Respiratory toxicity of cedar and pine wood:

Many pet owners, breeders and pet retailers favor wood chips as pet bedding for a variety of reasons. Most wood chips are inexpensive and depending on the wood used, wood chips can provide natural insecticidal, bactericidal or bacteriostatic properties. Such bedding can often kill or inhibit the spread of fleas, mites or other pests, and the resins and other aromatic chemicals emitted by the chips help to control pet odors. With all of these advantages, pet stores often sell prepackaged starter kits for housing small pets complete with a supply of wood chips for bedding. Many people have used cedar and pine chips as bedding for these reasons. Wood from western red cedar (Thuja plicata) has one of the most potent insecticidal compounds, which accounts for its popularity to repel or kill clothes' moths.