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Table 1 Characteristics of the cases (n = 1597)

From: Fine particulate matter constituents associated with emergency room visits for pediatric asthma: a time-stratified case–crossover study in an urban area

Characteristic Number %
Age (mean ± SD) 6.1 ± 3.5  
Male sex 1073 67.2
Cold season 971 60.8
Cold days (< 26.0 °C) 879 55.1