Polystyrene is light so you can use it to make large parts that otherwise (if you used sugar paste) would be very heavy. Polystyrene is not edible. If you want the cake topper to be food safe, stick to the guidelines below.
3. Don’t mix the sugar paste that touched the polystyrene, with the edibles. Throw it out or put in a labeled bag and use it for non-edible purposes.