Exposure to PM2.5 Related to Road Traffic: Comparison between Crossroads and Outside of Crossroads at Cotonou, Benin

摘要

Background: Several studies have analysed the pollution issues owing to road traffic in Cotonou, Benin. Concentration levels of particles are higher on high traffic than a low traffic. The exposure of human populations to air pollution is more intense on the roads. In Benin, the density of traffic on the crossroads is indeed more important. Are traffic locations such as crossroads, areas where the level of exposure PM_(2.5) is increased? Methods: This study was conducted along the 5 km high-traffic road in the city of Cotonou. It is a high traffic lane with two crossroads. Sampling and measurements were carried out in dry sea-son (January and February) and rainy season (June and July). For each season the measurements were made over two months from 7 am to 9 pm. PM_(2.5) measurements were made at different locations at crossroads and also along the track. To compare concentrations of PM_(2.5) at crossroads and outside of roundabout, we used the Generalized Linear Mixed Model. Results: In the rainy season the PM_(2.5) hourly concentrations ranged between 400 μg/m~(3) and 500 μg/m~(3) while in the dry season 100 μg/m~(3) and 300 μg/m~(3). In the rainy season, the average of PM_(2.5) concentration was 463.25 ± 66.21 μg/m~(3) at crossroads and 264.75 ± 50.97 μg/m~(3) outside of crossroads. In the dry season, the average of PM_(2.5 )concentration was 232.75 ± 97.29 μg/m~(3) at crossroads and 123.31 ± 63.79 μg/m~(3) outside of crossroads. Both in dry and rainy seasons, PM_(2.5) concentration level peaks are observed from 7 am to 9 am and from 7 pm to 9 pm. The Generalized Linear Mixed Model showed that there is high significant difference between concentrations of PM_(2.5) at crossroads compared to outside of crossroads. Occupation of the roadside (in particular crossroads) for various economic activities is common practice in Cotonou thus health risk for people working around crossroads increases. Conclusion: Locations such as crossroads are areas where the level of exposure PM_(2.5) is highest on road traffics.