If you are using regular newsprint I don't think there is anything you need to be concerned about other than the ink used on newsprint can rub off and show on lighter colored horses. Several years ago we did a study on paper bedding using virgin phone books after their expiration date and to my knowledge nothing was done to them except to shred them. News print is used many places and for different species, i.e., poultry and dogs. You don't have to worry about staples or glue or anything else when using newspapers.