A 30-year-old woman living near a busy traffic intersection complains of chronic cough, wheezing, and irritation of the eyes. Her symptoms improve when she visits her rural hometown. Which pollutant is most likely responsible for her symptoms in the urban setting?

• A Sulphur dioxide
• B Carbon monoxide
• C Ozone
• D Nitrogen dioxide ✓

Explanation

Nitrogen dioxide (NO2) from vehicular exhaust is a major traffic-related pollutant causing respiratory symptoms, bronchial hyperreactivity, and eye irritation. While ozone is also a traffic-related pollutant, it is a secondary pollutant formed in the atmosphere. NO2 is the primary pollutant directly emitted from vehicles and is most strongly associated with traffic-related respiratory symptoms. Sulphur dioxide is more from coal burning. Carbon monoxide causes hypoxia, not chronic cough.

Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.