One example is Dec. 26, when winds from the southeast blew pollution from Sterigenics toward monitors at Willowbrook Village Hall across the street; a neighborhood nearly 400 yards west of the facility; and Hinsdale South High School, about a half-mile northwest. The highest concentrations of ethylene oxide ranged from 10.5 micrograms per cubic meter of air at Village Hall to 1.17 at the west neighborhood site to 0.566 at the high school monitor.