Table 1.

Potential predictor variables.

Data Source	Variable	Data Description	Unit	Buffer Size (m)
Institute of Transportation digital map data	Road a	Major road	m	25–5000
		Local road
		All types of road (major road + local road)
The second national land use survey	Residential Areas	Purely residential area	m2	25–5000
		Residential area mixed with industrial area
		Residential mixed with commercial area
		Mixed residential area (residential area mixed with industrial and commercial area)
		All types of residential area (pure and mixed residential area)
The second national land use survey	Greenness	Paddy rice
		Non-irrigated crops
		Fruit orchard
		Mixed crops (rice + non-irrigated crops + fruit orchard)
		Forest
		Park
The second national land use survey	Industrial area
The second national land use survey	Water
Vegetation indices from remote sensing	NDVI		-	250–5000
Point of interest (POI) landmark database	Asian culture-specific emission sources	Temple	count	25–5000
		Chinese restaurant
		Temple + Chinese restaurant
		Cemetery and crematorium	m a	NA
The second national land use survey	Port
The second national land use survey	Airport
Taiwan Environmental Protection Agency (EPA) environmental database	Incinerator stack
Taiwan EPA environmental database	Thermal power plant
Taiwan EPA environmental database	Garbage incinerator
Taiwan EPA environmental database	Industrial park
Institute of Transportation digital map data	Main road
Central Weather Bureau database	Altitude		m b	NA
Taiwan EPA environmental database	Pollutants	CO	ppm	NA
		NOx
Central Weather Bureau database	Meteorological factor	Temperature	℃	NA
		Relative humidity	%	NA
		UV	nm	NA

^a distance to the nearest landmark; ^b elevation above sea level of the monitoring site.