A friend gave me a small bag of camphor wood chips. I have them in my car and like the smell. Someone told me that camphor can be toxic. Is is toxic to breathe or to burn, to humans or to plants? Is it safe to just keep in my car and enjoy the aroma?
Cinnamomum camphora (source of camphor wood) is in the Laurel family. According to Toxic Plants of North America (Burrows & Tyrl, 2013), “few toxicologic problems have been associated with the genus. However, when a camphor tree was planted in an aviary, 49 budgerigars died within 24 hours, apparently from its noxious fumes.” As implied by its common name [camphor tree], all parts of the tree contain camphor. The intensity is greater in the leaves than in the wood. The tree’s toxic properties have been known since the late 1800s, and most exposures are non-fatal and involve accidental ingestion of liniments that contain the oil from the plant. When inhaled, camphor is usually a mild irritant (perhaps not so mild at all if you are a bird!) and nervous system stimulant. It also contains low levels of toxic alkaloids.
If you wish to err on the side of caution, I would suggest not breathing the fumes, burning the wood, or using it in the garden (unless you are trying to suppress weeds, though the tree itself is considered a weedy species in some parts of the world, such as Australia). As you probably know, people have used camphor-based preparations in herbal and traditional medicine.
About medicinal uses and associated risks
The article “Camphor—A Fumigant during the Black Death and a Coveted Fragrant Wood in Ancient Egypt and Babylon—A Review,” by Weiyang Chen, Ilze Vermaak and Alvaro Viljoen, offers a historical perspective, and does mention that the tree may have some phytotoxic/allelopathic properties as well (toxic to other plants).
Abstract:
“The fragrant camphor tree (Cinnamomum camphora) and its products, such as camphor oil, have been coveted since ancient times. Having a rich history of traditional use, it was particularly used as a fumigant during the era of the Black Death and considered as a valuable ingredient in both perfume and embalming fluid. Camphor has been widely used as a fragrance in cosmetics, as a food flavourant, as a common ingredient in household cleaners, as well as in topically applied analgesics and rubefacients for the treatment of minor muscle aches and pains. Camphor, traditionally obtained through the distillation of the wood of the camphor tree, is a major essential oil component of many aromatic plant species, as it is biosynthetically synthesised; it can also be chemically synthesised using mainly turpentine as a starting material. Camphor exhibits a number of biological properties such as insecticidal, antimicrobial, antiviral, anticoccidial, anti-nociceptive, anticancer and antitussive activities, in addition to its use as a skin penetration enhancer. However, camphor is a very toxic substance and numerous cases of camphor poisoning have been documented. This review briefly summarises the uses and synthesis of camphor and discusses the biological properties and toxicity of this valuable molecule.”