Jeromy Choi, a fifth year engineering student at the University of Ottawa, shakes off excess dye submerging himself in the purple dye, an engineering tradition during the start of Frosh week at the University of Ottawa in Ottawa on Sept 5, 2010. Health Canada says a dye often used to stain engineering students' skin purple has been linked to a possible cancer risk. THE CANADIAN PRESS/Pawel Dwulit