There are scientific studies, and it's a fact that the phenols in pine can be respinsible for RIs, and enzyme changes in the livers of small animals.
This is why it is not used in laboratory settings.

HOWEVER. All studies were done on un-treated pine, and not treated pine. Supposedly the treated stuff is just as harmless as Aspen.

Here is some information on the subject: http://buckysbunnies.tripod.com/Pine.html/