Vehicle occupant exposure to carbon monoxide.

Area of Science:

• Environmental Science
• Occupational Health
• Transportation Engineering

Background:

• Vehicle emissions are a major source of urban air pollution.
• Understanding the auto commuting micro-environment is crucial for assessing commuter exposure to pollutants like carbon monoxide (CO).
• Previous studies have highlighted the health risks associated with CO exposure.

Purpose of the Study:

• To quantify carbon monoxide (CO) concentrations experienced by auto commuters in central Riyadh, Saudi Arabia.
• To identify key variables influencing indoor CO levels within vehicles.
• To assess the relative importance of traffic and environmental factors on CO exposure.

Main Methods:

• Monitoring of inside and outside CO levels in two test vehicles over an eight-month period.
• Data collection during both peak and off-peak traffic hours across four major arterial roadways.
• Variance component analysis to determine the impact of variables like traffic volume, vehicle speed, time of day, and wind velocity.

Main Results:

• During peak hours, mean CO exposure ranged from 30 to 40 ppm for trips lasting 25-40 minutes.
• The average ratio of indoor to outdoor CO concentrations was 0.84.
• Increased traffic volume (1,000-5,000 vph) raised mean CO exposure by 71%, while increased vehicle speed (14-55 km/h) reduced it by 36%.

Conclusions:

• Auto commuters in Riyadh face substantial CO exposure, with indoor levels significantly reflecting outdoor conditions.
• Traffic volume, vehicle speed, time of day, and wind velocity are critical determinants of indoor CO concentrations.
• Reducing traffic congestion and optimizing vehicle speed are potential strategies to mitigate CO exposure for commuters.