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Annual average ambient NO2 concentration (A) and area-specific distribution of NO2 concentrations (B) from 2005 to 2018 across ten study areas
In panel B, study areas are ranked in descending order of annual average NO2 levels in 2005. In the box plots, horizontal bolded lines represent medians across the whole 2005–18 period and the edges of the boxes represent IQRs. Vertical lines indicate 1·5 times the IQR. Black dots indicate outliers. NO2=nitrogen dioxide.
