In photochemical smog, the primary pollutant responsible for the secondary formation of peroxyacetyl nitrate (PAN) and ozone in the atmosphere is:
- A Nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) ✓
- B Sulphur dioxide (SO₂)
- C Carbon monoxide (CO)
- D Particulate matter PM2.5
Correct answer: A. Nitrogen oxides (NOₓ) and volatile organic compounds (VOCs)
Explanation
Photochemical smog (Los Angeles type) is formed when sunlight reacts with primary pollutants — nitrogen oxides (NOₓ from vehicular emissions) and volatile organic compounds (VOCs from hydrocarbons) — in a complex photochemical reaction to produce secondary pollutants including ozone (O₃), peroxyacetyl nitrate (PAN), aldehydes, and acrolein. PAN is a respiratory irritant and plant toxin. This differs from London-type smog (reducing smog), which is caused by SO₂ and particulates. CO causes CO poisoning but does not contribute to photochemical smog formation.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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