PMD and PMDRBO
What is PMD?
PMD is the abbreviation for p-menthane- 3,8-diol, also known as para-menthane- 3,8-diol, and is an active ingredient used in insect repellents. It is found in small quantities in the essential oil from the leaves of the Eucalyptus citriodora tree, also known as Corymbia citriodora. This tree is native to Australia, but is now cultivated in many warm places around the world.
What is PMDRBO?
PMDRBO (PMD Rich Botanic Oil) is a generic name for Citriodiol®, a naturally sourced active substance containing p-menthane- 3,8-diol (PMD) and other naturally occurring components from the Eucalyptus citriodora tree’s oil (common name: Lemon eucalyptus).
Is natural PMD the same as synthetic PMD?
No. PMD in Citriodiol® is generated directly from essential oils. The PMD from this oil is sold along-side the other naturally occurring constituents in the raw oil as a combined product with 100% purity. This natural PMD product, which is called PMD rich botanic oil or PMDRBO, has been notified under the BPR as “a mixture of cis-and trans-PMD/Citriodiol” and is about 50% more effective in repelling insects than like quantities of synthetic PMD.
By comparison, what is commonly referred to as synthetic PMD is not derived from an essential oil, but rather is typically a by-product of far more complicated multi-step chemical processes, for example making menthol. The resulting material contains only PMD and has no essential oil co-constituents.
Why is natural PMD (PMDRBO) better than synthetic PMD?
Simply put, in our view it is better for the consumer and better for the environment. Consumers benefit because naturally sourced PMD (i.e. PMDRBO) performs significantly better than synthetic PMD. An independent study published comparing synthetic PMD with PMDRBO shows that with like amounts of PMD, PMDRBO performed 50% better in repelling the target organism (in that case Aedes mosquitoes). (Drapeau 2011). In this study a 20% PMDRBO (which at a min 64% PMD contained ca. 13% PMD) alcohol spray offered over 5 hours complete protection against Aedes mosquitoes whereas the 13% synthetic PMD product provided only 3 ¼ hours of protection.
While both forms of PMD are readily biodegradable, the real benefit to the environment from PMDRBO is that it actually exists in nature in its final form. This means nothing is being added to the environment that has the potential to upset its natural order and balance. In addition, because the material used to make Citriodiol® is Eucalyptus citriodora oil, and this oil is distilled just from the leaves of some of the branches of the tree, allowing the tree to continue growing, using PMDRBO actually encourages the growth and maintenance of healthy trees to reduce the overall carbon dioxide content of our atmosphere. Even the waste product from the oil distillation process, known as “bagasse,” is added directly back to the soil around the trees as fertilizer, and is also dried and used to fire the boiler.
Is efficacy related to PMD content?
Yes, the PMD content is the principle factor in predicting the efficacy of a product. It evaporates slowly from the skin, and it is while it is in this vapour phase that it has a repellent effect.
It is worth noting that PMD, when applied in conjunction with the other naturally occurring constituents in the starting material (e. citriodora), is substantially more repellent to biting insects than pure PMD. Therefore it is more accurate to say that it is the PMDRBO content of a product that determines efficacy, not simply the PMD.