Benzyltoluene

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

2012-08-22 - 2012-10-18

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The GLP study was conducted according to an internationally accepted guideline. All study parameters are given in detail.Nevertheless, according to the ECHA's practical guide 6: "How to report read-across and categories" the maximum for read-cross is 2.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

(phenylethyl)benzene

EC Number:

254-179-7

EC Name:

(phenylethyl)benzene

Cas Number:

38888-98-1

Molecular formula:

C14H14

IUPAC Name:

1,1'-ethane-1,1-diyldibenzene

Test material form:

other: liquid

Details on test material:

Name: (phenylethyl)benzene

Appearance: colourless liquid
Composition: 99.68% 1,1 Diphenyiethane, 0.16% Diphenylmethane
CAS No.: 38888-98-1
EINECS-No.: 254-179-7
Molecular formula: C14H-14
Molecular weight: 182.3 g/mol
Purity: 99.68% 1,1 Diphenyiethane

Test animals

Species:

other: not applicable, human skin model

Strain:

other: not applicable, human skin model

Test system

Type of coverage:

other: not applicable, human skin model

Preparation of test site:

other: not applicable, human skin model

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

30 µl per tissue

Duration of treatment / exposure:

60 minutes

Details on study design:

P re-Tests

First, it was tested whether the test item develops a colour without MTT addition. 30pL were given in a test tube with 0.3 mL H20 demin. and incubated at 37 °C and 5 % C02 for 60 minutes. The resulting solution was colourless, therefore no binding capacity had to be tested.

Then, the test item (phenylethyi)benzene was tested for the ability of direct formazan reduction. To test for this ability, 30 pL were added to 1 mL of MTT solution and the mixture was incubated in the dark at 37 °C and 5 % CO2 for 60 minutes. Untreated MTT solution was used as control. The MTT solution didn't change its colour within one hour, therefore, direct MTT reduction had not taken place, and no data correction was necessary. Finally, (phenylethyl)benzene was tested for possible reaction with the nylon mesh which is used to ensure sufficient contact with the tissue surface. 30 |jL (phenylethyl)benzene were brought onto a nylon mesh on a microscope slide. No reaction with the mesh was visible after 1 h incubation at 37 °C.

Pre-lncubation of Tissues

Eight 6-well-plates were prepared with 0.9 mL assay medium in three of the six wells (upper row). The tissues were inspected for viability. Viable tissues were transferred (three per plate) in the wells with the medium using sterile forceps under the laminar air flow bank and placed into the incubator at 37 °C and 5% CO2 for one hour.

After the pre-incubation (one hour), the other three wells of each plate (lower row) were filled with fresh assay medium (0.9 mL). Every tissue was transferred into a well of the lower row. All 6-well-plates were set into the incubator at 37 °C and 5 % C02 for for 18 hours.

Treatment

The pre-incubated tissues were placed into fresh 6-weil-piates containing 0,9 mL assay medium per well, using the upper row only.

One plate (three tissues) was used as negative control; each tissue was treated with 30 pL DPBS buffer. One plate was used as positive control; each tissue was treated with 30 pL SDS-solution. One plate was used for treatment with the test item. 30 pL test item were applied, and a nylon mesh was added in order to ensure sufficient contact with the tissue surface.


MTT Assay
After a total incubation time of 42 hours, a 24-well-plate was prepared with 300 pL freshly prepared MTT-reagent in each well. The tissues were blotted on the bottom and then transferred into the 24-well-plate. Then the 24-well-plate was set into the incubator for 3 hours.
After this time, the MTT reagent was aspirated and replaced by PBS buffer. This was then aspirated, too, and replaced several times. At last, each insert was thoroughly dried and set into the empty, pre-warmed 24-well-plate. Into each well, 2 mL isopropanol were pipet¬ted, taking care to reach the upper rim of the insert. The plate was then shaked for two hours room temperature.
After two hours, the inserts in which formazan had been produced were pierced with an injection needle, taking care that all colour was extracted. The inserts were then discarded and the content of each well was thoroughly mixed in order to achieve homogenisation.
From each well, two replicates with 200 pL solution (each) were pipetted into a 96-well- plate which was read in a plate spectral photometer at 570 nm.

Skin irritation potential of the test item is assessed as given in the following table:
% Formazan production Assessment
< 50% of negative control Irritant
> 50% of negative control Non-irritant

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

other: other: % Formazan production Mean

Value:

33.8

Remarks on result:

other:

Remarks:

Basis: mean. Time point: 60 min. Max. score: 0.0. Reversibility: no data. (migrated information)

Any other information on results incl. tables

%Formazan Production

Designation	(phenylethyl)benzene	Positive Control
% Formazan production (Tissue 1)	38.0 %	8.2 %
% Formazan production (Tissue 2)	34.0 %	7.7 %
% Formazan production (Tissue 3)	29.6 %	7.8 %
% Formazan production Mean	33.8 %	7.9 %

Applicant's summary and conclusion

Interpretation of results:

irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test item (phenylethyl)benzene is considered irritant.

Executive summary:

Three tissues of the human skin mode! EpiDerm™were treated with (phenylethyl)benzene for 60 minutes.

30 µL of the liquid test item (using a nylon mesh) were applied to each tissue and spread to match the tissue size (0.63 cm²; as indicated by supplier).

DPBS-buffer was used as negative control, 5% SDS-solution was used as positive control.

After treatment with the negative control, the absorbance values were within the required acceptability criterion of 1.0 < mean OD < 2.5. The positive control showed clear irritating effects. Variation within tissues was acceptable (<18 %).

After the treatment with the test item, the relative absorbance values were reduced to 33.8 %. This value is well below the threshold for irritation potential (50 %). Therefore, (phenylethyl)benzene is considered as "irritant in the Human Skin Model Test".