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ARCHIVED - Safety Summary of Citronella Oil as a Flavouring Agent

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Chemical Health Hazard Assessment Division
July 19, 2004

ARCHIVED - Issue

The Pest Management Regulatory Agency (PMRA) has proposed the phase-out of citronella oil-based personal insect repellents, as a consequence of their decision not to permit the continued registration of the active ingredient citronella oil. Since citronella oil is also used as a food flavouring, the basis for the proposed de-registration of its use in personal products has implications with respect to its use as a food flavouring.

Background

The PMRA proposal is based on a recent re-evaluation of citronella oil, as part of PMRA's program to review older products (registered before January 1, 1995), to determine if their use is acceptable under today's standards for health and environmental protection. PMRA did not identify any imminent health risks. Nonetheless, the lack of safety data on the oil combined with the high and prolonged level of exposure, created uncertainty with regard to the safety of these products. Additional safety concerns were identified with some of the individual components of citronella oil, because these chemicals were associated with specific toxicities. Consequently, the PMRA was unable to conclude that the human health risk from the use of personal insect repellent products containing citronella oil were acceptable, and on this basis, they proposed a phaseout of these products (1).

Origins

Ceylon and Java citronella oils are the two main commercially available varieties of this essential oil. Ceylon citronella is obtained by steam distillation of the partially dried herb (Cymbopogon nardus; lenabatu variety). The Java variety is also made by steam distillation or by water distillation of the fresh or partially dried herb (Cymbopogon winterianus; mahapengira variety) (2).

General Characteristics

The Ceylon type of citronella oil is a pale-yellow to yellowish-brown liquid and contains 7-15% aldehyde and 55-65% total alcohol. The Java type is a clear, light-yellow to brownish liquid and has a content of 30-45% aldehyde and 32-35% total alcohol. The Ceylon type of oil has a characteristic citronellal-like smell, whereas the Java type has a strong lemon-like odour (2).

Food Uses

With regard to food, citronella oil is a strong food flavouring agent and is used in low concentrations in alcoholic beverages, baked goods, frozen dairy, breakfast cereals, gelatins, puddings, nonalcoholic beverages, soft candy, and hard candy (2).

Levels of Use

The level of use of citronella oil depends on the food to which it is added, but the usual level ranges from 3 to 35 ppm. The maximum level of use ranges from 13 to 48 ppm. Citronella oil has an intense flavour and consequentially its use in any particular food is limited by this property (2; see Table 1 for details).

Regulatory Status

In the United States of America, the Food and Drug Administration has placed citronella oil on its list of chemicals that are generally recognized as safe (GRAS), and the Flavor and Extract Manufacturers' Association (FEMA) has also approved GRAS status for citronella oil.

The Council of Europe has placed the Java type citronella oil in category 1 (items are not considered a safety concern at levels consumed) and the Ceylon type citronella oil in category 3 (items with a safety concern associated with the active ingredient; with Ceylon type citronella oil there are limits on methyl eugenol content).

In Canada, there are no standards defining permitted sources and composition of citronella oil used as a food flavouring agent, as exist for other essential oils listed in Part B, Division 10 of the Food and Drugs Act. Under the Food and Drugs Act, the safety of most flavouring substances, including essential oils such as citronella oil, is the responsibility of the manufacturer as indicated in Part A, Section 4a.

Safety Evaluation of Citronella Oil for Food Uses

The approach used here to evaluate the safety of citronella oil is the same as that proposed by JECFA to assess the safety of natural complex flavours. This evaluation process depends upon the composition of the flavouring agent that is added to food, the safety evaluations of the individual components and congeneric groups of the flavouring agent, and estimates of intake of the flavouring agent (3). This is an extension of earlier work by JECFA, where simple flavouring agents consisting of single or a few components were evaluated, using a procedure that considers chemical structure, known or predicted metabolism, estimated exposures, and available safety data on a compound or closely-related structure.

Both Ceylon and Java type citronella oils contain over 80 constituents, of which about 50 chemicals make-up over 90% of the oil. In the Ceylon type of citronella oil the main constituents are geraniol (18-20%), citronellol (6.4-8.4%), citronellal (5-15%), geranyl acetate (2%), limonene (9-11%), and methyl isoeugenol (7.2-11.3%). In the Java type citronella oil the main constituents are citronellal (32-45%), geraniol (21-24%), citronellol (11-15%), geranyl acetate (3-8%), limonene (1.3-3.9%), elemol and sesquiterpene alcohols (2-5%) (3; see Table 2 for details)

According to the safety evaluation process used by JECFA, the individual components of a natural food flavouring are not a safety concern if the intake of the individual component is less than 1.5 g/person/day. This general threshold is based on an estimate of the human intake of a chemical, which has the probability of 95% over a lifetime to result in cancer development at a rate of less than 1 in a million people. Since the threshold is based on conservative assumptions it is considered to be sufficient to cover all types of toxicity (4)

In addition to this general threshold, JECFA uses thresholds of 1800, 540 and 90 g/person/day for chemicals in Classes I, II, and III, respectively. Chemicals of Class I have a structure that suggests that the chemical is efficiently metabolized and has a low order of toxicity. Class II chemicals have structural features that are less innocuous than those of Class I but are not suggestive of toxicity. Class III chemicals have structural features that do not permit a strong initial presumption of safety or toxicity. These thresholds are based on the lower 5th percentile NOEL for chemicals in each of the structural classes from toxicity studies in animals, divided by an uncertainty factor of 100-fold.

With regard to citronella oil, the intake from food flavouring use is estimated to be 69 g/person/day (5). Using the general threshold value of 1.5 g/person/day, individual components of citronella oil that make-up less than 2.2% of the oil would not be considered a safety concern because of the low exposure level.1

The constituents that equal or exceed 2.2% of citronella oil include geraniol, citronellol, citronellal, camphene, -cubebene, limonene, methyl isoeugenol, elemol, and geranyl acetate. With the exception of -cubebene, all of these constituents have been evaluated by JECFA using chemical class thresholds and intake values or traditional toxicological evaluation procedures which result in the setting of an ADI. They concluded that the intake of these individual constituents from flavouring use did not exceed their respective class thresholds or their ADIs, that they were all predicted to be metabolized to innocuous products, and that there were no safety concerns for these constituents as flavouring agents based on current intake. Further JECFA considered the unlikely event that all chemicals of the same structural class were consumed together, and concluded these groups of chemicals would not constitute a safety concern.

JECFA has not as yet evaluated the group of chemicals to which -cubebene belongs, the sesquiterpene hydrocarbons. -cubebene constitutes 3.8% of the Ceylon type citronella oil and 2.3% of the Java type citronella oil. This means that the greatest exposure to -cubebene from citronella oil would be at most 2.6 g/person/day. Although this level of exposure exceeds the general threshold value of 1.5 g/person/day, it is less than two-fold greater. Given the conservative assumptions in establishing the general threshold, the level of exposure to -cubebene from citronella oil was not considered a safety concern.

Comments

The estimated intake of citronella oil from food is at least 65000-times less than the estimated exposure due to a topically applied citronella-based personal insect repellent (0.0686 mg/person/day vs 4610 mg/person/day)2. The relatively low exposure to citronella oil as a flavouring agent suggests that the risk of a health hazard is much less than with citronella used as a personal insect repellent.

The extremely low exposure to citronella oil and the application of JECFA's threshold approach to assess toxicity of complex flavouring agents from natural sources indicates that the individual components of citronella oil as a flavouring agent are not a safety concern.

This opinion also applies to methyl eugenol, a substance demonstrated to be a carcinogen in rats and mice, which is present in Ceylon and Java types of citronella oil at concentrations of 0.99 and 0.09%, respectively. In citronella oil used as a flavouring agent, intake of methyl eugenol is estimated to be below the threshold which may pose a cancer risk of 1 additional cancer per 1 million persons. Further, it was noted that the exposure to methyl eugenol from other food sources (nutmeg, basil, walnuts, candies, baked goods and others) far exceeds the amount consumed from citronella oil (0.00068 mg/person/day vs 13 mg/person/day)(6), and therefore citronella oil as a flavouring agent, does not add significantly to the total human exposure to methyl eugenol.

Limonene is also present in Ceylon and Java types of citronella oil, and it is also a carcinogen in rodents, specifically the male rat. However, researchers have determined that limonene was a carcinogen in the male rat due to the specific physiology of the male rat and was not a cancer concern for humans. For this reason limonene in citronella oil is not a cancer concern.

Recommendation

Citronella oil has an intense flavour and this characteristic limits its addition to food. Based on estimates of intake, and a safety assessment of the components of citronella oil using a procedure that takes into consideration chemical structure, metabolic fate, and available toxicity data, it is predicted that the use of citronella oil as a flavouring agent in foods would not present a safety concern.



1 For an exposure to an individual chemical in citronella oil to equal 1.5 g/person/day then it would have to equal to 2.3 % of the exposure to citronella oil (=1.5 g/person/day 66.0 g/person/day x 100%).

2 4610 mg of citronella oil/person/day is a low estimate of exposure for users, since it assumes only a single application of oil each day. Data suggest that an application every 30 minutes is required for citronella oil to be effective as an insecticide.
Table 1- Reported Food Uses for Citronella Oil
(derived from G.A. Brudock, Fenaroli's Handbook of Flavor Ingredients, 4th edition, pp. 314-315, 2002, CRC Press, New York, USA.)
Food Category Usual Level (ppm) Maximum Level (ppm)
Alcoholic beverages 32.96 40.00
Baked goods 34.95 47.61
Frozen dairy 31.60 42.58
Gelatin, pudding 24.95 38.92
Nonalcoholic beverages 16.60 26.23
Soft candy 33.24 45.88
Hard candy 3.28 12.98
Table 2- Chemical Composition of Two Commercial Varieties of Citronella Oils
(modified from M.H. Boelens et al., Perfumer & Flavorist, 19: 29-45, 1994)
Chemical Ceylon Type (%) Java Type (%)
geraniol 20.91 23.18
limonene 8.66 2.81
(E)-methyl isoeugenol 8.42 -
camphene 6.97 0.04
citronellol 6.15 11.19
citronellal 6.09 34.79
-cubebene 3.77 2.25
geranyl acetate 2.40 5.07
cis--ocimene 1.92 0.37
a-pinene 1.87 0.05
(Z)-methyl isoeugenol 1.18 -
elemol 1.14 3.16
citronellyl acetate 1.10 1.88
-elemene 1.10 1.96
tricyclene 1.09 0.01
trans--ocimene 1.07 0.19
a-terpineol 1.05 0.05
methyl eugenol 0.99 0.09
isopulegol 0.87 0.22
borneol 0.87 0.05
myrcene 0.83 0.09
terpinolene 0.74 0.06
terpinen-4-ol 0.65 0.04
linalool 0.56 0.72
T-amorphol/bulnesol 0.55 0.65
a-muurolene 0.46 0.46
-caryophyllene 0.44 0.22
bornyl acetate 0.42 -
muurolene 0.36 0.67
trans-muurolol 0.33 0.53
10-epi-eudesmol 0.23 0.17
a-humulene 0.21 0.13
decanal 0.18 0.10
-bourbonene 0.18 0.10
a-phellandrene 0.17 -
6-methyl-5-hepten-2-one 0.16 0.01
d-3-carene 0.12 0.01
melonal 0.11 0.08
neryl acetate 0.10 0.04
p-cymene 0.10 -
d-cadinene 0.09 1.17
(Z)-a-farnesol 0.07 0.10
3,3-dimethylbicycloheptan-2-one 0.07 -
-phellandrene+1,8cineole 0.06 0.07
(E)-a-farnesol 0.06 0.08
sabinene 0.06 0.07
-pinene 0.06 0.01
a-terpinene 0.06 0.01
a-copaene 0.04 0.08
d-elemene 0.03 0.01
a-thujene 0.02 -
a-terpinyl acetate 0.01 0.16
(Z)-3-hexenol - 0.01
Citronellic acid - 0.13
eugenol - 2.45
Total % of oil 90.48 97.54

- means not detected

References



1. PMRA, Proposed Acceptability for Continuing Registration, Re-Evaluation of Citronella Oil for use as Personal Insect Repellents and Related Active Compounds. DRAFT Document 2004.

2. Boelens, M.H., Sensory and Chemical Evaluation of Tropical Grass Oils, Perfumer & Flavorist. 19: 29-45, 1994.


3. Council of Europe, Natural sources of flavourings-Report No.1. pp.169-172, Council of Europe Publishing, 2000.

4. 61st Joint FAO/WHO EXPERT COMMITTEE ON FOOD ADDITIVES. The Safety evaluation of Individual Flavouring Agents and Natural Flavouring Complexes. World Health Organization. 2004.


5. Burdock, G.A., Fenaroli's Handbook of Flavor Ingredients, 4th edition, pp.314-315, CRC Press, New York, USA, 2002.


6. Scientific Committee on Food, European Commission, Opinion of the Scientific Committee on Food on Methyleugenol (4-Allyl-1,2-dimethoxybenzene), September 26, 2001.