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Ratios of 2013 to 2003 measurements for PM2.5 mass, OC, and EC concentrations in 14 cities (See Table 1 for site descriptions). No data available for Urumqui [UR], Taiyuan [TY], Xining [XN], Nanjing [NJ], and Chengdu [CD] in the 2003 study24.
