Ambient Air Quality in Transportation Environment: Establishing a Safe Distance at a Bus Station Microenvironment in Enugu Metropolis, Enugu State, South-East Nigeria

In a bus station microenvironment, idling buses have the potential to pollute the air, which could have negative health effects on commuters who usually wait a long time. This study aimed to model ambient air pollution in selected three bus station micro-environments in Enugu metropolis with a view to determining the safe distance for commuters in a bus stations. Real time measurements of ambient particulates (PM10 and PM2.5) and gaseous pollutants (SO2, NO2 and CO) were monitored, in conjunction with meteorological parameters (wind speed, temperature and relative humidity) on idling buses in selected three bus stations and a control station in Enugu Metropolis. The study covered both dry and wet seasons from September 2016 to August 2018. Hand- held Aeroqual Series - 200 gas monitor/sensors, particulates laser meter and ambient weather anemometer were used to collect data on gases, particulates and weather respectively. Results indicated that the monthly highest mean concentration of pollutants were as follows: PM10=216.02µg/m3 – ABC; PM2.5=63.98µg/m3 – Young-Shall-Grow; SO2=0.6601ppm – Ifesinachi; NO2= 0.7732ppm – Young-Shall-Grow; CO= 3.9583ppm – Ifesinachi, consistently maintained higher concentrations than those at the control station, implying that commuters are highly at risk in bus stations. Regression analysis was used to derive models. The simple regression models were more robust in predicting concentration levels. Most models are designed for large-scale and medium-scale settings, but the simple Predictive Micro-scale Regression Models that have been developed by this study can help authorities, especially development control department of ministries in approval processes. This study can also assist the relevant authorities to set strict ambient air quality objectives for pollutants in transport micro environments through adherence to regulated safe distance proposed by this study.