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(a). Comparison chart of Wuhan in four pollutants. (b). Comparison chart of New York in four pollutants. (c). Comparison chart of Milan in four pollutants. (d). Comparison chart of Madrid in four pollutants. (e). Comparison chart of Bandra in four pollutants. (f). Comparison chart of London in four pollutants. (g). Comparison chart of Tokyo in four pollutants. (h). Comparison chart of Mexico city in four pollutants.
