Wednesday, October 9, 2013

Reducing Proximity Errors for Exposure to Traffic –Related Air Pollution

Positional error and time-activity patterns in near-highway proximity studies: an exposure misclassification analysis(28 page pdf, Kevin J Lane, Madeleine Kangsen Scammell, Jonathan I Levy, Christina H Fuller, Ron Parambi, Wig Zamore, Mkaya Mwamburi, Doug Brugge, Environmental Health, Sep. 8, 2013)

Today we review research that examines the potential errors that might be introduced into an epidemiological study of health impacts resulting from exposure to roadside emissions where proximity within 50 m is critical. Results indicate that for pollutants that decay rapidly with distance from roadways, a significant error is possible in stipulating the distance from a residence to a roadway. proximity errors  

Key Quotes:

“Concentrations of these pollutants exponentially decay with increasing distance from the highway, with highest concentrations appearing over the first 50 meters and distribution observed up to 400–500 m”

“Two potentially significant sources of exposure error in near-roadway epidemiology are the time-activity patterns of populations, including time away from home, and the geographic accuracy of locating the residential position”

“for pollutants that decay rapidly as a function of distance from highways and major roadways, tens to hundreds of meters of positional error coupled with significant time spent away from home could have a profound effect on exposure misclassification, including possible differential misclassification.”

 “models that assign ambient exposure to the residence may be a concern if there is meaningful geographic misclassification.”

Exposure assessment models should consider adjustments for mobility patterns in their study populations and take into consideration inside home, on highway and work hour exposures to near-highway pollutants to reduce misclassification”

 “The magnitude of error related to geocoding practices was large relative to the steep concentration gradients of traffic-related air pollutants
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