 100 m away · median of 3 stations
Health signal
Sensitive groups should limit long or intense outdoor activity.
PM2.5
42.0
PM10
44.0
NO₂
53.2
O₃
6.3
SO₂
7.7
CO
704.5
Data: OpenAQ · Korea Air Ministry of Environment, Korea Environment Corporation · AirKorea
- Outdoor exercise
- Children, older adults and people with asthma or heart disease should cut down long or hard exercise
- Windows
- Close them to keep the outside air out
- Mask
- Sensitive groups: an N95 outdoors
- Air purifier
- Run one, especially in bedrooms
Over the last 7 days, the CAMS air-quality model put Sejong's daily AQI at 63 on average, from 47 on Nov 6 to an hourly peak of 88 on Nov 10.
Where Sejong stands: the most polluted cities in the world right now · the cleanest
Tree cover detail
Tree cover in Sejong: Critically low
17.3% tree cover against a 35% healthy-neighborhood target, across 12.53 km² of land.
Trees in this area
54,187
Target trees
109,626
More trees needed
55,439
CO₂ if planted / yr
1,220 t
Deforestation · 2001–2025
How much forest has Sejong lost?
Since 2001, the area within 10 km of Sejong has lost about 1,070 hectares of forest (about 1,500 football pitches): 15% of the forest it had in 2000. Most of it was lost to logging, so much of it can grow back. About 432 hectares (40%) was deforestation: forest cleared for good for farms, mines or towns.
2017: satellite photo from June 2017 of a 5 × 5 km area about 7 km west of the city center.
- Forest lost since 2001
- 1,070 haabout 1,500 football pitches
- Share of its forest
- 15%of what there was in 2000
- Cleared for good
- 432 hadeforestation: turned into farms, mines or towns
Forest loss has stayed about the same: about 64 hectares a year in 2021–2025, against 62 hectares a year in 2016–2020. The worst year was 2016, when about 108 hectares of forest were lost.
Hectares of forest lost each year
Show the figures as a table
| Year | Cleared for good | Can grow back | Total |
|---|---|---|---|
| 2001 | 3 ha | 3 ha | 6 ha |
| 2002 | 2 ha | 9 ha | 11 ha |
| 2003 | 2 ha | under 1 ha | 3 ha |
| 2004 | 12 ha | 8 ha | 20 ha |
| 2005 | 1 ha | 6 ha | 7 ha |
| 2006 | 5 ha | 12 ha | 17 ha |
| 2007 | 9 ha | 3 ha | 12 ha |
| 2008 | 39 ha | 12 ha | 50 ha |
| 2009 | 26 ha | 21 ha | 47 ha |
| 2010 | 42 ha | 16 ha | 58 ha |
| 2011 | 17 ha | 20 ha | 37 ha |
| 2012 | 22 ha | 9 ha | 30 ha |
| 2013 | 4 ha | 22 ha | 26 ha |
| 2014 | 12 ha | 42 ha | 53 ha |
| 2015 | 11 ha | 56 ha | 67 ha |
| 2016 | 36 ha | 72 ha | 108 ha |
| 2017 | 52 ha | 17 ha | 69 ha |
| 2018 | 20 ha | 12 ha | 32 ha |
| 2019 | 8 ha | 9 ha | 16 ha |
| 2020 | 18 ha | 64 ha | 83 ha |
| 2021 | 16 ha | 41 ha | 56 ha |
| 2022 | 28 ha | 78 ha | 106 ha |
| 2023 | 19 ha | 35 ha | 54 ha |
| 2024 | 18 ha | 41 ha | 59 ha |
| 2025 | 13 ha | 33 ha | 46 ha |
What is causing deforestation around Sejong?
- Loggingcan grow back60% · 639 ha
- Towns and roadscleared for good33% · 354 ha
- Mining and energycleared for good6.7% · 72 ha
Also: farms, pasture and plantations, unknown causes.
Causes for 2025 are estimates, based on what caused forest loss in the same places up to 2024.
Forest gained and lost, 2000–2020
- Forest in 2000
- 10,600 ha
- Forest in 2020
- 10,200 ha
- Overall change
- −419 haless forest than in 2000
Comparing satellite maps from 2000 and 2020, the forest around Sejong shrank from about 10,600 hectares to 10,200 hectares, a net loss of about 419 hectares (−3.9%). New forest grew on about 368 hectares, but 787 hectares were lost.
These 2000 and 2020 maps, from the University of Maryland, count any land with trees taller than 5 m as forest, including plantations and orchards. Forest that was cut or burned and had grown back by 2020 counts in both years, so the loss here is smaller than the yearly figures.
These figures cover everything within 10 km of the city center, a wider area than the report above, because forest is usually lost at a city's edges.
Source: Hansen/UMD/Google/USGS/NASA, Global Forest Change (GFC-2025-v1.13); causes: WRI/Google DeepMind drivers of forest loss; both CC BY 4.0, summed by Airleaf for each area. Forest gained and lost 2000–2020: Potapov et al. 2022, UMD GLAD Global Land Cover and Land Use Change, CC BY 4.0. Images: contains modified Copernicus Sentinel data. How it's measured
In the same region
Measured cities near Sejong
Same 2 km radius, same index — so they compare directly.
- Cheongju-si18.3 km
South Korea
- Tree cover
- 23%
- Air quality
- 115
- Cheonan26.9 km
South Korea
- Tree cover
- 13%
- Air quality
- 121
- Pyeongtaek48.3 km
South Korea
- Tree cover
- 10%
- Air quality
- 140
- Osan65.3 km
South Korea
- Tree cover
- 20%
- Air quality
- 90
- Chungju71.0 km
South Korea
- Tree cover
- 6%
- Air quality
- 82
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Frequently asked
Questions about Sejong
What is the air quality (AQI) in Sejong right now?
The latest reading for Sejong shows an AQI of 117 (Unhealthy for sensitive groups), measured Nov 12, 00:00 local time by 3 ground monitoring stations via OpenAQ (the median of their readings; the nearest is 조치원읍, 100 m away). The main pollutant is PM2.5. Sensitive groups should limit long or intense outdoor activity.
Is it safe to exercise outside in Sejong today?
At AQI 117 (Unhealthy for sensitive groups): children, older adults and people with asthma or heart disease should cut down long or hard exercise. Windows: close them to keep the outside air out. Masks: sensitive groups: an N95 outdoors. The reading changes through the day, so check again before a long run or ride.
What has the air quality in Sejong been like this week?
Over the last 7 days, the CAMS air-quality model put Sejong's daily AQI at 63 on average, from 47 on Nov 6 to an hourly peak of 88 on Nov 10. No day averaged above 100, the level where the air turns unhealthy for sensitive groups.
How much forest has the area around Sejong lost since 2001?
Since 2001, the area within 10 km of Sejong has lost about 1,070 hectares of forest (about 1,500 football pitches): 15% of the forest it had in 2000. Most of it was lost to logging, so much of it can grow back. About 432 hectares (40%) was deforestation: forest cleared for good for farms, mines or towns. Forest loss has stayed about the same: about 64 hectares a year in 2021–2025, against 62 hectares a year in 2016–2020. Comparing satellite maps from 2000 and 2020, the forest around Sejong shrank from about 10,600 hectares to 10,200 hectares, a net loss of about 419 hectares (−3.9%). New forest grew on about 368 hectares, but 787 hectares were lost.
What is the tree count in Sejong?
Sejong has an estimated 54,187 trees across the 12.53 km² of land measured — 17.3% tree cover, 18 percentage points short of the 35% tree-cover target set for this area.
How many more trees does Sejong need?
Sejong needs roughly 55,439 more trees to close a 18-point shortfall against its 35% tree-cover target — about 1,220 t of extra CO₂ absorbed per year once grown.
How are Sejong's air quality and tree cover measured?
Air quality is measured by ground monitoring stations near Guncheong-ro, via OpenAQ; the 7-day trend is the Open-Meteo / CAMS model's estimate. Tree cover is measured from Sentinel-2 L2A (ESA Copernicus) via Earth Search satellite imagery at 10 m detail across a 2 km radius around Guncheong-ro; the tree count is an estimate derived from that cover.
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