Smog
As our cities get more congested and the number of vehicles plying on the streets continues to grow, smog too is becoming an increasingly common sight during the winter months. The word “Smog” is essentially a combination of two words i.e. “Smoke” and “Fog”. It’s a kind of air pollution that may come from a variety of sources such as burning of coal, which would result in the formation of an unhealthy mixture of smoke and sulfur dioxide. Smog, these days is usually a result of vehicular and industrial emissions which when exposed to sunlight may form a pollutant called the photochemical smog.
Photochemical Smog
Photochemical smog is formed when various pollutants in the air are exposed to sunlight and they form a mixture of dangerous inimical chemicals. Some of these pollutants are nitrogen oxides, volatile organic compounds which when react with sunlight release particulate matter and ground-level ozone.
Photochemical smog, which includes chemicals, like nitrogen oxides, tropospheric ozone, volatile organic compounds, peroxyacyl nitrates and aldehydes has posed a serious threat to the atmosphere and is a direct result of modern industrialization. Photochemical smog is a constant feature in all modern cities but is more common in cities with a sunny warm and dry climate.
Health Hazards
Smog is extremely dangerous to human health and its constituents like sulfur dioxide, carbon monoxide and nitrogen dioxide are especially harmful for senior citizens, children and people suffering from emphysema, bronchitis and asthma. It can cause inflammation of breathing passages, shortness of breath, wheezing and coughing.
Smog can cause severe irritation to eyes. It can cause the protective membranes of the nose to dry up and increase the body’s susceptibility to external infections. Smog is a single major cause of respiratory diseases and death. Smog is responsible for around 9500 premature deaths in Ontario every year.
Areas Affected By Smog
Formation of smog is not dependent on a particular climate and is prevalent in cities that release a huge amount of air pollution in the form of smokes and gases. Smog is worse during warmer periods and is present in geological basins, which are surrounded by hills or mountains creating an airlock.
The cities that are most affected by smog are generally industrial and densely populated such as London, Dallas, New York, Los Angeles, Mexico City, Houston, Athens, Beijing, Hong Kong, Seoul, Atlanta, Phoenix and Cairo etc.
Smog has also been a problem in South East Asia and has been caused by land and forest fires. Farm and plantation owners who need to clear up land for further plantations initiate these forest fires. These types of fires cause economical losses of billions of dollars every year. For example, losses cause by forest fires in the year 1997 were approximately $3.5 billion and includes damage to agricultural land, health, tourism and transportation.
Measurement
The extent of smog in a given area can be calculated using specific automated optical instruments such as Nephelometers as it reduces visibility. Many countries have incorporated the use of specially built air indexes such as Air Quality Index (used in America), Air Pollution Index (Malaysia) and Pollutants Standard index (Singapore).