Methyl 2-naphthyl ether

Endpoint summary

Description of key information

The skin sensitization potential of test chemical was assessed in various experimental studies conducted on guinea pigs. Based on the available data for the target and supporting studies, it can be concluded that the test chemical is unable to cause skin sensitization and thus can be considered as not sensitizing. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Not Classified”.

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

Data is from peer reviewed journals

Qualifier:

according to guideline

Guideline:

other: as mentioned below

Principles of method if other than guideline:

An Open Epicutaneous Test (OET) was performed on guinea pigs to assess the skin sensitization potential of test chemical

GLP compliance:

no

Type of study:

open epicutaneous test

Justification for non-LLNA method:

Currently no LLNA study is available for assessment. The Guinea Pig Maximization Test (GPMT) has been carried out as an animal test to predict human sensitization for over a decade and is recommended by international test guidelines such as OECD.

Species:

guinea pig

Strain:

not specified

Sex:

male/female

Details on test animals and environmental conditions:

- Weight at study initiation: 300-450g

Route:

epicutaneous, open

Vehicle:

other: ethanol, acetone, H20, petroleum, PEG and/or other suitable vehicles

Concentration / amount:

Concentration:4%
Amount: 0.1ml

Day(s)/duration:

3 weeks (0-21 days)

Adequacy of induction:

not specified

No.:

#1

Route:

epicutaneous, open

Vehicle:

other: ethanol, acetone, H20, petroleum, PEG and/or other suitable vehicles

Concentration / amount:

4% - 0.025 ml

Day(s)/duration:

72 hours

Adequacy of challenge:

not specified

No. of animals per dose:

6–8 male and female guinea pigs

Details on study design:

RANGE FINDING TESTS: The Pretest was performed to establish the primary irritating threshold concentration of test substance. For this, a single application of 0.025 ml of each test concentration (e.g, 100, 30, 10 and 3%) is simultaneously performed on one of the areas measuring 2 cm2 of the flank skin previously clipped and marked with a circular stamp. Reactions are read 24 h after the application of the test material. On the basis of preliminary study, the maximal non-irritating concentration selected was 4%. Thus the sensitization test was conducted at a dose of 4% of test chemical.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 21
- Exposure period:24 hours
- Test groups:6-8 guinea pigs
- Control group:3 guinea pigs
- Site: an area measuring 8 cm2 on the clipped flank skin of the guinea pigs
- Frequency of applications: The applications are repeated daily for 3 weeks or done 5 times weekly during 4 weeks
- Duration: 21 days (3 weeks)
- Concentrations: 4% in vehicle.
Amount: 0.1ml

B. CHALLENGE EXPOSURE
- No. of exposures: 2
- Day(s) of challenge: on days 21 and 35
- Exposure period:24 hours
- Test groups: 6-8 guinea pigs
- Control group: 3 guinea pigs
- Site: contralateral flank measuring 2 cm2
- Concentrations: Concentration:4%
Amount: 0.025ml
- Evaluation (hr after challenge): 24,48 and/or 72h.

Challenge controls:

The 10 controls were either left untreated or treated with 0.1 ml aliquot of the vehicle for 21 days

Reading:

1st reading

Hours after challenge:

72

Group:

test chemical

Dose level:

4%

No. with + reactions:

0

Total no. in group:

6

Clinical observations:

no signs of dermal sensitization pbserved

Remarks on result:

no indication of skin sensitisation

Interpretation of results:

other: Not sensitizing

Conclusions:

The test chemical was considered to be not sensitizing on skin of guinea pigs at concentration of 4% in an Open Epicutaneous Test (OET).

Executive summary:

An Open Epicutaneous Test (OET) was performed on guinea pigs to assess the skin sensitization potential of test chemical. The Pretest was performed to establish the primary irritating threshold concentration of test substance. For this, a single application of 0.025 ml of each test concentration (e.g, 100, 30, 10 and 3%) is simultaneously performed on one of the areas measuring 2 cm2 of the flank skin previously clipped and marked with a circular stamp. Reactions are read 24 h after the application of the test material. On the basis of preliminary study, the maximal non-irritating concentration selected was 4%. Thus the sensitization test was conducted at a dose of 4% of test chemical. On day 1 during induction, 0.1 ml of test chemical was applied at concentrations of 4% in vehicle to an area measuring 8 cm2 on the clipped flank skin of the guinea pigs. The applications are repeated daily for 3 weeks or done 5 times weekly during 4 weeks, usually on the same skin sites. The application sites were left uncovered and the reactions, if continuous daily applications were performed, can be read 24 h after each application, or at the end of each week. To determine whether or not contact sensitization was induced, all groups of guinea pigs previously treated for 21 days, as well as 10 untreated, or only pretreated with the vehicle, controls are tested on days 21 and 35 on the contralateral flank with the test material. This test was performed by applying with a pipette 0.025 ml of each concentration to skin areas measuring 2 cm2. The reactions were read after 24, 48 and/or 72h. It was observed that none of the guinea pigs induced contact sensitization at challenge concentration of 4%.Thus, the test chemical was considered to be not sensitizing on skin of guinea pigs at concentration of 4% in an Open Epicutaneous Test (OET).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Various studies has been investigated for the test chemical and its structurally similar read across substances to observe the potential for skin sensitization of test chemical to a greater or lesser extent. The studies are based on in vivo experiments in guinea pigs and humans.The predicted data using the Danish QSAR database has also been compared with the experimental data and summarized as below;

 

An Open Epicutaneous Test (OET) was performed on guinea pigs to assess the skin sensitization potential of test chemical. The Pretest was performed to establish the primary irritating threshold concentration of test substance. For this, a single application of 0.025 ml of each test concentration (e.g, 100, 30, 10 and 3%) is simultaneously performed on one of the areas measuring 2 cm2 of the flank skin previously clipped and marked with a circular stamp. Reactions are read 24 h after the application of the test material. On the basis of preliminary study, the maximal non-irritating concentration selected was 4%. Thus the sensitization test was conducted at a dose of 4% of test chemical. On day 1 during induction, 0.1 ml of test chemical was applied at concentrations of 4% in vehicle to an area measuring 8 cm2 on the clipped flank skin of the guinea pigs. The applications are repeated daily for 3 weeks or done 5 times weekly during 4 weeks, usually on the same skin sites. The application sites were left uncovered and the reactions, if continuous daily applications were performed, can be read 24 h after each application, or at the end of each week. To determine whether or not contact sensitization was induced, all groups of guinea pigs previously treated for 21 days, as well as 10 untreated, or only pretreated with the vehicle, controls are tested on days 21 and 35 on the contralateral flank with the test material. This test was performed by applying with a pipette 0.025 ml of each concentration to skin areas measuring 2 cm2. The reactions were read after 24, 48 and/or 72h. It was observed that none of the guinea pigs induced contact sensitization at challenge concentration of 4%.Thus, the test chemical was considered to be not sensitizing on skin of guinea pigs at concentration of 4% in an Open Epicutaneous Test (OET).

 

The skin sensitization study was conducted for test chemical to assess its possible contact allergenic potential. For this purpose Human maximization test was performed, using a test material at the concentration of 4% in petrolatum. The test was conducted on 26 human. No skin sensitization effects were observed in any of 25 human volunteers. Therefore the test material was considered to be non-sensitizing to human skin.

 

According to Danish QSAR database, skin sensitization effects were estimated by using four different models i.e, Battery, Leadscope, SciQSAR and CASE Ultra for test chemical. Based on estimation, no Allergic Contact Dermatitis effects were observed when test chemical was exposed to human and guinea pig skin. Hence, the test chemical can be considered as not sensitizing to skin.

 

The above results were further supported by an Open Epicutaneous Test (OET) performed on guinea pigs to assess the skin sensitization potential of similar read across chemical. On day 1 during induction, 0.1 ml of the Ethyl 2-naphthyl ether was applied at concentrations of 100%, 30%, 10%, 3%, 1%, or 0.3% in vehicle to an area measuring 8 cm2 on the clipped flank skin of the guinea pigs. The applications are repeated daily for 3 weeks or done 5 times weekly during 4 weeks, usually on the same skin sites. The application sites were left uncovered and the reactions, if continuous daily applications were performed, can be read 24 h after each application, or at the end of each week. To determine whether or not contact sensitization was induced, all groups of guinea pigs previously treated for 21 days, as well as 10 untreated, or only pretreated with the vehicle, controls are tested on days 21 and 35 on the contralateral flank with the test material. This test was performed by applying with a pipette 0.025 ml of each concentration to skin areas measuring 2 cm2. The reactions were read after 24,48 and/or 72h. It was observed that none of the guinea pigs induced contact sensitization at challenge concentration of 2%.Thus the test chemical was considered to be not sensitizing on skin of guinea pigs at concentration of 2% in an Open Epicutaneous Test (OET).

 

The overall results were further supported by the Human maximization test was carried out in 25 volunteers for another similar read across chemical. Each subject was treated with 4% of test chemical in petrolatum dermally and later observed for any signs of contact allergy. None of the volunteer showed any signs of contact sensitization. Hence the chemical was considered to be not sensitizing to the skin of human volunteers.

 

All these studies lead to a conclusion that test chemical is indeed not sensitizing to skin. Hence, comparing the above annotations with the criteria of CLP regulation, test chemical can be classified under the category “Not Classified”.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

The skin sensitization potential of test substance and its structurally similar read across substances were observed in various studies. From the results obtained from these studies it is concluded that the chemical is not likely to cause skin sensitization and hence can be classified as non-skin sensitizer.