Hmm I am going to add my two cents to this. I don't know for sure but as I found this interesting I asked a colleague of mine and was told two things of interest. If it smells of pine it has phenols. He didn't know of any studies with reptiles but here is an article on human studies.
https://ietd.inflibnet.ac.in/bitstre...llchapters.pdf
"Workers exposed to pine and fibre dust have more respiratory problems and a greater risk of airway obstruction, since their FVC showed a significant inverse correlation with exposure (Choubrace, 1991). Several types of wood dust, especially western red cedar wood, was reported to cause occupational asthma in carpenters and timber workers"
Raw pine has tons of studies that seem to point to toxic effects in mammals. I have not found any that state anything about kiln dried. The OHSS doctor I asked said if it smells of pine there is phenols I have found no hard evidence on that so it is up for debate. I don't know myself.
I remember when I was first working a guy I worked with up to his arm pits in PCBs. Now you need a has-mat suit. He still lives around the corner from my family s house and just turned 95. He worked with PCBs for 50 years. Times change and ideas change aluminum pots good or bad I don't know anymore. My point is ideas change.
The kiln dried pine debate is just that a debate. I know and can back up with articles that raw untreated pine has phenols and that phenols cause respiratory issues in mammals. I also know that most of the wood in my house is rough pine and I don't have respiratory problems.
Most of the people whom have posted keep their snakes on pine even if they don't know it. Newspaper is made of (in north america anyway) Pine and spruce with some hemlock, larch an bits of hardwoods too. White paper is bleached, but newsprint is just natural. Washed and dried, chewed up and a handful of other things but it is still wood in there. Is it toxic? I don't know either.
I think there is no conclusive proof with kiln dried pine, toxic or not. My worry would be am I sure it is kiln dried and not air dried pine chips. I don't know if there is a way of telling and kiln drying is expensive and drying a low value product seems rather odd to me. I would be concerned with getting a mix. I certainly understand why it would be a great choice of bedding.
Alex