Urban city transportation mode and respiratory health effect of air pollution: a cross-sectional study among transit and non-transit workers in Nigeria

Objectives: To assess the respiratory health effect of city ambient air pollutants on transit and non-transit workers and compare such effects by transportation mode, occupational exposure and sociodemographic characteristics of participants. Design: Cross-sectional, randomised survey. Setting: A two primary healthcare centre survey in 2009/2010 in Uyo metropolis, South-South Nigeria. Participants: Of the 245 male participants recruited, 168 (50 taxi drivers, 60 motorcyclists and 58 civil servants) met the inclusion criteria. These include age 18-35 years, a male transit worker or civil servant who had worked within Uyo metropolis for at least a year prior to the study, and had no history of respiratory disorders/impairment or any other debilitating illness. Main outcome measure: The adjusted ORs for respiratory function impairment (force vital capacity (FVC) and/or FEV1<80% predicted or FEV1/FVC<70% predicted) using Global Initiative for Chronic Obstructive Lung Diseases (GOLD) and National Institute for Health and Clinical Excellence (NICE) criteria were calculated. In order to investigate specific occupation-dependent respiratory function impairment, a comparison was made between the ORs for respiratory impairment in the three occupations. Adjustments were made for some demographic variables such as age, BMI, area of residence, etc. Results: Exposure to ambient air pollution by occupation and transportation mode was independently associated with respiratory functions impairment and incident respiratory symptoms among participants. Motorcyclists had the highest effect, with adjusted OR 3.10, 95% CI 0.402 to 16.207 for FVC<80% predicted and OR 1.71, 95% CI 0.61 to 4.76 for FEV1/FVC<70% predicted using GOLD and NICE criteria. In addition, uneducated, currently smoking transit workers who had worked for more than 1 year, with three trips per day and more than 1 h transit time per trip were significantly associated with higher odds for respiratory function impairment at p<0.001, respectively. Conclusions: Findings of this study lend weights to the existing literature on the adverse respiratory health effect of ambient air pollution on city transit workers globally. The role of other confounders acting synergistically to cause a more deleterious effect is obvious. In all, the effect depends on the mode and duration of exposure.