BANGKOK: The northern Thai city of Chiang Mai was ranked as the seventh most polluted in the world on Tuesday (March 25), according to air-quality monitoring website IQAir.
Chiang Mai registered an air quality index (AQI) of 170 on Tuesday. The scale has six categories: 0-50 (good air quality), 51-100 (intermediate), 101-150 (unhealthy for some groups), 151-200 (unhealthy), 201-300 (very unhealthy), and over 301 (hazardous).
