I've been using pine for a few years with no problems. The only studies I've ever been able to find say that cedar is the one that has been proven in lab tests to cause organ failure in rats.

It is in fine print on the side of the bag but I checked every brand in every size of pine at Petsmart and they are ALL kiln dried so no worries.

Pine is OK (the fluffy stuff packed tightly) and it is the only thing that controls odor, ammonia, and moisture for a full week.

The pine pellets on the other hand, can become too dusty and kill babies by clogging their nose.