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Real Time, Size-resolved Prediction of Ultrafine and Accumulation-mode Particle Concentrations on Freeways

Aggarwal, Srijan; Jain, Ricky; Marshall, Julian

doi: 10.1097/01.ede.0000392119.49987.0c
Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August–1 September 2010: Air Quality and Exposures in Transportation Environments (ISIAQ Symposium)

University of Minnesota, Minneapolis, MN.

Abstracts published in Epidemiology have been reviewed by the societies at whose meetings the abstracts have been accepted for presentation. These abstracts have not undergone review by the Editorial Board of Epidemiology.


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Because on-freeway concentrations of ultrafine particles (UFP; diameter <100 nm) are relatively high, time spent on freeways can be a significant fraction of total daily UFP exposure. Here, we model size-resolved concentrations of UFP and some accumulation-mode particles (size: 100–600 nm) in freeway air.

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Our approach is analogous to land-use regression, but using real-time meteorological data (temperature, wind speed, humidity) and traffic data (traffic speed and volume, derived from in-roadway loop detectors). Size-resolved particle concentrations (size: 5.5–600 nm) were measured on Minnesota freeways during the summers of 2006 and 2007. The modeling involves 2-way stratified multi-regressions.

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Meteorological parameters play only a minor role in predicting real-time UFP concentrations on freeways; traffic speed and volume play a major role. Our regression model for particle number concentration has an adjusted R 2 of 0.77. Model performance is better for UFP (size: 10–100 nm; adjusted R 2: 0.79–0.89, average R 2: 0.85) than for the accumulation-mode particles studied here (size: 100–600 nm; adjusted R 2: 0.41–0.83, average R 2: 0.65).

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Our model estimates real-time, size-resolved concentrations of particles (size: 5.5–600 nm) on freeways. The approach developed here is useful for identifying hotspots and as an important step toward modeling population exposure to UFP.

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