OO-tert-butyl O-(2-ethylhexyl) peroxycarbonate

Endpoint summary

Description of key information

Skin sensitisation

GPMT

The delayed contact hypersensivity of TBEC has been evaluated in a GPMT (Manciaux, 1999). The induction phase was realized both by intradermal route on day 1, at the concentration of 10 % in corn oil, and by cutaneous route on day 8 (undiluted) in 2 groups of guinea pigs: 5 males and 5 females for control group and 10 males and 10 females for treated group. The challenge phase was realized on day 22 by cutaneous application of TBEC (100% in corn oil); the cutaneous reactions were scored 24 and 48 hours after the challenge phase. Following equivocal reactions, a second challenge application was performed at a concentration of 50% in corn oil after a rest period of 10 days, and skin samples were examined. The cutaneous reactions observed in the animals of the treated group after both challenge applications were of similar incidence and severity when compared to those recorded in the animals of the control group; they were attributed to irritant properties of the test substance but not to delayed contact hypersensitivity. This was supported by the fact that most of the observed cutaneous reactions decreased between the 24-hour reading and the 48-hour reading and by the absence of any observed edema. Histological examinations confirmed that TBEC was not sensitizing to guinea pig skin. In conclusion, under these experimental conditions, TBEC is considered as non-sensitizing in the Guinea Pigs Maximalisation Test.

 

QSAR assessment

The allergic contact dermatitis potential of TBEC in guinea pig and human was evaluated via the Danish QSAR database using MultiCASE Ultra, Leadscope Enterprise and SciMatics SciQSAR versions of commercial CASE Ultra model A33. No indication of skin sensitisation was reported, TBEC being inside the applicability domain of each model.

 

The presence of structural alert of skin sensitisation in the molecular structure of TBEC was evaluated with Toxtree (Version 2.6.13). The alerts for skin sensitization capture electrophilic mechanistic information and include “Michael-type addition reaction”, “Schiff base formation”, “acylation”, “nucleophilic aromatic substitution” (SNAr) and “second order nucleophilic aliphatic substitution” (SN2). The final alert “Reactivity domain alert” is true if any other alert is true. No skin sensitisation reactivity domains alerts were identified for TBEC.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The study was performed before the implementation of the REACH regulation

Species:

guinea pig

Strain:

Hartley

Sex:

male/female

Details on test animals and environmental conditions:

The choice of the vehicle was based on tests to check the homogeneity (visual check) of the preparation (for cutaneous application and intradermal injections) and its free passage through a needle (for intradermal injections). The highest concentrations which satisfied these criteria were called the maximal practicable concentrations.The vehicle used was corn oil.

Strain and sanitary status: Hartley Crl: (HA) BR, Caesarian obtained, Barrier sustained - Virus; Antibody Free (COBS- VAF@)
Reason for this choice: species generally accepted by regulatory authorities for this type of study. The strain used has been shown to produce a satisfactory sensitization response using known positive sensitizers.
Breeder: Charles River France, 76410 Saint-Aubin-lès-Elbeuf, France.
Main test: 30 animals (15 males and 15 females) for the main test. Females were nulliparous and non-pregnant.
Weight: on day 1, the animals of the main test were approximately 3 months old and had a mean body weight ±standard deviation of 358 ± 10 g for the males and 362 ± 14 g for the females. Acclimatization: at least 5 days before the beginning of the study.
Identification of the animals: ear-tattoo.

Environmental conditions:
. temperature: 21 ± 2°C
. relative humidity: 30 to 70%
. light/dark cycle: 12 h/12 h
. ventilation: approximately 12 cycles/hour of filtered, non-recycled air.

Food and water ad libitum. No contaminants were known to have been present in the diet, drinking water or bedding material at levels which may be expected to have interfered with or prejudiced the outcome of the study.

Route:

intradermal

Vehicle:

corn oil

Concentration / amount:

10%

Day(s)/duration:

D1

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

0.5 ml

Day(s)/duration:

D8

Adequacy of induction:

non-irritant substance, but skin pre-treated with 10% SDS

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

0.5 mL

Day(s)/duration:

D22

Adequacy of challenge:

highest non-irritant concentration

No.:

#2

Route:

epicutaneous, occlusive

Vehicle:

corn oil

Concentration / amount:

50%

Day(s)/duration:

D33

No. of animals per dose:

5 males and 5 females
Control group : 10 males and 10 females

Details on study design:

RANGE FINDING TESTS:
Preliminary test: one male and one female.
By intradermal route:
24 hours before treatment, the dorsal region of the animals was clipped,
intradermal administrations of the test substance formulation (0.1 ml) at different concentrations were performed in the interscapular region, cutaneous reactions were evaluated approximately 24, 48 hours and 6 days after the injections
By cutaneous route:
24 hours before treatment, both flank regions of the animals were clipped, a volume of 0.5 ml of the undiluted test substance or test substance formulation at the chosen concentration(s) was placed on a dry gauze pad (approximately 4 cm2 which was then applied to the skin and held in place by an occlusive dressing for 24 hours, cutaneous reactions were evaluated approximately 24 and 48 hours after removal of the dressings


MAIN STUDY


Induction by intradermal route:
Three injections of 0.1 ml were made into each side of this interscapular region (i.e. three pairs of sites), as follows:

Injection sites Treated group Control group

Anterior 1: FCA diluted at 50% (v/v) with 0.9% NaCl 1: FCA diluted at 50% (v/v) with 0.9% NaCl

Middle 2: test substance at 10% (w/w) in corn oil 2: vehicle

Posterior* 3: test substance at 10% (w/w) in a mixture FCA /0.9% NaCI 50/50 (v/v) 3: vehicle at 50% (w/w) in a mixture FCA /0.9% NaCl
50150 (v/v)

Induction by topical administration:
As the test substance was shown to be non-irritant during the preliminary test, the animals were treated at day 7 with 0.5 ml of sodium lauryl sulfate at the concentration of 10% (w/w) in vaseline, in order to induce local irritation.
Duration exposure for topical application: 48 hours, occlusive dressing

Challenge:
Topical application, duration exposure: 24 hours, occusive dressing

Positive control substance(s):

yes

Remarks:

DNCB (CIT/Study No. 17335 TSG) - September 1998

Positive control results:

According to the Magnusson and Kligman method, the test substance DNCB at the concentration of 1 % (w/w) induced positive skin sensitization
reactions in 90% guinea-pigs.

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

100 %

No. with + reactions:

5

Total no. in group:

10

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

100 %

No. with + reactions:

4

Total no. in group:

10

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

100 %

No. with + reactions:

12

Total no. in group:

20

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

100 %

No. with + reactions:

6

Total no. in group:

20

Reading:

rechallenge

Hours after challenge:

24

Group:

negative control

Dose level:

50 %

No. with + reactions:

4

Total no. in group:

10

Reading:

rechallenge

Hours after challenge:

48

Group:

negative control

Dose level:

50 %

No. with + reactions:

4

Total no. in group:

10

Reading:

rechallenge

Hours after challenge:

24

Group:

test chemical

Dose level:

50 %

No. with + reactions:

13

Total no. in group:

20

Reading:

rechallenge

Hours after challenge:

48

Group:

test chemical

Dose level:

50 %

No. with + reactions:

5

Total no. in group:

20

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

1%

No. with + reactions:

9

Total no. in group:

10

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

1%

No. with + reactions:

7

Total no. in group:

10

Remarks on result:

positive indication of skin sensitisation

Interpretation of results:

GHS criteria not met

Conclusions:

TBEC was considered as non-sensitizing in the Guinea Pigs Maximalisation Test.

Executive summary:

The delayed contact hypersensivity of TBEC was evaluated in Guinea pigs according to OECD N°406 guideline (July 17^th1992 - Magnusson and Kligman test). The induction phase has been realized both by intradermal route on day 1, at the concentration of 10 % in corn oil

and by cutaneous route on day 8 (undiluted) in 2 groups of guinea pigs: 5 males and 5 females for control group and 10 males and 10 females for treated group. The challenge phase was realized on day 22 by cutaneous application of TBEC (50% in corn oil); the cutaneous reactions were scored 24 and 48 hours after the challenge phase. As equivocal cutaneous reactions were noted, a second challenge application was perforrned under the same experimental conditions after a rest period of 10 days, except that the test substance and the vehicle were applied to the left and right flanks, respectively. At the end of the study, animals were killed and skin samples were taken from the challenge application sites of all the animals showing skin reactions. An histological examination was performed on the preserved tissue samples. After the first challenge application, at the 24-hour reading, a very slight erythema was observed in 4/10 animals of the control group and in 8/20 animals of the treated group. A well-defined erythema was noted in 1/10 animals of the control group and in 4/20 animals of the treated group. Most of these cutaneous reactions, associated with dryness of the skin, persisted at the 48-hour reading. A well-defined erythema was also recorded on the left control flank of 1/20 animals of the treated group.After the second challenge application, at the 24-hour reading, a very slight erythema was still observed in 3/10 animals of the control group and in 8/20 animals of the treated group. A well-defined erythema was noted in 1/10 animals of the control group (but was already noted before the second challenge application) and in 5/20 animals of the treated group. A few cutaneous reactions, associated with dryness of the skin, persisted at the 48-hour reading. As the cutaneous reactions observed in the animals of the treated group after both challenge applications were of similar incidence and severity when compared to those recorded in the animals of the control group, they were attributed to irritant properties of the test substance but not to delayed contact hypersensitivity. This was supported by the fact that most of the observed cutaneous reactions decreased between the 24-hour reading and the 48-hour reading and by the absence of any observed oedema. Histhological examinations confirmed that TBEC was not sensitizing to guinea pig skin. In conclusion, under these experimental conditions, TBEC was considered as non-sensitizing in the Guinea Pigs Maximalisation Test.

Reference 2

Endpoint:

skin sensitisation: in chemico

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Guideline:

other: Chapter R.6: QSARs and grouping of chemicals

Principles of method if other than guideline:

MultiCASE CASE Ultra commercial model A33 for allergic contact dermatitis (ACD) in guinea pig and human (MultiCASE CASE Ultra 1.4.6.6 64-bit)
Leadscope Enterprise version of commercial CASE Ultra model A33 for allergic contact dermatitis (ACD) in guinea pig and human (Leadscope Predictive Data Miner, a component of Leadscope Enterprise version 3.1.1-10.)
SciMatics SciQSAR version of commercial CASE Ultra model A33 for allergic contact dermatitis (ACD) in guinea pig and human (SciQSAR version 3.1.00.)

Specific details on test material used for the study:

Smiles: C(C)(C)(C)OOC(=O)OCC(CCCC)CC

Parameter:

other: Battery of QSAR models

Remarks on result:

no indication of skin sensitisation

Remarks:

inside applicability domain

Parameter:

other: Leadscope

Remarks on result:

no indication of skin sensitisation

Remarks:

inside applicability domain

Parameter:

other: SciQSAR

Remarks on result:

no indication of skin sensitisation

Remarks:

inside applicability domain

Parameter:

other: CASE Ultra

Remarks on result:

no indication of skin sensitisation

Remarks:

outside applicability domain

Interpretation of results:

other: Negative

Reference 3

Endpoint:

skin sensitisation: in chemico

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
Toxtree (Estimation of Toxic Hazard - A Decision Tree Approach)

2. MODEL (incl. version number)
Version 2.6.13

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
SMILES: C1CCSC1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: Skinsensitisation
- Unambiguous algorithm: see attached rules
- Defined domain of applicability: rules were developed for the identification of mechanisms of toxic action for skin sensitisation using a SMARTS pattern based approach
- Appropriate measures of goodness-of-fit and robustness and predictivity: not relevant
- Mechanistic interpretation: according to the rules and decision tree of the specific end-point

5. APPLICABILITY DOMAIN
- Descriptor domain: Defined by the rules
- Structural and mechanistic domains: Defined by the rules
- Similarity with analogues in the training set: not relevant

6. ADEQUACY OF THE RESULT
The estimation is coherent with the available in vivo data

Qualifier:

according to guideline

Guideline:

other: REACH guidance. Chapter R.6: QSARs and grouping of chemicals

Version / remarks:

May 2008

Principles of method if other than guideline:

Toxtree (Version 2.6.13) alerts for skin sensitization capture electrophilic mechanistic information and include “Michael-type addition reaction”, “Schiff base formation”,“acylation”, “nucleophilic aromatic substitution” (SNAr) and “second order nucleophilic aliphatic substitution” (SN2). The final alert “Reactivity domain alert” is true if any other alert is true.

Details on the study design:

Identification of mechanisms of toxic action for skin sensitisation using a SMARTS pattern based approach.
Available since ToxTree 2.1.0 (under name "Skin sensitisation alerts" and "Skin sensitisation alerts (M.Cronin)"). The name is changed to "Skin sensitisation reactivity domain" by P&G team suggestion in order to reflect the fact the alerts provide grouping into reactivity mode of action and do not predict skin sensitisation potential.

Parameter:

other: Toxtree

Remarks on result:

no indication of skin sensitisation

Skin sensitisation alerts (M. Cronin)	Alert for SNAr Identified.: NO Alert for Schiff base formation identified.: NO Alert for Michael Acceptor identified.: NO Alert for Acyl Transfer agent identified.: NO Alert for SN2 identified.: NO No skin sensitisation reactivity domains alerts identified.: YES
Protein binding	Alert for SNAr Identified.: NO Alert for Schiff base formation identified.: NO Alert for Michael Acceptor identified.: NO Alert for Acyl Transfer agent identified.: NO Alert for SN2 identified.: NO No protein binding alerts identified.: YES
Michael acceptors	Not reactive via Michael addition

 

Interpretation of results:

other: negative

Executive summary:

The presence of structural alert in the molecular structure of TBEC was evaluated with Toxtree (Version 2.6.13). The alerts for skin sensitization capture electrophilic mechanistic information and include “Michael-type addition reaction”, “Schiff base formation”,“acylation”, “nucleophilic aromatic substitution” (SNAr) and “second order nucleophilic aliphatic substitution” (SN2). The final alert “Reactivity domain alert” is true if any other alert is true. No skin sensitisation reactivity domains alerts were identified for tetrahydrothiophene.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

According to EU Regulation (EC) N0. 1272/2008 (CLP), TBEC is not classified for skin sensitization.