Dibutyl carbonate

Endpoint summary

Description of key information

Skin sensitizer, EC3 = 16.9% (BASF 2018)

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Version / remarks:

July 2010

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Version / remarks:

July 2012

Principles of method if other than guideline:

The study procedure was extended to include additional measures of lymph node response including lymph node cell count, lymph node weight and ear weight as an indicator of skin irritation to put the data into perspective.
The basis for these additions are described in:
- Kolle et al., Performance standards and alternative assays: practical insights from skin sensitization. Regul Toxicol Pharmacol. 2013 Mar; 65(2):278-85.
- Kolle et al., Further experience with the local lymph node assay using standard radioactive and nonradioactive cell count measurements. J Appl Toxicol. 2012 Aug; 32(8):597-607.
- Basketter et al., Experience with local lymph node assay performance standards using standard radioactivity and nonradioactive cell count measurements. J Appl Toxicol. 2012 Aug;32(8):590-6.

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: B16Q060201
- Purity test date: 2017-01-02

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature

Other:
pH value: 5

Species:

mouse

Strain:

CBA/Ca

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Envigo, Netherlands
- Age at study initiation: 8 weeks
- Weight at study initiation: 17.6 - 20.8g
- Housing: single
- Diet (e.g. ad libitum): ad lib.
- Water (e.g. ad libitum): ad lib.
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 30-70%
- Photoperiod (hrs dark / hrs light): 12h/12h

Vehicle:

methyl ethyl ketone

Concentration:

10%, 25%, 50%

No. of animals per dose:

5

Details on study design:

PRE-SCREEN TESTS:
- Compound solubility: Vehicle chosen because of good substance solubility
- # of animals per group: 2 females
- concentrations tested: 10%, 50%
- Irritation: none
- Systemic toxicity: none
- Ear thickness measurements: 10%: +3.5%, 50% +5%
- Erythema scores: no local findings
- lymph node weight stimulation index: 10%: 1.3, 50%: 1.8
- ear weight stimulation index: 10%: 0.87, 50%: 0.9

MAIN STUDY

TREATMENT PREPARATION AND ADMINISTRATION:
25µl per ear on 3 consecutive days

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Parameter:

EC3

Value:

16.9

Cellular proliferation data / Observations:

Stimulation index (3H-thymidine incorporation)
10%: 2.1
25%: 4.05
50%: 4.06

Lymph node cell count stimulation index
10%: 1.44
25%: 1.54
50%: 1.87

Lymph node weight stimulation index
10%: 1.44
25%: 1.72
50%: 1.76

Ear weights compared to control
10%: 102%
25%: 110%
50%: 106%

All test substance concentrations did not cause biologically relevant increases (SI > 1.25) in ear weights demonstrating the absence of relevant ear skin irritation, although a statistically significant increase in ear weights was noted at the 25% (but not at the 50%) concentration.

No signs of systemic toxicity were noted.

Very slight erythema and slight ear swelling was observed in the 50% dose group on day 2.

As one animal of the vehicle control group was identified as outlier, only the data of the remaining 4 animals were used for calculation of the mean values for the concurrent control group and for determination of the stimulation indices (SI) of the test item. Nevertheless, the calculation of the stimulation indices using the historical data for the vehicle MEK confirmed the results using the concurrent control group.

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The skin sensitizing potential of Dibutyl carbonate was assessed in the radioactive Murine Local Lymph Node Assay according to OECD 429 and GLP. Groups of 5 female mice each were treated with 10%, 25% and 50% (w/w) preparations of the test substance in methyl ethyl ketone (MEK) or with the vehicle alone.

No signs of systemic toxicity were noticed in all animals during general observation. When applied as 25% and 50% preparation in MEK, the test substance induced a biologically relevant (increase above the cut off Stimulation Index of 3) and statistically significant increase of ³H thymidine incorporation into the cells from the auricular lymph nodes. The increase of the 10% test-substance preparation was also statistically significant, but failed to reach the cut-off value of 3. Concomitantly, the 25% and 50% test-substance preparation induced a biologically relevant response (increase to 1.5-fold or above of control value = stimulation index (SI) ≥ 1.5) in the auricular lymph node cell counts. The increases at 10% and 50% were statistically significant. In addition, statistically significant increases in lymph node weights were noted at all concentrations, thus, corroborating the observed biologically relevant responses of the 25% and 50% preparations. All test substance concentrations did not cause biologically relevant increases (SI > 1.25) in ear weights demonstrating the absence of relevant ear skin irritation, although a statistically significant increase in ear weights was noted at the 25% concentration. However, very slight erythema and slight swelling of the ear skin was observed in all animals at the 50% concentration on study day 2.

Thus, it is concluded that Dibutyl carbonate exhibits a skin sensitizing potential under the test conditions chosen. The threshold for sensitization induction was > 10% and < 25%. The EC3 value was calculated to be 16.9%.

Justification for classification or non-classification

The substance caused skin sensitization in an LLNA. Based on the EC3 value far above 2%, the substance is classified as a skin sensitzier cat. 1B according to Regulation (EC) No 1272/2008 (CLP).