Using a mobile monitoring campaign to characterize average exposures to ultrafine particulate matter and black carbon for a Seattle-based cohort

Abstract

BACKGROUND AND AIM: A growing body of evidence has begun linking traffic-related air pollution (TRAP) to brain health, including dementia. Ultrafine particles (UFP, 100 nm diameter) and black carbon (BC) are important components of traffic pollution, both of which may play an important role in the adverse health effects associated with particulate matter. Still, epidemiologic investigations of UFP and BC are limited in part by the absence of relevant long-term exposure models. METHODS: We leveraged an innovative mobile monitoring campaign specifically designed to assess, at high spatial precision, long-term UFP and BC exposure for the Adult Changes in Thought (ACT) study, a Seattle-based, prospective cohort study of aging and the brain. We systematically collected repeated short-term monitoring samples (~275 drive days) and used these to build annual-average UFP and BC universal kriging models with partial least squares regression summarizing hundreds of geographic covariate predictors. RESULTS:The external validation results indicated low model bias and high precision (RMSE: 930 UFP particles/cm³, 58 BC ng/m³; R2: 0.87 for UFP, 0.85 for BC). Predicted annual-average UFP and BC exposure for the ACT cohort had a median (IQR) of 6,800 (6,000-7,800) pt/cm³ and 530 (460-590) ng/m³, respectively; those values are generally lower than levels reported in other cities around the world. Similar to past studies, predicted concentrations were highest near the airport, downtown and industrial areas as well as along major highways. Furthermore, airport locations had much higher UFP levels relative to BC. CONCLUSIONS:CONCLUSIONS: We successfully predicted annual-average concentrations of UFP and BC throughout a large metropolitan area using a novel and extensive mobile monitoring campaign. This use of mobile monitoring data as inputs to prediction models creates opportunities for epidemiologic investigations of traffic-related air pollution exposures, including UFP and BC. KEYWORDS: mobile monitoring, ultrafine particulate matter (UFP), exposure assessment, study design