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Operational definition of the pre-, during-, and post-Olympic periods in relation to the start and end dates for air pollutant measurements and clinical visits within each period. 0 = 0–23 hours before clinic visit; 1 = 24–47 hours before clinic visit; 2 = 48–71 hours before clinic visit; 3 = 72–95 hours before clinic visit; 4 = 96–119 hours before clinic visit; 5 = 120–143 hours before clinic visit; 6 = 144–167 hours before clinic visit.
