Land-use regression modelling of highway ultrafine particle number concentrations

Abstract

Ultrafine particles (UFP; diameter < 100 nm) are suspended atmospheric solids of concern to human health due to their small diameters. Vehicles emit significant numbers of UFP, leading to steep spatial gradients on, and near, high traffic roadways. Particle number concentrations were measured while driving a cyclic route on four Toronto highways during non-rush hour weekday periods during the summer. These data were averaged over roadway length segments to create a concentration map of the route. Road segment-averaged concentrations were bimodal, and ranged from 26,000 to 106,500 particles cm-3, which is significantly greater than the average background downtown Toronto concentration (15,500 cm-3). A land-use regression model incorporating diesel truck traffic, six land use types, and distance to Lake Ontario, accounted for 34% of the variability of on-road concentrations. Understanding the complex spatial distribution of urban UFP is integral to designing epidemiological studies and understanding commute...