Particulate matter concentrations and characterization in urban subway system-case study Tehran, Iran

Area of Science:

• Environmental Science
• Public Health
• Atmospheric Chemistry

Background:

• Urban air quality is a growing concern, particularly in enclosed public spaces.
• Subway systems, as major transportation hubs, can significantly impact indoor air quality due to high passenger traffic and operational factors.

Purpose of the Study:

• To assess and compare indoor and outdoor air quality in Tehran subway stations.
• To determine concentrations and elemental composition of PM₁₀ and PM_2.5.
• To evaluate potential health risks for subway passengers.

Main Methods:

• Particulate sampling for PM₁₀ and PM_2.5 conducted in four Tehran subway stations from March to July 2018.
• Analysis of elemental composition of collected particulate matter, including 11 key elements.
• Comparison of indoor (platform) and outdoor (ambient) air quality data.

Main Results:

• Indoor PM₁₀ and PM_2.5 concentrations were 2-5 times higher than outdoor levels.
• 100% of indoor and 84% of outdoor measurements exceeded US-EPA daily standards.
• Weekday indoor PM levels were 1.4-1.5 times higher than weekend levels.
• Iron (Fe) was the most abundant element in both indoor and outdoor samples.

Conclusions:

• Tehran subway stations exhibit poor indoor air quality with elevated PM₁₀ and PM_2.5.
• Commuters are exposed to significantly higher levels of harmful particulate matter.
• Further investigation into pollution sources and mitigation strategies is warranted.