Propyl 4-hydroxybenzoate

Endpoint summary

Description of key information

Skin irritation: not irritating
Eye irritation: not irritating

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin irritation: in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

other information

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reference 2

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

.

Justification for type of information:

see read-acorss justification attached in chapter 13.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Deviations:

no

GLP compliance:

not specified

Species:

rabbit

Strain:

other: HC:NWZ

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hacking & Churchill Ltd., Huntingdon, UK
- Weight at study initiation: 3500 g
- Housing: Animals were housed individually
- Diet: ssniff K, ad libitum
- Water: tap water, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 25
- Humidity (%): 40 - 60
- Photoperiod (hrs dark / hrs light): 12/12

Type of coverage:

semiocclusive

Preparation of test site:

clipped

Vehicle:

unchanged (no vehicle)

Controls:

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

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied: 0.5 g test substance, moistened with water

Duration of treatment / exposure:

4 h

Observation period:

7 d
reading time points: 1, 24, 48, 72 h and 7 d

Number of animals:

3 males

Details on study design:

TEST SITE
- Area of exposure: approximately 6 cm² on the back of the animal
- Type of wrap if used: The test substance was applied to a gauze patch, held in place by elastic tape that was permeable to air.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The treated skin sites were washed with water.
- Time after start of exposure: 4 h

SCORING SYSTEM: Draize scoring system

Irritation parameter:

erythema score

Basis:

mean

Remarks:

out of all 3 animals

Time point:

24/48/72 h

Score:

0

Reversibility:

other: reversibility: not applicable

Irritation parameter:

edema score

Basis:

mean

Remarks:

out of all 3 animals

Time point:

24/48/72 h

Score:

0

Reversibility:

other: reversibility: not applicable

Irritant / corrosive response data:

Dermal application of the test substance did not result in erythema or edema in any of the animals tested at any observation time point.

Other effects:

no data on body weight and clinical observations

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

CLP: not classified
DSD: not classified

Reference 3

Endpoint:

skin irritation: in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Study period:

December 1976

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to primary skin irritation test design in effect since 1976, but not according to OECD Guideline.

Justification for type of information:

Read-across justification is attached to chapter 13.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Primary skin irritation test design in effect since 1976.
The method is a modification of the Draize technique and is similar to that used in grading skin irritation in the Human Patch Test. The highest grade at either the 2 or 24 hour reading is used to calculate the Primary Irritation Index (PII).

GLP compliance:

no

Remarks:

study performed before GLP guidelines

Species:

rabbit

Strain:

other: Albino

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Specie: Albino rabbit
- Sex: female
- Age at study initiation: no data
- Weight at study initiation: no data
- Housing: no data
- Diet (e.g. ad libitum): no data

ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Photoperiod (hrs dark / hrs light): no data

Type of coverage:

occlusive

Preparation of test site:

shaved

Vehicle:

unchanged (no vehicle)

Controls:

yes

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.1 mL
- Frequency: once
- Product type: per se
- Concentration tested: 100%

VEHICLE: none

Duration of treatment / exposure:

24 hrs
Then the occlusive dressing was removed.

Observation period:

24 and 72 hrs after contact

Number of animals:

9

Details on study design:

METHODS:
Nine healthy female albino rabbits were used to study each material.
The test material was applied to a 1" filter disc which was held in contact with the clipped skin of the back of the animal by Blenderm tape. The trunk of each animal was then wrapped with an occlusive plastic sheet and secured with Elastoplast tape.

OBSERVATIONS:
The occlusive dressing was removed after 24 hours of contact, and the skin sites graded for irritation and edema after 24 and 72 hours according to the scoring system based on a maximum of

PSI Scores:
0 = no evidence of any effect
1/2 = (Barely Perceptible) = minimal faint uniform or spotty erythema
1 = (Mild) = pink uniform erythema covering most of contact site
2 = (Moderate) = Pink-red erythema visibly uniform in entire contact area
3 = (Marked) = Bright red erythema with accompaning edema, petachiae or papules
4 = (Severe) = Deep red erythema with vesiculation or weeping with or withourt edema

PSI = Primary Skin Irritation Score, Maximum Score = 4.0
PII = Primary Irritation Index - a value depicting the average skin response of the test panel as a whole. It is calculated by adding the Irritation Scores and dividing by the total number of test subjects.

Irritation parameter:

primary dermal irritation index (PDII)

Basis:

mean

Time point:

other: 24h / 72h

Score:

0.67

Max. score:

4

Reversibility:

other: no data

Remarks on result:

other: test sample

Irritation parameter:

primary dermal irritation index (PDII)

Basis:

mean

Time point:

other: 24h / 72h

Score:

0.44

Max. score:

4

Reversibility:

other: no data

Remarks on result:

other: control

SCORE	0	1/2	1	2	3	4
Number of Animals Test	1	6	1	1	0	0
Control	4	2	3	0	0	0

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test material, when evaluated for primary skin irritation by a 24-hour patch test conducted on intact skin, was found to be not irritating.

Executive summary:

The test material, when evaluated for primary skin irritation by a 24-hour patch test conducted on intact skin, was found to be not irritating to skin.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not 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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Version / remarks:

adopted in 2002

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.5 (Acute Toxicity: Eye Irritation / Corrosion)

Deviations:

no

GLP compliance:

yes

Species:

rabbit

Strain:

New Zealand White

Details on test animals or tissues and environmental conditions:

Test System:

Animals: Young Adult New Zealand White Rabbit, SPF
Rationale: Recognized by international guidelines as a recommended test system. An in vitro eye irritation study (CCR Study Number 1466000, Harlan Laboratories Study D48537, BCOP test) was performed and did not show any relevant effect.
Breeder: Harlan Laboratories U.K. Ltd., Hillcrest, Dodgeford Lane, Belton, Loughborough, Leics, LE12 9TE / UK
Number of Animals per Test: 3 males, nos. 1-3
Age (when treated): 15 - 16 weeks
Body Weight Range (when treated): 2434 - 2686 g
Identification: Unique cage number and corresponding ear number.
Randomization: Selected by hand at time of delivery. No computer generated randomization program.
Acclimatization: Under laboratory conditions after health examination. Only animals without any visual signs of illness were used for the study.

Husbandry:

Room Number: 137 / Harlan Laboratories Ltd., Itingen
Conditions: Standard laboratory conditions. The animal room was air-conditioned with 10 - 15 air changes per hour. The air was continuously monitored for temperature and relative humidity. The ranges for room temperature and relative humidity were 20 ± 3 °C and 30 - 70%, respectively. The animals were provided with an automatically controlled light cycle of 12 hours light and 12 hours dark. Music was played during the daytime light period.
Accommodation: Individually in stainless steel cages equipped with feed hoppers and drinking water bowls.
Diet: Pelleted standard Teklad Global High Fiber Rabbit Diet 2031C (batch no. 35/11, provided by Provimi Kliba AG, 4303 Kaiseraugst / Switzerland) ad libitum. Results of analyses for contaminants will be archived at Harlan Laboratories Ltd. A piece of wood (batch no. 122201, imported by Indulab AG, Gams / Switzerland from ABEDD® - LAB & VET GmbH, 1160 Vienna / Austria) and a haystick 4642 (batch no. 45/11, Provimi Kliba AG, 4303 Kaiseraugst / Switzerland) will be provided for environmental enrichment.
Water: Community tap water from Itingen ad libitum in water bottles. Results of bacteriological, chemical and contaminant analyses are archived at Harlan Laboratories Ltd.

Vehicle:

unchanged (no vehicle)

Controls:

other: The right eye remained untreated and was used for control purposes.

Amount / concentration applied:

The test item was used as delivered by the Sponsor.

The test item was applied as a weight of 0.1 g/animal, the dose specified in the test guidelines for solid test items.

Observation period (in vivo):

Approximately 1 hour and 24, 48 and 72 hours as well as 7 days following treatment

Number of animals or in vitro replicates:

3 animals were tested in total. (After consideration of the ocular responses produced in the first treated animal, two additional animals were treated. )

Details on study design:

Test Item Administration:

The test item was applied as a weight of 0.1 g/animal, the dose specified in the test guidelines for solid test items.

The eyes of the animals were examined one day prior to test item administration.

On the day of treatment, the test item was applied with an eye glass to the conjunctival sac of the left eye of each animal after gently pulling the lower lid away from the eyeball. The lids were then gently held together for about one second to prevent loss of test item. The right eye remained untreated and served as the reference control. The treated eyes were not rinsed after instillation.

One animal was treated first. As neither a corrosive effect nor a severe irritant effect was observed after the 1- and 24-hour examinations, the test was completed using the two remaining animals.

Rationale: The application form and dose were used to detect an irritating potential of the test item applied.

Observations

Viability / Mortality: Daily
Clinical Signs: Daily
Eye Reactions: See below
Body Weights: At start of acclimatization, on test day 1 and at termination of observation.

Assessment of Eye Reactions:

The eye reactions were assessed according to the numerical scoring system listed in the Commission Regulation (EC) No 440/2008, B.5, at approximately 1, 24, 48 and 72 hours, as well as 7 days after administration. Scleral reddening and ocular discharge were also assessed. Eye examinations were made with a Varta Cliptrix diagnostic-lamp (Roth AG, 4153 Reinach / Switzerland)

Data was summarized in tabular form, showing for each animal the irritation scores for the designated observation time, a description of the degree and nature of irritation, the presence of serious lesions and non-ocular effects. The scores of each animal at the following reading times (24, 48, 72 hours) were used in calculating the respective mean values (with the exception of the sclerae) for each type of lesion.

Irritation parameter:

cornea opacity score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility: not applicable

Irritation parameter:

cornea opacity score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility: not applicable

Irritation parameter:

cornea opacity score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility: not applicable

Irritation parameter:

iris score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

2

Reversibility:

other: reversibility: not applicable

Irritation parameter:

iris score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

2

Reversibility:

other: reversibility: not applicable

Irritation parameter:

iris score

Basis:

animal #3

Time point:

other: mean score over 24, 48 and 72 hours

Score:

0

Max. score:

2

Reversibility:

other: reversibility: not applicable

Irritation parameter:

conjunctivae score

Basis:

animal #1

Time point:

24/48/72 h

Score:

1

Max. score:

3

Reversibility:

fully reversible within: 7 days

Irritation parameter:

conjunctivae score

Basis:

animal #2

Time point:

24/48/72 h

Score:

2

Max. score:

3

Reversibility:

fully reversible within: 7 days

Irritation parameter:

conjunctivae score

Basis:

animal #3

Time point:

24/48/72 h

Score:

1.67

Max. score:

3

Reversibility:

fully reversible within: 7 days

Irritation parameter:

chemosis score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility: not applicable

Irritation parameter:

chemosis score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility: not applicable

Irritation parameter:

chemosis score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: reversibility: not applicable

Irritant / corrosive response data:

The instillation of propylparaben into the eye resulted in mild, early-onset and transient ocular changes, such as reddening of the conjunctivae, sclerae and ocular discharge. These effects were reversible and were no longer evident 7 days after treatment, the end of the observation period for all animals. No abnormal findings were observed in the cornea or for the iris light reflex of any animals at any of the examinations. No corrosion was observed at any of the examinations. No staining of the treated eyes by the test item was observed. No test item remnants were observed in the treated eyes of any animal at any examination. No clinical signs were observed.

Thus, the test item did not induce significant or irreversible damage to the rabbit eye.

The mean score was calculated separately for each animal across three scoring times (24, 48 and 72 hours after instillation) for corneal opacity, iris light reflex, redness and chemosis of the conjunctivae, respectively. The individual mean scores for corneal opacity and iris light reflex were 0.00 for all three animals. The individual mean scores for the conjunctivae were 1.00, 2.00 and 1.67 for reddening and 0.00 for chemosis for all animals, respectively.

Other effects:

Viability / Mortality: No intercurrent deaths occurred during the course of the study.

Clinical Signs: No clinical signs were recorded throughout the entire observation period.

Body Weights: The body weight of the animals was within the range commonly recorded for this strain and age.

Table 1. Results of eye irritation study.

Rabbit #	Time [h]	conjunctivae		iris	cornea		conjunctivae		iris	cornea
		redness	swelling				redness	swelling
1	1	1	0	0	0
	24	1	0	0	0
	48	1	0	0	0
	72	1	0	0	0
	average	1.0	0	0	0	Time to reversion	7 d	0	0	0
2	1	1	0	0	0
	24	2	0	0	0
	48	2	0	0	0
	72	2	0	0	0
	average	2.0	0	0	0	Time to reversion	7 d	0	0	0
3	1	2	0	0	0
	24	2	0	0	0
	48	2	0	0	0
	72	1	0	0	0
	average	1.67	0	0	0	Time to reversion	7 d	0	0	0

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Based upon the referred classification (Regulation (EC) No 1272/2008 of 16 December 2008), propylparaben is considered to be “not irritating” to the rabbit eye.

Executive summary:

The primary eye irritation potential of propylparaben was investigated according to OECD test guideline no. 405 and Commission Regulation 440/2008/EC. The test item was applied by instillation of 0.1 g into the left eye of each of three young adult New Zealand White rabbits. Scoring of irritation effects was performed approximately 1, 24, 48 and 72 hours, as well as 7 days after test item instillation.

 

The instillation of propylparaben into the eye resulted in mild, early-onset and transient ocular changes, such as reddening of the conjunctivae, sclerae and ocular discharge. These effects were reversible and were no longer evident 7 days after treatment, the end of the observation period for all animals. No abnormal findings were observed in the cornea or for the iris light reflex of any animals at any of the examinations. No corrosion was observed at any of the examinations. No staining of the treated eyes by the test item was observed. No test item remnants were observed in the treated eyes of any animal at any examination. No clinical signs were observed.

 

Thus, the test item did not induce significant or irreversible damage to the rabbit eye.

 

The mean score was calculated separately for each animal across three scoring times (24, 48 and 72 hours after instillation) for corneal opacity, iris light reflex, redness and chemosis of the conjunctivae, respectively. The individual mean scores for corneal opacity and iris light reflex were 0.00 for all three animals. The individual mean scores for the conjunctivae were 1.00, 2.00 and 1.67 for reddening and 0.00 for chemosis for all animals, respectively.

 

Based upon the referred classification criteria (Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008), propylparabendoes not have to be classifiedwith respect to eye irritation in rabbits.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

The skin irritation properties of propylparaben were investigated similar to OECD 404 (Sokol, 1952). A 10% solution of propylparaben in hydrophilic ointment base was applied to the skin of rabbits. No noticeable skin irritation was detected after 48 h. However, due to a limited documentation, this study is not sufficient for assessment of skin irritation properties of propylparaben. The result is supported by OECD Toolbox v4.0 and DEREK nexus v.6.0.1 profiling, which gave no evidence for skin irritation.

There are no further data available on the skin irritation potential of propylparaben. However, there are reliable data for methylparaben and ethylparaben which are structurally related to propylparaben. Therefore, read-across was performed based on an analogue approach. For a detailed justification of the analogue approach, please refer to section 13 of the technical dossier.

The target substance and the source substances form a homologue series of esters of p-hydroxybenzoic acid and differ only in the length of the alkyl side chain, which contains 1, 2 or 3 carbon atoms for methylparaben, ethylparaben and propylparaben, respectively.

No skin and eye irritation potential was observed in studies with the target and source substances in rabbits. Additionally, OECD Toolbox v.4.0 and DEREK nexus v.6.0.1

profiling gave no evidence for the source substance and the target substances for eye and skin irritation or corrosion.

In conclusion, as methylparaben, ethylparaben and propylparaben were shown to have comparable toxicological properties, it is considered appropriate to read-across from methylparaben and ethylparaben to propylparaben.

 

Methylparaben was investigated for skin irritation using a modified Draize test (Anonymous, 1976). Methylparaben (0.1 mL) was applied to the shaved skin sites of nine female rabbits and covered with an occlusive dressing for 24 h. The observation period after removal of the dressing was 72 h with reading time points at 24 and 72 h. Based on the primary dermal irritation index of 0.67, methylparaben was found to be not irritating to the skin.

The skin irritating properties of ethylparaben were examined similar to OECD 404 (Suberg, 1983). The test substance was applied on the clipped backs of three male New Zealand White rabbits and covered with a semiocclusive dressing. After 4 h, the dressing was removed and the treated skin sites were cleaned with water. Erythema and edema formation were assessed 1, 24, 48 and 72 h and 7 d after removal of the test substance using the Draize scoring system. No erythema and edema formation was observed in any animal. Under the test conditions, ethylparaben was not irritating to the skin.

In summary, the available data give no evidence that propylparaben has a skin irritation potential.

 

Initially, eye corrosion properties of propylparaben were investigated in a Bovine Corneal Opacity and permeability Test according to OECD 437 and GLP (Heppenheimer, 2012). A solution of 20% (v/v) propylparaben in physiological saline was applied to three bovine corneas for 240 minutes. After further incubation of the corneas with fluorescein for 90 minutes, the permeability of the corneas was determined spectrophotometrically. The mean in vitro irritation score was determined to be 13.03.

Under the test conditions, the test substance was not corrosive to the eyes.

 

The eye irritation potential of propylparaben was tested in a study performed by Sieber (2012) in accordance with OECD 405 and GLP. First, the unchanged test substance was instilled in one eye of one New Zealand White rabbit. The other eye was not treated and served as control. In a second step, two further rabbits were treated in the same way. The grades of ocular reaction (conjunctivae redness, conjunctivae chemosis, cornea, iris) were assessed 1, 24, 48 and 72 h and 7 d after instillation of the test substance.

No effects on iris and cornea or swelling of the conjunctivae were noted at any reading time point. However, redness of the conjunctivae was observed in all animals with scores of 1 or 2 at 1, 24, 48 and 72 h reading time points. The effect completely reversed in all animals within 7 days.

Under the test conditions, the test substance was not irritating to the eyes.

Justification for selection of skin irritation / corrosion endpoint:
Hazard assessment is conducted by means of read-across from structural analogues. All available studies are adequate and reliable based on the identified similarities in structure and intrinsic properties between source and target substances and overall quality assessment (refer to the endpoint discussion for further details).

Justification for selection of eye irritation endpoint:

Guideline study according to GLP with a Klimisch rating 1.

Justification for classification or non-classification

The available data on skin irritation and eye irritation of the test substance and on surrogate substances does not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and is therefore conclusive but not sufficient for classification.