Here's a link to the National Institute of Health's guidelines on Lab animals.

http://oacu.od.nih.gov/regs/guide/guide3.htm

It doesn't mention pine specifically and from some other sources I've read, its nowhere near as harmful as cedar, but in the guidelines, it says that by heating the substrate, it reduces the amount of harmful hydrocarbons. So, if anyone is at all concerned, they could try this.

Sorry its slightly offtopic, but i found it interesting and thought others might as well.

Jeremy

P.S.
Here's the links to Melissa Kaplan's site where she wrote a couple articles on pine. I've heard mixed opinions about her intentions, so take it for what its worth to you.

http://www.anapsid.org/cedar.html
http://www.anapsid.org/cedar2.html