Abstract
This study reports the benzene exposure levels of commuters traveling within the metropolitan area of Costa Rica using personal cars, buses, and urban trains. 47 in-vehicle samples were col- lected in the 2014 wet season under three different driving conditions: rush hour traffic, normal traffic and weekends. Samples were collected in Tedlar bags and analyzed using 75 µm carboxen- polydimethylsiloxane (CAR/PDMS) and gas chromatography with flame ionization detection (GC- FID). Additionally, duplicate samples were collected on adsorption tubes filled with Tenax TA and analyzed by thermal desorption (TD) and GC-FID. Results indicate that travelling in cars and buses under rush hour conditions exposes commuters to statistically equal average benzene concentra- tion of 48.7 and 51.6 µg/m3, respectively. Average benzene levels in urban trains (33.0 µg/m3) were measured only during morning rush hours. Greater benzene levels in buses than personal cars concentrations may be attributable to the immersion of traffic-related emission within the bus ca- bins. Factors, such as the driving pattern, the number of vehicles on the route, the road infrastruc- ture, and the prevalence of gasoline-fueled vehicles in Costa Rica, may increase ambient benzene concentrations. Benzene levels inside car cabins reported in this study are in the range of those reported in other urban areas; however, the corresponding concentrations inside buses and urban trains (rush hour only) are higher than previously published exposure levels.
Highlights
In past years, the exposure levels of commuters to volatile organic compounds (VOCs) inside public transport modes have been reported in several urban locations in Europe, Asia and megacities such as Mexico City [1]-[4]
The distance between the four major cities in the metropolitan area, namely Heredia, San Jose, Alajuela and Cartago, is only 10 - 20 km, the available road system is characterized by a slow-moving traffic pattern, especially during the rush hours (6:00 a.m. to 9:00 a.m.) in the morning and the afternoon (4:00 p.m. to 6:00 p.m.), which increases the amounts of vehicle-related pollutants emitted into the air
The aim of this study is to measure the levels of exposure of commuters to benzene in the public transportation means that are used to travel in the metropolitan area of Costa Rica, using solid-phase microextraction
Summary
The exposure levels of commuters to volatile organic compounds (VOCs) inside public transport modes have been reported in several urban locations in Europe, Asia and megacities such as Mexico City [1]-[4]. The distance between the four major cities in the metropolitan area, namely Heredia, San Jose, Alajuela and Cartago, is only 10 - 20 km, the available road system is characterized by a slow-moving traffic pattern, especially during the rush hours (6:00 a.m. to 9:00 a.m.) in the morning and the afternoon (4:00 p.m. to 6:00 p.m.), which increases the amounts of vehicle-related pollutants emitted into the air. Under these driving conditions, the stop-and-go traffic adversely affects the in-vehicle air quality, and increases the exposure of commuters to higher VOCs levels [4] [8]. The studied transportation routes cover an important traffic zone that enters San Jose from the north and urban areas that include the downtown of Heredia and San Jose, the surrounding commercial and business areas, and one of the three available urban train connections so far in Costa Rica
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