Air pollution episodes: brief history, mechanisms and outloo

The occurrences of pollution episodes have brought out the strong linkages of pollution with health subsequently catalysing numerous regulations worldwide. Pollution episodes have been driven by a variety of mechanisms such as accidental large emission, trapping of pollution by stagnant meteorology and intense photochemistry involving strong anthropogenic emissions. Few regions of the world, e.g. the Indo-Gangetic Plain (IGP) and Northern China Plain (NCP), experience recurring pollution episodes with enhanced levels of fine particulate matter (PM2.5), ozone (O3) and other pollutants. Reductions in industrial and vehicular emissions should be planned by taking unfavourable meteorology also into account, besides control measures on burning of the crop residues and forest biomass to reduce the severity of pollution episodes. The development of greenbelts in residential and commercial areas and green roofing over buildings could reduce dust and other pollutants. Air quality monitoring over dense networks and high-resolution modelling with assimilation of observations would be of paramount importance for more accurate forecasts and better preparedness to minimize potential impacts.