Gum of Cistus ladaniferus (Cistaceae) obtained from stems and leaves by extraction with alkaline solution

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

- Ames test: non mutagenic (OECD 471, GLP, K, rel. 1)

- HPRT test: non mutagenic (OECD 476, GLP, K, rel.1)

- Micronucleus test in vitro: ambiguous results (OECD 487, GLP, K, rel. 1): increases in micronuclei considered of questionable biological relevance in cultured human peripheral blood lymphocytes following 3-hour treatment in the absence metabolic activation system (S‑9) and small increases in micronuclei considered of questionable biological importance were observed following both 3-hour treatment in the presence of S-9 and 24 hour treatment in the absence of S-9

- Micronucleus test in vivo: negative (OECD 474, GLP, K, Rel.1)

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

TBC

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP study conducted according to OECD Guideline 476 without any deviation.

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Version / remarks:

2016

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Type of assay:

other: mammalian cell gene mutation assay

Target gene:

hypoxanthine-guanine phosphoribosyl transferase (hprt) locus

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

CELLS USED
- Source of cells: Dr Donald Clive, Burroughs Wellcome Co.
- Suitability of cells:
Mouse lymphoma L5178Y systems are statistically more sensitive than CHO and V79 systems.

MEDIA USED
- Type and identity of media including CO2 concentration:
RPMI A: Horse serum (heat inactivated, 0 % v/v). Penicillin (100 units/mL), streptomycin (100 μg/mL), amphotericin B (2.5 μg/mL), Sodium pyruvate acid (0.2 mg/mL) and pluronic (0.5 mg/mL)
RPMI 10: Horse serum (heat inactivated, 10 % v/v), penicillin (100 units/mL), streptomycin (100 μg/mL), amphotericin B (2.5 μg/mL), Sodium pyruvate acid (0.2 mg/mL) and pluronic (0.5 mg/mL)
RPMI 20: Horse serum (heat inactivated, 20 % v/v), penicillin (100 units/mL), streptomycin (100 μg/mL), amphotericin B (2.5 μg/mL) and Sodium pyruvate acid (0.2 mg/mL)
RPMI 5 consisted of RPMI 10 diluted with RPMI A [prepared as RPMI 10 but with no serum added] to give a final concentration of 5% serum
- For each experiment, at least one vial was thawed rapidly, the cells diluted in RPMI 10 and incubated at 37 ± 1 °C. When the cells were growing well, subcultures were established in an appropriate number of flasks
- Properly maintained: Yes
- Periodically checked for Mycoplasma contamination: Yes
- Periodically 'cleansed' against high spontaneous background: Yes

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

2 % S9 (final concentration); S9 fraction was prepared from liver homogenates of rats treated with Aroclor 1254.

Test concentrations with justification for top dose:

Range-Finder Experiment: 15.63, 31.25, 62.5, 125, 250, 500, 1000 and 2000 µg/mL, with and without S9
Justification: A maximum concentration of 2000 µg/mL was therefore selected for the cytotoxicity Range-Finder Experiment, in order that treatments were performed up to 2000 µg/mL (the maximum recommended concentration according to current regulatory guidelines).

Mutation Experiment:
Without S9: 25, 50, 100, 150, 175, 200, 210, 220, 230, 240, 250 and 300 µg/mL
With S9: 25, 50, 100, 150, 175, 200, 250, 260, 270, 280, 290 and 300 µg/mL
Justification: Concentrations selected for the Mutation Experiment were based on the results of this cytotoxicity Range-Finder Experiment.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Dimethylformamide (DMF)
- Preliminary solubility trials indicated that dimethylformamide (DMF) was the most suitable vehicle. Labdanum gum formed a suitable, homogeneous suspension at concentrations up to approximately 200 mg/mL. The solubility limit in culture medium was in the range of 125 to 250 µg/mL, as indicated by precipitation at the higher concentration which persisted for at least 3 hours after test article addition.
- Test article stock solutions were prepared by suspending Labdanum gum under subdued lighting in DMF, with the aid of vortex mixing, warming at 37°C and ultrasonication (where required), to give the maximum required concentration. Subsequent dilutions were made using DMF. The test article suspensions were protected from light and used within approximately 2 hours of initial formulation.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMF diluted 100 fold in treatment medium

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

Without S9

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMF diluted 100-fold in the treatment medium

True negative controls:

no

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

Remarks:

With S9

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium; RPMI 1640 media supplied containing L-glutamine and HEPES
- Cell density at seeding:
Cytotoxicity Range-Finder Experiment: Cell concentrations were adjusted to 8 cells/mL and, for each concentration, 0.2 mL was plated into each well of a 96-well microtitre plate for determination of relative survival.
Mutation Experiment: At least 10^7 cells in a volume of 18.8 mL of RPMI 5 (cells in RPMI 10 diluted with RPMI A [no serum] to give a final concentration of 5% serum) were placed in a series of sterile disposable 50 mL centrifuge tubes.

DURATION
- Exposure duration: 3 h
- Expression time (cells in growth medium): 7 days
- Selection time (if incubation with a selection agent): 12 to 14 days
- Plating for Survival: 7 days
- Plating for viability: 8 to 9 days
- All incubations were performed at 37 ± 1 °C in a humidified incubator gassed with 5 ± 1 % v/v CO2 in air

SELECTION AGENT (mutation assays): 6-thioguanine (6TG) at a final concentration of 15 μg/mL

NUMBER OF REPLICATIONS:
- Preliminary toxicity test: Single cultures/dose for test item
- Main test: Two cultures for vehicle, test article, culture medium for the UTC or positive control solution; single cultures for positive control solution

NUMBER OF CELLS EVALUATED: 192 wells averaging 1.6 cells/well, 192 wells averaging 1.6 cells/well and 384 wells at 2 x 104 cells/well for survival, viability and 6TG resistance respectively.

DETERMINATION OF CYTOTOXICITY
- Method: Percentage Relative Survival
Cloning efficiency (CE) = P / No of cells plated per well; and as an average of 1.6 cells/well were plated on all survival and viability plates, CE = P/1.6.
Percentage relative survival (% RS) = [CE (test)/CE (control)] x 100.
Adjusted % RS = % RS x (Post-treatment cell concentration for test article treatment / Post-treatment cell concentration for vehicle control)

- OTHER:
Mutant Frequency (MF) per 10^6 viable cells for each set of plates was calculated as: MF = [CE (mutant)/CE (viable)] x 10^6.

Evaluation criteria:

For valid data, the test article was considered to induce forward mutation at the hprt locus in mouse lymphoma L5178Y cells if:
- The MF at one or more concentrations was significantly greater than that of the vehicle control (p≤0.05)
- There was a significant concentration-relationship as indicated by the linear trend analysis (p≤0.05)
- If both of the above criteria were fulfilled, the results should exceed the upper limit of the last 20 studies in the historical negative control database (mean MF +/ 2 standard deviations.

Results that only partially satisfied the assessment criteria described above were considered on a case-by-case basis.

Statistics:

Statistical significance of mutant frequencies was carried out according to the UKEMS guidelines (Robinson et al., 1990). The control log mutant frequency (LMF) was compared with the LMF from each treatment concentration and the data were checked for a linear trend in mutant frequency with test article treatment. These tests require the calculation of the heterogeneity factor to obtain a modified estimate of variance.

Key result

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH and osmolality: No marked changes in osmolality or pH were observed in the Range-Finder at the highest concentration analysed (250 µg/mL), compared to the concurrent vehicle controls.
- Precipitation: Upon addition of the test article to the cultures and following the 3 hour treatment incubation period, precipitate was observed at the highest four concentrations (250-2000 µg/mL). The lowest concentration at which precipitate was observed at the end of the treatment incubation period in the absence and presence of S-9 was retained and the higher concentrations discarded.
- Other confounding effects: None

RANGE-FINDING/SCREENING STUDIES:
In the cytotoxicity Range-Finder Experiment, eight concentrations were tested in the absence and presence of S-9 ranging from 15.63 to 2000 µg/mL (an acceptable maximum concentration for in vitro genetic toxicology studies according to current regulatory guidelines). Upon addition of the test article to the cultures and following the 3 hour treatment incubation period, precipitate was observed at the highest four concentrations (250-2000 µg/mL). The lowest concentration at which precipitate was observed at the end of the treatment incubation period in the absence and presence of S-9 was retained and the higher concentrations discarded. The highest concentration to give >10% RS was 125 µg/mL in the absence of S-9 and 250 µg/mL in the presence of S-9, which gave 69% and 16% RS, respectively.

HISTORICAL CONTROL DATA (with ranges, means and standard deviation and confidence interval (e.g. 95%)
The historical control ranges for the last 20 experiments performed in the laboratory are as follows:
- Negative (solvent/vehicle) historical control data:
Vehicle Controls
In the absence of S-9
Mean: 4.91 mutants per 10^6 viable cells, Range* = 1.15 to 8.68 mutants per 10^6 viable cells.
In the presence of S-9
Mean: 5.12 mutants per 10^6 viable cells, Range* = 1.23 to 9.01 mutants per 10^6 viable cells.
*Range = Mean ± 2 x SD.

- Positive historical control data:
NQO 0.15 µg/mL in the absence of S-9
Mean: 43.86 mutants per 10^6 viable cells, Range* = 1.51 to 86.22 mutants per 10^6 viable cells.
NQO 0.20 µg/mL in the absence of S-9
Mean: 56.98 mutants per 10^6 viable cells, Range* = 9.44 to 104.52 mutants per 10^6 viable cells.
B[a]P 2 µg/mL in the presence of S-9
Mean: 26.89 mutants per 10^6 viable cells, Range* = 0 to 55.24 mutants per 10^6 viable cells.
B[a]P 3 µg/mL in the presence of S-9
Mean: 41.64 mutants per 10^6 viable cells, Range* = 7.71 to 75.57 mutants per 10^6 viable cells.
*Range = Mean ± 2 x SD.

MUTATION EXPERIMENT
- In the Mutation Experiment, twelve concentrations, ranging from 25 to 300 µg/mL, were tested in the absence and presence of S-9. Upon addition of the test article to the cultures, precipitate was observed at the highest eight concentrations (175 to 300 µg/mL) in the absence of S-9 and at the highest seven concentrations (200 to 300 µg/mL) in the presence of S-9. Following the 3 hour treatment incubation period, precipitate was observed at 300 µg/mL in the absence of S-9 and in the highest seven concentrations (200 to 300 µg/mL) in the presence of S-9. Therefore, in the presence of S-9, the lowest concentration at which precipitate was observed at the end of the treatment incubation period was retained and the higher concentrations discarded. Seven days after treatment, in the absence of S-9, the highest five concentrations (220 to 300 µg/mL) were considered too toxic for selection to determine viability and 6TG resistance (RS <10%). All other concentrations were selected in the absence and presence of S-9. The highest concentrations analysed were 210 µg/mL in the absence of S-9 (limited by cytotoxicity) and 200 µg/mL in the presence of S-9 (limited by the appearance of post-treatment precipitate) which gave 14% and 66% RS.
- No statistically significant increases in MF were observed following treatment with Labdanum gum at any concentration tested in the absence and presence of S-9 and there were no statistically significant linear trends, indicating a clear negative result.

Table 7.6.1/1: Range-finder experiment - 3 h treatment in the absence and presence of S-9

 

Concentration	3 h treatment –S-9	3 h treatment +S-9
µg/mL	% RS	% RS
0	100	100
UTC	107	99
15.63	73	87
31.25	60	101
62.5	75	75
125	69	75
250 P PP	0	16

UTC: Untreated control

% RS: Percent relative survival adjusted by post treatment cell counts

P: Precipitation observed at the time of treatment

PP: Precipitation noted at end of treatment incubation period

Table 7.6.1/2: Mutation experiment - 3 h treatment in the absence and presence of S-9

 

3h treatment -S9			3h treatment +S9
Concentration (µg/mL)	% RS	MF §	Concentration (µg/mL)	% RS	MF §
0	100	4.50	0	100	7.06
0 UTC	112	7.74	0 UTC	108	7.17
25	94	7.40 NS	25	90	6.82 NS
50	103	6.11 NS	50	89	5.33 NS
100	105	5.90 NS	100$	101	6.50 NS
150	74	3.16 NS	150	81	4.52 NS
175 P	38	7.17 NS	175	75	5.44 NS
200 P	19	7.95 NS	200 P PP	66	5.48 NS
210 P	14	7.79 NS	B[a]P 2	81	53.15
NQO 0.150	70	46.73	B[a]P 3	55	57.92
NQO 0.200	50	43.97	-	-	-

Linear trend tests on mutant frequency +/-S-9: Not significant (negative trends) 

UTC: Untreated control

§: 6‑TG resistant mutants/10⁶viable cells 7 days after treatment

$: Heterogeneity observed between repllicate cultures

% RS: Percent relative survival adjusted by post treatment cell counts

P: Precipitation noted at time of treatment

PP: Precipitation noted at end of treatment incubation period

NS: Not significant

Conclusions:

Under the test conditions, test substance did not induce mutation at the hprt locus of L5178Y mouse lymphoma cells when tested up to the limit of solubility, for 3 hours in the presence of a rat liver metabolic activation system (S-9) and up to toxic concentrations for 3 hours in the absence of S-9.

Executive summary:

In an in vitro mammalian cell gene mutation test performed according to OECD Guideline 476 and in compliance with GLP, L5178Y tk^+/-(3.7.2C) mouse lymphoma cells were exposed to test substance for 3 h at the following concentrations:

 

Range-Finder Experiment: 15.63, 31.25, 62.5, 125, 250, 500, 1000 and 2000 µg/mL, with and without S9

Mutation Experiment:

Without S9: 25, 50, 100, 150, 175, 200, 210, 220, 230, 240, 250 and 300 µg/mL

With S9: 25, 50, 100, 150, 175, 200, 250, 260, 270, 280, 290 and 300 µg/mL

 

Negative (untreated culture media), vehicle and positive control groups were also included in each mutagenicity test. Metabolic activation system used in this test was 2 % S9 mix (final concentration). S9 fraction was prepared from liver homogenates of rats treated with Aroclor 1254.

 

In the cytotoxicity Range-Finder Experiment, eight concentrations were tested in the absence and presence of S-9 ranging from 15.63 to 2000µg/mL (an acceptable maximum concentration forin vitrogenetic toxicology studies according to current regulatory guidelines).Post-treatment precipitate was observed in the four highest concentrations (250 to 2000 µg/mL). The highest concentration to give>10% relative survival (RS) was 125 µg/mL in the absence of S-9 and 250 µg/mL in the presence of S-9, which gave 69% and 16% RS, respectively.

In the Mutation Experiment, twelve concentrations, ranging from 25 to 300 µg/mL, were tested in the absence and presence of S-9. Post-treatment precipitation was observed at 300 µg/mL in the absence of S-9 and in the highest seven concentrations (200 to 300 µg/mL) in the absence of S-9. Seven days after treatment, the highest concentrations analysed to determine viability and 6TG resistance were 210 µg/mL in the absence of S-9 (limited by cytotoxicity) and 200 µg/mL in the presence of S-9 (limited by the appearance of post-treatment precipitate) which gave 14% and 66% RS, respectively.

Vehicle and positive control treatments were included in the Mutation Experiment in the absence and presence of S-9. Mutant frequencies (MF) in vehicle control cultures fell within acceptable ranges and clear increases in mutation were induced by the positive control chemicals 4-nitroquinoline 1-oxide (NQO) (without S-9) and benzo(a)pyrene (B[a]P) (with S-9). Therefore the study was accepted as valid.

No statistically significant increases in MF were observed following treatment withLabdanum gumat any concentration analysed in the absence and presence of S-9 and there were no statistically significant linear trends, indicating a clear negative result.

Under the test conditions, test substance did not induce mutation at the hprt locus of L5178Y mouse lymphoma cells when tested up to the limit of solubility, for 3 hours in the presence of a rat liver metabolic activation system (S-9) and up to toxic concentrations for 3 hours in the absence of S-9.

Reference 2

Endpoint:

in vitro cytogenicity / micronucleus study

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 20 March 2017 to 5 June 2017.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Well conducted and well described study in accordance with GLP and OECD Guideline 487.

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 487 (In vitro Mammalian Cell Micronucleus Test)

Version / remarks:

2016

Deviations:

no

Principles of method if other than guideline:

Not applicable.

GLP compliance:

yes

Type of assay:

in vitro mammalian cell micronucleus test

Target gene:

Not applicable.

Species / strain / cell type:

lymphocytes: Human

Details on mammalian cell type (if applicable):

CELLS USED
- Source of cells: Blood from two healthy, non-smoking female volunteers from a panel of donors at Covance.
- Sex, age and number of blood donors : female, 27 and 33 years for the range finder and 28 and 33 years for the main experiment.
- For each experiment, an appropriate volume of whole blood was drawn from the peripheral circulation into heparinised tubes within two days of culture initiation. Blood was stored refrigerated and pooled using equal volumes from each donor prior to use.

MEDIA USED
- Type and identity of media: HEPES-buffered RPMI medium containing 10% (v/v) heat inactivated foetal calf serum and 0.52% penicillin / streptomycin, so that the final volume following addition of S-9 mix/KCl and the test article in its chosen vehicle was 10 mL. The mitogen Phytohaemagglutinin (PHA, reagent grade) was included in the culture medium at a concentration of approximately 2% of culture to stimulate the lymphocytes to divide.

Additional strain / cell type characteristics:

not applicable

Cytokinesis block (if used):

Cytochalasin B (formulated in DMSO) was added to post wash-off culture medium to give a final concentration of 6 µg/mL per culture.

Metabolic activation:

with and without

Metabolic activation system:

The mammalian liver post-mitochondrial fraction (S-9) was prepared from male Sprague Dawley rats induced with Aroclor 1254. The final S-9 volume in the test system was 1% (v/v).

Test concentrations with justification for top dose:

Preliminary Toxicity Test:
- 0, 7.256, 12.09, 20.16, 33.59, 55.99, 93.31, 155.5, 259.2, 432, 720, 1200 and 2000 µg/mL (3-hour exposure to the test item without S9-mix or with S9-mix (1%))
- 0, 7.256, 12.09, 20.16, 33.59, 55.99, 93.31, 155.5, 259.2, 432, 720, 1200 and 2000 µg/mL (24-hour continuous exposure to the test item without S9-mix)

Main Experiment:
3-hour exposure to the test item without S9-mix: 0, 25, 75, 100, 150, 200, 250, 275, 300, 325, 350, 375 and 400 µg/mL.
3-hour exposure to the test item with S9-mix (2%): 0, 25, 75, 100, 150, 200, 250, 275, 300, 325, 350, 375 and 400 µg/mL.
24-hour continuous exposure to the test item without S9-mix: 0, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 250 and 300 µg/mL.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Dimethylformamide (DMF)
- Justification for choice of solvent/vehicle: Preliminary solubility trials indicated that DMF was the most suitable vehicle. Labdanum gum formed a fine, homogeneous suspension at concentrations up to approximately 200 mg/mL that were considered suitable for use. The solubility limit in culture medium was in the range of 125 to 500 µg/mL, as indicated by visible precipitation at the higher concentration which persisted following a 26 hour incubation period. A maximum concentration of 2000 µg/mL was selected for the cytotoxicity Range-Finder Experiment, in order that treatments were performed up to a regulatory suitable maximum.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMF

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

With S9 mix - CPA: 2 - 3 µg/mL for 3-hour exposure.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

DMF

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

mitomycin C

other:

Remarks:

Without S9 mix - Mitomycin C: 0.2 - 0.3 µg/mL for 3-hour exposure; Vinblastine: 0.04 - 0.06 µg/mL for 24-hour continuous exposure

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Exposure duration: 3 h (± S9) and 24 h continuous exposure (-S9) in preliminary toxicity test; 3 h (± S9) and 24 h continuous exposure (-S9) in main experiment
- At the end of the exposure period, the cell cultures were pelleted and washed twice with sterile saline and resuspented in fresh pre-warmed medium and then incubated for a further 21 h in the presence of Cytochalasin B for 3 h (± S9) and 24 h continuous exposure (-S9) respectively.

SPINDLE INHIBITOR (cytogenetic assays): Prior to the mitosis (after exposure of the test substance), Cytochalasin-B (formulated in DMSO) was added to post wash-off culture medium to give a final concentration of 6 µg/mL per culture.

STAIN (for cytogenetic assays): Slides were stained with Acridine orange solution (12.5 µg/mL using purified water) for 10 minutes

NUMBER OF REPLICATIONS:
- Preliminary toxicity test: Single culture for test item and untreated control. Duplicate for vehicle control.
- Main test: Duplicate cultures per dose for test item, untreated control and positive controls. Quadruplicate for vehicle control (DMF).

NUMBER OF CELLS EVALUATED:
- Cytotoxicity: A minimum of approximately 500 cells per culture were scored for the incidence of mononucleate, binucleate and multinucleate cells and the Replication index value expressed as a percentage of the vehicle controls.
- Scoring of Micronuclei: A minimum of one thousand binucleate cells from each culture (2000 per concentration) were analysed for micronuclei. The number of cells containing micronuclei and the number of micronuclei per cell on each slide was recorded.

DETERMINATION OF CYTOTOXICITY
- Method: Cytotoxicity of test item in the lymphocyte cultures was determined using the the replication index (RI):
RI, which indicates the relative number of nuclei compared to vehicle controls was determined using the formula as follows:
RI = number binucleate cells + 2 (number multinucleate cells)/total number of cells in treated cultures
Relative RI (expressed in terms of percentage) for each treated culture was calculated as follows:
Relative RI (%) = (RI of treated cultures/RI of vehicle controls )x100
Cytotoxicity (%) is expressed as (100 – Relative RI).

Evaluation criteria:

For valid data, the test article was considered to induce clastogenic and/or aneugenic events if:
1. A statistically significant increase in the frequency of MNBN cells at one or more concentrations was observed
2. An incidence of MNBN cells at such a concentration that exceeded the normal range in both replicates was observed
3. A concentration-related increase in the proportion of MNBN cells was observed (positive trend test).
* The test article was considered positive in this assay if all of the above criteria were met.
* The test article was considered negative in this assay if none of the above criteria were met.
* Results which only partially satisfied the above criteria were dealt with on a case-by-case basis. Evidence of a concentration-related effect was considered useful but not essential in the evaluation of a positive result (Scott et al., 1990). Biological relevance was taken into account, for example consistency of response within and between concentrations, or effects occurring only at very toxic concentrations (Thybaud et al., 2007).

Statistics:

The proportions of MNBN cells in each replicate were used to establish acceptable heterogeneity between replicates by means of a binomial dispersion test (Richardson et al., 1989).
The proportion of MNBN cells for each treatment condition were compared with the proportion in vehicle controls by using Fisher's exact test (Richardson et al., 1989). A Cochran-Armitage trend test was applied to each treatment condition. Probability values of p≤0.05 were accepted as significant

Key result

Species / strain:

lymphocytes: Human

Metabolic activation:

with and without

Genotoxicity:

ambiguous

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: no marked changes in pH (shifts of greater than 1 pH unit) was observed in the citotoxicity Range finder Experiment
- Effects of osmolality: no marked changes in osmolality (shifts of greater than 50 mOsm/kg) was observed in the citotoxicity Range finder Experiment


RANGE-FINDING/SCREENING STUDIES (See Tables 1, 2 and 3):
- The dose range for the Preliminary Toxicity Test was 7.256 to 2000 µg/mL.
- A precipitate of the test item was observed from 93.31 µg/mL (with and without S9/3 hours exposure) and 259.2 µg/mL (without S9/24 hours exposure).
- The selection of the maximum dose level for the Main Experiment was based on toxicity in the exposure groups in the absence of S9-mix and the lowest precipitating dose level for the exposure group in the presence of S9.

COMPARISON WITH HISTORICAL CONTROL DATA:
- The concurrent vehicle and positive controls were within the laboratory historical control data range.

ADDITIONAL INFORMATION ON GENOTOXICITY/CYTOTOXICITY:
Main experiments:
- The 3-hour treatment of cells with Labdanum gum in the absence of S-9 resulted in frequencies of MNBN cells which were significantly (p≤0.05) higher than those observed in concurrent vehicle controls for the highest two concentrations analysed (350 and 375 µg/mL) with a clear concentration related response apparent (statistically significant linear trend). The MNBN cell frequencies of both Labdanum gum treated cultures at both of these concentrations and single cultures at lower concentrations of 250 and 300 µg/mL exceeded the historical vehicle control (95th percentile of the observed) range. These data indicated a positive induction of MNBN cells.
- The 3-hour +S-9 treatment of cells with Labdanum gum resulted in frequencies of MNBN cells that were similar to and not significantly (p≤0.05) higher than those observed in concurrent vehicle control cultures for all five concentrations analysed. Frequencies of MNBN cells exceeded the normal range for both treated cultures at concentrations of 275 and 375 µg/mL, and in single cultures for concentrations of 325 and 350 µg/mL though the magnitude of these increases was not large and similar in magnitude to slight increases observed in vehicle control. No notable concentration related effect was apparent (linear trend test was negative) such that these slight increases in MNBN cell frequency were considered of questionable biological relevance.
- Extended 24-hour treatment in the absence of S-9 resulted in small but significantly (p≤0.05) elevated frequencies of MNBN cells for two intermediate concentrations analysed (120 and 160 µg/mL). However, these increases were small with the MNBN cell values of single cultures marginally exceeding normal ranges. No such increase was observed in the replicate cultures at either of these concentrations, or for any other Labdanum gum treated culture at lower or higher concentrations analysed (80 and 180 µg/mL inducing 12% and 46% cytotoxicity respectively). The small increases observed (poorly reproduced between replicate cultures) were therefore considered of questionable biological importance.

Table1: Data for 3-Hour Treatments -S-9, Range-Finder:

Treatment (µg/mL)	Replicate	Mono	Bi	Multi	Total	RI	Cytotoxicity Based on RI (%)	% Excluded Cells
Vehicle (Total)	A/B	121	273	7	401	0.72	-	-
UTC	A	63	135	2	200	0.70	-	10%
7.256	A	NSc	-	-	-	-	-	-
12.09	A	NSc	-	-	-	-	-	-
20.16	A	43	155	2	200	0.80	0	10%
33.59	A	66	131	3	200	0.69	4	10%
55.99	A	55	143	2	200	0.74	0	10%
93.31	A	73	126	1	200	0.64	11E	10%
155.5	A	76	124	0	200	0.62	13E	20%
259.2	A	119	81	0	200	0.41	43PE	30%
432	A	195	5	0	200	0.03	97PE	80%
720	A	T	-	-	-	-	-PEH	-
1200	A	T	-	-	-	-	-PEH	-
2000	A	T	-	-	-	-	-PEH	-

Table2: Data for 3-Hour Treatments +S-9:

Treatment (µg/mL)	Replicate	Mono	Bi	Multi	Total	RI	Cytotoxicity Based on RI (%)	% Excluded Cells
Vehicle (Total)	A/B	127	256	17	400	0.73	-	NR
UTC	A	70	125	5	200	0.78	-	NR
7.256	A	NSc	-	-	-	-	-	-
12.09	A	NSc	-	-	-	-	-	-
20.16	A	51	137	12	200	0.81	0	NR
33.59	A	42	153	5	200	0.82	0	10%
55.99	A	61	136	3	200	0.71	2	10%
93.31	A	60	140	0	200	0.70	3E	10%
155.5	A	81	117	2	200	0.61	17E	10%
259.2	A	107	90	3	200	0.48	34PE	30%
432	A	194	6	0	200	0.03	96PE	70%
720	A	T	-	-	-	-	-PEH	-
1200	A	T	-	-	-	-	-PEH	-
2000	A	T	-	-	-	-	-PEH	-

Table3: Data for 24-Hour Treatments -S-9

Treatment (µg/mL)	Replicate	Mono	Bi	Multi	Total	RI	Cytotoxicity Based on RI (%)	% Excluded Cells
Vehicle (Total)	A/B	132	261	7	400	0.69	-
UTC	A	24	150	26	200	1.09	-	NR
7.256	A	56	140	4	200	0.74	0	5%
12.09	A	57	141	2	200	0.73	0	5%
20.16	A	67	129	4	200	0.69	0	5%
33.59	A	71	126	3	200	0.66	4	5%
55.99	A	82	116	2	200	0.60	13	5%
93.31	A	122	77	1	200	0.40	43	10%
155.5	A	135	64	1	200	0.33	52	20%
259.2	A	189	11	0	200	0.06	92P	80%
432	A	T	-	-	-	-	-P	-
720	A	T	-	-	-	-	-PH	-
1200	A	T	-	-	-	-	-PEH	-
2000	A	T	-	-	-	-	-PEH	-

UTC = Untreated control

NSc = Not scored 

P = Precipitation observed at treatment

E = Precipitation observed at the end of treatment incubation

H = Precipitation observed at harvest

T = Toxic

Mono = Mononucleate

Bi = Binucleate

Multi = Multinucleate

RI = Replication index

 Table 4: Micronucleus data:

Treatment	Concentration (µg/ml)	Cytotoxicity (%)***	Mean MNBN Cell Frequency (%)	Historical Control Range (%)	Statistical Significance
3-hour -S-9	Vehicle*	-	0.73	0.20-1.00	-
	UTC	-	0.80		NS
	150	15	0.65		NS
	250	28	0.95		NS
	300	41	1.15		NS
	350	32	1.40		p<0.01
	375****	38	1.65		p<0.001
	**MMC, 0.20	42	4.75		p<0.001
3-hour +S-9	Vehicle*	-	1.08	0.20-1.07	-
	UTC	-	0.60		NS
	150	11	0.75		NS
	275	19	1.15		NS
	325	20	0.95		NS
	350	24	1.35		NS
	375****	27	1.30		NS
	**CPA, 2*	31	1.85		p<0.01
24-hour-S-9	Vehicle	-	0.38	0.10 – 0.90	-
	UTC	-	0.25		NS
	80	12	0.65		NS
	120	26	0.75		p<0.05
	160	46	0.95		p<0.01
	180****	47	0.45		NS
	**VIN, 0.04	39	6.20		p<0.001

*Vehicle control was DMF

**Positive control

***Based on replication index (RI)

NS: Not significan

**** Maximum concentrations analysed were limited by cytotoxicity to the maximum practicable concentrations that could be scored. Test article treatment at high concentrations impacted on  the cellular cytoplasm. Cells without cytoplasm are excluded from RI analysis such that under these circumstances RI may underestimate the true levels of cytotoxicity.

Conclusions:

Under the test conditions of this study, the test item induced increases in micronuclei in cultured human peripheral blood lymphocytes following 3-hour treatment in the absence of metabolic activation system (S-9), considered of questionable biological relevance. In the same test system, small increases in micronuclei considered of questionable biological importance were observed following both 3-hour treatment in the presence of S-9 and 24-hour treatment in the absence of S-9. The maximum concentrations analysed under each treatment condition were limited by cytotoxicity. However, this cytotoxicity may have been underestimated, as evidenced with the increase in the percentage of excluded cells (effects on cytoplasm indicating probable excessive cytotoxicity, membrane effects) at higher concentrations (from 200-250 µg/mL) in the preliminary and the main expriments as well as with the flat Replication Index (RI) dose-response in the main study (RI not appropriate for this substance). In addition, discordant precipitate observations were recorded in 3+21h +/- S9 conditions between the preliminary and main tests, with precipitate observed from 93 µg/mL vs. no precipitate at the end of the treatment up to 375 µg/mL, respectively. Now, in the HPRT study with the same test item, 200 µg/mL was the limit dose in the presence of S9 because of precipitate at the end of the exposure period. The possible underestimation of cytotoxicity and the discrepancy in precipitate observations weaken the relevance of the effects observed from 200 µg/mL in all treatment conditions.

Executive summary:

In an in vitro micronucleus test performed according to OECD Guideline 487 and in compliance with GLP, cultured peripheral human lymphocytes were exposed to test item in the presence and absence of a metabolic activation system. Three exposure conditions in a single experiment were used for the study using a 3‑hour exposure in the presence and absence of a standard metabolizing system (S-9 at a 1% final concentration) and a 24-hour exposure in the absence of metabolic activation. At the end of the exposure period, the cell cultures were washed and then incubated for a further 21 or 24  hours in the presence of Cytochalasin B.

The dose levels used in the Main Experiment were selected using data from the preliminary toxicity test where the results indicated that the maximum concentration should be limited by the toxicity and the precipitation of the test item both in the absence and presence of S9-mix. The dose levels selected for the Main Test were as follows:

3-hour without S9: 0, 150, 250, 300, 350 and 375 μg/mL

3-hour with S9 (1%): 0, 150, 275, 325, 350 and 375 μg/mL

24-hour without S9: 0, 80, 120, 160 and 180 μg/mL

All vehicle (DMF) controls had frequencies of cells with micronuclei within the range expected for normal human lymphocytes. The positive control items induced statistically significant increases in the frequency of cells with micronuclei. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

 

- The 3- hour treatment of cells with the test item in the absence of S-9 resulted in frequencies of MNBN cells which were significantly (p≤0.05) higher than those observed in concurrent vehicle controls for the highest two concentrations analysed (350 and 375 µg/mL) with a clear concentration related response apparent (statistically significant linear trend). The MNBN cell frequencies of both test item treated cultures at both of these concentrations and single cultures at lower concentrations of 250 and 300 µg/mL exceeded the historical vehicle control (95th percentile of the observed) range. These data indicated a positive induction of MNBN cells.

- The 3-hour + S-9 treatment of cells with test item resulted in frequencies of MNBN cells that were similar to and not significantly (p≤0.05) higher than those observed in concurrent vehicle control cultures for all five concentrations analysed. Frequencies of MNBN cells exceeded the normal range for both treated cultures at concentrations of 275 and 375 µg/mL, and in single cultures for concentrations of 325 and 350 µg/mL though the magnitude of these increases was not large and similar in magnitude to slight increases observed in vehicle control. No notable concentration related effect was apparent (linear trend test was negative) such that these slight increases in MNBN cell frequency were considered of questionable biological relevance.

- Extended 24-hour treatment in the absence of S-9 resulted in small but significantly (p≤0.05) elevated frequencies of MNBN cells for two intermediate concentrations analysed (120 and 160 µg/mL). However, these increases were small with the MNBN cell values of single cultures marginally exceeding normal ranges. No such increase was observed in the replicate cultures at either of these concentrations, or for any othertest item culture at lower or higher concentrations analysed (80 and 180 µg/mL inducing 12% and 46% cytotoxicity respectively). The small increases observed (poorly reproduced between replicate cultures) were therefore considered of questionable biological importance.

Under the test conditions of this study, the test item induced increases in micronuclei in cultured human peripheral blood lymphocytes following 3-hour treatment in the absence of an Aroclor-induced rat liver metabolic activation system (S‑9). In the same test system, small increases in micronuclei considered of questionable biological importance were observed following both 3-hour treatment in the presence of S-9 and 24 hour treatment in the absence of S-9. The maximum concentrations analysed under each treatment condition were limited by cytotoxicity. However, this cytotoxicity may have been underestimated, as evidenced with the increase in the percentage of excluded cells (effects on cytoplasm indicating probable excessive cytotoxicity, membrane effects) at higher concentrations (from 200-250 µg/mL) in the preliminary and the main expriments as well as with the flat Replication Index (RI) dose-response in the main study (RI not appropriate for this substance). In addition, discordant precipitate observations were recorded in 3+21h +/- S9 conditions between the preliminary and main tests, with precipitate observed from 93 µg/mL vs. no precipitate at the end of the treatment up to 375 µg/mL, respectively. Now, in the HPRT study with the same test item, 200 µg/mL was the limit dose in the presence of S9 because of precipitate at the end of the exposure period. The possible underestimation of cytotoxicity and the discrepancy in precipitate observations weaken the relevance of the effects observed from 200 µg/mL in all treatment conditions.

Reference 3

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

November 2014 - March 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Target gene:

Histidine and tryptophan.

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Metabolic activation:

with and without

Metabolic activation system:

10% S9: S9-mix from the livers of male rats treated with phenobarbitone/β-naphthoflavone (80/100 mg/kg bw/day by oral route).

Test concentrations with justification for top dose:

Test for Mutagenicity (Experiment 1) – Plate Incorporation Method: 1.5, 5, 15, 50, 150, 500, 1500 and 5000 µg/plate in all strains with and without S9-mix

Test for Mutagenicity (Experiment 2) – Pre-Incubation Method:50, 150, 500, 1500 and 5000 μg/plate in all strains with and without S9-mix;

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: dimethyl sulphoxide
- Justification for choice of solvent/vehicle:The test item was insoluble in sterile distilled water, dimethyl sulphoxide, dimethyl formamide and acetonitrile at 50 mg/mL, acetone at 100 mg/mL and tetrahydrofuran at 200 mg/mL in solubility checks performed in–house. The test item formed the best doseable suspension in dimethyl sulphoxide, therefore, this solvent was selected as the vehicle.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Remarks:

dimethyl sulphoxide

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

9-aminoacridine

N-ethyl-N-nitro-N-nitrosoguanidine

benzo(a)pyrene

other: 2-Aminoanthracene

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation); preincubation

DURATION
- Exposure duration: Plates were incubated at 37 °C ± 3 °C for approximately 48 hours

NUMBER OF REPLICATIONS: Triplicate plates per dose level.

DETERMINATION OF CYTOTOXICITY
- Method: The plates were viewed microscopically for evidence of thinning (toxicity).

OTHERS:
After incubation, the plates were assessed for numbers of revertant colonies using an automated colony counting system. Manual counts were performed at and above 500 μg/plate because of test item precipitation.

Evaluation criteria:

There are several criteria for determining a positive result. Any, one, or all of the following can be used to determine the overall result of the study:
1. A dose-related increase in mutant frequency over the dose range tested (De Serres and
Shelby, 1979).
2. A reproducible increase at one or more concentrations.
3. Biological relevance against in-house historical control ranges.
4. Statistical analysis of data as determined by UKEMS (Mahon et al., 1989).
5. Fold increase greater than two times the concurrent solvent control for any tester strain (especially if accompanied by an out-of-historical range response (Cariello and Piegorsch, 1996)).
A test item will be considered non-mutagenic (negative) in the test system if the above criteria are not met.
Although most experiments will give clear positive or negative results, in some instances the data generated will prohibit making a definite judgment about test item activity. Results of this type will be reported as equivocal.

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA: All tester strain cultures exhibit a characteristic number of spontaneous revertants per plate in the vehicle and positive controls. The comparison was made with the historical control ranges for 2013 and 2014 of the corresponding Testing Laboratory.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
- There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the first mutation test (plate incorporation method) and consequently the same maximum dose level was used in the second mutation test. Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation, in the second mutation test (pre-incubation method). An opaque test item film was noted at and above 1500 μg/plate in Experiment 1 (plate incorporation method) and at 5000 μg/plate in Experiment 2 (pre-incubation method).

OTHERS:
- Prior to use, the master strains were checked for characteristics, viability and spontaneous reversion rate (all were found to be satisfactory). The test material formulation, amino acid supplemented top agar and S9-mix used in this experiment were shown to be sterile.

Conclusions:

Under the test condition, test material is not mutagenic with and without metabolic activation in S. typhimurium (strains TA1535, TA1537, TA98 and TA100) and E.coli WP2 uvrA- according to the criteria of the Annex VI of the Regulation (EC) No. 1272/2008 (CLP).

Executive summary:

In a reverse gene mutation assay performed according to the OECD test guideline No. 471 and in compliance with GLP,Salmonella typhimurium strains TA 1535, TA 1537, TA 98 and TA 100 and Escherichia coli strain WP2 uvrA- were exposed to test material both in the presence and absence of metabolic activation system (10% liver S9 in standard co-factors).

Test for Mutagenicity (Experiment 1) – Plate Incorporation Method: 1.5, 5, 15, 50, 150, 500, 1500 and 5000 µg/plate in all strains with and without S9-mix

Test for Mutagenicity (Experiment 2) – Pre-Incubation Method: 50, 150, 500, 1500 and 5000 μg/plate in all strains without S9-mix

Negative, vehicle ( dimethyl sulphoxide) and positive control groups were also included in mutagenicity tests.

The vehicle control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

 

There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without S9-mix in Experiment 1 (plate incorporation method). Similarly, no significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test item, either with or without S9-mix in Experiment 2 (pre-incubation method).

 

Under the test condition, test material is not mutagenic with and without metabolic activation inS. typhimurium (strains TA1535, TA1537, TA98 and TA100) andE.coli WP2 uvrA- according to the criteria of the Annex VI of the Regulation (EC) No. 1272/2008 (CLP).

This study is considered as acceptable and satisfies the requirement for reverse gene mutation endpoint.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Link to relevant study records

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 14 May to 22 June, 2019.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study performed according to OECD test guideline No. 474 and in compliance with GLP.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

no

Principles of method if other than guideline:

Not applicable.

GLP compliance:

yes (incl. QA statement)

Remarks:

Inspected on 2019-04-02 / Signed on 2019-08-01

Type of assay:

mammalian erythrocyte micronucleus test

Species:

rat

Strain:

other: Crl:CD(SD)

Details on species / strain selection:

The rat was chosen as the test species because of the requirement for a rodent species by regulatory agencies. The Crl:CD(SD) was used because of the historical control data available at this laboratory.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Ltd.
- Females (if applicable) nulliparous and non-pregnant: Yes
- Age at study initiation: Males 69 to 75 days old. Females: 83 to 89 days old.
- Weight at study initiation: Males: 322-400 g; Females: 238 to 311 g
- Housing: Cages comprised of a polycarbonate body with a stainless steel mesh lid; changed at appropriate intervals. Solid (polycarbonate) bottom cages were used during the acclimatization and pre-treatment periods.
- Number of animals per cage:
* Pre-pairing, toxicity phase females and recovery animals: up to four animals of one sex
* Pairing: one male and one female
* Males after mating: up to four animals
* Gestation: one female
* Lactation: one female + litter
- Acclimatization and pre-treatment: Males: six days before commencement of treatment.Females: 20 days before commencement of treatment.
- Diet: SDS VRF1 Certified powdered diet, ad libitum (removed overnight before blood sampling for hematology and blood chemistry investigations and during urine collection)
- Water: Potable water from the public supply via polycarbonate bottles with sipper tubes, ad libitum (removed overnight during urine collection)
- Acclimation period:

ENVIRONMENTAL CONDITIONS
- Temperature: 20-24 °C
- Humidity: 40-70 %
- Air changes: Filtered fresh air which was passed to atmosphere and not recirculated.
- Photoperiod: Artificial lighting, 12 h light : 12 h dark
- Environmental Enrichment
Aspen chew block: A soft white untreated wood block; provided to each cage throughout the study (except during pairing and lactation) and replaced when necessary.
Plastic shelter: Provided to each cage throughout the study (except during pairing and lactation) and replaced at the same time as the cages.

IN-LIFE DATES: from 13 March to 12 July 2019.

Route of administration:

oral: feed

Vehicle:

None.

Details on exposure:

DIET PREPARATION
- Diet: SDS VRF1 Certified powdered diet
- Correction factor: A correction factor was not required.
- Stabilizer: Corn oil (test material to corn oil ratio 5:1).
- Method of preparation: The test substance was incorporated into the diet to provide the required concentrations by initial preparation of a premix. The test item was melted at 70°C before weighing. On each occasion of the preparation of the premix the required amount of test item and solvent (acetone) were weighed out and magnetically stirred until the test item was fully dispersed. The mixture was added to the appropriate amount of plain diet. A further amount (approximately 100 g) of plain diet was used to clean the weighing container and then added to the mixture. This mixture was stirred well, then left for the solvent (acetone) to evaporate for at least 45 minutes while stirred frequently, until a constant weight was achieved and at least 90% of the initial weight of added solvent was removed. The required amount of corn oil was added to the mixture. Additional diet was used to rinse the corn oil weighing container which was then added to the mixture. This was ground using a mechanical grinder then made up to the correct weight with plain diet. The formulation was transferred to a plastic container and mixed using a Turbula mixer for 100 cycles at 16 rpm to ensure all the
test item was dispersed in the diet. Aliquots of the premix were then diluted with further quantities of plain diet to produce the required dietary concentrations. Each batch of treated diet was mixed for a further 100 cycles in a Turbula mixer.
- Storage of formulation: Frozen (-10 to -30°C).

Duration of treatment / exposure:

Toxicity phase males: Three weeks before pairing up to necropsy after minimum of six weeks of treatment.
Toxicity phase females: At least six weeks.

Frequency of treatment:

Continuously

Post exposure period:

None

Dose / conc.:

0 ppm

Remarks:

Control group (Basal diet + corn oil) / Group 1

Dose / conc.:

15 000 ppm

Remarks:

Group 2 (Low dose)

Dose / conc.:

3 500 ppm

Remarks:

Group 3 (Mid dose)

Dose / conc.:

7 500 ppm

Remarks:

Group 4 (High dose)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent no treatment

Positive control(s):

Five bone marrow smears previously prepared from rats administered cyclophosphamide (Envigo Study Number GY05QJ) will be stained and coded along with the bone marrow smears prepared in this study.
- Route of administration: diet
- Doses / concentrations: 20 mg/kg

Tissues and cell types examined:

Bone marrow smears

Details of tissue and slide preparation:

- Preparation of bone marrow smears
Animals were killed on the day after receiving their last daily dose. One femur was dissected from the first five male and female animals per group (surviving to necropsy) and the proximal head removed. Using a syringe and needle, bone marrow was flushed from the marrow cavity with approximately 3 mL pre filtered foetal calf serum into appropriately labelled centrifuge tubes (1 per animal). The resulting cell suspensions were centrifuged at 1000 rpm for 5 minutes and the supernatant discarded. The final cell pellet was resuspended in a small volume of foetal bovine calf serum to facilitate smearing in the conventional manner on glass microscope slides (Schmid 1976). At least 4 smears/slides were prepared from each animal. The bone marrow smears were air-dried and then fixed for a minimum of 10 minutes in absolute methanol.
- Fixation and staining of slides
The slides were rinsed in purified water and stained using an acridine orange solution at 0.0125 mg/mL and stored at room temperature in the dark until required. The remaining unstained slides were kept in reserve.
- Microscopic examination
At least 3 slides (prepared in a separate study [GY05QJ]) from animals treated with Cyclophosphamide (CPA), a well characterized clastogen, were stained and coded along with the bone marrow smears prepared from this study.
Prior to scoring the slides were wet mounted with coverslips using purified water. Coded slides were examined by fluorescence microscopy and 4000 polychromatic erythrocytes per animal were examined for the presence of micronuclei. At least one smear was examined per animal, any remaining smears being held temporarily in reserve in case of technical problems with the first smear.
The proportion of polychromatic erythrocytes was assessed by examination of a total of at least 1000 erythrocytes per animal and the number of micronucleated normochromatic erythrocytes was recorded.

Evaluation criteria:

Providing that all acceptability criteria are fulfilled, the test article is considered clearly negative if, in all experimental conditions examined:
a) None of the treatment groups exhibits a statistically significant increase in the frequency of micronucleated polychromatic erythrocytes compared with the concurrent negative control,
b) There is no dose-related increase when evaluated by an appropriate trend test,
c) All results are inside the distribution of the historical negative control data (e.g. Poisson-based 95% control limits),
and d) Bone marrow exposure to the test substance(s) occurred.

Providing that all acceptability criteria are fulfilled, a test chemical is considered clearly positive if:
a) At least one of the treatment groups exhibits a statistically significant increase in the frequency of micronucleated polychromatic erythrocytes compared with the concurrent negative control,
b) This increase is dose-related when evaluated with an appropriate trend test,
and c) Any of these results are outside the distribution of the historical negative control data (e.g. Poisson-based 95% control limits).
When conducting a dose-response analysis, at least three treated dose groups should be analysed. Statistical tests should use the animal as the experimental unit. Positive results in the micronucleus test indicate that a test chemical induces micronuclei, which are the result of chromosomal damage or damage to the mitotic apparatus in the erythroblasts of the test species.

Statistics:

Analysis of data: The results obtained for each treatment group will be compared with the results obtained for the vehicle control group using non-parametric statistical methods. Analysis will be performed for the study using data from all animals that survive to scheduled termination to maximise the power of statistical analysis. If less than five animals per group survive to scheduled termination the study may be repeated.
For the proportion of polychromatic erythrocytes at 24 hours, an asymptotic one-tailed Jonckheere’s test for trend (Jonckheere 1954) with “step-down” will be used on Groups 1 to 4 for a decrease from control. Exact one-tailed Wilcoxon pairwise tests (Wilcoxon 1945), for a decrease from control, will also be carried out on Group 1 (control) versus Groups 2, 3, 4 and 5 (positive control slides).
For incidences of micronucleated polychromatic erythrocytes at 24 hours, an exact one-tailed Linear-by-Linear association test (Cytel 1995) with “step-down” will be used on Groups 1 to 4 for an increase from control. Also, exact one-tailed pairwise Permutation tests (Cytel 1995), for an increase from control, will be carried out on Group 1 (control) versus Groups 2, 3, 4 and 5 (positive control slides). Statistical significance will be declared at the 5% level for all tests.
Quasar (version 1.4) and/or SAS (version 9.1.3) and/or StatXact 3 in-house statistical analysis packages may be used for statistical analysis.

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range:
The target dietary concentrations selected for investigation in this OECD 422 combined repeated dose toxicity study and reproductive/developmental toxicity screening study (0, 1500, 3500 and 7500 ppm) were chosen in conjunction with the Sponsor and were based on the results of a 14-day preliminary study conducted at these laboratories (Envigo Study No. HX59HH).
- Solubility: no data
- Clinical signs of toxicity in test animals:
There were no clinical signs observed during the treatment period for Toxicity and Recovery phase animals or for Reproductive phase females prior to pairing, during gestation or during lactation that were considered related to dietary administration of Labdanum Gum. There were no signs observed during the recovery period that were considered to be associated with previous treatment with Labdanum Gum.
- Rationale for exposure:
Continuously (OECD 422)
RESULTS OF DEFINITIVE STUDY
- Induction of micronuclei (for Micronucleus assay):
* Percentage of Micronucleated Polychromatic Erythrocyte Counts (%MPCE):
The data for the concurrent vehicle control were within the ranges determined by the laboratory historical control data, therefore, the performance of the vehicle was consistent with a valid assay. The coded positive control slides prepared from study GY05QJ demonstrated the ability of the analyst to detect increases in micronucleated polychromatic erythrocytes.
There were no statistically significant increases in %MPCE observed in male or female Crl:CD(SD) rats administered Labdanum Gum at any dose level compared to vehicle control values. All individual and group mean values were within the current vehicle historical control range (95% confidence limits).
* Micronucleated Normochromatic Erythrocytes (MNCE):
Labdanum Gum did not cause any substantial increases in the incidence of micronucleated normochromatic erythrocytes in male or female Crl:CD(SD) rats.
* Proportion of Polychromatic Erythrocytes (%PCE):
The data for the concurrent vehicle control %PCE were within or close to the ranges determined by the laboratory historical control data (95% confidence limits), therefore, the performance of the vehicle was consistent with a valid assay.
A statistically significant decrease in %PCE (p<0.01) was observed in male Crl:CD(SD) rats administered Labdanum Gum at 3500 and 7500 ppm compared to vehicle control values. A statistically significant trend was also observed from Group 1 to 4 (p<0.001), upon exclusion of Group 4, the trend was again statistically significant (p<0.001). However, individual and group mean values from all treatment groups did not exceed the lower 95% confidence limit of the current vehicle historical control range. In additional to this the group mean vehicle control was marginally higher than the upper 95% confidence limit. Therefore, the statistically significant decreases observed are considered to be of questionable biological relevance.
There were no statistically significant decreases in %PCE observed in female Crl:CD1(SD) rats administered Labdanum Gum at any dose level compared to vehicle control values. All individual and group mean values were within or close to the current vehicle historical control range (95% confidence limits).

Table7.6.2/1: Summary of results and statistical analysis

Male data

Treatment	Treatment (ppm)	Proportion of PCE % # (SD)	Incidence MPCE mean # (SD)	Group mean % MPCE #
Control	0	55.5 (4.4)	4.0 (3.1)	0.10
Labdanum Gum	1500	52.1 (3.9)	3.4 (1.5)	0.09
Labdanum Gum	3500	46.7**^^^ (2.1)	3.6 (1.8)	0.09
Labdanum Gum	7500	45.8**^^^ (3.6)	4.2 (0.8)	0.11
Cyclophosphamide^a	20 mg/kg	45.4* (2.0)	60.0* (9.6)	1.50

Female data

Treatment			Treatment (ppm)		Proportion of PCE % # (SD)		Incidence MPCE mean # (SD)	Group mean % MPCE #
Control			0		51.8 (0.8)		4.0 (2.3)	0.10
Labdanum Gum			1500		51.0 (0.7)		4.4 (0.5)	0.11
Labdanum Gum			3500		57.9 (3.3)		3.8 (1.3)	0.10
Labdanum Gum			7500		56.5 (4.2)		4.0 (1.9)	0.10
Cyclophosphamide^a			20 mg/kg		45.6* (1.9)		73.3* (6.8)	1.83
Control	Basal diet + corn oil
PCE	Polychromatic erythrocytes
MPCE	Number of micronucleated polychromatic erythrocytes observed per 4000 polychromatic erythrocytes examined
SD	Standard deviation
a	Positive control slides from study GY05QJ
# Occasional apparent errors of ± 1% may occur due to rounding of values for presentation in the table.
Results of statistical analysis using the appropriate nonparametric method of analysis based on permutation (one-sided probabilities):
Pairwise		*		p< 0.05		(significant)
		**		p< 0.01		(significant)
Trend		^^^		p< 0.001		(significant)
		otherwise		p> 0.05		(not significant)

Conclusions:

Under the test conditions of this study, the test substance did not show any evidence of causing an increase in the induction of micronucleated polychromatic erythrocytes or bone marrow cell toxicity in male or female Crl:CD(SD) rats when administered orally by diet in this in vivo test procedure.

Executive summary:

In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test conducted according to OECD Guideline 422 and in compliance with GLP, the test item was administered to groups of Crl:CD(SD) rats at dietary concentrations of 1500, 3500 and 7500 ppm. An additional subgroup was used to assess reversibility, persistence or delayed occurrence of systemic effects for 14 days post treatment. A similarly constituted control group was assigned to each phase, and received the vehicle, powdered SDS VRF1 Certified diet with corn oil, throughout the same relative treatment period.

Toxicity phase males were treated for three weeks prior to pairing up to necropsy after aminimum of six weeks. Toxicity phase females were treated for at least six weeks.

During the study, bone marrow micronucleus test (OECD 474) was undertaken.This phase of the study was designed to assess the potential induction of micronuclei the test substance in bone marrow cells of male and female Crl:CD(SD) rats following 6 weeks of dietary administration.

Bone marrow smears were obtained from the first 5 male and female animals,surviving to scheduled necropsy,from the vehicle control group and each of the test item groups on the day after administration of the final dose.

One smear from each animal was examined for the presence of micronuclei in 4000 polychromatic erythrocytes. The proportion of polychromatic erythrocytes was assessed by examination of at least 1000 erythrocytes from each animal. A record of the incidence of micronucleated normochromatic erythrocytes was also kept.

The data for the concurrent vehicle control (group mean % polychromatic erythrocytes [%PCE] and % micronucleated polychromatic erythrocytes [%MPCE]) were within or close to the ranges determined by the laboratory historical control data (95% confidence limits), therefore, the performance of the vehicle was consistent with a valid assay. The coded positive control slides prepared from study GY05QJ demonstrated the ability of the analyst to detect increases in micronucleated polychromatic erythrocytes.

There were no statistically significant increases in %MPCE observed in male Crl:CD(SD) rats administered Labdanum Gum at any dose level compared to vehicle control values. All individual and group mean values were within the current vehicle historical control range (95% confidence limits).

A statistically significant decrease in %PCE (p<0.01) was observed in male Crl:CD(SD) rats administered Labdanum Gum at 3500 and 7500 ppm compared to vehicle control values. A statistically significant trend was also observed from Group 1 to 4 (p<0.001), upon exclusion of Group 4, the trend was again statistically significant (p<0.001). However, individual and group mean values from all treatment groups did not exceed the lower 95% confidence limit of the current vehicle historical control range. In additional to this the group mean vehicle control was marginally higher than the upper 95% confidence limit. Therefore, the statistically significant decreases observed are considered to be of questionable biological relevance.

There were no statistically significant increases in %MPCE and no statistically significant decreases in %PCE observed in female Crl:CD1(SD) rats administered Labdanum Gum at any dose level compared to vehicle control values. The group mean values were within or close to the current vehicle historical control range (95% confidence limits).

Under the test conditions of this study, Labdanum Gum did not show any evidence of causing an increase in the induction of micronucleated polychromatic erythrocytes in male and female Crl:CD(SD) rats following 6 weeks of dietary administration in this in vivo test procedure.

This study is considered as acceptable and satisfies the requirement for genetic toxicity in vivo endpoint.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Ames test:

In a reverse gene mutation assay performed according to the OECD test guideline No. 471 and in compliance with GLP,Salmonella typhimurium strains TA 1535, TA 1537, TA 98 and TA 100 and Escherichia coli strain WP2 uvrA- were exposed to test material both in the presence and absence of metabolic activation system (10% liver S9 in standard co-factors).

Test for Mutagenicity (Experiment 1) – Plate Incorporation Method: 1.5, 5, 15, 50, 150, 500, 1500 and 5000 µg/plate in all strains with and without S9-mix

Test for Mutagenicity (Experiment 2) – Pre-Incubation Method:50, 150, 500, 1500 and 5000μg/plate inall strains without S9-mix

Negative, vehicle (dimethyl sulphoxide) and positive control groups were also included in mutagenicity tests.

The vehicle control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

 

There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without S9-mix in Experiment 1 (plate incorporation method). Similarly, no significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test item, either with or without S9-mix in Experiment 2 (pre-incubation method).

 

Under the test condition, test material is not mutagenic with and without metabolic activation inS. typhimurium (strains TA1535, TA1537, TA98 and TA100) and E.coli WP2 uvrA.

In vitro Micronucleus test:

In an in vitro micronucleus test performed according to OECD Guideline 487 and in compliance with GLP, cultured peripheral human lymphocytes were exposed to test item in the presence and absence of a metabolic activation system. Three exposure conditions in a single experiment were used for the study using a 3‑hour exposure in the presence and absence of a standard metabolizing system (S-9 at a 1% final concentration) and a 24-hour exposure in the absence of metabolic activation. At the end of the exposure period, the cell cultures were washed and then incubated for a further 21 or 24  hours in the presence of Cytochalasin B.

The dose levels used in the Main Experiment were selected using data from the preliminary toxicity test where the results indicated that the maximum concentration should be limited by the toxicity and the precipitation of the test item both in the absence and presence of S9-mix. The dose levels selected for the Main Test were as follows:

3-hour without S9: 0, 150, 250, 300, 350 and 375μg/mL

3-hour with S9 (1%): 0, 150, 275, 325, 350 and 375μg/mL

24-hour without S9: 0, 80, 120, 160 and 180μg/mL

All vehicle (DMF) controls had frequencies of cells with micronuclei within the range expected for normal human lymphocytes. The positive control items induced statistically significant increases in the frequency of cells with micronuclei. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

 

- The 3-hour treatment of cells with the test item in the absence of S-9 resulted in frequencies of MNBN cells which were significantly (p≤0.05) higher than those observed in concurrent vehicle controls for the highest two concentrations analysed (350 and 375 µg/mL) with a clear concentration related response apparent (statistically significant linear trend). The MNBN cell frequencies of both test item treated cultures at both of these concentrations and single cultures at lower concentrations of 250 and 300 µg/mL exceeded the historical vehicle control (95th percentile of the observed) range. These data indicated a positive induction of MNBN cells.

- The 3-hour + S-9 treatment of cells with test item resulted in frequencies of MNBN cells that were similar to and not significantly (p≤0.05) higher than those observed in concurrent vehicle control cultures for all five concentrations analysed. Frequencies of MNBN cells exceeded the normal range for both treated cultures at concentrations of 275 and 375 µg/mL, and in single cultures for concentrations of 325 and 350 µg/mL though the magnitude of these increases was not large and similar in magnitude to slight increases observed in vehicle control. No notable concentration related effect was apparent (linear trend test was negative) such that these slight increases in MNBN cell frequency were considered of questionable biological relevance.

- Extended 24-hour treatment in the absence of S-9 resulted in small but significantly (p≤0.05) elevated frequencies of MNBN cells for two intermediate concentrations analysed (120 and 160 µg/mL). However, these increases were small with the MNBN cell values of single cultures marginally exceeding normal ranges. No such increase was observed in the replicate cultures at either of these concentrations, or for any othertest item culture at lower or higher concentrations analysed (80 and 180 µg/mL inducing 12% and 46% cytotoxicity respectively). The small increases observed (poorly reproduced between replicate cultures) were therefore considered of questionable biological importance.

Under the test conditions of this study, the test item induced increases in micronuclei in cultured human peripheral blood lymphocytes following 3-hour treatment in the absence of an Aroclor-induced rat liver metabolic activation system (S‑9).

In the same test system, small increases in micronuclei considered of questionable biological importance were observed following both 3-hour treatment in the presence of S-9 and 24 hour treatment in the absence of S-9. The maximum concentrations analysed under each treatment condition were limited by cytotoxicity.However, this cytotoxicity may have been underestimated, as evidenced with the increase in the percentage of excluded cells (effects on cytoplasm indicating probable excessive cytotoxicity, membrane effects) at higher concentrations (from 200-250 µg/mL) in the preliminary and the main expriments as well as with the flat Replication Index (RI) dose-response in the main study (RI not appropriate for this substance). In addition, discordant precipitate observations were recorded in 3+21h +/- S9 conditions between the preliminary and main tests, with precipitate observed from 93 µg/mL vs. no precipitate at the end of the treatment up to 375 µg/mL, respectively. Now, in the HPRT study with the same test item, 200 µg/mL was the limit dose in the presence of S9 because of precipitate at the end of the exposure period. The possible underestimation of cytotoxicity and the discrepancy in precipitate observations weaken the relevance of the effects observed from 200 µg/mL in all treatment conditions.

HPRT test:

In an in vitro mammalian cell gene mutation test performed according to OECD Guideline 476 and in compliance with GLP, L5178Y tk^+/-(3.7.2C) mouse lymphoma cells were exposed to test substance for 3 h at the following concentrations:

 Mutation Experiment:

Without S9: 25, 50, 100, 150, 175, 200, 210, 220, 230, 240, 250 and 300 µg/mL

With S9: 25, 50, 100, 150, 175, 200, 250, 260, 270, 280, 290 and 300 µg/mL

 Negative (untreated culture media), vehicle and positive control groups were also included in each mutagenicity test. Metabolic activation system used in this test was 2 % S9 mix (final concentration). S9 fraction was prepared from liver homogenates of rats treated with Aroclor 1254.

 

In the cytotoxicity Range-Finder Experiment, eight concentrations were tested in the absence and presence of S-9 ranging from 15.63 to 2000µg/mL (an acceptable maximum concentration forin vitrogenetic toxicology studies according to current regulatory guidelines).Post-treatment precipitate was observed in the four highest concentrations (250 to 2000 µg/mL). The highest concentration to give>10% relative survival (RS) was 125 µg/mL in the absence of S-9 and 250 µg/mL in the presence of S-9, which gave 69% and 16% RS, respectively.

In the Mutation Experiment, twelve concentrations, ranging from 25 to 300 µg/mL, were tested in the absence and presence of S-9. Post-treatment precipitation was observed at 300 µg/mL in the absence of S-9 and in the highest seven concentrations (200 to 300 µg/mL) in the absence of S-9. Seven days after treatment, the highest concentrations analysed to determine viability and 6TG resistance were 210 µg/mL in the absence of S-9 (limited by cytotoxicity) and 200 µg/mL in the presence of S-9 (limited by the appearance of post-treatment precipitate) which gave 14% and 66% RS, respectively.

Vehicle and positive control treatments were included in the Mutation Experiment in the absence and presence of S-9. Mutant frequencies (MF) in vehicle control cultures fell within acceptable ranges and clear increases in mutation were induced by the positive control chemicals 4-nitroquinoline 1-oxide (NQO) (without S-9) and benzo(a)pyrene (B[a]P) (with S-9). Therefore the study was accepted as valid.

No statistically significant increases in MF were observed following treatment withLabdanum gumat any concentration analysed in the absence and presence of S-9 and there were no statistically significant linear trends, indicating a clear negative result.

Under the test conditions, test substance did not induce mutation at the hprt locus of L5178Y mouse lymphoma cells when tested up to the limit of solubility, for 3 hours in the presence of a rat liver metabolic activation system (S-9) and up to toxic concentrations for 3 hours in the absence of S-9.

In vivo micronucleus test:

In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test conducted according to OECD Guideline 422 and in compliance with GLP, the test item was administered to groups of Crl:CD(SD) rats at dietary concentrations of 1500, 3500 and 7500 ppm. An additional subgroup was used to assess reversibility, persistence or delayed occurrence of systemic effects for 14 days post treatment. A similarly constituted control group was assigned to each phase, and received the vehicle, powdered SDS VRF1 Certified diet with corn oil, throughout the same relative treatment period.

Toxicity phase males were treated for three weeks prior to pairing up to necropsy after aminimum of six weeks. Toxicity phase females were treated for at least six weeks.

During the study, bone marrow micronucleus test (OECD 474) was undertaken.This phase of the study was designed to assess the potential induction of micronuclei the test substance in bone marrow cells of male and female Crl:CD(SD) rats following 6 weeks of dietary administration.

Bone marrow smears were obtained from the first 5 male and female animals,surviving to scheduled necropsy,from the vehicle control group and each of the test item groups on the day after administration of the final dose.

One smear from each animal was examined for the presence of micronuclei in 4000 polychromatic erythrocytes. The proportion of polychromatic erythrocytes was assessed by examination of at least 1000 erythrocytes from each animal. A record of the incidence of micronucleated normochromatic erythrocytes was also kept.

The data for the concurrent vehicle control (group mean % polychromatic erythrocytes [%PCE] and % micronucleated polychromatic erythrocytes [%MPCE]) were within or close to the ranges determined by the laboratory historical control data (95% confidence limits), therefore, the performance of the vehicle was consistent with a valid assay. The coded positive control slides prepared from study GY05QJ demonstrated the ability of the analyst to detect increases in micronucleated polychromatic erythrocytes.

There were no statistically significant increases in %MPCE observed in male Crl:CD(SD) rats administered Labdanum Gum at any dose level compared to vehicle control values. All individual and group mean values were within the current vehicle historical control range (95% confidence limits).

A statistically significant decrease in %PCE (p<0.01) was observed in male Crl:CD(SD) rats administered Labdanum Gum at 3500 and 7500 ppm compared to vehicle control values. A statistically significant trend was also observed from Group 1 to 4 (p<0.001), upon exclusion of Group 4, the trend was again statistically significant (p<0.001). However, individual and group mean values from all treatment groups did not exceed the lower 95% confidence limit of the current vehicle historical control range. In additional to this the group mean vehicle control was marginally higher than the upper 95% confidence limit. Therefore, the statistically significant decreases observed are considered to be of questionable biological relevance.

There were no statistically significant increases in %MPCE and no statistically significant decreases in %PCE observed in female Crl:CD1(SD) rats administered Labdanum Gum at any dose level compared to vehicle control values. The group mean values were within or close to the current vehicle historical control range (95% confidence limits).

Under the test conditions of this study, Labdanum Gum did not show any evidence of causing an increase in the induction of micronucleated polychromatic erythrocytes in male and female Crl:CD(SD) rats following 6 weeks of dietary administration in this in vivo test procedure.

Justification for classification or non-classification

Harmonized classification:

The substance has no harmonized classification for human health according to the Regulation (EC) No. 1272/2008.

 

Self classification:

Based on the available data, no additional classification is proposed regarding genetic toxicity according to the Annex I of the Regulation (EC) No. 1272/2008 (CLP) and to the GHS.