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Description of key information

Toxicokinetic evaluation of Cedarwood Virginia oil based on existing data

REACH indicates that an “assessment of the toxicokinetic behaviour of the substance to the extent that can be derived from the relevant available information” should be performed at Annex VIII level.

 

General information

Cedarwood Virginia oil is a substance of Unknown or Variable composition, Complex reaction products or Biological material (UVCB substances), or more specifically a NCS (Natural Complex Substance). As such, Cedarwood Virginia oil is an essential oil of Cedarwood obtained from the wood ofJuniperus virginiana (Cupressaceae) by steam distillation, and consists of the following identified constituents:

Name - Constituent

CAS Number - Constituent

EC Number - Constituent

Concentration

Range in NCS

(% w/w)

 

Thujopsene

470-40-6

207-426-8

10-35

α-Cedrene

β-Cedrene

469-61-4

546-28-1

207-418-4

208-898-8

20-45

4-9

α-Chamigrene

β-Chamigrene

19912-83-5

18431-82-8

 

0-3

0-3

Cuparene

16982-00-6

241-061-5

0.8-7

Cedrol

77-53-2

201-035-6

10-31

α-Duprazianene

79801-29-9

 

0-3

α-Himachalene

β-Himachalene

3853-83-6

1461-03-6

 

0-2

0-3

β-Caryophyllene

87-44-5

201-746-1

0-3

Widdrol

6892-80-4

 

1-7

α-Bisabolol

23089-26-1

245-423-3

0-3

β-funebrene

50894-66-1

 

0-5

Unknown (non-volatile fraction)

 

 

0-10

Other minor and unknown volatile fraction

 

 

0-20

The main constituents are Thujopsene, Cedrol and Cedrene α/β, which add up to a percentage range of 44-120%, and can therefore be considered representative of the substance.

 

ADME data

Absorption, distribution, metabolism and excretion data onCedarwood Virginia oil itself are not available and therefore the toxicokinetic assessment is based on the available toxicology data for Cedarwood Virginia oil, as well as data for the main constituents.

 

Information from physico chemical and toxicity studies

An overview of the relevant physicochemical parameters for Cedarwood Virginia oilis provided below.

Parameter

Cedarwood Virginia oil

Physical state

Liquid

Structure

UVCB

Molecular weights

202.34 - 222.37 g/mol

Particle size

Not relevant

Log Kow

Min. 4.33 Max. 7.02

Water solubility (mg/l)

Min. 0.03 Max. 29.25

Boiling point (°C)

252.8

Vapour pressure

2.5 at 25°C (OECD104)

Absorption

Oral: As the molecular weight range of this UVCB is below 500, the molecules in this UVCB are likely to be absorbed via the oral/GI tract.Uptake throughaqueous pores or carriage of such molecules across membranes with the bulk passage of water in the GI tract can be expected. Furthermore uptake by passive diffusion is likely based on the moderate log Kow values of Cedarwood Virginia oil. The oral absorption of the more highly lipophilic constituents of this UVCB (log Kow > 4) may be more dependent on micellar solubilisation.

Based on the previous,the substance could be absorbed in the human body via the oral route. This is supported by the findings in an oral acute toxicity study, which reported slight lethargy treated animals following oral administration of 5000 mg/kg bw ofCedarwood Virginia oil. Furthermore, in an OECD TG 422 study systemic effects such as nephropathy in male rats, liver effects and reduced T4 levels were observed. These findings confirm that systemic absorption of the substance via the gastrointestinal tract takes place.

 

Dermal: No acute dermal toxicity was observed in rabbits exposed to 5000 mg/kg bw Cedarwood Virginia oil. Even though it is not a corrosive, the skin irritating propertie sobserved in the OECDTG 439 in vitro skin irritation test suggest that this UVCB may damage the skin and there by increase its penetrating potential. As sensitisation is also observed for this substance in an OECD TG 429 study, some uptake must occur. Based on the physico chemical properties of the substance, its molecular weight would not exclude dermal uptake, and its water solubility and logP value would predict low to moderate absorption of at least a part of its constituents (ECHA guidance, 7.12, Table R.7.12-3).

 

In order to assess the potential for dermal absorption, the absorption of all components in this UVCB was calculated using the IH Skinperm tool version 2.0. In the model the following input was used as a worst-case, which resulted in the highest dermal absorption:

Instantaneous deposition: 100 mg;

Affected skin area: 1,000 cm2;

Maximum skin adherence: 3 mg/cm2 (due to the high melting points of constituents);

Thickness of stagnant air: 10 cm;

Weight fraction: 1;

Observation time: 24 hours;

Calculated intervals: 10,000.

The substance specific input for Skinperm was taken from the QPRF document and Substance Identity Profile. Missing information was taken from reliable sources such as the ECHA substance database, the Gestis substance database, Dohsbase or Chemspider. The following input was used:

Name

CAS

Average conc.

(% w/w)

MW

Vapour pressure(Pa)

Water solubility (mg/L)

Log Kow

Density(g/mL)

Melting point

Max skin adh. (mg/cm2)

Weighted Dermal fraction absorbed8hrs

Cedrene alpha

469-61-4

29.72%

204.36

0.0184

0.042587

5.74

0.9

43.77

9

0.9956%

Cedrene beta

546-28-1

5.46%

204.36

6.08

0.032021

5.82

0.9

41.79

9

0.0108%

Cedrol

77-53-2

20.30%

222.37

0.0165

8.7229

4.33

1

75.52

10

3.3089%

Cuparene

16982-00-6

0.93%

202.34

0.773

0.50078

6.19

0.9

60.05

9

0.0027%

Thujopsene

470-40-6

16.04%

204.36

9.37

0.059998

6.12

1

48.5

10

0.0367%

Widdrol

6892-80-4

4.15%

222.37

0.00951

29.254

4.84

1

78.8

10

1.0334%

Himachalene alpha

3853-83-6

0.46%

204.35

2.8

0.54268

6.3

0.9

43.42

9

0.0059%

Himachalene beta

1461-03-6

0.93%

204.35

1.47

1.1378

6.35

0.9

54.06

9

0.0181%

Chamigrene alpha

19912-83-5

0.71%

204.35

2.28

1.0168

6.94

0.9

50.66

9

0.0146%

Chamigrene beta

18431-82-8

1.19%

204.36

3.053082

0.76453

7.02

0.9

48.82

9

0.0205%

Bisabolols alpha

23089-26-1

0.67%

223.66

0.0182

19.126

5.63

0.9

55.96

9

0.2486%

Duprezianene alpha

79801-29-9

0.90%

204.35

4.52

0.042587

5.74

0.9

84.85

9

0.0016%

Caryophyllene beta

87-44-5

1.09%

204.36

4.159658

0.54268

6.3

0.9

43.42

9

0.0099%

Beta funebrene

79120-98-2

below the level of detection

 

 

 

 

 

 

 

The weighted permeability of the whole UVCB, calculated using the IH Skinperm tool was 6.91% and this will be used for risk assessment. This number is corrected for the unknown and minor constituents not taken into account in the Skinperm modelling.

 

Inhalation: The lipophilicity of the main constituents (log Kow >4), and a low water solubility indicate that uptake via the lungs may be mainly via micellar solubilisation. The constituents with a more moderate log Kow values (between -1 and 4) would favour absorption directly across the respiratory tract epithelium by passive diffusion. These physico-chemical propertieswould also facilitate absorption directly across the respiratory tract epithelium following aspiration.

 

Distribution

Distribution of Cedarwood Virginia oil and its major constituent is expected based on the relatively low molecular weights. Also distribution throughout the body would be possible due to the low to moderate water solubility, while the higher Log Kow range also suggests possible distribution into cells. A higher intracellular concentration is expected, especially in fatty tissues. Signs of toxicity and target organs suggest that the substance is at least distributed to the liver and kidney.

Metabolism

No information on metabolism can be derived from the physicochemical data that is available for Cedarwood Virginia oil.No information on metabolism of the UVCB is available from studies, but the main constituents of the UVCB substance Cedarwood Virginia oil; Thujopsene, Cedrol and Cedrene α/β are known to have an (inhibitory) effect on Cytochrome p450 enzyme activities[1]. Hepatic phase 1 metabolism mediated by P450 is therefore a likely mechanism. This is expected to be followed by attachment of the phase II polar groups in the liver before elimination. Hepatic involvement is supported by the liver effects that were observed in the OECD TG 422 study.

 

Elimination

Based on the systemic renal effects observed in the OECD TG 422 study, excretion is expected to take place though the kidney. This is supported by the relatively low molecular weights. Excretion via bile is not likely, as in the rat it has been found that substances with molecular weights below around 300 do not tend to be excreted into the bile (Renwick, 1994) [2]. Some excretion via breast milk, saliva and sweat cannot be excluded, as some constituents of the UVCB can be regarded as lipophilic (Log Kow > 4).

 

Accumulation

There is the potential for the more highly lipophilic constituents of this UVCB (log P >4) to accumulate in individuals that are frequently exposed (e.g. daily at work) to these substances. Once exposure stops, the concentration within the body will decline at a rate determined by the half-life of the substance (Rozman and Klaassen, 1996)[3].

 

Data from other studies

 

Cedarwood Virginia oil

Oral toxicity data

OECD TG 401 Not classified, slight lethargy observed

Dermal toxicity data

OECD TG 402 Not classified

Skin irritation / corrosivity

OECD TG 439 Skin irritant (Cat. 2) / OECD TG 431 not corrosive

Eye irritation

OECD TG 437 not irritant

Skin sensitisation data

OECD TG 429 Skin Sens. 1B / H317

Target organs

OECD TG 422 Nephropathy in male rats (hyaline droplet accumulation), hepatocellular hypertrophy in female rats.

Conclusion

Oral uptake is expected based on information from the available studies (acute and repeated dose oral toxicity) and the favourable physico chemical parameters. Dermal absorption would be possible based on information from available studies (sensitisation), physicochemical parameters and modelling of the skin permeability using the IH Skinperm tool. Relatively wide distribution and excretion through urine is expected based on low/moderate water solubility and low molecular weights. The absorption values to be used for hazard assessment are therefore taken as 100% for the inhalation route, 50% for the oral route and 6.91% for the dermal route.


[1]Hyeon-Uk Jeong, Soon-Sang Kwon, Tae Yeon Kong, Ju Hyun Kim & Hye Suk Lee (2014) Inhibitory Effects of Cedrol, β-Cedrene, and Thujopsene on Cytochrome P450 Enzyme Activities in Human Liver Microsomes. Journal of Toxicology and Environmental Health, Part A Vol. 77 , Iss. 22-24.

[2]Renwick AG (1994) Toxicokinetics - pharmacokinetics in toxicology. In Hayes, A.W. (ed.) Principles and Methods of Toxicology. Raven Press, New York, USA, pp.103.

[3]Rozman KK and Klaassen CD (1996) Absorption, Distribution, and Excretion of Toxicants.In:Klaassen CD (Ed.) Cassarett and Doull's Toxicology: The Basic Science of Poisons. McGraw-Hill, New York, USA.

 

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
50
Absorption rate - dermal (%):
6.91
Absorption rate - inhalation (%):
100

Additional information