Air pollution from vehicles — identify the most dangerous pollutant among the choices Which of the following is considered the most acutely dangerous pollutant in typical vehicular emissions?

Introduction / Context:
Vehicle exhaust contains a mixture of gases and particulates. While carbon dioxide (CO2) drives climate change, acute toxicity to humans from short-term exposure is dominated by carbon monoxide (CO), especially in enclosed or poorly ventilated spaces (tunnels, garages). Selecting the most dangerous pollutant here focuses on immediate health risk in typical traffic environments.

Given Data / Assumptions:

• Conventional petrol engines without perfect after-treatment.
• Acute toxicity perspective rather than long-term climate impact.
• Urban roadside exposure scenarios.

Concept / Approach:

CO binds to hemoglobin with much greater affinity than oxygen, forming carboxyhemoglobin and reducing oxygen delivery to tissues, which can lead to headaches, dizziness, and at high levels, death. SO2 is present mainly from sulfur in fuel but is typically lower for vehicular gasoline; ozone (O3) is a secondary pollutant formed photochemically, not directly emitted. CO2 is non-toxic at ambient levels but is a greenhouse gas.

Step-by-Step Solution:

Verification / Alternative check:

CO poisoning incidents in enclosed traffic spaces are well documented; occupational and ambient air quality standards set stringent limits on CO exposure.

Why Other Options Are Wrong:

(b) SO2 is more characteristic of high-sulfur fuels and stationary sources. (c) CO2 is not acutely toxic at environmental concentrations. (d) O3 forms downwind via NOx and VOCs; acute exposure is harmful but it is not directly emitted by vehicles.

Common Pitfalls:

Confusing chronic climate impact (CO2) with acute toxicity (CO); assuming all pollutants are directly emitted by vehicles.

Final Answer:

CO