According to the World Health Organization, the safe limit of PM2.5 concentration for humans is 25 micrograms/cubic metre. But, the fact that at any given time, the PM2.5 levels in Delhi hover between 303.9 and 408.2 -- way above the safe level -- is no news! Newspaper headlines scream on toxic pollution levels and people wearing protective masks has become a common sight.
An IIT Bombay study using satellite data shows rising greenhouse gas levels over Delhi and Mumbai and also identifies emission hotspots in these cities.