Delhi sits in the Indo-Gangetic airshed. Pollution can travel across this region, so a city boundary does not contain every source of the particles you breathe. Use nearby readings for today and check the time of your next outing.
A reading near central Mumbai is a starting point, not a result for every coastal neighbourhood or commute. Check your departure point and destination separately; the measurement time matters as much as the city name.
Kolkata is in the lower Gangetic region, where air-quality planning includes pollution transported through a shared airshed. For a walk or commute, combine the regional context with a recent reading near the actual route.
The World Bank identifies the Indo-Gangetic Plains and Himalayan Foothills as a shared airshed with serious air-pollution challenges. That regional picture explains why regular checks matter. It does not tell you today’s concentration on a particular street.
India’s AQI and US AQI differ
India’s Central Pollution Control Board publishes a National Air Quality Index with its own pollutant thresholds and health categories. Atmiq labels its concentration-derived US AQI explicitly. Compare the same pollutant, units, time and method; the same number on two scales need not mean the same category.
Check current conditions near your actual route and follow local advisories. Consider a different time for strenuous outdoor activity, then check observations before departure.