Sodium 4-(methoxycarbonyl)phenolate

Endpoint summary

Description of key information

To evaluate skin irritating properties of the test item follwing studys were evaluated:

- in vitro skin irritation (accordig to OECD 439)

- In vitro skin corrosion (according to OECD 431)

- in vivo skin irritation in rabbit (according to Code of Federal Regulations, Title 16, Section 1500.41)

To evaluate skin irritating properties of the test item follwing studys were evaluated:

- in vivo eye irritation (according to Code of Federal Regulations, Title 16, Section 1500.42)

Based on the results of these studies the test item has folloing properties:

Skin irritation (OECD 439- OECD 431): 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

Reference 1

Endpoint:

skin irritation: in vitro / ex vivo

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:

guideline study

Qualifier:

according to guideline

Guideline:

other: EU Method b.46 (Skin Irritation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, München, Germany

Test system:

human skin model

Source species:

human

Cell type:

other: EpiDerm( MatTek) rganotypic reconstructed three-dimensional model of the human epidermis

Cell source:

other: EpiDerm( MatTek)

Details on animal used as source of test system:

organotypic reconstructed three-dimensional model of the human epidermis

Justification for test system used:

Ths test method is able to detect chemicals that cause skin irritation, i.e. produce reversible daamage to the skin and allows for hazard identification in accordance with UN GHS category 2.

Vehicle:

other: Dulbecco's Phosphate Buffrered Saline (DPBS)

Details on test system:

This test used the EpiDerm TM reconstructed human epidermis model (MatTk) which consists of human keratinocytes (NHEK) and therefore represents in vitro the target organ of the species of ntrest and closely mimics the biochemical and physiological properties of the upper parts of the human, i.e. the epidermis.

Control samples:

yes, concurrent negative control

yes, concurrent vehicle

yes, concurrent positive control

Amount/concentration applied:

25 mg test substance in 25 µL DPBS

Duration of treatment / exposure:

60 ± 1 min

Duration of post-treatment incubation (if applicable):

Post-treatment incubation period: 42 ± 4 h

Number of replicates:

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 / corrosion parameter:

% tissue viability

Run / experiment:

Negative control / 60 min exposure / mean

Value:

>= 100

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Positive control / 60 min exposure / mean

Value:

ca. 2.2

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks:

5 % SDS

Remarks on result:

positive indication of irritation

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

test item/ 60 min exposure/ mean

Value:

ca. 6.2

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Other effects / acceptance of results:

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

Executive summary:

In the present study the skin irritant potential of Sodium methyl-4-hydroxybenzoate was analysed. The EpiDerm TM-Standard Model (EPI-200 TM), a reconsituted three-dimensional human epidermis model, was used as a replacement of the Draize skin irritation test (OECD 404) to distinguish between UN GHS and EU CLP "Category 2" skin irritating test substances and not categorized test substances ("no category") which may be considered as non-irritant. Hereby, the test item was applied topically, cytotoxicity is expressed as the reduction of mitochondrila dehydrogenase activity measured by formazan production from MTTafter a 60 min exposure and 42 h post incubation period and compared to those of the concurrent negative controls. In this study under the given conditions the test item showed irritant effects. The relative mean tissue viability after 60 min of exposure and 42 h post incubation was < 50%. The test item is therefore classified as "irritant" in accordance with UN GHS and EU CLP "Category 2".

Reference 2

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-12-15 to 2011-12-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method B.40 (In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test (TER))

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 431 (In Vitro Skin Corrosion: Human Skin Model Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

(Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, München, Germany)

Test system:

human skin model

Source species:

human

Cell type:

other: EpiDerm human epidermis model (MatTek) - organotypic reconstituted three-dimensional model of the human epidermis

Amount/concentration applied:

25 mg test substance in 25 µL H2O

Duration of treatment / exposure:

3 and 60 min

Number of replicates:

The test was performed in duplicates for each test or control group and treatment period (3 and 60 min).

Controls:

other: Concurrent control tissues treated with the vehicle served as negative controls, positive controls were exposed to 8 N KOH.

Details on study design:

2 replicate tissues per treatment period are dosed with the neat test item moistened with water, the negative control (distilled water) and the positive control (8 N KOH), respectively. After each treatment period the test item and controls are rinsed off and the tissues are stained with MTT for 3 h. Isopropanol extracts are measured photometrically at 550 nm.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

negative cotrol / 3 min

Value:

100

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Remarks:

Basis: other: mean value of negative controls (distilled water). Time point: 3 min. Reversibility: other: not applicable.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

positive control / 3 min

Value:

27

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Remarks:

Basis: other: mean value of positive controls (8 N KOH). Time point: 3 min.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

test item / 3 min

Value:

59

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Remarks:

Basis: other: mean value of the test substance. Time point: 3 min. Reversibility: other: not applicable. (migrated information)

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

negative control / 60 min

Value:

100

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Remarks:

Basis: other: mean value of negative controls (distilled water). Time point: 60 min. Reversibility: other: not applicable. (migrated information)

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Positive control/ 60 min

Value:

23

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Remarks:

Basis: other: mean value of positive controls (8 N KOH). Time point: 60 min. Reversibility: other: not applicable. (migrated information)

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

test item/ 60 min

Value:

26

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Remarks:

Basis: other: mean value of the test substance. Time point: 60 min. Reversibility: other: not applicable. (migrated information)

Other effects / acceptance of results:

The test item showed no direct MTT-reducing capability and no colouring potential.

3 min.

Name	Negative Control		Test Item		Positive Control
Tissue	1	2	1	2	1	2
absolute OD550 -values	1.311	1.115	0.670	0.731	0.287	0.352
	1.340	1.098	0.704	0.785	0.305	0.360
	1.366	1.108	0.696	0.764	0.319	0.360
OD550(mean of             3 aliquots)	1.339	1.107	0.690	0.760	0.303	0.358
SD	0.028	0.009	0.018	0.027	0.016	0.004
OD550(mean of             2 replicate tissues)	1.223*		0.725		0.330
mean relative tissue viability [%]	100		59		27**
mean inter tissue viability difference [%]***	19.0		9.7		16.3

^*       mean OD₅₅₀ ≥ 0.8

^**      mean relative tissue viability of the 3 min. positive control ≤ 30%

^***     inter tissue viability difference ≤ 30%

60 min.

Name	Negative Control		Test Item		Positive Control
Tissue	1	2	1	2	1	2
absolute OD550 -values	1.418	1.232	0.361	0.327	0.319	0.282
	1.416	1.224	0.355	0.330	0.340	0.279
	1.441	1.230	0.361	0.339	0.339	0.281
OD550(mean of             3 aliquots)	1.425	1.229	0.359	0.332	0.333	0.281
SD	0.014	0.004	0.003	0.006	0.012	0.001
OD550(mean of             2 replicate tissues)	1.327*		0.345		0.307
mean relative tissue viability [%]	100		26		23
mean inter tissue viability difference [%]***	14.8		7.7		17.0

^*       mean OD₅₅₀ ≥ 0.8

^***         inter tissue viability difference ≤ 30%

Interpretation of results:

other: not corrosive

Remarks:

Criteria used for interpretation of results: EU

Conclusions:

There is regulatory acceptance in the EU that a substance can be considered corrosive (Skin Corrosive Cat.1A) based on a positive result in the human epidermis model test. Negative in vitro corrosivity responses are not conclusive with respect to non-classification or classification as irritant and shall therefore be subject to further evaluation.

Executive summary:

In the present study the skin corrosivity potential of Sodium methyl-4-hydroxybenzoate was analysed. Since corrosive chemicals are cytotoxic after a short time exposure to the stratum corneum of the epidermis the cytotoxic effects of the test item on EpiDerm TM, a reconstituted three dimensional human epidermis model, was determined. hereby, the test item was applied topically. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazanproduction from MTTafter 3 min. and 60 min. exposure period and compared to those of the concurrent negative controls. In this study under the given conditions the test item showed no corrosive effects. The relative mean tissue viability after 3 min. treatment was >= 50% and after 60 min. treatment >= 15 %. The test item is therefore classified as non corrosive.

Reference 3

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions. An occlusive dressing was used and 48 h scores are missing. Not performed according to GLP. No analytical purity was given in the study report.

Qualifier:

according to guideline

Guideline:

other: Code of Federal Regulations, Title 16, Section 1500.41

Deviations:

no

GLP compliance:

no

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system 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

Type of coverage:

occlusive

Preparation of test site:

other: clipped or abraded

Vehicle:

water

Controls:

other: Not required, the untreated skin sites of the same animal served as control.

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 500 mg test substance, moistened with water

Duration of treatment / exposure:

24 h

Observation period:

8 d
reading time points: 24 and 72 h

Number of animals:

6 males

Details on study design:

TEST SITE
- Area of exposure: 6.25 cm²
- Type of wrap if used: The treated skin was covered with gauze and PVC foil, held in place with adhesive tape.

SCORING SYSTEM: Draize scoring system

Irritation parameter:

erythema score

Basis:

mean

Remarks:

over all 6 animals

Time point:

other: mean over 24, 48 and 72 h

Score:

1.44

Max. score:

4

Reversibility:

fully reversible within: 3-8 d

Remarks on result:

other: no 48 h data are available; for calculation of mean scores, the 48 h values were assumed to be the same as those at 24 h (worst case assumption: persistence of effects seen at 24 h over 48 h)

Irritation parameter:

edema score

Basis:

mean

Remarks:

over all 6 animals

Time point:

other: mean over 24, 48 and 72 h

Score:

0.72

Max. score:

4

Reversibility:

fully reversible within: 3-8 d

Remarks on result:

other: no 48 h data are available; for calculation of mean scores, the 48 h values were assumed to be the same as those at 24 h (worst case assumption: persistence of effects seen at 24 h over 48 h)

Table 1. Results of skin irritation study.

Observation time	Rabbit no.
	1		2		3		4		5		6
	Erythema	Edema	Erythema	Edema	Erythema	Edema	Erythema	Edema	Erythema	Edema	Erythema	Edema
24 h	2	3	2	0	2	1	1	0	2	1	1	0
48 h	No experimental data available; for calculation of mean scores, the 48 h values were assumed to be the same as those at 24 h (worst case assumption).
72 h	2	1	1	0	1	0	1	1	1	1	0	0
8 d	0	0	0	0	0	0	0	0	0	0	0	0
Mean value 24 + 48 + 72 h*	2.00	2.33	1.67	0	1.67	0.67	1.00	0.33	1.67	1.00	0.67	0

*No 48 h data are available: for calculation of mean scores, the 48 h values were assumed to be the same as those at 24 h (worst case assumption: persistence of effects seen at 24 h over 48 h).

Interpretation of results:

other:

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

CLP: not classified
DSD: not classified

Executive summary:

In this study the skin irritating properties of sodium methyl4 -hydoxybenzoate was 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.

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

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:

24/48/72 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:

24/48/72 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:

24/48/72 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:

24/48/72 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

Executive summary:

he eye irritating potential of sodium methyl-4-hydroxybenzoate 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).

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 irritating properties of teh test item.

In an in vitro study, sodium methyl-4-hydroxybenzoate 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 methyl-4-hydroxybenzoate 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.

Skin irritation (OECD 439 and OECD 431): irritating
Eye irritation (Code of Federal Regulations, Title 16, Section 1500.42): corrosive