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Description of key information

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study in accordance with OECD TG 406
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:
guinea pig maximisation test
Species:
guinea pig
Strain:
Hartley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Hilltop Lab Animals, Inc., Scottdale, PA
- Age at study initiation: males: 8 weeks, females: 9 weeks
- Weight at study initiation: males: 424 - 500 g, females: 385 - 474 g
- Housing: individually in suspended stainless steel cages
- Diet (e.g. ad libitum): PMI Certified Guinea Pig Chow #5026 (Purina Mills, Inc.) ad libitum
- Water (e.g. ad libitum): municipal tap water treated by reverse osmosis ad libitum
- Acclimation period: acclimated to the laboratory conditions for a minimum of five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20- 24
- Humidity (%): 42 - 55
- Air changes (per hr): 10 - 15
- Photoperiod (hrs dark / hrs light): 12/12
Route:
intradermal and epicutaneous
Vehicle:
unchanged (no vehicle)
Concentration / amount:
Day 0, intradermal induction: 5%
Day 7, topical induction: 100%
Day 20, challenge: 100%
Route:
other:
Vehicle:
unchanged (no vehicle)
Concentration / amount:
Day 0, intradermal induction: 5%
Day 7, topical induction: 100%
Day 20, challenge: 100%
No. of animals per dose:
Test group: 10 males, 10 females
Control group: 5 males, 5 females
Details on study design:
RANGE FINDING TESTS:
- Topical range-finding study: The results of the range-finding study indicated that a test article concentration of 100% (as received) was appropriate for topical induction and challenge. This was the highest possible concentration which did not produce any significant skin irritation.
- Interdermal range-finding study: The results of the range-finding study indicated that a test article concentration of 5.0% w/v in deionised water was appropriate for intradermal induction since mild skin irritation was observed at this concentration. While there were some unexpectedely high range-finding scores at the lower concentrations, these differences were not sufficient to warrant dosing at a lower concentration.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2
- Exposure period: 48 h (topical induction)
- Test groups: Intradermal induction: 0.1 mL of FCA emulsion, 0.1 mL of 5.0% w/v EXP 3982 N-2-hydroxyethylurea/deionised water, 0.1 mL of 5.0% w/v EXP 3982 N-2-hydroxyethylurea/FCA emulsion. Topical application: 0.8 mL pure test material
- Control group: Intradermal induction: 0.1 mL of FCA emulsion, 0.1 mL of deionized water, 0.1 mL of 5.0% w/v deionized water/FCA emulsion.
- Site: scapular area
- Frequency of applications: interdermal induction on day 0, topical induction on day 6
- Duration: topical application: 48 h
- Concentrations: 5% for intradermal induction, 100% for topical induction

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 1
- Exposure period: 24 h
- Test groups: 0.3 mL pure test substance
- Control group: 0.3 mL pure test substance
- Site: scapular area
- Concentrations: pure test substance
- Evaluation (hr after challenge): 24 and 48
Positive control substance(s):
yes
Remarks:
alpha-Hexylcinnamaldehyde
Positive control results:
Using alpha-Hexylcinnamaldehyde (HCA) as a positive control, Springborn Laboratories, Inc., Spencerville, Ohio, had completed a study dwhich provided historical control data for contact sensitisation to this agent utilising the test system described herein (Maximisation Design). Following intradermal induction at 5.0% w/v HCA in propylene glycol, topical induction at 5.0% w/v HCA in propylene glycol and challenge at 0.5% and 1% w/v HCA in propylene glycol, a contact sensitisation response was observed, thereby demonstrating the susceptibility of the test system to this sensitising agent.
Reading:
1st reading
Hours after challenge:
24
Group:
test group
Dose level:
0.3 mL
No. with + reactions:
1
Total no. in group:
20
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 0.3 mL. No with. + reactions: 1.0. Total no. in groups: 20.0.
Reading:
2nd reading
Hours after challenge:
48
Group:
test group
Dose level:
0.3 mL
No. with + reactions:
0
Total no. in group:
20
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 0.3 mL. No with. + reactions: 0.0. Total no. in groups: 20.0.
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
0.3 mL
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 0.3 mL. No with. + reactions: 0.0. Total no. in groups: 10.0.
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
0.3 mL
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 0.3 mL. No with. + reactions: 0.0. Total no. in groups: 10.0.

Noticeable irritation outside of test site was observed in the test group and the negative control group probably due to the binding tape material. The reactions do not interfere with the scoring of the test site.

Interpretation of results:
not sensitising
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
Based on the results of this study, EXP 3982 N-2-hydroxyethylurea is not considered to be a contact sensitizer in guinea pigs.
Executive summary:

The dermal sensitisation potential of EXP 3982 N-2-hydroxyethylurea containing 57.58% of the active ingredient hydroxyethyl urea was evaluated under GLP in Hartley-derived albino guinea pigs according to OECD TG 406. Ten male and ten female guinea pigs received intradermal injections of 5.0% w/v EXP 3982 N-2-hydroxyethylurea in deionised water along with injections of FCA and 5.0% w/v EXP 3982 N-2-hydroxyethylurea in FCA. One week later, the test animals received a topical application of 100% (as received) EXP 3982 N-2-hydroxyethylurea. Challenge and rechallenge control animals received similar intradermal and topical treatments with deionised water that was used in place of the test article.

Following a two-week rest period, a challenge was performed whereby the twenty test and ten challenge control guinea pigs were topically treated with 100% (as received) EXP 3982 N-2-hydroxyethylurea. Challenge responses in the test animals were compared with those of the challenge control animals. Following challenge with 100% (as received) EXP 3982 N-2-hydroxyethylurea, dermal scores were limited to 0 in the test and challenge control animals at the 24- and 48-hour scoring intervals with the exception of one ± at 24 hours. Group mean dermal scores were noted to be 0.0 in both the test and challenge control animals.

Using alpha-Hexylcinnamaldehyde (HCA) as a positive control, Springborn Laboratories, Inc., Spencerville, Ohio, had completed a study which provided historical control data for contact sensitisation to this agent utilising the test system described herein (Maximisation Design). Following intradermal induction at 5.0% w/v HCA in propylene glycol, topical induction at 5.0% wlv HCA in propylene glycol and challenge at 0.5% and 1% w/v HCA in propylene glycol, a contact sensitisation response was observed, thereby demonstrating the susceptibility of the test system to this sensitising agent.

Based on the results of this study, EXP 3982 N-2-hydroxyethylurea is not considered to be a contact sensitizer in guinea pigs. The results of the HCA positive historical control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitizers. Hydroxyethyl urea is therefore not classified as a skin sensitiser by GHS criteria.

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

There is a Klimisch 1, GLP compliant guinea pig maximization (Magnusson and Kligman) study to OECD406 on a 57.58% solution of hydroxyethyl urea in water (EXP3982). The intradermal induction dose was 5% of the neat solution with the epicutaneous induction and subsequent challenge doses using the neat 57.58% solution. Only one guinea pig showed a slight skin response and then only at the 24 hour challenge dose and then not at the 48 hour challenge. A true skin sensitizing chemical would have been expected to show a response at both 24 and 48 hours, therefore in the absence of any other responses in the 20 test guinea pigs it is concluded that the study showed no evidence for skin sensitization potential.


Migrated from Short description of key information:
There is a high quality Guinea pig maximization study on a 57.58% solution of hydroxyethyl urea in water (EXP 3982) carried out to OECD406 (Magnusson and Kligman). This study did not show any indication of skin sensitization.

Justification for selection of skin sensitisation endpoint:
There is a Klimisch 1, GLP compliant guinea pig maximization (Magnusson and Kligman) study to OECD406 on a 57.58% solution of hydroxyethyl urea in water (EXP3982). The intradermal induction dose was 5% of the neat solution with the epicutaneous induction and subsequent challenge doses using the neat 57.58% solution.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available
Additional information:

There is no standard validated animal test available to detect respiratory sensitisers. All respiratory sensitisers of human significance are also skin sensitisers, however not all skin sensitisers are respiratory sensitisers.    Hydroxyethyl urea has been shown to not have skin sensitisation potential and there is no known human evidence that hydroxyethyl urea is a respiratory sensitiser. The testing was of 57.58% solution of hydroxyethyl urea in water (EXP3982). This concentration is considered sufficiently high that any potential for skin sensitization would be expected to have been detected. Therefore hydroxyethyl urea is not considered to be a respiratory sensitiser.


Migrated from Short description of key information:
There is no standard validated animal test available to detect respiratory sensitisers. Hydroxyethyl urea has been shown in a guinea pig maximization test to have no skin sensitisation potential. Therefore it is not expected to be a respiratory sensitiser.

Justification for selection of respiratory sensitisation endpoint:
There is no standard validated animal test available to detect respiratory sensitisers. All respiratory sensitisers of human significance are also skin sensitisers, however not all skin sensitisers are respiratory sensitisers. Hydroxyethyl urea has been shown to not have skin sensitisation potential and there is no known evidence that hydroxyethyl urea is a respiratory sensitiser.

Justification for classification or non-classification

Hydroxyethyl urea did not show any potential for skin sensitisation in Guinea pig maximization (Magnusson and Kligman) test, when tested as a 57.58% solution in water (EXP3982). This concentration is consideredsufficiently high that any potential for skin sensitization would be expected to have been detected. There is no known evidence from human experience of respiratory sensitisation associated with exposure to hydroxyethyl urea. Therefore there is no requirement to classify hydroxyethyl urea as either a skin or respiratory sensitiser against the EU CLP or global GHS criteria.