Chandigarh, Oct. 7 -- The city's air quality has, for the first time this season, slipped to the moderate level (102) after remaining in the good to satisfactory category for at least a week (see box).

The rise in pollution, India Meteorological Department (IMD) officials say, is due to the dropping temperatures and weaker winds. Explaining the science behind it, an IMD official said temperature inversion - an atmospheric condition where a layer of warm air sits on top of a layer of cooler air near the Earth's surface - is a big factor as it traps pollutants closer to the ground

An anticyclonic movement prevalent over the region, which keeps winds from blowing, is also reducing the dispersion of pollutants, officials added.

The situati...