Five years ago, in March 2016, 110 groups submitted an application under the Great Lakes Water Quality Agreement (GLWQA) to designate radionuclides as Chemicals of Mutual Concern (CMCs) under Annex 3 of that Agreement. We submitted our nomination in reply to Environment and Climate Change Canada’s (ECCC) and the U.S. Environmental Protection Agency’s (EPA) call for nominations from the public.