Estimation of gaseous criteria air pollutants from road transport system in Lagos metropolis of Nigeria

Ambient air pollution by vehicular emissions is underestimated, especially in the major cities of Nigeria. The buildup of the emissions in the atmosphere is a major health concern. This study estimated the emissions of gaseous criteria air pollutants (CAPs) from the road transport system in the Lagos metropolis from the year 2004 to 2007. The study also determined the ground‐level concentrations of these pollutants for the years under review. Estimation of the emission rates of all types of vehicles was performed using an emission factor approach, while the ground‐level concentrations of the CAPs were determined using the Industrial Source Complex Short Term 3 view model. The results showed that the mean concentrations of carbon monoxide in the ambient air were 26,741.12, 31,675.95, 54,515.48, and 72,388.09 micrograms per cubic meter (μg/m3) for years 2004, 2005, 2006, and 2007, respectively, while the estimated concentrations for oxides of nitrogen were 1,377.91 μg/m3 for year 2004, and 1,620.76, 2,897.33, and 3,839.68 μg/m3, respectively, for the years 2005, 2006, and 2007. The estimated concentrations of sulfur dioxide during the study period were 51,354.16, 57,244.76, 113,083.26, and 136,332.01 μg/m3 for 2004, 2005, 2006, and 2007, respectively. For volatile organic compounds, the estimated concentrations were 3,839.68, 6,839.65, 7,067.62, and 8,431.35 μg/m3 for years 2004, 2005, 2006, and 2007, respectively. The results also show that the maximum ground‐level concentrations were highest along the roadside, and the average CAPs concentrations and cumulative exposure concentrations that were estimated throughout the study period are a major health concern, as these concentrations are several times higher than international limits.