A Land Use Regression Model for Ultrafine Particles in Vancouver, Canada

摘要

Methods to characterize chronic exposure to ultrafine particles (UFP)rncan help to clarify potential health effects. Since UFP are not routinely monitored inrnNorth America, spatiotemporal models are one potential exposure assessmentrnmethodology. Portable condensation particle counters were used to measure particlernnumber concentrations (PNC) to develop a land use regression (LUR) model. PNC,rnwind speed and direction were measured for sixty minutes at eighty locations during arntwo-week sampling campaign. We conducted continuous monitoring at four additionalrnlocations to assess temporal variation. LUR modeling utilized 13S potential geographicrnpredictors including: road length, vehicle density, restaurant density, populationrndensity, land use and others. A novel approach incorporated meteorological datarnthrough wind roses as alternates to traditional circular buffers. The range of measuredrn(sixty-minute median) PNC across locations varied seventy-fold (1500-105000rnparticles/cm~3, mean [SD] = 18200 [15900] particles/cm~3). Correlations between PNCrnand concurrently measured two-week average NO_x concentrations were 0.6-0.7. A PNC LUR model (R~2 = 0.48, leave-one-outrncross validation R~2 = 0.32) including truck route length within 50 m, restaurant density within 200 m, and In-distance to the portrnrepresents the first UFP LUR model in North America. Models incorporating wind roses did not explain more variability inrnmeasured PNC.