No More Homeless Pets Forum - 3/18/05
Are pine shavings really dangerous?
Question from a member:
Please present research that proves that wood shavings are harmful.
I've done a lot of research into softwood bedding and rabbits and there just isn't any credible evidence that it causes problems with rabbits, at least. People talk about liver problems, but all non-heated treated softwood bedding does is induce Hepatic Micorsomal Enzymes (HME) as do many things such as grapefruit juice, and is a natural function of the body and not a sign of damage. As far as causing respiratory problems, people are basing that on studies done on sawmill workers which would not be the same environment that a pet is living in. You can have a rabbit with an allergy to softwood bedding. I ended up writing an article about pine shavings and the myth they are dangerous.
Response from Dr Mark Burgess:
Well, I don't know where the study was published that I recall reading; it was in a university setting, that's all I remember. It involved rats which are easy study candidates to use, and the study found that all softwoods tested (pine, cedar, fir) caused significant changes in the liver, not just activation of microsomal enzyme systems, but significant increase in liver size and weight, indicating a heavy load placed on the liver to detoxify and metabolize these oils.
Cedar oil, in particular, is widely recognized as potentially toxic, and even is a moderate flea repellent... as hardy as fleas are, it even is noxious to them to some degree. The rats in the study also showed exacerbation of lung diseases (they tend to carry longterm respiratory infections such as mycoplasma; the rats housed on softwoods had more advanced lung disease lesions).
Remember, activation of microsomal enzyme systems in the liver is "normal" in response to chemical exposure, but does not mean that such chemicals are harmless... the same changes occur in human livers with exposure to alchohol, but with longterm exposure the person can end up with cirrhosis and a failing liver. Activation of liver enzyme systems also indicates that there IS significant absorption of these oils into the body, not just on the skin surface. I don't think anyone knows just what the extent of the effects of these can be with longterm exposure.
How thorough was the study you conducted in order to find softwood harmless? Was it just literature searches, or was there independent research to show new information? If so, how many animals were used, and for how long was the study conducted? Ideally a study with rabbits should be for at least 5 years...they age slower than rats, with a slower metabolism, therefore changes would take longer to show up. Thorough blood workups should have been done regularly, at
least every few months, and a control group on non-softwood bedding would need to be used to compare results. At the end of the study histopathology should have been done on all internal organs of the animals. Was this done? And where were the results published? Unless the study was done on significant numbers of animals, to allow for statistical omparison, and unless methodology was meticulous and thorough, it would be very premature based on one piece of work to proclaim that there is absolutely no risk with these aromatic oils.
There is enough evidence that softwoods are questionable at best. The real question is, why use them if there is any doubt at all, when paper or hardwood beddings are agreed by all to be safe? The only reason softwoods have been abundantly used is that they smell pleasant and are cheap, hardly reasons to promote them if some studies have indicated potential longterm toxicity problems. You've noted the studies in humans linking these wood oils to human lung disease; yes the exposure route is different, but still the same wood oils.
You have brought up another point: rabbits or other animals can have true allergic response to these woods, which is more likely with woods giving off high levels of oils compared to inert bedding materials that don't. Other aromatic oils such as pennyroil have been promoted by some as natural flea repellents, etc, but I've seen information on significant toxicity effects with some of these as well.
As with many areas of exotic animal medicine, there are still things to be learned (and hopefully they will be!), and much is not set in stone...but when giving advice professionally, the responsible choice is to err on the side of safety, if one must err at all. And the safest approach is tonot use woods with high aromatic oil content; no one I know in exotic pet medicine disagrees with that at this time.
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Posted on SHARE Yahoo group Mar.18, 2005