Untapped Mailbag: How “Green” is the Chicago River St. Patrick’s Day Celebration?

Yesterday on our Instagram feed, we posted the above photo taken by @gweets this past weekend during Chicago’s five-decade-old tradition of dying their river green for the festivities surrounding St. Patrick’s Day. One of our readers, Sarah Marder, asked us this question: “I can’t help but wonder what that does to the river’s eco-system. Do you know anything about it?” Well, for today’s Untapped Mailbag, we’ve dug up the inside scoop about how they dye the river as well as exactly how “green” or eco-friendly the practice actually is.

When the tradition began in 1961, the river dye was much too potent. They had used a plumber’s dye used to detect leaks of sewage pollution and it dyed the river green for one entire week. Adjusting the dosage of the dye, a disodium salt called fluorescein, the plumbers were able to detect the source of illegal waste disposal in the river, and it only stuck around for about a day. Environmentalists in 1966 found the dye to be toxic to goldfish species in the river, and the committee changed their dye to one that was “vegetable based.”

According to this Christian Science Monitor report, “the dye’s exact ingredients are a closely guarded secret. The parade committee compares the formula to that of Coca-Cola,” it would be like “telling where the leprechaun hides its gold.” Here is a video of some of the workers setting up for the parade in 2011:

CSM also reports that although the committee promises that the dye is not harmful to the Chicago River’s ecosystem, it is notable that other cities have rejected several plans to adopt the celebratory dying, including cities in Michigan and Florida. The final answer, it seems, is not so clear-cut. Although the environmentalists involved with the celebration swear by it, other cities are hesitant to dye their rivers in the same way.

A popular quote on Instagram photos from Saturday’s Chicago River St. Patrick’s Day Parade was: “If we can dye the river green 1 day out of the year, why can’t we dye it blue for the remainder of the year?” It seems several people, like Sarah, were thinking about the environment during the celebration. Thanks for your question.

If you have something about your city you want answered, feel free to tweet us @untappedcities or use the hashtag #untappedcities on Twitter or Instagram. Get in touch with the author @uptownvoice.