Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th St., New York, NY 10032, United States; Institute of Nuclear Science and Technology, College of Architecture and Engineering, University of Nairobi, P.O. Box 30197, G.P.O., Nairobi, Kenya; Center for Sustainable Urban Development, Earth Institute, Columbia University, 475 Riverside Drive, Suite 520, New York, NY 10115, United States; Columbia University, Sustainable Development in the College of Arts and Sciences, School of International and Public Affairs, 420 West 118th Street, New York, NY 10027, United States; Department of Civil Engineering, College of Architecture and Engineering, University of Nairobi, P.O. Box 30197, G.P.O.. Nairobi, Kenya; Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya; Lamont-Doherty Earth Observatory, Columbia University, 61 Rt 9W, Palisades, NY 10964, United States
Kinney, P.L., Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th St., New York, NY 10032, United States; Gichuru, M.G., Institute of Nuclear Science and Technology, College of Architecture and Engineering, University of Nairobi, P.O. Box 30197, G.P.O., Nairobi, Kenya; Volavka-Close, N., Center for Sustainable Urban Development, Earth Institute, Columbia University, 475 Riverside Drive, Suite 520, New York, NY 10115, United States; Ngo, N., Columbia University, Sustainable Development in the College of Arts and Sciences, School of International and Public Affairs, 420 West 118th Street, New York, NY 10027, United States; Ndiba, P.K., Department of Civil Engineering, College of Architecture and Engineering, University of Nairobi, P.O. Box 30197, G.P.O.. Nairobi, Kenya; Law, A., Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th St., New York, NY 10032, United States; Gachanja, A., Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya; Gaita, S.M., Institute of Nuclear Science and Technology, College of Architecture and Engineering, University of Nairobi, P.O. Box 30197, G.P.O., Nairobi, Kenya; Chillrud, S.N., Lamont-Doherty Earth Observatory, Columbia University, 61 Rt 9W, Palisades, NY 10964, United States; Sclar, E., Center for Sustainable Urban Development, Earth Institute, Columbia University, 475 Riverside Drive, Suite 520, New York, NY 10115, United States, Columbia University, Sustainable Development in the College of Arts and Sciences, School of International and Public Affairs, 420 West 118th Street, New York, NY 10027, United States
Motor vehicle traffic is an important source of particulate pollution in cities of the developing world, where rapid growth, coupled with a lack of effective transport and land use planning, may result in harmful levels of fine particles (PM2.5) in the air. However, a lack of air monitoring data hinders health impact assessments and the development of transportation and land use policies that could reduce health burdens due to outdoor air pollution. To address this important need, a study of traffic-related PM2.5 was carried out in the city of Nairobi, Kenya, a model city for sub-Saharan Africa, in July 2009. Sampling was carried out using portable filter-based air samplers carried in backpacks by technicians on weekdays over two weeks at several sites in and around Nairobi ranging from high-traffic roadways to rural background. Mean daytime concentrations of PM2.5 ranged from 10.7 at the rural background site to 98.1μg/m3 on a sidewalk in the central business district. Horizontal dispersion measurements demonstrated a decrease in PM2.5 concentration from 128.7 to 18.7μg/m3 over 100m downwind of a major intersection in Nairobi. A vertical dispersion experiment revealed a decrease from 119.5μg/m3 at street level to 42.8μg/m3 on a third-floor rooftop in the central business district. Though not directly comparable to air quality guidelines, which are based on 24-h or annual averages, the urban concentrations we observed raise concern with regard to public health and related policy. Taken together with survey data on commuting patterns within Nairobi, these results suggest that many Nairobi residents are exposed on a regular basis to elevated concentrations of fine particle air pollution, with potentially serious long-term implications for health. © 2011 Elsevier Ltd.