Epidemiological studies have shown that long-term exposure to fine particulate matter (PM < 2.5 micrometers, or PM_2.5) is significantly associated with adverse human health effects. Building land use regression (LUR) models, based on air monitoring data collected at multiple locations and predictor variables obtained through the geographic information system (GIS), rapidly becomes an important approach to predict intraurban PM_2.5 exposures. However, most LUR models for PM_2.5 were developed in western countries, and they general did not consider the vertical variations.

[Photo: Dr. Chang-Chuan Chan]

According to two recent articles published in the May issue of Science of the Total Environment (doi:10.1016/j.scitotenv.2015.01.091) and the March issue of Atmospheric Environment (doi:10.1016/j.atmosenv.2015.01.024), the LUR modeling approach can be applied to Asian cities with high densities of roads and significant industrial, commerce and construction activities. Furthermore, since people live in high-rise buildings in many urban environments, vertically distributed measurements should be considered to reduce exposure misclassification.

[Photo: Chang-fu Wu]

The research team, led by professors Dr. Chang-Chuan Chan and Dr. Chang-fu Wu at the National Taiwan University, collected PM_2.5 samples in more than 20 locations in the Taipei metropolis. The LUR models performed well with a R² of 0.95. PM_2.5 levels were increased by local traffic variables, industrial, construction, and residential land-use variables and decreased by rivers. It was further demonstrated that road area, rather than road length, is a better surrogate for traffic intensity when traffic intensity data were not available.

In the follow-up study, additional vertically samples were collected. On average, the PM_2.5 exposures at the low-level sites (first to third floors) were 13 percent to 17 percent higher than the mid-level (fourth to sixth floors) and high-level sites (seventh to ninth floors), respectively. Traffic and resuspended road dust were the possible contributors to the higher PM_2.5 exposures at the low-level sites. The authors concluded that “To improve exposure assessment, vertically distributed measurements should be considered in future LUR studies in urban areas with high-rise buildings”.