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Description of key information

Short description of key information:
The test substance did not produce skin sensitization in laboratory animals. Additionally, no sensitization was observed in laboratory animals in the read across chemical, 2,2'-azobus(isobutyronitrile).

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Referenceopen allclose all

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: See Remark
Remarks:
The data provided in conjunction with that of report DuPont-19883-1234 provide a weight of evidence for the hazard endpoint that is sufficient for the purpose of classification and labelling and/or risk assessment.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
Remarks:
The study was conducted according to the guideline in effect.
GLP compliance:
no
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
test was conducted before LLNA method was adopted
Specific details on test material used for the study:
Purite: 100%
Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: not reported
- Age at study initiation: not reported
- Weight at study initiation: contol animals average weight - 508 g; test animals average weight - 518 g
- Housing: not reported
- Diet (e.g. ad libitum): not reported
- Water (e.g. ad libitum): not reported
- Acclimation period: not reported

ENVIRONMENTAL CONDITIONS: not reported
Route:
intradermal
Vehicle:
other: See Remark
Remarks:
Dimethyl phthalate (DMP)
Concentration / amount:
8% and 80% in DMP
Day(s)/duration:
4 weeks
Route:
other: epicutaneous
Vehicle:
other: see Remark
Remarks:
Dimethyl phthalate (DMP)
Concentration / amount:
8% and 80% in DMP
Day(s)/duration:
24 and 48 hrs
No. of animals per dose:
10
Details on study design:
RANGE FINDING TESTS: No sensitisation was observed at 10, 21, 42, or 83% (w/v) when tested in 3 guinea pigs per concentration.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 4
- Exposure period: 4 weeks
- Test groups: 1, 80% and an 8% suspension of the test material in the primary irritation test on same animal
- Control group: yes, no treatment
- Site: sacral intradermal injection
- Frequency of applications: 1 each week beginning 2 days after the test for primary irritation
- Duration: 4 weeks
- Concentrations: 0.1 ml of a 1.0% suspension in DMP,

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 2 days
- Exposure period: 24 hours and 48 hours
- Test groups: 1, 80% and an 8% suspension of the test material on same animal
- Control group: yes, At the same time 10 unexposed guinea pigs (controls) of the same age received identical topical applications.
- Site: shaved, intact shoulder skin.
- Concentrations: 0.05 ml of an 80% and an 8% suspension of test material in DMP
- Evaluation (hr after challenge): 24 hours and 48 hours
Challenge controls:
At the same time 10 unexposed guinea pigs (controls) of the same age received identical topical applications (0.05 ml of an 80% and an 8% suspension of test material in DMP).
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
all
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
all
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
no indication of skin sensitisation

The test substance caused no irritation on shaved intact skin of 10 guinea pigs at 24 or 48 hours in both the primary irritation test and in the sensitization challenge. None of the test guinea pigs showed a sensitization response.

Interpretation of results:
GHS criteria not met
Remarks:
not sensitizing
Conclusions:
Not sensitising

This study and the conclusions which are drawn from it fulfill the quality criteria (validity, reliability, repeatability).
Executive summary:

The primary irritation test was conducted on 10 unexposed guinea pigs by applying and lightly rubbing in 0.05 mL of an 80% and an 8% suspension of the test material in DMP on shaved, intact shoulder skin. The induction phase began 2 days after the primary irritation test and continued for 4 weeks, one injection each week. After a 13-day rest period, the test guinea pigs were challenged for sensitization by applying and lightly rubbing in 0.05 mL of an 80% and an 8% suspension of test material in DMP on shaved, intact shoulder skin. The test substance caused no irritation on shaved intact skin of 10 guinea pigs at 24 or 48 hours. None of the test guinea pigs showed a sensitization response.

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The data provided in conjunction with that of report HL-511-80 provide a weight of evidence for the hazard endpoint that is sufficient for the purpose of classification and labelling and/or risk assessment. This study is used for read-across and therefore has been assigned a reliability of 2 (reliable with restrictions). Otherwise the study has a reliability of 1 (reliable without restriction).
Justification for type of information:
see 13.2 for attached read across rationale
Reason / purpose for cross-reference:
read-across source
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
no
Remarks:
The study was conducted according to the guideline in effect.
Qualifier:
according to guideline
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Remarks:
The study was conducted according to the guideline in effect.
GLP compliance:
yes
Type of study:
mouse local lymph node assay (LLNA)
Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: CBA/JHsd mice were received from Harlan Sprague Dawley, Frederick, Maryland, U.S.A.
- Age at study initiation: approximately 12 weeks old
- Weight at study initiation: weighed between 21.8 and 27.0 grams.
- Housing: solid bottom cages
- Diet: PMI® Nutrition International, LLC Certified Rodent LabDiet® 5002 ad libitum
- Water: tap water ad libitum
- Acclimation period: for 8 days.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-26ºC
- Humidity (%): 30-70%.
- Photoperiod (hrs dark / hrs light): approximate 12-hour light/dark cycle

Vehicle:
dimethylformamide
Concentration:
0, 5, 10, 25 and 50%
No. of animals per dose:
5
Details on study design:
ANIMAL ASSIGNMENT AND TREATMENT
- Criteria used to consider a positive response: A stimulation index (SI) was derived for each experimental group by dividing the mean dpm of each experimental group by the mean dpm of the vehicle control group. The decision process in regard to a positive response includes an SI of greater than or equal to 3.0 together with consideration of dose response and, where appropriate, statistical significance. When possible, an EC3 value for the SI data was derived from linear interpolation of points on the dose-response curve immediately above and below the 3-fold threshold.

TREATMENT PREPARATION AND ADMINISTRATION: At the request of the sponsor, methacrylonitrile (MAN) was added to the test substance to achieve a concentration of 0.2% MAN based on the amount of test substance in each dose level. Twenty-five μL of vehicle control, test substance preparation, or positive control were administered topically to the dorsum of each mouse ear for 3 consecutive days (test days 0-2) at concentrations of 0, 5, 10, 25 and 50%. Test days 3-4 were days of rest followed by intravenous injection of 20 μCi of ³H-thymidine in PBS per mouse on test day 5.
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
see below
Positive control results:
A 25% concentration of the positive control, HCA, produced a dermal sensitization response in mice.
Parameter:
SI
Remarks on result:
other: Stimulation index was 1.55, 1.38, 1.88, and 1.52 at 5, 10, 25, and 50%, respectively.
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: Mean DPM was 312.90, 484.50, 432.50, 588.90, and 474.30 at 0, 5, 10, 25, and 50%, respectively.

One mouse, 302, was found dead on test day 5 and underwent a gross pathology examination. No treatment-related abnormalities were observed. The death of the mouse was not considered treatment related, no deaths occurred at higher concentrations, and no clinical signs were observed at any concentration.

 

 

 

MEAN

(dpm)

S.D.

(dpm)

SI

GROUP

MATERIAL TESTED

n

1

0% Vehicle Control

5

312.90

142.87

N/A

2

5%

5

 

484.50

243.28

1.55

3

10%

4

432.50

319.32

1.38

4

25%

5

588.90

326.79

1.88

5

50%

5

474.30

207.57

1.52

6

25% Positive Control

5

3520.30

1010.82

11.25

No statistically significant increases in cell proliferation measurements compared to the vehicle control group were observed at any test concentration. SIs of less than 3.0 were observed at all test concentrations of the test substance. Therefore, the EC3 value (the estimated concentration required to induce a threshold positive response, i.e., SI = 3) for the test substance under the conditions of this study was not calculable. A 25% concentration of the positive control, HCA, produced a dermal sensitization response in mice. Therefore, the LLNA test system was valid for this study.

Interpretation of results:
GHS criteria not met
Remarks:
Criteria used for interpretation of results: EU
Conclusions:
Not sensitising

This study and the conclusions which are drawn from it fulfill the quality criteria (validity, reliability, repeatability).
Executive summary:

The objective of this study was to evaluate the potential of the test substance to produce a dermal sensitization response in mice using the local lymph node assay (LLNA). Five groups of 5 female CBA/JHsd mice were dosed for 3 consecutive days with 0% (vehicle control), 5%, 10%, 25%, or 50% of the test substance on both ears. On test day 5 of the assay, mice received ³H-thymidine by tail vein injection and were sacrificed approximately 5 hours later. The cell proliferation in the draining auricular lymph nodes of the ears from the test substance groups was then evaluated and compared to the vehicle control group.

No test substance-related changes in body weights were observed at any test concentration. No clinical signs of toxicity were observed in the study. One mouse was found dead on test day 5 and underwent a gross pathology examination. No treatment-related abnormalities were observed. The death of the mouse was not considered treatment related, no deaths occurred at higher concentrations, and no clinical signs were observed at any concentration.

No statistically significant increases in cell proliferation measurements compared to the vehicle control group were observed at any test concentration. Stimulation indices (SIs) of less than 3.0 were observed at all test concentrations. Therefore, the EC3 value (the estimated concentration required to induce a threshold positive response, i.e., SI = 3) for the test substance under the conditions of this study was not calculable. A 25% concentration of the positive control, HCA, produced a dermal sensitization response in mice. Therefore, the LLNA test system was valid for this study. Under the conditions of this study, the test substance did not produce a dermal sensitization response in mice. Based on these data, it is not a dermal sensitizer in mice.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

A maximization test in guinea pigs revealed that the test substance did not produce skin sensitization in laboratory animals. In addition, mouse local lymph node assay data is available for the read across chemical, 2,2’-azobis(isobutyronitrile). The underlying hypothesis for the read-across between the test substance and 2,2’-azobis(isobutyronitrile is that the postulated reaction scheme is driven by the azo functionality that is present in both substances. Additional documentation, provided within the IUCLID Assessment Reports section, supports the read-across approach. In the OECD guideline, GLP study, no cutaneous reactions were observed after the challenge application, while the control animals showed a satisfactory sensitization response in 75% of the animals using the positive sensitizer. Taken together the weight of evidence of these two studies support the conclusion that the test substance is not considered a skin sensitizer.


Justification for selection of skin sensitisation endpoint:
In addition to the guinea pig study with the test substance, a mouse local lymph node assay with the read across chemical, 2,2’-azobis(iosbutyronitrile) was selected to fulfill a weight of evidence approach for this endpoint.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

The test substance did not produce skin sensitization in laboratory animals, and the read across chemical, 2,2’-azobis(isobutyronitrile), did not produce a sensitization response in the mouse local lymph node assay. Based on the weight of evidence provided, the test substance does not need to be classified for sensitization according the EU Directive 67/548/EEC and EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.