Every substrate you can use comes with a risk of impaction, some are just less risky than others. He can't get coco fiber or soil he said and he asked if he can use paper towel, which you can. Paper towel is a much better option than what he is using currently, gravel. It does pose a risk, but not as big of a risk as gravel would. Just be careful when feeding, perhaps even remove the paper towel when you do feed and use that time to do your daily change as well.