you could use a service like TerraCycle to recycle used blades.Right, so I guess you can't recycle a can that you opened with a can opener, either? That has sharp edges and is much more likely to injure somebody working recycling than my blades in the Altoids tin.
People who work in this industry understand that it is inevitable that there will be potentially injurious items in the recycling. It's part of the job.