Fig. 7: Distributions of the exposed population fractions categorized by annual cumulative durations exceeding the 1-h and 24-h mean high ultrafine particle (UFP) exposure levels recommended by World Health Organization Air Quality Guidelines (WHO AQG).
From: Machine learning-enhanced high-resolution exposure assessment of ultrafine particles
a Exposed population fraction based on the 1-h high UFP level (2 × 104 particles‧cm−3), including four categories of total population, the population in urban centers, urban clusters, and rural areas. b Correlation between the fractions of the population exposed to the 1-h high UFP level in urban centers and urban clusters. c Exposed population fraction based on the 24-h mean high UFP level (1 × 104 particles‧cm−3). d Correlation between the fractions of the population exposed to the 24-h mean high UFP level in urban centers and urban clusters.
