Pollution Free Cities: How Polluted is the Air Inside Buses?

Friday, July 13, 2012

How Polluted is the Air Inside Buses?

An Examination of the Sensitivity of Sulfur Dioxide, Nitric Oxide, and Nitrogen Dioxide Concentrations to the Important Factors Affecting Air Quality Inside a Public Transportation Bus (22 page pdf, Akhil Kadiyala and Ashok Kumar, Atmosphere, Jun.15, 2012)

While there is much evidence that the air quality near and in heavy traffic is poor, there has been less research into the quality of air inside commuting vehicles. The journal article reviewed today examines the changes that occur by weather type, season and time of day for each pollutant found inside a bus in Toledo, a city in the northern USA. The worst conditions appear to be in late fall/ winter, during the morning rush hour and when it is not raining. This should prompt public health and urban transportation planners to look more closely at health impacts from air pollution during the winter rather than just summer when smog alerts
are usually issued.

Key Quotes:

“people spend 90% of their time indoors and about 7% of their daily time is spent commuting, mostly between the workplace and their residences.. people are exposed to high concentrations of traffic contaminants when they drive in heavy traffic, stand near idling vehicles, and spend time at places near roads that have high traffic”

“There are no in-vehicle sources for SO2, NO, and NO2 concentrations. slow-moving traffic in combination with the increased idling times at traffic signals during the winter contribute to large amounts of local SO2, NO, and NO2 concentrations that are not normally experienced at other times”

“Urban areas with colder climates…experience higher atmospheric SO2 concentrations during the late fall and winter because it is less reactive in these climates”

“Outdoor NO2 concentrations are expected to be the highest, early in the mornings, due to exhaust emissions from the morning vehicular rush and the reaction of newly emitted NO with O3 without sunlight to form NO2”

“significantly lower in-bus SO2 concentrations were observed on days with haze, rain, thunderstorm, and mist weather types, when compared with the foggy and normal weather type days”

“Medium in-bus SO2 concentrations were observed only in the fall-winter months, when the lead heavy vehicular density was a minimum of 56 per hour”