November 6, 2025: Seoul among the most polluted cities in the world

Is the air quality good in Seoul?

As of November 6, 2025, at 4 AM PT, air quality in Seoul, South Korea, is unhealthy for sensitive groups with an Air Quality Index (AQI) of 117. Residents are advised to limit prolonged outdoor exposure, especially individuals with respiratory or cardiovascular sensitivities.

Air quality is dynamic and, like the weather, can change frequently, Seoul ranks 14th among the most polluted major cities in the world today.

The affected region extends across western South Korea, impacting nearby cities such as Incheon, Suwon, Sejong, Gunsan, Jeonju, Seosan and Cheonan.

Click here for a real-time air quality map of Seoul.

While the  air quality conditions today are poor, it’s worth noting that the average PM2.5 concentration in 2024 for Seoul was 17.5 µg/m3, corresponding to an AQI of 62 (“moderate”), and was 3.5 times the WHO annual guideline of 5 µg/m3.

Seoul, South Korea ranked as the 14th most polluted major city on Nov 6, 2025 at 4 AM PT. Source: IQAir.

When will air quality improve in Seoul?

Air quality is forecasted to improve later in the day as wind conditions are expected to disperse fine particulate matter. Meteorological models indicate that PM2.5 levels will gradually decrease by the evening, returning to a range closer to “moderate” levels overnight.

Air quality forecast for Seoul, South Korea on Nov 6, 2025. Source: IQAir.

However, recurring episodes of high particulate matter are likely due to consistent traffic emissions and regional transport of pollutants from industrial and transboundary sources. Short-term improvement should be viewed as temporary, with overall pollution levels fluctuating based on weather and wind direction.

Air quality map of Seoul, South Korea on Nov 6, 2025. Source: IQAir.

What is causing poor air quality in Seoul?

Several factors are contributing to the poor air quality in Seoul:

• Traffic-related emissions: Continuous exposure to road traffic noise and pollution in Seoul contributes to both air and noise health burdens (1).
• Fine particulate matter (PM2.5): Seoul’s PM2.5 is composed largely of sulfate and nitrate compounds, which scatter sunlight and create a cooling optical effect but still contribute to health risks when inhaled (2).
• Urban density and weather conditions: Limited air circulation in the city traps emissions from vehicles, industrial areas, and heating systems.

Recent studies highlight that despite similar PM2.5 concentrations to other cities, Seoul’s aerosol composition differs chemically and optically. Sulfate and nitrate components dominate its atmosphere, reflecting light rather than absorbing it. Yet, these fine particles penetrate deep into the lungs, posing serious cardiovascular and respiratory health risks.

How can I protect myself from poor air quality?

• Get a free air quality app for real-time air quality alerts and forecasts.
• Shut doors and windows and set the HVAC to recirculate mode.
• Contribute to your community’s outdoor air quality data.
• Stay indoors when air quality is poor; if you do need to go outdoors, wear a KN95/FFP2 mask.
• Run a high-performance air purifier to filter particles, gases, and other pollutants.