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Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
From 02 May, 2005 to 04 October, 2005
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was well conducted in accordance with OECD 406 and US EPA OPPTS 870.2600 guidelines as well as in compliance with GLP.
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes
Type of study:
Buehler test
Species:
guinea pig
Strain:
Hartley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Elm Hill Breeding Labs, Chelmsford, MA, USA
- Age at study initiation: Young adult animals
- Weight at study initiation: 327-399 g
- Housing: The animals were group housed in suspended stainless steel caging with mesh floors or plastic perforated bottom caging which conform to the size recommendations according to ‘Guide for the care and use of laboratory animals DHEW (NIH). Litter paper was placed beneath the cage and was changed at least three times/wk.
- Diet: Pelleted Purina guinea pig chow # 5025, ad libitum
- Water: Filtered tap water, ad libitum
- Acclimation period: 3-17 d

ENVIRONMENTAL CONDITIONS
- Temperature: 19-22°C
- Humidity: 31-58%
- Photoperiod (hrs dark / hrs light): 12-h light/dark cycle

IN-LIFE DATES: From: May 2, 2005 To: June 10, 2005
Route:
epicutaneous, occlusive
Vehicle:
water
Concentration / amount:
Induction: 1% w/w mixture of the test substance in distilled water (0.4 mL)
Challenge: 0.25% w/w mixture of the test substance in distilled water (0.4 mL)
Route:
epicutaneous, occlusive
Vehicle:
water
Concentration / amount:
Induction: 1% w/w mixture of the test substance in distilled water (0.4 mL)
Challenge: 0.25% w/w mixture of the test substance in distilled water (0.4 mL)
No. of animals per dose:
20 animals in the test substance group and 10 animals in the control group
Details on study design:
RANGE FINDING TESTS: A preliminary irritation study was performed to determine the highest non-irritating concentration. 8 guinea pigs (5 males and 3 females) were exposed for 6 h period to various concentrations of the test substance as follows: 100, 75, 50, 25, 1.25, 1.0, 0.75, 0.25 and 0.10%.w/w in distilled water. The fur was removed by clipping the dorsal area and flanks of each guinea pig. The area was divided into two or four test sites on each animal. Two to four concentrations of the test substance were applied to the sites. 0.4 mL of each concentration was applied to a test site using a 25 mm Hill Top Chamber. The test sites were wrapped with non-allergenic adhesive tape. All animals were evaluated at approximately 24 hours, 2 days and one animal on Day 5. Each site was evaluated for erythema.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 3
- Exposure period: 6 h
- Test groups: One test group, including 20 guinea pigs
- Control group: No control animals were employed in induction phase
- Site: Left side of each animal
- Frequency of applications: Once a week for three consecutive weeks
- Duration: 6 h/application
- Concentrations: 1 % w/w mixture of the test substance in distilled water (0.4 mL)
- Procedure for application: Once a week for three weeks, 0.4 mL of a 1% w/w mixture of the test substance in distilled water was applied to the left side of each animal. Due to residual irritation from the previous doses, the dose site was moved each induction. Approximately 24 and 48 h after each induction exposure, the skin was evaluated for local reactions (erythema).

B. CHALLENGE EXPOSURE
- No. of exposures: One
- Day(s) of challenge: Twenty-seven days after the first induction dose
- Exposure period: 6 h
- Test groups: One test group (20 animals) exposed with 0.25% w/w mixture of the test substance in distilled water
- Control group: One naive control group (10 animals) exposed with 0.25% w/w mixture of the test substance in distilled water
- Site: The test substance was applied to a naïve site on the right side of each test animal.
- Concentrations: 0.25% w/w mixture of the test substance in distilled water
- Evaluation (hr after challenge): These sites were evaluated for a sensitisation response approximately 24 and 48 h after the challenge exposure.

OTHER: Historical Positive Control Validation Study: The procedures used in this study were validated using alpha-Hexylcinnamaldehyde Technical (HCA) grade as a positive control substance. A positive control validation study is run at no less than six months intervals at the testing laboratory. The results from the most recent positive control validation study performed on March 2005 are provided in the study report.
Challenge controls:
10 naive animals exposed with 0.25% w/w mixture of the test substance in distilled water
Positive control substance(s):
yes
Remarks:
alpha-Hexylcinnamaldehyde
Positive control results:
Induction: Very faint to faint erythema (0.5-1.0) was noted for all of the positive control sites during the induction phase.
Challenge: Four of nine positive control animals exhibited signs of skin sensitisation response 24 and 48 h after exposure. Very faint erythema was observed for four other sites after challenge. Very faint erythema was observed in three of five positive control naive test sites after 24 h. Irritation persisted at one of these sites through 48 h.

Reading:
1st reading
Hours after challenge:
24
Group:
test group
Dose level:
0.25% w/w mixture of the test substance in distilled water
No. with + reactions:
0
Total no. in group:
20
Clinical observations:
No animals with positive response
Remarks on result:
other: see Remark
Remarks:
Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 0.25% w/w mixture of the test substance in distilled water. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: No animals with positive response .
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
0.25% w/w mixture of the test substance in distilled water
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No animals with positive response
Remarks on result:
other: see Remark
Remarks:
Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 0.25% w/w mixture of the test substance in distilled water. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No animals with positive response .
Reading:
2nd reading
Hours after challenge:
48
Group:
test group
Dose level:
0.25% w/w mixture of the test substance in distilled water
No. with + reactions:
0
Total no. in group:
20
Clinical observations:
No animals with positive response
Remarks on result:
other: see Remark
Remarks:
Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 0.25% w/w mixture of the test substance in distilled water. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: No animals with positive response .
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
0.25% w/w mixture of the test substance in distilled water
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No animals with positive response
Remarks on result:
other: see Remark
Remarks:
Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 0.25% w/w mixture of the test substance in distilled water. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No animals with positive response .

Summary of results in the main study:

Induction Phase: Very faint to faint erythema (0.5-1.0) was observed for all sites during the induction phase.

Challenge Phase: 

Test group -None of the test animals exhibited a positive skin sensitisation response (score greater than 0.5) at 24 or 48 h after challenge. Very faint erythema (0.5) was noted in 9 out of 20 test animals at 24 h after challenge. Similar irritation persisted at two sites through 48 h.

Naive Control group - Very faint erythema (0.5) was observed in 5 out of 10 test animals at 24 h after challenge. Similar irritation persisted at two sites through 48 h.

Table. The severity index of test and control group

Treatment

Severity

24 h

48 h

Test

0.23

0.05

Control

0.25

0.10

Interpretation of results:
not sensitising
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
Under the study conditions, the test substance was determined to be non-sensitising in a Buehler test when applied topically to albino Hartley guinea pigs.
Executive summary:

A study was performed to assess the skin sensitisation potential of the read-across substance C12-16 ADBAC using the modified Draize technique. For the induction phase, 0.1 mL of 0.1% test substance in water was injected intradermally into the back of each six guinea pigs. This procedure was repeated every other day, using a different injection site on each occasion, until a total of nine injections had been given. Injection sites were examined 24 hours after each injection and scored for erythema and oedema using the Draize scale. After a two week interval, a single challenge intradermal injection of the same concentration and volume was given as for induction. Injection sites were examined 24 hours after this challenge dose as before for erythema and oedema. The effects were compared to those produced by the priming doses in order to determine whether sensitisation had been produced. The priming injections elicited very slight to well defined erythema, and very slight to slight oedema on all occasions. The challenge dose produced a well-defined erythema and very slight oedema in all occasions. As the challenge doses did not produce any greater reaction in any animal, the substance was not considered to be skin sensitizing under the conditions of the study (Thomas MB, 1974).

A guideline compliant study was conducted to assess the skin sensitisation potential of C12-16 ADBAC in a Buehler test. The study was conducted in two phases, induction and challenge exposure. To determine the highest non-irritating concentration (HNIC) for the challenge phase, a preliminary irritation study was performed with 8 guinea pigs. The concentrations used were 100, 75, 50, 25, 1.25, 1.0, 0.75, 0.25 and 0.10%. w/w in distilled water. After treatment, the application sites were evaluated and scored. During the induction phase of the main study, 0.4 mL of a 1% w/w mixture of the test substance in distilled water was applied to the left side of each animal, once per week for three weeks. Twenty-seven days after the first induction dose, 0.4 mL of a 0.25% w/w (HNIC) mixture of the test substance in distilled water was applied to a naïve site on the right side of each test animal for challenge exposure. Ten additional animals exposed with 0.25% w/w mixture of the test substance in distilled water served as naive control group in the challenge phase only. Approximately 24 and 48 h after each induction and challenge dose, the animals were scored for erythema. Very faint to faint erythema (0.5 to 1) was observed in all test animals during induction. None of the test animals exhibited a positive skin sensitisation response (score greater than 0.5) at 24 or 48 hours after challenge. Based on the above results, C12-16 ADBAC was determined to be non-sensitising in the Buehler test in albino Hartley guinea pigs (Durando J, 2005).

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

Skin sensitisation

A guideline compliant study was conducted to assess the skin sensitisation potential of the read-across substance C12-C16 ADBAC in a Buehler test. The study was conducted in two phases, induction and challenge exposure. To determine the highest non-irritating concentration (HNIC) for the challenge phase, a preliminary irritation study was performed with 8 guinea pigs. The concentrations used were 100, 75, 50, 25, 1.25, 1.0, 0.75, 0.25 and 0.10%. w/w in distilled water. After treatment, the application sites were evaluated and scored. During the induction phase of the main study, 0.4 mL of a 1% w/w mixture of the test substance in distilled water was applied to the left side of each animal, once per week for three weeks. Twenty-seven days after the first induction dose, 0.4 mL of a 0.25% w/w (HNIC) mixture of the test substance in distilled water was applied to a naïve site on the right side of each test animal for challenge exposure. Ten additional animals exposed with 0.25% w/w mixture of the test substance in distilled water served as naive control group in the challenge phase only. Approximately 24 and 48 h after each induction and challenge dose, the animals were scored for erythema. Very faint to faint erythema (0.5 to 1) was observed in all test animals during induction. None of the test animals exhibited a positive skin sensitisation response (score greater than 0.5) at 24 or 48 hours after challenge. Based on the above results, C12-C16 ADBAC was determined to be non-sensitising in the Buehler test in albino Hartley guinea pigs (Durando J, 2005).

 

A study was performed to assess the skin sensitisation potential of the read-across substance C12-C16 ADBAC using the modified Draize technique. For the induction phase, 0.1 mL of 0.1% test substance in water was injected intradermally into the back of each six guinea pigs. This procedure was repeated every other day, using a different injection site on each occasion, until a total of nine injections had been given. Injection sites were examined 24 hours after each injection and scored for erythema and oedema using the Draize scale. After a two week interval, a single challenge intradermal injection of the same concentration and volume was given as for induction. Injection sites were examined 24 hours after this challenge dose as before for erythema and oedema. The effects were compared to those produced by the priming doses in order to determine whether sensitisation had been produced. The priming injections elicited very slight to well defined erythema, and very slight to slight oedema on all occasions. The challenge dose produced a well-defined erythema and very slight oedema in all occasions. As the challenge doses did not produce any greater reaction in any animal, the substance was not considered to be skin sensitizing under the conditions of the study (Thomas MB, 1974).


Migrated from Short description of key information:
The available in vivo skin sensitisation studies suggest that the read-across substance C12-16 ADBAC is not a skin sensitiser. C12-14 ADBAC is also not expected to be a skin sensitiser based on the adopted read-across approach.

Justification for selection of skin sensitisation endpoint:
Most recent and robust study conducted according to guidelines.

Respiratory sensitisation

Link to relevant study records
Reference
Endpoint:
respiratory sensitisation
Data waiving:
other justification
Justification for data waiving:
other:
Endpoint conclusion
Endpoint conclusion:
no study available
Additional information:

As respiratory sensitisers also elicit positive results in predictive tests for contact sensitisation, a negative outcome for dermal sensitisation is also predictive for the respiratory pathway. Furthermore, the substance is a sticky solid with a low vapour pressure. Due to it physical state and physico-chemical properties, it is unlikely that it will form inhalable dust, mist or fumes when handled and used in solid form. In case inhalable forms of the substance (either pure or in aqueous solutions) are created under particular conditions (e.g., spraying, elevated temperature/pressure), appropriate risk management measures such as closed systems, exhaust ventilation or wearing of respirators are implemented to control exposure. Under such conditions, the risk to humans following inhalation exposure can be considered minimal and further testing involving vertebrate animals may be omitted, in accordance with Annex XI (1.2) of the REACH regulation.

Justification for classification or non-classification

The available in vivo skin sensitisation studies suggest that the read-across substance C12-16 ADBAC is not a skin sensitizer. C12-14 ADBAC is also not expected to be a skin sensitiser based on the adopted read-across approach. Therefore no classification is required for this endpoint according to DSD (67/548/EEC) and CLP (EC 1272/2008) criteria.