Generally, newspapers are printed with a vegetable based ink and are totally safe--been using shredded paper in boxes for 15 years + with no problems and they love playing in it too. Same is true with cardboard boxes--the ones you want to avoid are those that have photo quality pictures as they are a plastic applique and definitely not good but ones with inked surfaces from inside the U S are also done with vegetable ink, probably due to our "sue" over anything society and EPA mandates. There was a whole bunch of box uses under "Cardboard Castles" here once upon a time. I used to have a mini Rex that would get into a big pan I had filled with hand shredded newspaper and she would "submarine" under the paper and move all around and then "prairie dog" and pop up through the paper and look around--funny to watch and she'd entertain herself for hours.