Air quality comparison · South Korea, 140 km apart
Daejeon vs Seoul Air quality index (AQI) today
Daejeon has cleaner air than Seoul right now: AQI 79 (Moderate) against 90 (Moderate).
Both sit in the same EPA band, so the health advice is the same for each today. Over the past 6 days, on modeled daily averages, Daejeon averaged AQI 60 against 66, and it was the cleaner of the two on 5 of those days. Daejeon has lost more forest since 2001. Seoul has more tree cover.
Updated . Lower is better on the US EPA index: 0–50 is Good, above 300 is Hazardous. Measured by Airleaf.
Daejeon79Seoul90
Head to head
Daejeon vs Seoul at a glance
Daejeon and Seoul are level, each ahead on 3 of 6 measures. The better figure in each row is marked.
| Daejeon | Seoul | |
|---|---|---|
| Air quality nowUS AQI. Lower is better. | 79 (better) | 90 |
| PM2.5Fine particles, µg/m³. | 24 (better) | 30 |
| Past week's averageUS AQI, 6 days. | 60 (better) | 66 |
| Forest lost since 2001Within 10 km of the center. | 191 ha | 14 ha (better) |
| Tree coverWithin 2 km of the center. | 13.6% | 20.3% (better) |
| Trees still neededTo reach a healthy canopy. | 51.3K | 30.3K (better) |
Air quality today
What is the air like in Daejeon and Seoul right now?
Daejeon has cleaner air than Seoul right now: AQI 79 (Moderate) against 90 (Moderate). PM2.5 is setting the index in both.
Daejeon's PM2.5 is about 1.6× the WHO's 24-hour guideline of 15 µg/m³. Seoul's PM2.5 is about 2.0× the WHO's 24-hour guideline of 15 µg/m³.
Both readings come from nearby ground stations.
DaejeonSeoul
Concentrations at the same moment as the index above, for the pollutants both places report. Lower is better. The dark marks on the PM2.5 and PM10 rows show the WHO's 24-hour guidelines (15 and 45 µg/m³).
Daejeon: Ground station · 둔산동, 600 m away · median of 14 stations. Data: OpenAQ · Korea Air Ministry of Environment, Korea Environment Corporation · AirKorea.
Seoul: Ground station · 중구, 300 m away · median of 25 stations. Data: OpenAQ · Korea Air Ministry of Environment, Korea Environment Corporation · AirKorea.
The past week
Which had cleaner air over the past 6 days?
Over the past 6 days, on modeled daily averages, Daejeon averaged AQI 60 against 66, and it was the cleaner of the two on 5 of those days. A single reading can catch a city on a bad afternoon; the week says whether it was the weather or the place.
- Cleaner days
- Daejeon5Seoul1
- Average AQI
- Daejeon60Seoul66
- Worst day, AQI
- Daejeon66Seoul92
The daily numbers (6 days)
| Day | Daejeon | Seoul |
|---|---|---|
| Nov 5 | 66 | 92 |
| Nov 6 | 47 | 52 |
| Nov 7 | 53 | 54 |
| Nov 8 | 66 | 68 |
| Nov 9 | 62 | 58 |
| Nov 10 | 65 | 69 |
Daily averages from the CAMS atmospheric model for both places, so the week compares like with like. They can differ from today's reading at the top of the page wherever that comes from a ground station.
What it means today
Is it safe to go outside in Daejeon and Seoul today?
Unusually sensitive people should consider limiting long outdoor exertion. Both are in the same EPA band today (Moderate), so the advice is the same.
Exercise outdoors
Fine for most people; unusually sensitive people should take long or hard exercise easier.
Windows
Fine to open; close them if you are sensitive to pollution.
Masks
Not needed for most people.
Air purifier
Worth running if you are sensitive.
Against everywhere else
How do Daejeon and Seoul compare with the rest of the world?
Right now Daejeon's air is cleaner than 31% of the 5,420 places Airleaf tracks, and Seoul's is cleaner than 26%. Within South Korea, that is 47% and 24% of its 56 measured places.
Cleaner air than…
- Daejeon
- Beats 31%
- Seoul
- Beats 26%
More tree cover than…
- Daejeon
- Beats 31%
- Seoul
- Beats 48%
Includes model estimates as well as station readings, so it can differ from our most polluted and cleanest air rankings, which use station readings only.
Deforestation · 2001–2025
Which has lost more forest, Daejeon or Seoul?
Daejeon has lost more: about 191 ha of forest within 10 km of its center from 2001 to 2025, against 14 ha around Seoul. 121 ha of that was cleared for good, for farms, mines or towns.
Measured within 10 km of each center, from the yearly satellite maps of forest loss: a wider circle than the one for tree cover, because forest is usually lost at a city's edges.
Worst year: 2020, with 23 ha lost.
Worst year: 2023, with 2 ha lost.
| Daejeon | Seoul | |
|---|---|---|
| Forest lost since 2001Cleared, burned or logged. | 191 ha | 14 ha (better) |
| Share of its forestOf what it had in 2000. | 2.2% | under 1% (better) |
| Cleared for goodTurned into farms, mines or towns. | 121 ha | 7 ha (better) |
| Recent trend2021–2025 against the five years before. | Too little to call | Too little to call |
| Main known cause | Towns and roads (62%) | Towns and roads (53%) |
Satellite timelapses
Watch both change, year by year
A clear satellite photo a year of the land around each city. Press play, turn on the forest cleared since the first year, or drag the before and after.
Daejeon
2017: satellite photo from June 2017 of a 5 × 5 km area about 7 km northeast of the city center.
Seoul
2017: satellite photo from June 2017 of a 5 × 5 km area in the city center.
Trees
Which has more trees, Daejeon or Seoul?
Seoul has more tree cover: 20.3% of the land within 2 km of its center against 13.6% around Daejeon, or about 63,328 trees against 42,512.
The dark mark is each place's canopy target: 30% of the land, raised where air quality is poor.
| Daejeon | Seoul | |
|---|---|---|
| Trees standingEstimated from the canopy area. | 42.5K | 63.3K (better) |
| Trees still neededTo reach the target. Fewer is better. | 51.3K | 30.3K (better) |
| CO₂ absorbed each yearBy the trees already standing. | 935K kg | 1.4M kg (better) |
Tree cover on the satellite image
The same 2 km radius around each center, with the tree cover the satellite found marked on it.
Reading these numbers
How this comparison is made
Air quality index
The US EPA index, computed from current pollutant concentrations: ground stations where a place has them nearby, and the CAMS atmospheric model everywhere else. It moves hour to hour, so it is a snapshot rather than a verdict on either place. The guideline marks are from the WHO's 2021 air quality guidelines.
Trees and forest
Tree cover is the share of ground under canopy within 2 km of each center, read from Sentinel-2 satellite imagery at 10 m detail. It measures that circle, not the whole municipality, which is what makes the two comparable. Forest loss comes from the University of Maryland's Global Forest Change maps.
More on the method on the About Airleaf page.
Frequently asked
Daejeon vs Seoul: your questions answered
Is Daejeon cleaner than Seoul?
On air quality, yes, right now: Daejeon reads AQI 79 against 90, a gap of 11 points on the US EPA index. This is a live reading rather than an annual average, so it can reverse within a day. Over the past 6 days, on modeled daily averages, Daejeon averaged AQI 60 against 66, and it was the cleaner of the two on 5 of those days.
Is it safe to exercise outdoors in Daejeon and Seoul today?
The advice is the same for both today. Unusually sensitive people should consider limiting long outdoor exertion. Daejeon reads AQI 79 and Seoul reads AQI 90.
Which has lost more forest, Daejeon or Seoul?
Daejeon has lost more: about 191 ha of forest within 10 km of its center from 2001 to 2025, against 14 ha around Seoul. 121 ha of that was cleared for good, for farms, mines or towns.
Which has more trees, Daejeon or Seoul?
Seoul has more tree cover: 20.3% of the land within 2 km of its center against 13.6% around Daejeon, or about 63,328 trees against 42,512. Both figures describe the same-sized circle of ground around each center, not the whole municipality.
How many more trees do Daejeon and Seoul need?
Daejeon needs about 51,265 more to reach its canopy target of 30%, and Seoul about 30,260 to reach 30%. The target starts at 30% of the land and rises where air quality is poor.
Are Daejeon and Seoul measured the same way?
The method is the same: the US EPA index for air, and Sentinel-2 satellite imagery at 10 m detail over an identical radius for trees. Both readings come from nearby ground stations. Nothing is adjusted for population, city limits or climate.
How often does the Daejeon vs Seoul comparison update?
The air readings refresh about once an hour, and each reading's local time is shown at the top of the page. Tree cover comes from the latest clear satellite image of each area (Sep 8, 2026 and Sep 18, 2026), and the forest figures are published yearly.
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