(Smoke + Fog + Air Pollutants = Smog)
Agnes Krocha
With the onset of winter, the days have been turning foggier and mistier. In some places of the world I guess it’s so foggy that you can’t see the person walking just some footsteps away from you. Fog we all know is a shroud of cloud made up of tiny droplets of water suspended in the atmosphere and that which reduces visibility. At low temperatures condensation of water vapor into fogs and mists can be caused. The water droplets in fogs and mists are of microscopic size and are suspended in the air. Fogs are associated with urban and industrial areas where there are large volumes of water vapor emitted into the air from combustion processes, together with pollutants of particulate size.
With the ever increasing human population, there is also an ever increasing number of automobiles everywhere. And with increasing number of vehicles the atmosphere in the lower region of the earth has almost become a free smoking zone. Smoke and fumes as automobile exhausts and as emissions from factories and industries are contributing to increasing atmospheric turbidity.
Polluted atmosphere which is loaded with large quantities of automobile exhausts, smoke from various sources, dust particles and other air pollutants combined with fog and exposed to sunlight results in a deadly smog. The word ‘smog’ said to have been coined by H.A. Des Voux in 1905 by combining smoke and fog, characterizes the air pollution episode in London, Glasgow, Manchester and other cities of UK in the 1950s. The deadly smog which is said to have lasted five days in London in 1952 resulted in the dead of 4000 to 5000 people due to respiratory failure.
During the 1940s, the ‘Los Angeles Smog’ occurred due to air pollution caused by domestic fires (50%) and by the exhaust from motor vehicles (50%) adversely affecting human beings as it caused eye irritation and reduced visibility. This smog formation occurred only during night or cloudy days. The mystery was unraveled only in 1950 that smog was due to an oxidizing mixture of nitrogen oxides, hydrocarbons emitted from fumes and exhausts of automobiles in the presence of sunlight when it was cloudy. While the smog in UK was reducing smog, the smog in LA was oxidizing smog. Smog problems also occur in Mexico, Sydney, Melbourne, and Tokyo.
Now this phenomenon of photochemical smog is not a strange phenomenon to our country. In 1987 Bombay experienced heavy smog for about 10 days. With the chief source of pollution in the towns and cities of our country being automobiles and industries the situation seems to be alarming in our country especially in big cities like Delhi, Mumbai, Kolkota, Chennai, Bangalore, etc. And with increasing vehicular pollution and traffic congestion becoming a regular problem in Kohima and Dimapur, can we be far away from the deadly smog?
The oxidants enter as part of inhaled air and alter, impair or interfere with respiratory and other processes. Serious outbreak of smog in 1946 caused Tokyo – Yokohoma asthma. And in 1970 smog outbreak in New York, Sydney, Tokyo and Rome caused asthma and bronchitis in epidemic form. Emphysema is another serious disease caused by smog. Photochemical smog also adversely affects plants and materials.
