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Toxicological information

Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Terephthalaldehyde
EC Number:
210-784-8
EC Name:
Terephthalaldehyde
Cas Number:
623-27-8
Molecular formula:
C8H6O2
IUPAC Name:
benzene-1,4-dicarbaldehyde
Test material form:
solid: particulate/powder
Specific details on test material used for the study:
Batch (Lot) Number: 180401
Expiry date: 01 April 2020 (retest date)
Physical Description: Light yellow powder
Purity/Composition: 99.6%
Storage Conditions: At room temperature

In vitro test system

Test system:
human skin model
Source species:
human
Cell type:
non-transformed keratinocytes
Cell source:
foreskin from a single donor
Source strain:
not specified
Justification for test system used:
In the interest of sound science and animal welfare, a sequential testing strategy is recommended to minimize the need of in vivo testing. One of the validated in vitro skin irritation tests is the EPISKIN test, which is recommended in international guidelines (e.g. OECD and EC).
Vehicle:
unchanged (no vehicle)
Details on test system:
EPISKIN Small ModelTM (EPISKIN-SMTM, 0.38 cm2, Batch no.: 18 EKIN 039)

This model is a three-dimensional human epidermis model, which consists of adult human-derived epidermal keratinocytes which have been seeded on a dermal substitute consisting of a collagen type I matrix coated with type IV collagen.
The keratinocytes were cultured for 13 days, which results in a highly differentiated and stratified epidermis model comprising the main basal, supra basal, spinous and granular layers and a functional stratum corneum.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
yes, concurrent MTT non-specific colour control
Amount/concentration applied:
16.3 to 18.2 mg per tissue
Duration of treatment / exposure:
15 ± 0.5 minutes at room temperature
Duration of post-treatment incubation (if applicable):
42 hours at 37°C
Number of replicates:
3 (three)

Results and discussion

In vitro

Results
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
1
Value:
ca. 98
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation

Any other information on results incl. tables

Terephthaldehyde was checked for possible direct MTT reduction and color interference in the Skin corrosion test using EpiDerm as a skin model (Test Facility Study No. 20152366). Because no color changes were observed it was concluded that Terephthaldehyde did not interact with the MTT endpoint. 

The mean absorption at 570 nm measured after treatment with Terephthaldehyde and controls are presented inAppendix 1,Table1.

The individual OD570measurements are presented inAppendix 2.

Table2shows the mean tissue viability obtained after 15 ± 0.5 minutes treatment with Terephthaldehyde compared to the negative control tissues. Skin irritation is expressed as the remaining cell viability after exposure to the test item. The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with Terephthaldehyde compared to the negative control tissues was 98%. Since the mean relative tissue viability for Terephthaldehyde was above 50% Terephthaldehyde is considered to be non-irritant.

The positive control had a mean cell viability after 15 ± 0.5 minutes exposure of 32%. The absolute mean OD570of the negative control tissues was within the laboratory historical control data range (SeeAppendix 3). The standard deviation value of the percentage viability of three tissues treated identically was ≤ 14%, indicating that the test system functioned properly.

Table1          
Mean Absorption in theIn VitroSkin Irritation Test with Terephthaldehyde

 

A

(OD570)

B

(OD570)

C

(OD570)

Mean

(OD570)

 

SD

Negative control

0.963

0.925

1.034

0.974

±

0.055

Terephthaldehyde

0.966

0.886

1.019

0.957

±

0.067

Positive control

0.184

0.310

0.449

0.314

±

0.132

OD = optical density

SD = Standard deviation

Triplicate exposures are indicated by A, B and C.

In this table the values are corrected for background absorption (0.043). Isopropanol was used to measure the background absorption.

 

Table2          
Mean Tissue Viability in the In Vitro Skin Irritation Test with Terephthaldehyde

 

Mean tissue viability (percentage of control)

Standard deviation (percentage)

Negative control

100

5.7

Terephthaldehyde

98

6.9

Positive control

32

14


 OD measurements/ tissue

 

A

(OD570)

B

(OD570)

C

(OD570)

Negative control

OD570measurement 1

OD570measurement 2

1.0090

1.0020

0.9765

0.9579

1.0830

1.0697

Terephthaldehyde

OD570measurement 1

OD570measurement 2

1.0062

1.0101

0.9393

0.9184

1.0664

1.0574

Positive control

OD570measurement 1

OD570measurement 2

0.2247

0.2284

0.3537

0.3511

0.4913

0.4909

OD = Optical density

Triplicate exposures are indicated by A, B and C.

HIstorical control data

 

Negative control

(absorption; OD570)

Positive control

(absorption; OD570)

Range

0.422 – 1.547

0.023 – 0.437

Mean

0.98

0.13

SD

0.18

0.08

n

174

173

SD = Standard deviation

n = Number of observations

The above mentioned historical control data range of the controls were obtained by collecting all data over the period of November 2014 to November 2017.


 

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
In conclusion, Terephthaldehyde is non-irritant in the in vitro skin irritation test under the experimental conditions described in this report.
Executive summary:

The objective of this study was to evaluate Terephthaldehyde for its ability to induce skin irritation on a human three dimensional epidermal model (EPISKIN Small model (EPISKIN-SMTM)). The possible skin irritation potential of Terephthaldehyde was tested through topical application for 15 minutes.

The study procedures described in this report were based on the most recent OECD and EC guidelines.

Batch 180401 of Terephthaldehyde was a light yellow powder. Skin tissue was moistened with 5 µL of Milli-Q water and at least 10 mg of Terephthaldehyde was applied directly on top of the skin tissue for 15 ± 0.5 minutes. After a 42 hour post-incubation period, determination of the cytotoxic (irritancy) effect was performed. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from MTT at the end of the treatment.

Skin irritation is expressed as the remaining cell viability after exposure to the test item. The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with Terephthaldehyde compared to the negative control tissues was 98%. Since the mean relative tissue viability for Terephthaldehyde was above 50% after 15 ± 0.5 minutes treatment Terephthaldehyde is considered to be non-irritant.

The positive control had a mean cell viability of 32% after 15 ± 0.5 minutes exposure. The absolute mean OD570(optical density at 570 nm) of the negative control tissues was within the laboratory historical control data range. The standard deviation value of the percentage viability of three tissues treated identically was ≤ 14%, indicating that the test system functioned properly.

In conclusion, Terephthaldehyde is non-irritant in the in vitro skin irritation test under the experimental conditions described in this report.