Question

Classical smog is –
A. Dark brown smog
B. Yellow brown smog
C. Los Angeles smog
D. Smog with secondary pollutants.

Answer 1

Hint:The term smog is derived from two words - Smoke and fog and is a kind of intense air pollution. There are two different types of smog - classical smog and photochemical smog.

Complete answer:
Let us analyse the options to find the correct answer.
Option A: Classical smog has smoke, fog and sulphur dioxide components and is found in humid conditions. They are present where there is a high concentration of particulate matter and sulphur dioxide is produced because of combustion of fuels. They generally cause a dark brownish atmosphere and that is why they are known as dark brown smog. Therefore, this is the correct option.
Classical smog pollutes air and has adverse effects on human health. It can inflate the respiratory pathway, decreasing lung capacity, causes shortness of breath, cough etc. It can cause nose and eye irritation and it dries out the protective membrane of nose and throat, also interfere with the body’s ability to fight infections. It is also known as London smog or sulphurous smog.
Option B, C and D: Photochemical smog is also known as yellow brown smog or Los Angeles smog as it contains high levels of nitrogen which gives it a characteristic yellow brown colour. It also contains secondary pollutants like ozone, nitric acids, etc. Therefore, this is the incorrect option.
  In a new type of smog, known as photochemical smog was described. Photochemical smog is produced when sunlight reacts with the nitrogen oxide and volatile organic compounds in the atmosphere. Los Angeles, California and Mexico City have high smog levels hence photochemical smog is also known as Los Angeles smog.

Thus, the correct answer is option (A) Dark brown smog.

Note: A few ways by which smog can be controlled are,
>Promoting the use of renewable sources of energy.
>Using smog towers.
>By reducing the number of vehicles, and promoting use of public transport and car pooling.
>By increasing energy efficiency.