The same PM2.5 concentration can produce sharply different air quality scores in India, the US and the UK, as differences in formulas and averaging periods shape how pollution is reported. Same Air, Three Scores: Why Delhi’s Pollution Looks Different On Each AQI Scale Snehal SrivastavaUpdated on: 9 November 2026 4:25 pm Published at: 9 November 2026 4:09 pmThe same PM2.