Why AQI readings are hazy

A thick blanket of haze continued to cling to Mumbai, a day after the city experienced some of its worst air quality in recent times.

- Shreya Jachak and Sabah Virani

MUMBAI: Oddly, though, the city's Air Quality Index (AQI) dropped on Friday, from 160 to 154 (both figures in the 'moderate' range) a day earlier, suggesting cleaner air and improved visibility. Clearly, it doesn't add up.

A study of data from all 30 monitoring stations showed that Mumbai's AQI readings may not be entirely accurate. As a result, what you read and what you see could be markedly different.

On Friday's hazy conditions, Sushma Nair, scientist with the Indian Meteorological Department, Mumbai, said, "The weather conditions continued to be the same as they were on Thursday." She said a weather phenomenon called Western Disturbance is bringing increased moisture to the city, allowing suspended particles, mostly pollutants, to cling to it. Add to this slow wind speeds that don't allow particles to disperse. The result is a thick haze.