Exposure to fine particulate matter (PM_2.5) and noise at bus stops in Chennai, India

Abstract

Introduction: Millions of people in developing countries depend on public transportation for their daily commute to and from work. In particular, buses are the preferred mode of transportation, as they are easily accessible and inexpensive. However, since the bus stops are located on urban arterial roads carrying a high volume of traffic, the passengers waiting for the bus are exposed to a high concentration of particulate matter and noise. Methods: In this study, PM_2.5 (particulate matter with an aerodynamic diameter less than 2.5 μm) concentrations and noise levels were measured at six bus stops in Chennai, India in two phases. The PM_2.5 concentrations were measured using a low-cost portable optical sensor, and the noise levels were measured using an android application installed in a smartphone. Traffic volume and composition data on the road adjacent to the bus stop was also collected. Results: The average of the measured 1-h PM_2.5 concentrations at the bus stops during January and October were 44.2 μg/m³ and 48.5 μg/m³, respectively. On average, the dose of PM_2.5 for all bus stops assuming a waiting time of 15 min was 7.6 μg. The average of the noise levels at the bus stops was 76.8 dBA, and the noise levels exceeded 95 dBA frequently due to the extensive use of horns by the drivers. The results indicate that the passengers waiting at bus stops are exposed to unhealthy magnitudes of air and noise pollution. Conclusion: Considering the effects of exposure to high pollution levels at bus stops, appropriate steps to improve facilities and services (such as providing air conditioning and noise barriers) need to be taken. Also, the location and design of the bus stops should take into consideration the exposure to pollutants for the waiting passengers during the planning phase of development itself.