This was originally written for a post on the Yahoo! group RFRB in 2004.  I couldn’t find any references attached to it; this article may be rewritten in the near future.

Phenols – the chemicals that makes pine and cedar smell so good – are the reason that softwood shavings are dangerous for small animals.  Phenols are caustic (corrodes and destroys animal tissue), poisonous, acidic compounds – the very things which are routinely diluted and used in over-the-counter disinfectants. And since phenols are so caustic, their direct connection to respiratory ailments is clear.  The constant irritation to the nasal passages, throat and lungs gives harmful bacteria an easy opening.

The above data – plus the fact that an animal with a damaged liver will also have a depressed immune system – are generally sufficient evidence to lead to the conclusion that wood litters and beddings must be avoided.

Animals may also react to the dust from wood shavings.  Prolonged exposure to wood dust has been shown to cause nasal adenocarcinomas (cancer), allergic dermatitis and respiratory sensitization – enough that it’s considered a hazard to work with and is a regulated toxic substance.  Wood dust has an OSHA rating of 3.3 – moderately toxic.

Unless you have your rats necropsied, you won’t be able to tell what effects the bedding had.  You won’t see an enlarged liver that isn’t functioning properly just by looking at your rat.  You won’t be able to see the scar tissue in the lungs just by looking either.

The problems caused by phenols don’t directly kill rats. They simply compromise their organ systems. If two genetically similar rats were kept, one on pine and cedar for two years and the other on a bedding like SaniChips, and both infected with a Mycoplasma/pneumonia combo, the rat that had the already scarred lungs would succumb more quickly and harder than the one kept on the non-phenol-based litters. If your rats are on pine, it alters their liver enzyme effectiveness. They alter rats ability to handle standard drugs that your vet would use for treatment.

As for saving money, a bag of SaniChips only costs about $10 and it lasts about 16-20 cages. Ask your pet store if they can special order it; most stores don’t carry it because they don’t have a demand for it.

To get a general idea of its effects, the phenol chemicals are what’s added to moth balls and the cleaner PineSol to make them so toxic. It’s why cedar sachets and cedar chests repel insects, and why phenols mixed with formaldehyde are used as a common wood coating/sealant. Phenols are the natural volatile chemicals in the wood; they’re also called carbonic acids and aromatic hydrocarbons (HCs). Small animal livers try to remove the phenols by producing more of certain enzymes that destroy these chemicals; this is a natural part of their defense against environmental toxins. They always produce a low constant level of these protective agents; the problem occurs when constant exposure to phenols causes them to produce substantially larger quantities. However, those enzymes are the ones used to process and remove drugs. In rodents, constant exposure to phenol-containing litters reduced drug effectiveness by greater than 40%!

HCs are made primarily of carbon and hydrogen molecules. HCs are formed by distilling wood (or petroleum) and consist of aliphatic (carbon chain) or aromatic (carbon ring) molecules. Toxicity results from the volatility and viscosity of an HC product and the chemical characteristics of the HC and any additives. HC toxicity is divided into clinical syndromes based on the organ system most severely affected. The lungs are affected most commonly, but instances of neurologic, cardiac, gastrointestinal, renal, hematologic, and skin pathology are well documented. Excessive HC inhalation can even displace oxygen. Even small amounts of HC may cause a chemical pneumonitis; because many HCs have poor water solubility, they penetrate deep into the bronchopulmonary tree, casing bronchospasm followed by an inflammatory response. In the alveoli, volatile HCs may displace oxygen and surfactant, leading to hypoxia and a diffuse hemorrhagic exudative alveolitis. Alveolar dysfunction, in turn, leads to ventilation-perfusion ratio mismatch, hypoxemia, and possibly the resultant respiratory failure. Most HCs cause direct mucosal irritation and are absorbed quickly across tissue layers. Some can cause chemical burns. HCs are lipophilic and thus are attracted to lipid-rich neural tissue. Systemic absorption of HCs can cause acute and chronic central nervous system and peripheral nervous system toxicity. Long-term exposure to HCs may result in chronicheadaches, cerebellar ataxia, and encephalopathic findings of cognitive and psychopathic impairment in humans. HCs are what is being abused when humans ‘sniff’ certain products like Glade, butane, benzene and xylene. There are tons of ways HCs can affect rats that we can’t see: arterial blood gases, CBCs, electrolytes, urinalysis, blood urea nitrogen, hepatic function, and chest radiographs are ALL affected!

The EPA states: “Phenol is a colorless-to-white solid when pure; however, the commercial product, which contains some water, is a liquid. Phenol has a distinct odor that is sickeningly sweet and tarry. Most people begin to smell phenol in air at about 40 parts of phenol per billion parts of air (ppb), and begin to smell phenol in water at about 1-8 parts per million parts of water (ppm; 1 ppm is 1,000 times more than 1 ppb). These levels are lower than the levels at which adverse health effects have been observed in animals that breathed air containing phenol, or that drank water containing phenol. Phenol evaporates more slowly than water, and a moderate amount can form a solution with water. Phenol can catch on fire.”

As for kiln-dired (aka cured) pine, heat treatment generally releases most of the phenols. There have been a few remote instances where the batch was not properly heated. Those batches smell extra ‘piney’ and have caused multiple animal deaths by excessive phenol release.

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