Pollution Probe began as a professor and student action group at the University of Toronto that focussed on the issue of pollution in the Great Lakes. The group campaigned against the widespread use of phosphates, which are harmful to the Great Lakes’ ecosystems. It remained based in Toronto, and by 1970 had over 1,000 members. The organization conducted research on many pollution issues, and successfully fought to have most uses of the harmful pesticide DDT phased out by the mid-1970s.