PEDESTRIANS’ EXPOSURE TO AIR POLLUTION: PM2.5, THE CASE FOR INTERNATIONAL DISTRICT, SEATTLE

Abstract

Pedestrians are always near to vehicular traffic and street-side activities, chief sources of outdoor air pollution, and are directly exposed to it. Different activities produce pollutants, which affects pedestrians directly. In this thesis, it was tried to find the level of exposure and sources of PM2.5, one of the six ‘criteria pollutants’ designated by United States Environmental Protection Agency, along a roadways in a busy mixed use area in International District, Seattle, which has a good connectivity to transit. The aim of this experiment is to find out sources of PM2.5 emission that affects pedestrians directly while walking, and its level/concentration. The data was collected while walking with the help of a backpack nephelometer, in both winter (Dec 31st, 2014- Jan 9th, 2015) and spring (March 21st - March 30th , 2015) seasons, for 3 times a day, 20 days total to find out pollution levels at different times of a day and seasonal trends . Field collected data was also compared with the nearby fixed-site monitoring stations to understand the difference, if any, between the data recorded and the actual level of pollution pedestrians are exposed to. The result shows that winter is more polluted than spring, and in morning pollution level is much higher than other times of the day. The reasons behind the pollution have been identified as vehicular traffic, construction activity and roadside smoking, along with weather condition. A linear regression model was fit to observe whether the pollutant level at near road are similar to monitoring station data, and was also subjected to ANOVA test. However, it has been acknowledged that several factors may affect the difference between the two, which could not be fitted exactly in a linear model, rather than providing a probabilistic scenario.