Kiln dried dust free is supposedly safe. But don't medicate your rats if they're on pine. That can cause death due to changes in enzymes in the liver. I assume you're a feeder breeder, so that probably won't apply to you.

Being kiln dried is -very- important. Otherwise, you will end up with un-happy, and sick rats.

Here's a long discussion we've recently been having on another board about whether or not it's safe to use pine shavings: http://mouselovers.com/viewtopic.php?f=6&t=2348