Particulate air pollution and noise: Assessing commuter exposure in Africa's most populous city

Africa is rapidly urbanising, consequently, there is the growing relevance of daily air pollution and noise exposure during urban commuting. Yet, little is known about commuter exposures in Africa. Lagos has a population in excess of nine million people, and approximately 788,000 registered motor vehicles. We monitored exposures of commuters within the Lagos metropolis to various size fractions of particulate air pollution, black carbon, and noise while traveling by car (taxi), microbus and larger bus with an aim to determine exposure levels and compare between modes. We conducted, altogether, 139 trips on nine designated commuting routes. The highest exposures were recorded when vehicle windows were open and air-conditioners turned off. For example, mean gravimetric PM₁₀ levels of 364, 489 and 280 µg/m³, and mean particle number count (PNC) levels of 92, 52 and 27 (x 10³ pc /cm³) were recorded in the car, microbus and larger bus, respectively. With the closed window setting, considerable reduction in particulate matter (PM) concentration was recorded on larger buses compared with cars. The highest mean (85 dB(A)) and highest mean 99^th percentile (92 dB(A)) noise levels were obtained during trips on microbuses when windows were left open. This study observed remarkably high particulate air pollution and noise exposures during commuting in the major African city. A major shift to modern mass transportation systems would limit commuter exposure.