Nearly a half million people descended on downtown Chicago last Saturday for its annual St. Patrick’s Day festivities. Dying the Chicago River a vivid green remains among the world’s most famous rituals in observance of the holiday.The tradition began in 1961 after local plumbers used fluorescein dye to trace the source of illegal pollution discharges that would seep into the river and turn it green. For this reason, the EPA outlawed the use of fluorescein once it was found to be harmful to the environment. Today, members of Chicago Journeyman Plumbers Union Local 130 use 40 pounds of powdered vegetable
