No pine for the rats! Baked or dried aspen is okay, but pine still contains aromatic oils which are more likely to irritate their lungs and give them a URI.
I've been keeping my rats on kiln dried pine for a year now with no problems. Many rat breeders I know have been using kiln dried pine for years wihout any problems.
"We are artists using locus and alleles as our paint; the ball python as our canvas" - Colin Weaver