fine dust PM2.5 30 µg/m³ — AQI 90
fine dust PM2.5 at 30 µg/m³ scores 90 on the US index, and the Korean grade calls it moderate.
Both systems agree here
- Concentration
- 30 µg/m³
- US index (AQI)
- 90
- US category
- moderate
- Korean grade
- moderate
- Concentration that makes 100
- 35.4 µg/m³
- A day of this in cigarettes
- 1.36
Same number, different verdict
A Korean forecast calls PM10 of 150 "bad", but the same value in the US index is 98 — still moderate. The other way round, PM2.5 of 40 has only just crossed into "bad" in Korea while the US index already reads 112, unhealthy for sensitive groups. Neither is wrong; they hold different rulers. Move country and the same air reads differently.
Put in cigarettes
Breathing air at 22 µg/m³ of PM2.5 for a day is reckoned to be about one cigarette. The figure comes from Berkeley Earth, and it turns an abstract number into something the body understands: a day outdoors at 75 µg/m³ works out to three cigarettes.
Nearby cells
Same pollutant, other concentrations
How to read this
- On the left is the US index, on the right the Korean grade — the same concentration measured with two rulers.
- Index values of 50, 100 and 150 are the boundaries; that is where the category name changes.
- Forecast grades are usually daily averages, not the reading at this moment.
- The cigarette figure is only for PM2.5 and assumes a full day of exposure.
Frequently asked questions
Q. How bad is fine dust PM2.5 at 30 µg/m³?
90 on the US index, and moderate on the Korean scale.
Q. Do the two systems agree?
Yes, both read it the same way here.
Q. What concentration would make the index 100?
35.4 µg/m³. This page is at 30 µg/m³.
Q. How many cigarettes is a day of this?
About 1.36. It follows from reckoning a day at 22 µg/m³ of PM2.5 as one cigarette.