Methyl p-toluate

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: well performed OECD study with GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2014

Report date:

2014

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

Methyl p-toluate

EC Number:

202-784-1

EC Name:

Methyl p-toluate

Cas Number:

99-75-2

Molecular formula:

C9H10O2

IUPAC Name:

methyl 4-methylbenzoate

Details on test material:

purity: 97.8%
expiry date: 2015-10-15

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River UK Ltd
- Age at study initiation: 9 - 11 weeks
- Weight at study initiation: 15.86 g - 20.92 g
- Housing: individually, in solid floor standard polysulfone cages (Size: Approximately L 360 x B 205 x H 140 mm)
- Diet: Ssniff mice pellet food – Ssniff Spezialdiäten GmbH., Ferdinand-Gabriel-Weg 16, D-59494 Soest, Germany (ad libitum)
- Water: deep bore-well water passed through activated charcoal filter and exposed to UV rays (ad libitum)
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 22
- Humidity (%): 64 - 65
- Air changes (per hr): 13.4
- Photoperiod: 12 hrs dark / 12 hrs light

Study design: in vivo (LLNA)

Vehicle:

dimethylformamide

Concentration:

0, 10, 25, 75 %

No. of animals per dose:

6

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Results and discussion

Positive control results:

25% α – Hexylcinnamaldehyde (HCA) in DMF SI = 7.43+-1.15

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Remarks on result:

other: see above

Results 2

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: see Remark

Remarks:

Group and Dose concentration No. of mice DPM/Mouse SI G1 vehicle DMF 6 554+-90 1.00+-0.26 G2 25% HCA in DMF 6 4116+-640 7.43+-1.15 G3 10% substance in DMF 6 1096+-166 1.98+-0.30 G4 25% substance in DMF 6 2180+-562 3.93+-1.01 G5 75% substance in DMF 6 3023+-521 5.45+-0.94

Any other information on results incl. tables

  EC₃calculation:

                       EC₃  = X_L+ [(3-Y_L)/ (Y_h-Y_L)](X_h-X_L)

                Where, Y_L = SI value below 3

                             X_L = chemical concentration that elicits Y_L

                               Y_h =  SI value above 3

                             X_h = chemical concentration that elicits Y_h

_{EC3 value for the substance is 17.85%}

Applicant's summary and conclusion

Interpretation of results:

sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test item demonstrated skin sensitization potential in the mouse LLNA, as the lymph nodes draining the area of topical application elicit a proliferative response greater than the threshold (SI ≥ 3, i.e. 3-fold greater proliferation than vehicle control).

Executive summary:

The substance was tested for skin sensitisation according to OECD guideline 429 (Local lymph node assay, LLNA) in DMF.

In a sceening study the vehicle- N,N-dimethylformamide (DMF), 5, 10, 25, 50 and 75% w/v of the substance in DMF were applied to one animal at each dose level for 3 days. There were no clinical signs, no erythema at the site of application, no significant increase in the ear thickness and ear punch weights and no effect on body weight.

In the LLNA main study six female CBA/Ca mice/group received the vehicle  (DMF) or 25% α-hexylcinnamaldehyde (HCA: positive control in DMF) or  10, 25 and 75%w/v test item in DMF on days 1 to 3. On day 6, uptake of³H-methyl thymidine into the auricular lymph nodes draining the site of test item application was measured approximately five hours post administration. Proper conduct of the LLNA was confirmed via a positive response using 25% α-hexylcinnamaldehyde, a contact sensitizer, which elicited proliferation with a Mean Stimulation Index (SI) value of 7.43, in comparison to vehicle-treated mice.

There were no clinical signs, no local skin reactions,no significant increase in  % ear thickness and ear punch weight at the tested concentrations and treatment had no significant effect on body weight gain.

The test item at dose concentrations of 10, 25 and 75% w/v elicited proliferative response with SI of 1.98, 3.93 and 5.45, respectively in comparison with the vehicle-treated mice. The EC₃value was 17.85%.