Have you ever opened your window in the morning, taken a deep breath, and suddenly felt your throat sting and your chest tighten? Even though you heard the fine dust levels were "moderate" today. Why does this happen? Many people feel reassured by the word "moderate," but in reality, a variety of factors are influencing air quality at any given time.
AQI: A Composite Index, Not a Single Number
The AQI (Air Quality Index) does not refer to a single fine dust measurement. It is an index that combines six different pollutants: ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO), PM10, and PM2.5. In other words, even if PM10 is low, elevated PM2.5 levels or high ozone concentrations can still affect your health.
💡 AQI Components
- PM10 (Particulate matter 10 micrometers or smaller)
- PM2.5 (Fine particulate matter 2.5 micrometers or smaller)
- Ozone (O₃)
- Nitrogen Dioxide (NO₂)
- Carbon Monoxide (CO)
- Sulfur Dioxide (SO₂)
PM2.5 vs PM10: Why Your Throat Hurts
While PM10 particles are largely filtered out in the nose and throat, PM2.5 is far smaller and can penetrate deep into the alveoli of the lungs. As a result, even a "moderate" level of fine dust can cause a sore throat or coughing if PM2.5 temporarily spikes. Children, the elderly, and those with respiratory conditions are especially sensitive to these changes.
📊 PM2.5 vs PM10 Comparison
- PM10: diameter 10㎛ or less, mostly filtered in the bronchi
- PM2.5: diameter 2.5㎛ or less, penetrates deep into the lungs
- Health impact: PM2.5 is far more severe and long-lasting
Seasonal and Regional Differences in Air Quality
In spring, yellow dust blowing in from China combines with domestic pollutants, often causing both PM10 and PM2.5 to rise simultaneously. In summer, ozone becomes the primary pollutant — it forms when ultraviolet light reacts with vehicle emissions, and is particularly severe in urban areas.
For example, even with the same "moderate" reading, the perceived difference between Seoul and a mountainous area in Gangwon Province can be significant. Seoul's high traffic density and population lead to complex pollution, while mountainous regions benefit from greater natural air purification.
What Can You Do?
Don't rely solely on the AQI — always check the detailed figures. In particular, PM2.5 levels and ozone concentrations can directly affect sensitive individuals, so it's a good idea to check real-time concentrations on a reliable source like AirKorea.
✅ Practical Tips
- Run an indoor air purifier
- Wear a KF80 or higher-rated mask
- Avoid unnecessary outdoor activities
- Keep windows closed; wash your face and brush your teeth after going out
Conclusion
Don't feel too reassured by the word "moderate." The AQI is a composite index, and when individual components like PM2.5 or ozone are elevated, they can still impact your health. Building a habit of checking forecasts is important, but so is listening to what your body is telling you.
※ This content is based on general health information and is not a substitute for medical diagnosis or treatment.