Answer the question on the basis of the passage given below:
Molecular nitrogen is very little reactive chemically. During lightning discharge, atmospheric nitrogen and oxygen combine to form nitric oxide which also combines with oxygen to form nitrogen dioxide. Both \(NO\) and \(NO_2\) constitute smog which is very poisonous. It can cause a burning sensation in the eyes and adversely affect the respiratory system.
What is the value associated with the control of photochemical smog?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Control of photochemical smog can provide relief from diseases linked with the respiratory system such as cough, cold, bronchitis, asthma.
Photochemical smog forms in warm, sunny weather when sunlight acts on nitrogen oxides and hydrocarbons from vehicle exhaust. Its main components are ozone, nitric oxide, acrolein, formaldehyde and peroxyacetyl nitrate (PAN).
These gases are breathed in. Ozone and PAN irritate the eyes, while ozone and nitric oxide irritate the nose and throat; high concentrations cause chest pain, dryness of the throat, cough and difficulty in breathing, and worsen asthma and bronchitis. The passage itself says that smog adversely affects the respiratory system. So controlling photochemical smog gives relief mainly from respiratory diseases.
Why the other options are incorrect
Option (2) digestive system such as stomach pain — Incorrect. Smog is inhaled, not swallowed; it does not act on the stomach.
Option (3) nervous system such as headaches, brain problem — Incorrect. A headache can occur at high ozone levels, but it follows the irritation of the airways; smog is not a disease of the nervous system.
Option (4) circulatory system such as Anemia — Incorrect. Anaemia is a shortage of haemoglobin or red blood cells (for example from iron deficiency). The air pollutant that affects the blood is carbon monoxide, which binds haemoglobin; it is not a component of photochemical smog.