The United States Environmental Protection Agency (EPA) outlawed the use of fluorescein for this purpose, since it was shown to be harmful to the river. The parade committee has since switched to a mix involving forty pounds of powdered vegetable dye. Though the committee closely guards the exact formula, they insist that it has been tested and verified safe for the environment. Furthermore, since the environmental organization Friends of the Chicago River believes the dye is probably not harmful, they do not oppose the practice.
how do they make the chicago river green
forty pounds of powdered vegetable dye