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Carcinogenic Myth Busted

In Challenges Facing Essential Oil Therapy: Proof of Safety, Robert Tisserand writes: The essential oil constituents that are generally regarded as carcinogens are:
• methyleugenol
• estragole
• safrole
• asarone

Tisserand writes: "The mathematical exercise undertaken in establishing safety levels for ME [methyleugenol] include a safety factor of 10 to allow for interspecies differences, i.e. assuming a human susceptibility 10 times greater than that of a rodent. However, this makes no sense, since rodents are much more susceptible than humans to cancers, especially of the liver (Battershill and Fielder 1998, Toth 2001). Estragole, for example, is metabolized more efficiently in human liver, suggesting much reduced toxicity, compared to that in rats (Guenthner and Luo 2001). The setting of arbitrary safety factors is, in any case, unscientific, and not evidence-based.

The presence of carcinogens in essential oils should not be ignored, and this remains an area where risk has not been clearly determined. In this case, the toxicity of whole essential oils should be under consideration, and the case for constituent extrapolation is poor. In fact, essential oils containing carcinogens are sometimes found to have an anticarcinogenic effect in rodents.
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Ron Guba wrote in “Toxicity Myths Part II - Essential Oils and Their Carcinogenic Potential” (found in Essential Oils and Cancer, Proceedings of the 4th Aromatherapy Conference on the Therapeutic Uses of Essential Oils p. 212-215):

Here are some excerpts from Guba's presentation, for more information, please email HEO:
Overall, the results of these testing procedures and the publicity generated has led to an inflated, false view of the potential cancer risk for many compounds, including those from essential oils (mostly the family of allylbenzene compounds).

However, from both long-term human experience and research, it is clear that the occasional, low-dose therapeutic use of such essential oils or herbal extracts do not pose any cancer risk.

In using the essential oil or herbal extract of Sassafras or Calamus, as natural products, they are not ‘banned’ as such for individuals or therapists to use in making up preparations. However, given the ‘banned’ status of the individual compounds, it will be difficult to reverse their undeserved “bad reputation.”

There is no good reason to continue to class high-estragole containing essential oils as “hazardous” or “not to be used during pregnancy” by Aromatherapy associations, training providers or authors, either for topical or ingested applications.

However, in the realm of essential oil compounds, there are a number of compounds that have demonstrated protective and anti-tumoural effects. This includes essential oils containing d- limonene (Citrus oils), geraniol (Palmarosa, Geranium, etc), B-ionene (Boronia absolute), Arthumerone (Turmeric) and B-atlantone (Atlas Cedar, Turmeric). Hence, such essential oils could be fruitfully used in combination with any “suspect” essential oils.

Aromatherapists would be well advised to be the best informed relative to the real facts, the potential problems and appropriate dosages for essential oils used in practice. Otherwise, therapists will tend to accept and promote unrealistic “toxicity myths” that ultimately create more problems (not less) for the practice of Aromatherapy to be accepted as an effective and safe modality.