A Statistical Study of the Variables Associated with Particulate Matter Exposure Levels at Bus Shelters

摘要

This study expands upon previous work that examined differences in exposure to particulate matter in andaround bus stop shelters for passengers waiting along a busy urban corridor in Portland, OR. An extensivebody of literature has demonstrated the negative health effects of exposure to particulate matter. Whileconcentrations of particulate matter are known to be greater near busy roadways, little research has beenconducted on exposure in and around bus stop shelters. Two sizes of particulate matter are examined inthis study: PM_(2.5) and ultrafine particles. Pearson association tests are run between particulateconcentrations and three categories of independent variables: location, traffic, and weather. Significantcorrelations are primarily observed between particulates and weather (temperature and relative humidity).Using one-minute data intervals, a series of log-linear regression models with and without laggedvariables are used to estimate the effects of location, traffic, and weather variables on particulateconcentrations. The presence of a transit bus stopped at the shelter significantly increases both sizes ofparticulate matter concentrations. Wind, temperature, and shelter location also have significant impacts onultrafine and PM_(2.5) levels. The estimated models for particulate concentrations inside and outside the busstop shelters are compared to demonstrate differences in particulate behavior. Suggestions are made forshelter configuration given environmental and traffic considerations.