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Administrative data

Description of key information

Skin irritation (OECD 439): irritating
Eye irritation (Code of Federal Regulations, Title 16, Section 1500.42): corrosive

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records
Reference
Endpoint:
skin irritation / corrosion
Remarks:
other: in vitro
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-02-13 to 2012-02-17
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study.
Qualifier:
according to
Guideline:
other: EU Method b.46 (Skin Irritation)
Deviations:
no
Qualifier:
according to
Guideline:
other: OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, München, Germany
Species:
human
Strain:
other: EpiDerm reconstructed human epidermis model (MatTek Corp.)
Details on test animals and environmental conditions:
organotypic reconstructed three-dimensional model of the human epidermis
Type of coverage:
other: in vitro system; direct application
Preparation of test site:
other: intact reconstructed human epidermis
Vehicle:
other: DPBS (Dulbecco's Phosphate Buffered Saline)
Controls:
other: Concurrent control tissues treated with the vehicle served as negative controls, positive controls were exposed to 5% SDS.
Amount / concentration applied:
25 mg test substance in 25 µL DPBS
Duration of treatment / exposure:
60 ± 1 min
Observation period:
Not applicable. Post-treatment incubation period: 42 ± 4 h
Number of animals:
Not applicable. The test was performed in triplicates for each treatment and control group.
Details on study design:
3 replicate tissues are dosed with the test item, the negative control (DPBS) and the positive control (5% SDS), respectively. The tissues are incubated for 35 ± 1 minutes in a humidified incubator (37 ± 1 °C, 5 ± 1% CO2, 95% RH) and further 25 minutes at room temperature. Then the test item and the controls are rinsed off with DPBS and the tissues are post-incubated for 24 ± 2 h and, after medium renewal, for further 18 ± 2 h. Then the tissues are stained via MTT for 3 hours. Isopropanol extracts are measured photometrically at 550 nm.
Irritation parameter:
other: cell viability (%)
Basis:
other: mean value of negative controls (DPBS)
Time point:
other: 60 min
Score:
100
Reversibility:
other: not applicable
Irritation parameter:
other: cell viability (% of negative control)
Basis:
other: mean value of positive controls (5% SDS)
Time point:
other: 60 min
Score:
2.2
Reversibility:
other: not applicable
Irritation parameter:
other: cell viability (% of negative control)
Basis:
other: mean value of test substance
Time point:
other: 60 min
Score:
6.2
Reversibility:
other: not applicable
Other effects:
The test item showed no direct MTT reducing capability and no colouring potential.

Name

Negative Control

Positive Control

Test Item

Tissue

1

2

3

1

2

3

1

2

3

corrected OD550

2.171

2.167

2.186

0.052

0.048

0.044

0.094

0.172

0.132

2.111

2.203

2.114

0.050

0.046

0.048

0.099

0.176

0.134

mean corrected OD550
of the duplicates

2.141

2.185

2.150

0.051

0.047

0.046

0.097

0.174

0.133

mean corrected OD550
of 3 replicate tissues

2.159*

0.048

0.134

mean SD OD550

0.038

0.003

0.035

tissue viability [%]

99.2

101.2

99.6

2.4

2.2

2.1

4.5

8.1

6.2

SD tissue viability [%]***

1.1

0.1

1.8

CV [% viability]

1.1

5.5

28.7

mean tissue viability [%]

100.0

2.2**

6.2

*       Corrected mean OD550 of the negative control corresponds to 100% absolute tissue viability.

**      mean relative tissue viability of the three positive control tissues is  20%

***    standard deviation (SD) obtained from the three concurrently tested tissues is < 18%

Interpretation of results:
irritating
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
CLP: Skin Irrit. 2, H315
DSD: Xi, R38
Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Eye irritation

Link to relevant study records
Reference
Endpoint:
eye irritation: in vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions. Not performed according to GLP. No analytical purity.
Qualifier:
according to
Guideline:
other: Code of Federal Regulations, Title 16, Section 1500.42
Deviations:
no
GLP compliance:
no
Species:
rabbit
Strain:
New Zealand White
Details on test animals or tissues and environmental conditions:
TEST ANIMALS
- Source: Lippische Versuchstierzucht, Extertal, Germany
- Weight at study initiation: average of 2.1 kg
- Housing: Animals were housed individually.
- Diet: mümmel z, ssniff, Soest, Germany, ad libitum
- Water: ad libitum
- Acclimation period: 7 - 14 d

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16 - 18
- Humidity (%): 40
- Photoperiod (hrs dark / hrs light): 12/12
Vehicle:
unchanged (no vehicle)
Controls:
other: Not required, the untreated eye of each animal served as control.
Amount / concentration applied:
TEST MATERIAL
- Amount(s) applied: 100 µL (bulk volume)
Duration of treatment / exposure:
single application without washing
Observation period (in vivo):
8 d
reading time points: 24, 48 and 72 h
Number of animals or in vitro replicates:
6 males
Details on study design:
SCORING SYSTEM: Draize scoring system
Irritation parameter:
cornea opacity score
Basis:
mean
Remarks:
out of all 6 animals
Time point:
other: mean over 24, 48 and 72 h
Score:
0.89
Max. score:
4
Reversibility:
not fully reversible within: 8 d in 2 animals
Remarks on result:
other: fully reversible in 2 animals each within 48 h and 72 h, respectively
Irritation parameter:
iris score
Basis:
mean
Remarks:
out of all 6 animals
Time point:
other: mean over 24, 48 and 72 h
Score:
0.83
Max. score:
2
Reversibility:
not fully reversible within: 8 d in 3 animals
Remarks on result:
other: fully reversible within 48 h in 2 animals and within 8 d in 1 animal
Irritation parameter:
conjunctivae score
Basis:
mean
Remarks:
out of all 6 animals
Time point:
other: mean over 24, 48 and 72 h
Score:
2.17
Max. score:
3
Reversibility:
not fully reversible within: 8 d in 3 animals
Remarks on result:
other: fully reversible within 8 d in 3 animals
Irritation parameter:
chemosis score
Basis:
mean
Remarks:
out of all 6 animals
Time point:
other: mean over 24, 48 and 72 h
Score:
1.33
Max. score:
4
Reversibility:
not fully reversible within: 8 d in 2 animals
Remarks on result:
other: fully reversible within 8 d in 4 animals

Table 1. Results of eye irritation study.

Rabbit #

Time

conjunctivae

iris

cornea

redness

swelling

1

24 h

2

1

1

2

48 h

2

1

1

2

72 h

2

1

1

1

8 d

1

0

1

1

average

2,0

1,0

1,0

1,7

2

24 h

2

1

0

1

48 h

2

1

1

0

72 h

2

1

1

0

8 d

0

0

0

0

average

2,0

1,0

0,7

0,3

3

24 h

2

1

1

1

48 h

2

1

1

1

72 h

2

1

1

0

8 d

2

1

1

0

average

2,0

1,0

1,0

0,7

4

24 h

2

1

1

1

48 h

2

1

1

1

72 h

2

1

0

0

8 d

0

0

0

0

average

2,0

1,0

0,7

0,7

5

24 h

2

1

1

1

48 h

2

1

1

0

72 h

2

1

0

0

8 d

0

0

0

0

average

2,0

1,0

0,7

0,3

6

24 h

3

3

1

1

48 h

3

3

1

2

72 h

3

3

1

2

8 d

1

1

1

1

average

3,0

3,0

1,0

1,7

 

 

Time

conjunctivae

iris

cornea

redness

swelling

 

24 h

2,17

1,33

0,83

1,17

48 h

2,17

1,33

1,00

1,00

72 h

2,17

1,33

0,67

0,50

24+48+72

2,17

1,33

0,83

0,89

After the 8 d-observation period, the effects on cornea and the swelling of conjunctivae were not fully reversible in 2 animals and the effects on iris and the redness of the conjunctivae were not fully reversible in 3 animals.

Interpretation of results:
corrosive
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
CLP: Eye dam. 1, H318
DSD: Xi, R41
Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Skin irritation

Three studies are available addressing skin irritation and corrosion.

In a in vitro study, sodium methylparaben was investigated in a reconstructed human epidermis model (EpiDerm™) for skin corrosion according to OECD 431 and GLP (Lehmeier, 2012a). The tissues were exposed with 25 mg of the test substance in distilled water for 3 and 60 min.

Afterwards, the tissues were stained with MTT solution for 3 h. The estimation of tissue viability based on the reduction of MTT to a blue formazan product. A test substance has to be classified as skin corrosive if the mean tissue viability after 3 min is < 50% and after 60 min is < 15% relative to the respective mean negative control value. Tissue treatment with the test substance for 3 or 60 min resulted in mean tissue viabilities of 59% and 26%, respectively. The positive control substance (8 N KOH) led to tissue viabilities of 27% and 23% after 3 and 60 min incubation time, respectively.

Under the test conditions, the test substance was not considered to be skin corrosive.

In a second in vitro study, sodium methylparaben was investigated in a reconstructed human epidermis model (EpiDerm™) for skin irritation according to OECD 439 and GLP (Lehmeier, 2012b). The tissues were exposed with 25 mg of the test substance in phosphate buffered saline for 60 min. After a post-treatment period of 42 h, the tissues were stained with MTT solution for 3 h. The estimation of tissue viability based on the reduction of MTT to a blue formazan product.

A test substance has to be classified as skin irritant if the mean tissue viability is ≤ 50% relative to the mean negative control value. Tissue treatment with sodium methylparaben led to a mean tissue viability of 6.2% relative to the mean negative control value. The positive control substance (5% sodium dodecyl sulfate (SDS)) caused a mean tissue viability of 2.2% relative to the mean negative control value.

Under the test conditions, the test substance was irritating to the skin (Category 2).

  

In the third study, the skin irritating properties of sodium methylparaben were tested in an in vivo study according to the Code of Federal Regulations, Title 16, Section 1500.41 (Schreiber, 1981a). An amount of 500 mg sodium methylparaben moistened with water was applied on the clipped and abraded skin of 6 New Zealand White rabbits and covered with an occlusive dressing for 24 h. The reading time points for erythema and edema formation were at 24 and 72 h after removal of the test substance. At the 24 h reading time point, erythema formation was observed in all animals (scores 1 or 2) and edema formation was observed in 3/6 animals (scores 1 or 3). After 72 h, erythema formation was observed in 5/6 animals (scores 1 or 2) and edema formation was observed in 3/6 animals (score 1). The effects were fully reversible in all animals within the 8 d observation period.

In summary, the available in vitro data show that the test substance was not corrosive but irritating to the skin. The in vivo study resulted in slight erythema and edema formation which was reversible within 8 days. However, since the in vitro studies are more reliable than the in vivo study, the test substance meets the criteria for classification as skin irritant (Category 2).

 

 

Eye irritation

The eye irritating potential of sodium methylparaben was investigated in a study performed by Schreiber (1981b) according to the Code of Federal Regulations, Title 16, Section 1500.42. 0.1 mL of the unchanged test substance was instilled in one eye of each of 6 male New Zealand White rabbits without washing afterwards. The second eye of each animal was left untreated and served as control. The grades of ocular reaction (conjunctivae redness, conjunctivae chemosis, cornea, iris) were assessed 24, 48 and 72 h and 8 d after instillation of the test substance.

At 24 h post-application, swelling (score 1-3) and redness (score 2-3) of the conjunctivae were observed in all animals. The effects on conjunctivae persisted during the 48 and 72 h reading time point in all animals. After 8 d, the conjunctivae redness had fully reversed in 3/6 animals and the swelling of conjunctivae had fully reversed in 4/6 animals. Redness of the conjunctivae (score 1-2) was still noted in 3/6 rabbits and 2/6 rabbits still showed conjunctivae swelling (score 1). At 24 h post-application, effects on the iris (score 1) were observed in 5/6 rabbits. At the 48 h reading time point, the iris irritation (score 1) was noted in all animals. After 72 h, the effect persisted in 4/6 animals and reversed in 2/6 animals. After 8 d, the iris irritation had resolved in 3/6 animals. In all other rabbits the iris irritation still persisted. Corneal opacity (score 1-2) was noted in all rabbits after 24 h. The observation reversed in 2/6 animals within 48 h and in 2/6 other animals within 72 h. After 8 d, corneal opacity (score 1) was still noted in 2/6 animals.

Under the test conditions, the test substance was corrosive to the eyes (Category 1).


Justification for selection of skin irritation / corrosion endpoint:
The selected study is the most reliable study based on the overall quality assessment.

Justification for selection of eye irritation endpoint:
There is only one study on sodium methylparaben available. This study is reliable.

Effects on skin irritation/corrosion: irritating

Effects on eye irritation: corrosive

Justification for classification or non-classification

The available data on skin irritation and eye irritation of the test substance meet the criteria for classification as Skin Irritant (H315) and Irreversible effects on the eye (H318) according to Regulation (EC) 1272/2008 and as Xi, R38 and R41 according to Directive 67/548/EEC.