It is well-known that the car density on the roads in cities like New York, London, Singapore and Moscow is higher than that in New Delhi. How then is the PM2.5 particulate level higher in Delhi than in other cities? (Choking in the capital,” Oct.3) Is it because of any improved technology of combustion in the engine in the other cities or added physical equipment like filters to the vehicles in the advanced countries? This is not likely. Or is it possibly due to higher octane number of the fuel used? Or is it due to a different sampling and analysis procedure being followed? The article is not explicit on these points. Further, in Delhi, the solutions suggested would either involve bringing improvement to the factories concerned or shifting the same to other locations. A straightforward technical solution can be to add a suitably designed cyclone separator in the exiting gas path to catch bigger particles followed by a powerful electrostatic precipitator to detain and retain the finer ones.
Krishnaswami K.R.,
Chennai
