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The Anatomy of Adulteration

The Adulteration of Essential Oils
and the Consequences to Aromatherapy & Natural Perfumery Practice.
Copyright ©Tony Burfield 2003-2005. [Slightly updated from a Presentation to the IFA Annual AGM London Oct 11th 2003].

Part 1. Oil Adulteration.

Introduction.
As far as adulteration is concerned, producers and distributors of essential oils are frequently painted as “the bad guys”, but it should be pointed out that their oil customers frequently demand oils below the market price while still wanting to be told that they are authentic. In this climate, the honest oil trader may find it virtually impossible to survive on the margins he is allowed to make (many have already gone bust). For example, in the late 20th Century, lavender oil (Lavandula angustifolia) was being sold almost as a loss leader by many French producers as the market was unwilling to pay a realistic price; currently, the aroma industry is dominated by a handful of large and powerful international houses whose corporate buyers often attempt to drive raw material prices to impossibly low levels, not allowing workable profits to be made. This sets the scene for unethical practices.

Essential oils - a definition.
An essential oil (e.o.) is the volatile oil containing odiferous elements of the plant, produced by steam or hydro-distillation of aromatic vegetable plant matter. E.O. components arise via the secondary metabolism of plants and are stored within specialized structures; ideally they are isolated with minimum chemical changes from human intervention. Citrus oils, produced by the mechanical pressing of citrus peels, are also called essential oils, and, according to the International Standards Organisation (ISO), so are dry-distilled oils - such as cade oil (from the branches of Juniperus oxycedrus) and styrax pyrogenée (from Liquidamber spp).

Essential oils should be produced by purely physical means, and be 100% pure and wholly derived from the named botanical source - but how are these standards to be guaranteed? No quality standards for the authentication of essential oils exist in aromatherapy, in spite of the revelations of gross adulteration of aromatherapy oils for retail sale (Health Which 2000). Professional aromatherapy organizations have failed to issue standards, in spite of individual schemes being put forward (Jones 1998) but, in contrast, other essential oil-using industries are served by the following standards:

The Pharmaceutical Trade: British Pharmacopoeia (BP) 2004 is published on recommendation of the Medicines Commission UK. Oils specifications are also published in the European Pharmacopoeia 4th edn 2002 (Eur. Pharm 4th edn); United States Pharmacopoeia (USP); also the pharmacopoeia’s of individual nations such as China, India etc. Earlier editions of The British Pharmaceutical Codex (BPC), such as BPC 1949, contain many essential oil standards still in use today.
Essential Oil Trade: Monographs on individual essential oils (EOA Standards) were produced by the Scientific Committee of the Essential Oil Association Inc.
Flavorings Industry: Food Chemicals Codex IV (1996, US) produced at the request of the FDA (1992), is widely used for guidance by the food flavorings industry.
Aroma Companies: Many larger established Flavor & Fragrance Houses have their own internal purchasing standards.
Independent Certifying Bodies: International Standards Organisation (ISO Standards TC 54) & Association Française de Normalisation (AFNOR) both have detailed standards for e.o.’s.*

*An example is ISO 3515 for Oil of Lavender (2001) which includes minimum and maximum percentages of thirteen natural components, and their occurrence in French (spontaneous and clonal), Bulgarian, Russian, Australian and ‘other origin’, lavender oils. Limits for lavandulyl acetate, for example, are set at 2.0-5.0% in Bulgarian lavender oil by the standard.

Aromatherapy
Whilst it is apparent that the current European Pharmacopoeia, USP or ISO standards may serve the needs of particular industrial sectors, they do not entirely address the unique needs of the aromatherapy profession, since:

Holistic aromatherapists demand that “pure” and “complete” oils are used, rather than oils only distilled for economically short periods e.g. tea tree oil. It is now suggested that in some cases longer distillations may be disadvantageous e.g. for tea tree oil distillation again, increases, the proportion of sesquiterpenes rises and these are considered by some researchers as responsible for adverse skin reactions when applied topically. Secondly unnecessary energy ‘wastage’ associated with excessively long distillation times may not be seen currently as a particularly “deep green” strategy!

Many essential oils used in aromatherapy are particular to that industry, and not necessarily extensively used elsewhere e.g. Ravensara aromatica, Rosemary oil verbenone chemotype, Helichrysum italicum ssp.­ serotinum etc.

As well as “pure and natural”, the words “wild-crafted”, “organic” and “clinical grade” are frequently over-hyped descriptor terms used by both aromatherapy and by “naturals” traders, which need more careful definition prior to professional endorsement.

Natural perfumery
Natural perfumers are other potential users of pure essential oils. Grimshaw (1989) discussed “purist” perfumers (who employ no chemically produced or chemically modified ingredients), but also discussed reasons why others may wish to use up to 50% synthetics in formulations. This was, in a way, a prediction today’s situation, whereby aromachology perfumes (worth £611 million for years 1999-2001 according to Mintel Database 2002) contain a proportion of synthetics stipulated by the perfume house, mixed in with the e.o.’s. The alleged psychopharmaceutical effects of these products still depend on the utilization of authentic essential oils in the formulation – as far as marketing claims/hype are concerned anyway. A realistic “in-practice” distinction between mass-marketed aromatherapy perfumes (as opposed to 100% e.o. blends) and aromachology perfumes, other than at a hypothetical level, has yet to be defined, since both commonly employ synthetics. The synthetics content can presumably have either symbiotic, neutral or opposing effects (mood changing etc.) to those claimed for the e.o.’s in the perfumes in question, hence the need for clinical testing of the finished formulations to support advertising claims.

Types of adulteration.
There are several distinct categories of adulteration:

1. Addition of single raw materials. This simple form of adulteration can be conveniently divided into two groups:

“Invisibles” – i.e. those materials undetectable by a gas chromatograph (GC) analysis operating under routine conditions to analyse essential
oils.
“Visibles – those materials normally detectable by GC.

“Invisibles”: an example of this type is the deliberate addition of vegetable or mineral oil to essential oils (Nour-el-Din et al. 1977) - rapeseed oil in the EU is a particularly cheap vegetable oil which has been used for this purpose. Theoretically the “total area” of the detectable components of the oil’s gas chromatogram should be reduced by this latter type of adulteration, creating suspicion for the analyst and the need for further investigation. These adulterant materials may be revealed by aqueous alcohol solubility tests, and their presence further verified by using a different GC column & operating conditions (to detect mineral oil), or by derivatisation (for example the use of a methylating agent for vegetable oils – whereby the volatile methyl esters of the fatty acid components of glyceryl esters are revealed by subsequent GC analysis).

“Visible” diluents in this context include a number of solvents and perfumery materials. For example the following have been found in commercial essential oils: in a few instances resulting in a warning or prosecution by regulatory authorities:

Abitol (a primary hydroabietyl alcohol) – often used for extending resinoids.
Benzyl alcohol (now classified as a sensitiser by SCCNFP opinion)
Benzyl benzoate (now classified as a sensitiser by SCCNFP opinion; formerly
widely used to extend resinoids)
Carbitol (diethylene glycol monoethyl ether or DEGME)
Diacetone alcohol
Dipropylene glycol (DPG)
Dipropylene glycol methyl ether (DPGME) and tripropylene glycol methyl ether
(TPGME) - both of these substances are in air freshener technology.
Herculyn DÔ (hydrogenated methyl ester of rosin)
Isoparä (odourless kerosene fractions often used as a candle perfume diluent)
Isopropyl myristate (IPM)
Phthalate esters such as di-n-butylphthalate (DNP), diethyl phthalate (DEP) and di-
iso-octyl phthalate (DIOP)
Polyethylene glycols
Triacetin (the anti-fungal compound glycerol triacetate - a popular food
flavourings vehicle).
3,3,5-Trimethyl-hexan-1-ol.

Use of materials like isotridecyl acetate (ITDA, Fixateur 404Ô), Herculyn D and Abitol, can be moderately difficult to spot, because the materials may show a myriad of late-eluting small peaks on a GC trace representing their different constituent isomers, which could be overlooked by an inexperienced analyst especially at low levels.

In all the above instances of “visible” and “non-visible” adulterants, the added material is merely a diluent, and makes no odor contribution of its own. Addition of 10-14% of such a material may pass un-noticed if the material is evaluated against a retained standard solely on an odor basis – even by an expert nose – but it will in all probability be revealed by subsequent physio-chemical testing e.g. added vegetable oil in patchouli oil can often be revealed by a solubility test in 90% alcohol at 20°C.

2. The addition of cheaper essential oils and adjuncts.
Blending in cheaper oils to meet a customers’ target purchasing price, or to make additional profit for the producer, is commonplace in the oil trade. Some practices mentioned by Arctander (1960) - for example, the practice of extending of Amyris oil (Amyris balsamifera) with Cedarwood oil Virginia (Juniperus virginiana) and Copaiba Balsam (Copaifera spp.) – are unlikely to fool too many potential customers in these present & more educated times, but other more common adulteration practices still remain, which include:

Bergamot oil (Citrus bergamia): addition of lemon oil, rectified ho oil (Cinnamomum
spp.) and acetylated ho oil.
Bitter orange oil (Citrus aurantium subsp. aurantium): addition of sweet orange
oil (Citrus sinensis) & orange terpenes, plus trace amounts of character
compounds.
Cedarwood oil Virginia (Juniperus virginiana): addition of cedarwood oil
Chinese (Cupressus funebris).
Cinnamon bark oil (Cinnamomum zeylanicum): addition of cinnamon leaf oil.
Cinnamon leaf oil (Cinnamomum zeylanicum): addition of clove fractions,
eugenol, cinnamic aldehyde etc.
Clove Bud oil (Syzygium ­aromaticum): addition of clove stem oil & isolates
(eugenol) & eugenyl acetate.
Fir Needle oils (Abies spp.): addition of turpentine fractions, camphene, (-)-
bornyl acetate etc.
Geranium oil Chinese (Pelargonium hybrids): addition of adulterated Indian
geranium oil (which itself has been known to contain diphenyl oxide!)
Grapefruit oil (Citrus paradisi): addition of orange terpenes or sweet orange oil
distilled + minor amounts of (+)-nootkatone & others.
Lavender oil (Lavandula angustifolia): addition of cheaper lavandin (Lavandula
x intermedia) oil varieties; the addition of spike lavender oil (Lavandula
latifolia); the addition of ho oil rectified (Cinnamomum spp) and acetylated
ho or acetylated lavandin oils etc.
Lemon oil (Citrus limon): addition of orange terpenes, lemon terpenes & by-
products (e.g. steam-stripped lemon oil). For lemon oil BP, expressed lime or
grapefruit oil is added to poor grades to raise the UV absorbance level
sufficiently to pass the BP specifications.
Nutmeg oil (Myristica fragrans): the addition of nutmeg terpenes, a- pinene,
limonene, turpentine fractions etc.
Patchouli oil (Pogostemon cablin): addition of gurjun balsam (Dipterocarpus
spp.); vegetable oils, Hercolyn D; patchouli and vetiver distillation residues.
The superior Indonesian patchouli oil is often blended with the cheaper
Chinese oil.
Petitgrain oils (Citrus spp): addition of other citrus leaf oils & fractions, fatty
aldehydes, linalyl acetate, orange terpenes etc.
Peppermint oil (Mentha X piperita): addition of cornmint oil (Mentha arvensis).
Sandalwood oil EI (Santalum album): addition of sandalwood terpenes,
sandalwood fragrance chemicals etc.
Rosemary oil (Rosmarinus officinalis) addition of eucalyptus oil Eucalyptus
globulus) & camphor oil white (Cinnamomum camphora).
Verbena oil (Lippia citriodora): L. citriodora herb distilled over lemon oil.
Violet Leaf absolute (Viola odorata): addition of spinach absolute (Spinacia
oleracea).
Ylang Ylang oil qualities (Cananga odorata subsp. genuina): addition of
cananga oil (Cananga odorata), ylang ylang oil tails etc., ylang ylang oil
reconstitutions.

And also addition of these synthetics to “convert” one oil to another:

Basil oil exotic: add linalol to convert to Basil oil Sweet (Arctander 1960).
Eucalyptus globulus: add a-terpineol & others to convert to Eucalyptus radiata.
Geranium oil Chinese to Geranium oil Bourbon: addition of balancing
materials (monoterpene alcohols and esters, especially formates), copper
chlorophyll (for colour) and frequently a trace of dimethyl and/or dibutyl
sulphides.
Tangerine oil (Citrus reticula var. tangerine): addition of g-terpinene, dimethyl
anthranilate, a-sinesal & perilla aldehyde to convert to Mandarin oil (Citrus
reticulata var. mandarin).

3. The addition of cheap (nature identical) synthetics to oils that naturally contain these materials. Little detailed guidance has been previously published in this area. The older work of Arctander (1960) mentions a number of adulteration practices, but the sophistication of customer quality control procedures probably means that of the noted practices are now too obvious for today’s market. Looking at other published material on adulteration, Singhal et al. (2001) remarks on the adulteration of spice oils by simple additions of single raw materials e.g. the addition of synthetic citral to Litsea cubeba oil. My own guide to questionable practices include the following:

Anise oil (Pimpinella spp.): addition of technical grade anethol.
Basil oil exotic (Ocimum spp.): addition of methyl chavicol & linalol.
Benzoin resinoid (Styrax spp.): addition of small amounts of vanillin, benzyl
benzoate, ethyl & benzyl cinnamates, benzoic acid etc. to enhance odour (or
to pass off cheaper “Sumatra” grades as “Siam”).
Bergamot oil (Citrus bergamia): addition of linalol and linalyl acetate.
Bitter almond oil (Prunus amygdalus var. dulcis ): addition of, or passing off
benzaldehyde, as the oil.
Buchu leaf oil (Barosma betulina & B. crenulata): addition to cutters of
monoterpene sulphide fractions synthesised from the hydrogen sulphide
treatment of pulegone, including p-menthan-8- thiol-3-one.
Cassia oil (Cinnamomum aromaticum): the addition of synthetic cinnamic
aldehyde, methyl cinnamic aldehyde & coumarin.
Chamomile oil Roman (Anthemis nobilis): addition of isobutyl angelate and
bisabolols.
Cinnamon bark oil (Cinnamomum zeylanicum): the addition of synthetic
benzaldehde, eugenol and cinnamic aldehyde.
Citrus oils: the addition of fatty aldehydes and monoterpene alcohols and
esters to terpeneless and folded citrus oils.
Caraway seed oil (Carum carvii): the addition of limonene and (+)-carvone
Cardamom oil (Elletaria cardamomum): addition of linalyl acetate, 1,8-cineole and
a-terpinyl acetate.
Celery seed oil (Petroselenium crispum): the addition of limonene + touches of
alkyl phthalides.
Cognac oil: addition of ethyl esters of aliphatic acids e.g. ethyl oenanthate.
Coriander seed oil (Coriandrum sativum): addition of linalol and trace amounts
of certain pyrazines. NB price fluctuates – not always economic!
Cypress oil (Cupressus sempervirens): addition of a-pinene, d-3-carene &
myrcene.
Cumin seed oil (Cuminum cyminum): addition of cuminaldehyde and others.
Dill seed oil (Anethum graveolens): addition of a-phellandrene & limonene.
Elemi oil (Canarium luzonicum): addition of a-phellandrene & limonene.
Galbanum resinoid (Ferula galbaniflua): addition of b-pinene, undecatrienes and
others.
Garlic oil (Allium sativa): addition of aliphatic sulphide mixtures containing
2-propenyl disulphide, 1-propenyl disulphide etc.
Jasmine absolute (Jasmimum spp): reconstructions frequently added.
Juniper oil (Juniperus communis var. erecta): addition of terpene
hydrocarbon mixtures containing a-pinene & d-3-carene, also Juniper branch
oil and second grade oils from spoiled Juniper berries.
Labdanum resinoid (Cistus landiferus): formerly, the addition of DEP (now
discontinued) or Abitol, with small amounts of ambroxan and p-methyl
acetophenone to enhance odour.
Lavender oil, spike (Lavandula latifolia): addition of eucalyptus & white
camphor oil fractions, spanish sage oil etc.
Lemongrass oil (Cympogon spp.): addition of citral.
Mentha citrata oil: addition of linalol + linalyl acetate.
Mustard oil (Brassica nigra & B. juncea): allyl isothiocyanate passed off as the
oil (which is used in flavourings, but is banned in perfumery &
aromatherapy).
Neroli oil (Citrus aurantium subsp. aurantium): reconstructions frequently
added to, or passed off as the authentic oil.
Origanum oil (Origanum spp.): addition of para-cymene and carvacrol.
Onion oil (Allium cepa): addition of aliphatic sulphide mixtures.
Palmarosa oil (Cymbopogon martinii var. motia): the addition of geraniol.
Petitgrain oil Paraguay (Citrus aurantia subsp. aurantium ): addition of
admixture of linalol, linalyl acetate, a-terpineol, geranyl & neryl acetates &
trace amounts of pyrazines etc.
Pine needle oils (Pinus spp.): addition of (-)-bornyl acetate, isobornyl acetate, (-)-
limonene, a-pinene, camphene etc.
Rose oil: reconstructions using damascones, b-ionone plus (-)-citronellol
and other rose alcohols, plus rose steroptenes. Occasionally adulterated with b-
phenylethyl alcohol, rhodinol fractions and cheaper rose oils (Morocco, Crimea
etc.).
Rosemary oil (Rosmarinus officialis): addition of camphor, isobornyl acetate (+
Eucalyptus & turpentine oil fractions).
Rosewood oil (Aniba spp): addition of linalol, plus trace amounts of methyl
heptenone, methyl heptenol, 3-octanol, para-methyl acetophenone etc.
Spearmint oil (Mentha spicata): addition of (-)-carvone.
Thyme oil (Thymus spp.): addition of para-cymene & thymol. “Red thyme oil” is
often wholly synthetic.
Vetiver oil acetylated (Vetivera spp): the addition of cedrenyl acetate.
Wintergreen oil (Gaultheria procumbens): the adding of, or passing off methyl
salicylate, as the oil.
Ylang ylang oil (Cananga odorata var. genuina): addition of benzyl acetate,
methyl benzoate, para-cresyl methyl ether, geranyl acetate, benzyl benzoate,
benzyl cinnamate, cedarwood oil and others or complete
reconstitutions/bases.

Boelens (1997) described four types of odorants in essential oils: character compounds, essential compounds, balance compounds and artifacts. Adulterants such as monoterpene hydrocarbons, being balance compounds in Boelens scheme above, do little for the characteristic odor of the cut oils, since the added materials have little odor value in themselves. In practice, the addition of certain adulterants “flattens” the odor profile of the authentic oil, or otherwise dilutes or represses some true character, sparkle and richness. To compensate for this, a practiced oil counterfeiter will add small amounts of character compounds. Taking the example of Cypress oil Cupressus sempervirens var. stricta, the oil is often adulterated by the addition of the monoterpene hydrocarbons a-pinene and d-3-carene, which creates a crude terpinic aspect. The addition of a small amount of deca-2-(E),4-(Z)-dienyl isovalerate to the somewhat insipid cutting agent, will give a better impression of the oil’s normal character, a lead which follows on from the work of Garnero et al. (1978) who identified the compound above in cypress shoots, and found it strongly reminiscent of the typical odor of cypress oil.

Commercial oils, adulterated by such synthetics, can often fool the less sophisticated nose, or satisfy those oil customers buying to a price, where authenticity is sometimes not a primary consideration. Depending on exact market conditions, some oils have a selling price which is so cheap that it is generally unrewarding for a trader to reconstitute, or even add, nature identicals to the product, except for some solvent-like diluents. This category includes the following oils:

Sweet orange oil (Citrus sinensis)
Clove leaf oil & stem oils (Syzygium aromaticum)
Citronella oil (Cymbopogon spp.): (but the oil has been known to have been
crudely adulterated with dipentine and citronella terpenes)
Camphor oil white (Cinnamomum camphora fractions)
Cornmint oil (Mentha arvensis subspp).
Eucalyptus globulus oil
Tea tree oil (Melaleuca altenaria) (NB a collapse in market price means potential
adulterants such as terpinen-4-ol and a- & g-terpinenes can now be as expensive
as the oil).

Other oils are difficult to reconstitute with anything other than diluents because the major components are not commercially available; this class of oils includes patchouli oil, vetiver oil and to some extent ginger oil.

4. The addition of isolates or natural components to essential oils e.g. the addition of pure natural eucalyptol ex E. globulus oil (Eucalyptus globulus) to rosemary oil (Rosemarimus officinalis) or rectified ho oil (very high in
(-)-linalol) to lavender and bergamot.

5. The addition of bases or reconstituted essential oils to genuine oils & absolutes. It is particularly economically attractive to extend high value floral absolutes such as rose (Rosa spp.), jasmin (Jasminum grandiflora other spp.) and osmanthus (Osmanthus fragrans var. auranticus), and the more valuable oils such as neroli oil and rose otto, and this practice occurs extensively within the trade.

6. The addition of individual unnatural components to oils and aromatic raw materials.
Absolutes have been traditionally produced for the consumption of the perfumery industry, but are being increasingly employed in aromatherapy (in spite of using un-natural solvents in their manufacture). Revelations that materials such as Linden Blossom absolute (Tilia spp.) contain hydroxycitronellal, or that Gardenia absolute (Gardenia spp.) has added styrallyl acetate, or that added Schiff’s bases have been found in floral absolutes, should not therefore come as a complete surprise. It has been suggested that if the synthetic fragrance compound is added in to the aromatic plant material during manufacture, the added material will “blend in” better. In other instances, absolutes may well contain perfume bases or reconstitutions, rather than a single key character compound.

Glossary.

Adulteration: the purposeful addition of cheaper alternative oils, oil fractions, by-products, isolates, natural or non-natural synthetics etc., to reduce the cost price of the oil.

Extending: a term for adulteration almost implying a degree of legitimacy.

Isolate: a specific fraction of an essential oil. May be composed of a single chemical e.g. eugenol from Clove oil.

Organic oil: a more expensive essential oil, which has been derived from vegetable matter which has been grown in a pesticide free environment, but which still liable to have a pesticide content reflecting background contamination/incorporation.

Reconstituted oil: An oil made from nature identical synthetics, to look like analytically as far as possible -, and to give an accurate odor impression of -, the named essential oil.

ANISEED: Often adulterated with fennel and dill.

BASIL: Often by addition of synthetic linalool to exotic basil oils.

BERGAMOT: Synthetic linalyl acetate, linalool, limonene, synthetic or natural citral, terpinyl acetate, diethyl phthalate, bitter orange, lime.

CAJEPUT: Replaced by eucalyptus. Added: terpinyl acetate, terpinyl propionanate, terpineol, esters.

CALENDULA: Commercial oil not easily available; may be macerated.

CAMPHOR: Not likely because of wide availability and low cost, but PKC can vary widely.

CEDAR: Blending of the different kinds fairly common.

CHAMOMILE (GERMAN): Addition of synthetic chamazulene. Solvent extracted oil can be added grade oils to improve colour.

CINNAMON BARK OIL: Often cut with leaf oil, canella bark oil, clove leaf oil, eugenol, cinnamic aldehyde. Substituted with cassia oil. Also kerosene fuel oil.

CITRONELLA: Unlikely because of low cost.

CLARY SAGE: Easily synthesized; cut with synthetic linalyl acetate, linalool, lavender oil, bergamot mint oil.

CLOVE: Bud oil often cut or substituted with leaf oil. Synthetic eugenol and caryophyllene cost more, therefore not used as adulterants.

DILL: Cut with limonene, carvone, caraway.

EUCALYPTUS: Generally not justified due to low cost of oil, but possibility of cutting with synthetic cineole. Often redistilled for pharmaceutical rating.

FENNEL: Often adulterated with bitter fennel, synthetic trans-anethole, fenchone, methylchavicol, limonene.

FRANKINCENSE: Synthetic components often added, especially alpha-pinene. Quality of oils varies, depending on extraction and locale.

GERANIUM: Often cut with palmarosa, citronella, synthetic components.

GINGER: Can be adulterated with galanga oil, but due to wide availability of ginger, not often done.

JASMINE: Commonly adulterated or synthesized: ylang-ylang, benzyl acetate, indole, cinnamic aldehyde, fractions.

JUNIPER: True oil is rare, usually fermented. Cut with pinene, camphene, myrcene, turpentine oil fractions, wood and twig oil.

LAVENDER: Often adulterated by acetylated lavandin, aspic, synthetic linalool, linalyl acetate, Ho leaf fractions, rosewood.

LEMON: Folded or washed. Cut with orange, distilled lemon oil, concentrated juice from vacuum extraction, synthetic limonene, citral, dipentene. BHA, BHT.

LEMONGRASS: Cheap, so unlikely to be adulterated with synthetic citral. Occasionally cut with litsea in China. Occasionally substituted with jammu oil.

LINDEN BLOSSOM: Macerated oil may be sold as essential oil.

LITSEA: Occasionally substituted with lemongrass. Any other unlikely.

MELISSA: Most commercial oils adulterated. Often with lemon, lemongrass, citronella, isolated aldehydes, lemon, verbena and fractions.

MYRRH: Often adulterated with opoponax.

NEROLI: Easily adulterated, especially with synthetic linalyl acetate, linalool, nerol, nerolidol, petitgrain and its terpenoids, bitter orange.

NUTMEG: Terpenes often added, especially from nutmeg, myristicin from other sources, terpenes from tea tree

ORANGE (SWEET): BHA, BHT; often fractionated, distilled orange oil is added, or sweet and bitter are mixed.

PALMAROSA: Can be adulterated with ginger grass.

PATCHOULI: Often cut with cedarwood, clove oil, terpenes, methyl abietate, vetiver residues, castor oil, residues, gurjun balsam and others.

PEPPERMINT: The most adulterated oil. Usually with cornmint (difficult to detect even at 85%).

PETITGRAIN: Often adulterated with lemongrass, synthetic citral, lemon oil and others.

PINE NEEDLE: Can be cut with camphene, pinenes, isobornyl acetate.

ROSE: Adulteration is sophisticated and difficult to detect. Often adulterated with palmarosa, citronella, many fractions, synthetic and natural.

ROSEMARY: Extra eucalyptol often added, as well as terpenes from cypress, camphor, eucalyptus, sage and synthetic terpineol.

ROSEWOOD: Often adulterated with Ho wood and Ho leaf oil, synthetic linalool and linalyl acetate. Ho is similar to rosewood in effect, therefore adulteration is ecologically positive.

SAGE: Often adulterated with American cedarwood and palmarosa.

SANDALWOOD: Often cut with amyris, araucaria, cedarwood, castor and copaiba. Also diluted with glyceryl acetate, benzyl benzoate and synthetic copies.

TEA TREE: Often blended with other tea tree oils to attain standards set. Terpinen-4-ol often added, along other terpenes.

THYME: Can be adulterated with oregano. White thyme often contains compounds of pine, rosemary, eucalyptus, red thyme and terpenes.

TURPENTIN / OCEAN PINE: Marine pollutant (synthesized turpentine used to remove paint).

VETIVER: Often adulterated with other grass roots at distillation. Also cut with vetiverol, terpenes, cedarwood, amyris.

YLANG YLANG: Very easily adulterated with, Peru balsam, copaiba, inferior fractionations and synthetics. Different grades are mixed.

Copied with permission from Aromatherapy for Natural Health and Beauty by Cecilia Salveson. Cecilia Salveson is a Qualified Therapeutic Aromatherapist and Reflexologist and Practitioner of Complementary Medicine. She is the founder of the Natural Health and Beauty School in South Africa and is also the Regional Director for the International School of Reflexology and Meridian Therapy. She has written numerous books and articles.

Background.
Aromatherapists and natural perfumers have long required that their essential oil’s are genuine, but conversely, the essential oil trade has traditionally offered oils to the perfumery and flavorings trades on a “buyer beware” principle. Therefore, the finding in the Health Which report (Health Which 2001) on aromatherapy oils, citing a case where a labeled sandalwood oil turned out to be a synthetic sandalwood aroma chemical, cannot come as a complete surprise.

Whilst many essential oils used in aromatherapy are sourced from commercial oil trade outlets, other items are offered by smaller dedicated aromatherapy oil producers. In attempt to make themselves uniquely positioned in the oil market, aromatherapy oil suppliers have previously boasted that their oils are distilled longer and under gentler conditions to produce superior oils. This is a complete nonsense – longer treatment can only encourage greater artifact production via thermal degradation, and any perceived more pleasing odor effect is possibly due the increased oil complexity (via the creation of artifacts). Even more curious is the easy acceptance of hype that CO2 extracts are suitable for the aromatherapy community. In many cases the CO2 extracts are of unknown composition and toxicity, extractions are not standardized (depending on operating conditions CO2 extracts can resemble either resinoids or essential oils, and all stages in between) and the use of any co-solvents during processing is often omitted by suppliers. Furthermore the concentration of pesticide residues during the CO2 extraction of spices are from seven to fifty three times greater than the values obtained by use of conventional solvents, according to Guba R. (2002).

Consequences.
The adulteration of essential oils leads to the following concerns:

1. Toxicity of the adulterant's).
Phthalates such as DEP are still occasionally found as adulterants in essential oils. Phthalate esters have been withdrawn as ingredients by many cosmetics manufacturers on toxicity grounds; specific phthalates (DEHP & DBP) are classified by the EU as reproductive toxicants. Whilst consumer pressure groups campaign for awareness in this area (see for example: http://www.nottoopretty.org/); the other side of the argument can be viewed on http://cms.phthalates.com/index.asp?page=3.

Traces of residual organic solvents (such as hexane and cyclohexane) in oils and absolutes are found as a result of extraction & co-distillation practices.

The presence of pesticides in tainted essential oil’s in cosmetics has been described as a serious health & safety issue by Buchbauer (1998); their inevitable presence in aromatherapy oils is an unresolved issue.

2. The interference of adulterants on the expected physiological or psychophysiological effects of the essential oil.

Point 2 above has long been a concern of aromatherapists, but proof of adverse effects has been harder to find, although the following section below might furnish the beginnings of a case:

Chiral Issues from added adulterants.
Addition of racemic synthetics to natural essential oils may distort the enantiomeric ratios of the naturally occurring substances within the make-up of oils, and thus may have an untoward effect on the expected physiological outcome. The logic behind this may be predicted from data accrued on the contrasting physiological effects of different chiral isomers of the same substance. A few examples are given below:

Huenberger et al. (2001) have demonstrated that inhalation of (+)-limonene caused increases in systolic blood pressure and changed alertness and restlessness in subjects, whereas (-)-limonene only affected blood pressure.
(-)-Carvone was reported to increase pulse rate, diastolic blood pressure and restlessness whereas (+)-carvone increased systolic and diastolic blood pressure. Traynor (2001) reports that when evaluated by Contingent Negative Variation, (+)-rose oxide confers relaxing physiological effects, whilst (-)-rose oxide (which occurs in Bulgarian Rose oil and geranium oils) possesses a significantly higher stimulatory effect.

Sugawara et al. (2000) looked at the effects of 10 mins inhalation of the different linalool isomers [(-)-linalol purified from lavender, (+)-linalol from coriander, and synthetic (+/-)-linalol] inhaled before and after work. Effects were examined by sensory scoring and portable forehead surface EEG measurements. They found inhaling (-)-linalol after hearing environmental sounds produced a more favorable impression produced a more favorable impression in the sensory test but was accompanied by a greater decrease in beta waves after than before work. Conversely with mental work, there was a tendency for agitation accompanied by an increase in beta waves. (+/-)-Linalol gave results similar to (-)-linalol, but (+)-linalol gave the reverse results.

Buchbauer (1998) maintains that each constituent of an essential oil contributes to the beneficial or adverse effects of the oil. I contend that changing the distribution of chiral components of oils by deliberate adulteration with racemic synthetic odorants, may in fact change the beneficial properties of the oil.