tetraethyl N,N'-(methylenedicyclohexane-4,1-diyl)bis-.sc.dl.sc.-aspartate

Endpoint summary

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

GLP compliance:

yes (incl. QA statement)

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Interfauna U. K. Ltd., Wyton, Huntingdon, England
- Strain: HC: NZW
- Sex: females
- Housing: individually
- Nutrition: once per day in the morning
- Water: ad libitum
- Acclimation period: at least 14 days in the quarantine station

Type of coverage:

semiocclusive

Preparation of test site:

shaved

Vehicle:

unchanged (no vehicle)

Controls:

other: The contralateral skin area not treated with test substance served as control.

Amount / concentration applied:

500 µl

Duration of treatment / exposure:

4 h

Observation period:

Demal irritation was scored 1, 24, 48 and 72 hours after termination of exposure and furthermore after 7 and 14 days .

Number of animals:

6 females

Details on study design:

STUDY DESIGN
The animals were weighed immediately before application of the test substance.
Approximately 24 hours before the test, fur was shorn from the dorso-lateral area of the trunk.

TEST SITE
- Area of exposure: approximately 6 cm²
- Type of wrap if used: Test substance applicated on a hypoallergenic patch (Beiersdorf No 2342 PV3), the patches loosely held in place with a semiocclusive dressing (Beiersdorf no. 2293).

REMOVAL OF TEST SUBSTANCE
- After an exposure period of 4 hours, the dressing and patches were removed.
- Washing: The exposed skin areas were carefully washed with water without altering the existing response, or the integrity of the epidermis.

SCORING SYSTEM: Draize

Irritation parameter:

erythema score

Basis:

animal #1

Time point:

other: 24, 48, 72 hours

Score:

>= 1 - <= 2

Max. score:

4

Reversibility:

not fully reversible within: 14 days

Remarks on result:

other: mean score: 1.3

Irritation parameter:

erythema score

Basis:

animal #2

Time point:

other: 24, 48, 72 hours

Score:

>= 1 - <= 2

Max. score:

4

Reversibility:

fully reversible within: 7 days

Remarks on result:

other: mean score: 1.3

Irritation parameter:

erythema score

Basis:

animal #4

Time point:

other: 24, 48, 72 hours

Score:

0

Max. score:

4

Irritation parameter:

erythema score

Basis:

animal: #3, #6

Time point:

other: 24, 48, 72 hours

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 14 days

Irritation parameter:

erythema score

Basis:

animal #5

Time point:

other: 24, 48, 72 hours

Score:

>= 0 - <= 1

Max. score:

4

Reversibility:

fully reversible within: 48 hours

Remarks on result:

other: mean score: 0.3

Irritation parameter:

edema score

Basis:

animal: #1, #2, #3, #4, #5, #6

Time point:

other: 24, 48, 72 hours

Score:

0

Max. score:

4

Irritation parameter:

other: mean irritation index for erythema

Basis:

mean

Time point:

other: 24, 48, 72 hours

Score:

1.2

Max. score:

4

Irritation parameter:

other: mean irritation index for edema

Basis:

mean

Time point:

other: 24, 48, 72 hours

Score:

0

Max. score:

4

Irritant / corrosive response data:

mean irritation index: For each animal the Draize scores recorded 24, 48, and 72 hours after application were added and divided by three. Then the mean value for all animals is calculated.

Other effects:

not reported

Study was performed with Aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-, 1,1',4,4'-tetraethyl ester which is a structural analogue to Aspartic acid, N,N'-(methylenedi-4,1-cyclohexanediyl)bis-, 1,1',4,4'-tetraethyl ester. Both substances are diethyl esters of aspartic acid linked to a dicyclohexylmethyldiamine moiety. The difference between these two substances is merely the presence of two methyl groups connected to the cyclohexane rings. This structural analogy was confirmed by the Member State responsible for the notification of both substances under the NONS regulation. The Member State decided that test results obtained for one substance can be transferred to the other substance and that testing of both substances is usually not required. This decision is in accordance with the grouping of substances and read-across approach in Annex XI, 1.5 of the REACH Regulation.

Executive summary:

In an OECD TG 404 study aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-,1,1',4,4'-tetraethyl ester was applied under semiocclusive dressings for 4 hours to the intact but shaved skin of a group of 6 female rabbits. Skin irritation was assessed after 1, 24, 48, 72 hours and 7 and 14 days using the Draize scale. The mean irritation index for erythema was 1.2 of max. 4 (1.0 -1.99 = slight irritating), the mean irritation index for edema was 0 of max. 4. Signs did not prove to be fully reversible in all animals within one week, and in one animal within 14 days (still erythema score 1). The weight of these evidences indicates that the test substance may be considered as "slightly to moderately irritating to the skin".

No systemic signs were reported.

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:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

GLP compliance:

yes (incl. QA statement)

Species:

rabbit

Strain:

New Zealand White

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: Interfauna U. K. Ltd., Wyton, Huntingdon, England
- Strain: HC: NZW
- Sex: females
- Housing: individually
- Nutrition: once per day in the morning
- Water: ad libitum
- Acclimation period: at least 14 days in the quarantine station

Vehicle:

unchanged (no vehicle)

Controls:

other: The second eye of each rabbit remained untreated and served as control.

Amount / concentration applied:

100 µl

Duration of treatment / exposure:

After instillation of the test substance into conjunctival sac the eye-lids were gently held together for about one second in order to limit loss of the material. 24 hours after instillation the eye was rinsed with saline.

Observation period (in vivo):

Eye irritation was scored at 1, 24, 48, 72 hours after administration and after 7, 14 and 21 days.

Number of animals or in vitro replicates:

3 females

Details on study design:

STUDY DESIGN
After gently pulling the lower lid away from the eyeball 100 µl test substance were instilled into the conjunctival sac of one eye of each rabbit.

REMOVAL OF TEST SUBSTANCE
24 hours after instillation of the test substance the treated eye was rinsed with saline.

SCORING SYSTEM: Draize

TOOL USED TO ASSESS SCORE:
The examinations were facilated using optical instruments (e.g. hand slit-lamp). To define epithelial damage, one drop of a 1% fluorescein solution was applied to the cornea surface 24 hours after administration of the test substance; where positive effects were recorded this was repeated at the later observation times. The eye was then rinsed with saline to remove excess and nonabsorbed fluorescein.

Irritation parameter:

cornea opacity score

Basis:

animal: #1, #2, #3

Time point:

other: 24, 48, 72 hours

Score:

0

Max. score:

4

Irritation parameter:

iris score

Basis:

animal: #1, #2, #3

Time point:

other: 24, 48, 72 hours

Score:

0

Max. score:

2

Irritation parameter:

conjunctivae score

Basis:

animal: #1, #2, #3

Time point:

other: 24, 48, 72 hours

Score:

>= 0 - <= 1

Max. score:

3

Reversibility:

fully reversible within: 48 hours

Remarks on result:

other: mean score: 0.3

Irritation parameter:

chemosis score

Basis:

animal: #1, #2, #3

Time point:

other: 24, 48, 72 hours

Score:

0

Max. score:

4

Irritation parameter:

other: mean irritation index for conjunctivae

Basis:

mean

Time point:

other: 24, 48, 72 hours

Score:

0.3

Max. score:

3

Irritant / corrosive response data:

mean irritation index: For each animal the Draize scores recorded 24, 48, and 72 hours after application were added and divided by three. Then the mean value for all animals is calculated.

Other effects:

not reported

Study was performed with Aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-, 1,1',4,4'-tetraethyl ester which is a structural analogue to Aspartic acid, N,N'-(methylenedi-4,1-cyclohexanediyl)bis-, 1,1',4,4'-tetraethyl ester. Both substances are diethyl esters of aspartic acid linked to a dicyclohexylmethyldiamine moiety. The difference between these two substances is merely the presence of two methyl groups connected to the cyclohexane rings. This structural analogy was confirmed by the Member State responsible for the notification of both substances under the NONS regulation. The Member State decided that test results obtained for one substance can be transferred to the other substance and that testing of both substances is usually not required. This decision is in accordance with the grouping of substances and read-across approach in Annex XI, 1.5 of the REACH Regulation.

Executive summary:

In a study according to OECD TG 405 aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-,1,1',4,4'-tetraethyl ester was instilled into the conjunctival sac of one eye of 3 female rabbits. Eye irritation was assessed using the Draize scale. In this study the test substance was considered to be not irritating to the eye with a mean irritation index for conjunctivae of 0.3 (< 1 = not irritating), and mean irritation indices for cornea, iris and chemosis of 0. No systemic signs were reported.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

The structural analogue aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-,1,1',4,4'-tetraethyl ester was slightly to moderately irritating to the skin of rabbits (OECD TG 404; Maertins, Bayer AG, 1991) and not irritating to the eye of rabbits (OECD TG 405; Maertins, Bayer AG, 1991).

The substance indicated a low sensory respiratory tract irritation potential in a special aerosol inhalation study on rats (RD50: 841 mg/m³; study according to ASTM E981-84, Pauluhn, Bayer AG, 1998b; see chapter "acute toxicity: inhalation"). Lung function measurement revealed changes on breathing patterns resemble those stereotypical patterns known to occur following exposure to 'upper respiratory tract sensory irritants', because of a characteristic bradypneic period (pause between inspiration and expiration).

All studies investigating the irritation were performed with aspartic acid, N,N’-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-, 1,1',4,4'-tetraethyl ester which is a structural analogue to aspartic acid, N,N’-(methylenedi-4,1-cyclohexanediyl)bis-, 1,1',4,4'-tetraethyl ester. Both substances are diethyl esters of aspartic acid linked to a dicyclohexylmethyldiamine moiety. The difference between these two substances is merely the presence of two methyl groups connected to the cyclohexane rings. This structural analogy was confirmed by the Member State responsible for the notification of both substances under the NONS regulation. The Member State decided that test results obtained for one substance can be transferred to the other substance and that testing of both substances is usually not required. This decision is in accordance with the grouping of substances and read-across approach in Annex XI, 1.5 of the REACH Regulation.

Justification for selection of skin irritation / corrosion endpoint:
Only one study available.

Justification for selection of eye irritation endpoint:
Only one study available.

Justification for classification or non-classification

No classification for skin/eye irritation required according to EU-Directive 67/548/EEC, Annex I.

No classification for skin/eye irritation required according to Regulation (EC) No 1272/2008, Annex VI.

No classification required for respiratory tract irritation according to EU-Directive 67/548/EEC, Annex I, or Regulation (EC) No 1272/2008, Annex VI, because the low vapour pressure of the substance prevents inhalative exposure, and the results of the available acute inhalation studies with exposure to a highly respirable aerosol does only lead to a low sensory respiratory tract irritation potential.