Chicago River dyeing does not harm fish during St. Patrick's Day celebrations

In the United States, on March 15, 2025, the Chicago River was dyed bright green to celebrate St. Patrick's Day, attracting large crowds to the festivities. This annual tradition, now established for decades, involved the Plumbers Local Union 130 who possess a secret recipe for the dye used, which is nontoxic and environmentally friendly. The transformation of the river into a vibrant green spectacle is often accompanied by a parade, with many Chicagoans and visitors reveling in the atmosphere that embodies the celebration of Irish culture. Observers noted the event was even livelier due to favorable weather conditions, contributing to a robust spirit of community during the day and evening. Recent studies conducted by scientists on the impact of the dye on local fish populations have suggested that the bright green dye does not negatively affect the aquatic life in the river. Researchers have been monitoring the behavior of tagged fish, which showed no signs of distress during the dyeing process. The study indicated that active tagging of over 80 fish allowed scientists to gather data on their movements, revealing that the tagged fish did not seek shelter or alter their usual behavior when the dye entered the water. This finding has significant implications particularly for the ongoing debate surrounding the environmental impacts of such events. Environmentalists had previously raised concerns about the ecological effects of dyeing the river, especially during its inception in 1962 when petroleum-based dyes left harmful residues. However, since then, the approach has shifted to using a vegetable-based dye sanctioned by the Illinois Environmental Protection Agency, which is deemed safe for use around wildlife. Despite past environmental worries, the current consensus among researchers is that the fish are largely unaffected by the dyeing process, though they continue to monitor other factors that may pose threats to biodiversity, such as rainfall runoff and sewage discharges into the river. Sustainable practices have contributed to improvements in the ecosystem of the Chicago River, which is now home to more than 80 species of fish, a remarkable recovery from the fewer than 10 species recorded in the 1970s. The ongoing celebration highlights not only a cherished tradition but also a positive narrative regarding the health of the river and its wildlife. The St. Patrick's Day festivities in Chicago embody a mix of cultural celebration and scientific inquiry, blending community engagement with ecological awareness, encouraging both residents and tourists to come together and appreciate the vibrant atmosphere of the city while being conscious of the environmental factors at play. As these traditions continue, they foster both local pride and environmental stewardship, reminding participants of the importance of maintaining a balance between celebration and conservation in urban settings.