N-[3-(dimethylamino)propyl]docosanamide

Endpoint summary

Description of key information

Skin irritation/corrosion: 
not corrosive (TER, equivalent to OECD Guideline 430, GLP). After 24 hours application of DIMAPDO and the positive/negative control substances to the epidermal surface of three skin discs TERs were recorded. DIMAPDO was considered not to have the potential to be corrosive to skin in vivo under the conditions of the test.
not irritating (OECD Guideline 404, GLP). 3 adult New Zealand white rabbits were dermally exposed to 0.5 g of the test substance. Animals were then observed for 10 days. There were low scores in the first 72 hours for erythema. Read-across to N-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50 (w/w %)
Eye irriation/corrosion:
Irreversible effects on the eye (OECD Guideline 405, GLP). The test substance was instilled into the conjunctival sac of the left eye of one young adult female New Zealand White rabbit for 48 hours. The eye was washed with physiological saline at 24 and 48 hours. Evolvement of signs of serious eye damage within the first 48 hours. Due to severe signs of pain during the examination of the eye at the 48-hour reading it was sacrificed immediatly thereafter. Read-across to N-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50 (w/w %).

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:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that source and target substances have similar toxicological properties because
• they are manufactured from similar or identical precursors under similar conditions
• they share structural similarities with common functional groups: tertiary amines, amides, and fatty acid chains with comparable length and degree of saturation (corresponding to scenario 2 of the read-across assessment framework)

The read-across hypothesis is based on structural similarity of target and source substances. The target and source chemicals have a very similar structure in that they are comprised of a hydrophobic (alkyl) and hydrophilic (amine headgroup) end. Due to this motif they form micelles (colloidal dispersions) and have surfactant properties.
Based on available experimental data, including key physicochemical properties and data from genotoxicity studies, the read-across strategy is supported by a similar toxicological profile of all substances.

Therefore, read-across from the existing toxicity studies conducted with the source substances is considered as an appropriate adaptation to the standard information requirements of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation.

A justification for read-across is attached to IUCLID section 13.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See justification for read-across attached to IUCLID section 13.

3. ANALOGUE APPROACH JUSTIFICATION
See justification for read-across attached to IUCLID section 13.

4. DATA MATRIX
See justification for read-across attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Species:

rabbit

Strain:

New Zealand White

Type of coverage:

semiocclusive

Preparation of test site:

clipped

Vehicle:

water

Irritation parameter:

erythema score

Basis:

mean

Time point:

24/48/72 h

Score:

<= 2

Max. score:

4

Reversibility:

fully reversible

Remarks on result:

other: not irritating to skin

Irritation parameter:

edema score

Basis:

mean

Time point:

24/48/72 h

Score:

<= 2

Max. score:

4

Reversibility:

fully reversible

Remarks on result:

other: not irritating to skin

Interpretation of results:

GHS criteria not met

Reference 2

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2004-04-26 to 2004-04-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 430 (In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test Method (TER))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

isolated skin discs

Source species:

rat

Cell type:

other: skin discs prepared from rat

Cell source:

other: skin discs prepared from rat

Source strain:

Wistar

Details on animal used as source of test system:

TEST ANIMALS
-strain: one female BK:Wistar rat
- Age at skin disc preparation: 28-30 days
- Acclimation period: 2 days

PREPARATION OF SKIN DISCS
- the animal was shaved on the dorsal surface and two antibiotic washs were performed
- the animal was humanely killed by inhalation of a rising concentration of CO2 followed by cervical dislocation
- the dorsal skin was carefully removed from the rat as a single pelt and excess fat was removed
- the pelt was mounted, epidermal side uppermost, onto a polytetrafluoroethylene (pTFE) tube and secured in place using a rubber “O” ring
- Excess tissue was trimmed away and the "O" ring/PTFE inter face sealed with soft paraffin wax
- The tube was supported by a clamp inside a labelled 30 mL glass receptacle containing 10 mL electrolyte solution (154 mM MgS04)

Details on test system:

The TER was measured using a Wheatstone Bridge with a low voltage alternating current. Prior to measurement of the resistance, the surface tension of the skin disc was reduced by adding a sufficient volume of 70% ethanol to cover the epidermis. The PTFE tube was then placed in the labelled receptor chamber and the tissue was hydrated by the addition of 3 ml MgS04 solution (154 μM) to the inside ofthe PTFE tube.
The stainless steel electrodes of the databridge were placed on either side of the skin disc. The measurement was taken and a value in Ω/kΩ per skin disc was displayed on the databridge display.
The mean TER for the skin discs was calculated.
As part of a Quality Control procedure, three positive and negative control discs were assayed.

The test material and positive/negative controls were applied to the epidermal surface of three skin discs for a contact period of 24 hours. At the end of the exposure period, the test material was removed by washing the skin disc with a jet of warm tap water until no further test material could be removed.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

Sufficient test material was applied to cover the epidermal surface. 150 μl of distilled water was a pplied to ensure good contact with the skin.

Duration of treatment / exposure:

24 h

Number of replicates:

3

Irritation / corrosion parameter:

transcutaneous electrical resistance (in kΩ)

Value:

16.33

Vehicle controls validity:

not examined

Negative controls validity:

valid

Remarks:

23.8 ± 9.2 kΩ

Positive controls validity:

valid

Remarks:

820.9 ± 30.6 Ω

Other effects / acceptance of results:

The mean TER recorded for the 24 hour test material contact period was greater than 5 kΩ (16.33 ± 2.5 kΩ)

The TER recorded for the positive and negative control discs were as follows:

Positive control disc, Hydrochloric acid (approximately 36%): 820.9 ± 30.6 Ω
Negative control disc, Sterile distilled water: 23.8 ± 9.2 kΩ

Results are accepted on the condition of adherence to the ranges given:

If the positive and negative control results for the assay do not fall within the accepted ranges, the data on the test substance cannot be interpreted as being reliable, and the experiment must be repeated.

Hydrochloric acid (approximately 36%), Positive control range: 0.5 to 1.0 kΩ

Sterile distilled water, Negative control range: 10 to 25 kΩ.

The test substance will be classified as 'Non-Corrosive' if the mean TER value recorded for the 24 hour contact period is greater than 5 kΩ. The test substance will be classified as 'Corrosive' if the mean TER value recorded for the 24 hour contact period is 5 kΩ or lower. A 'Non-Corrosive' classification may require further investigation using an in vivo skin corrosivity test.

Interpretation of results:

other: non corrosive

Remarks:

Criteria used for interpretation of results: expert judgment

Conclusions:

The test material was considered not to have the potential to be corrosive to skin in vivo under the conditions of the test.

Executive summary:

The skin corrosivity potential of DIMAPDO was assessed using the Transcutaneous Electrical Resistance Assay (TER) equivalent to OECD430.

 

After 24 hours application of the test material and the positive/negative control substances to the epidermal surface of three skin discs each the following TERs were recorded:

 

DIMAPDO: 16.33 ± 2.5 kΩ

Positive control disc, Hydrochloric acid (approximately 36%): 820.9 Ω

Negative control disc, Sterile distilled water: 23.8 kΩ

 

Test materials that give a mean electrical resistance of 5 kΩ or less are considered likely to be corrosive in vivo. Therefore DIMAPDO was considered not to have the potential to be corrosive to skin in vivo under the conditions of the test.

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:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that source and target substances have similar toxicological properties because
• they are manufactured from similar or identical precursors under similar conditions
• they share structural similarities with common functional groups: tertiary amines, amides, and fatty acid chains with comparable length and degree of saturation (corresponding to scenario 2 of the read-across assessment framework)

The read-across hypothesis is based on structural similarity of target and source substances. The target and source chemicals have a very similar structure in that they are comprised of a hydrophobic (alkyl) and hydrophilic (amine headgroup) end. Due to this motif they form micelles (colloidal dispersions) and have surfactant properties.
Based on available experimental data, including key physicochemical properties and data from genotoxicity studies, the read-across strategy is supported by a similar toxicological profile of all substances.

Therefore, read-across from the existing toxicity studies conducted with the source substances is considered as an appropriate adaptation to the standard information requirements of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation.

A justification for read-across is attached to IUCLID section 13.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See justification for read-across attached to IUCLID section 13.

3. ANALOGUE APPROACH JUSTIFICATION
See justification for read-across attached to IUCLID section 13.

4. DATA MATRIX
See justification for read-across attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Species:

rabbit

Strain:

New Zealand White

Vehicle:

unchanged (no vehicle)

Observation period (in vivo):

48 hours

Number of animals or in vitro replicates:

1

Irritation parameter:

cornea opacity score

Basis:

animal #1

Time point:

24/48/72 h

Score:

2.5

Max. score:

4

Reversibility:

other: not applicable

Remarks on result:

other: animal was killed for ethical reasons after 48 h

Irritation parameter:

iris score

Basis:

animal #1

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

other: not applicable

Remarks on result:

other: animal was killed for ethical reasons after 48 h

Irritation parameter:

conjunctivae score

Basis:

animal #1

Time point:

24/48/72 h

Score:

3

Max. score:

4

Reversibility:

other: not applicable

Remarks on result:

other: animal was killed for ethical reasons after 48 h

Irritation parameter:

chemosis score

Basis:

animal #1

Time point:

24/48/72 h

Score:

4

Max. score:

4

Reversibility:

other: not applicable

Remarks on result:

other: animal was killed for ethical reasons after 48 h

Table 1: Individual eye irritation scores of animal #1

Irritation parameter	Time point	Score
Corneal opacity	1 hour	0
Area of corneal opacity	1 hour	0
Iris score	1 hour	0
Conjunctivae score	1 hour	2
Chemosis score	1 hour	2
Sclera	1 hour	2
Corneal opacity	24 hour	2
Area of corneal opacity	24 hour	4
Iris score	24 hour	2
Conjunctivae score	24 hour	3
Chemosis score	24 hour	4
Corneal opacity	48 hour	3
Area of corneal opacity	48 hour	4
Iris score	48 hour	2
Conjunctivae score	48 hour	3
Chemosis score	48 hour	4

No staining produced by the test item of the treated eye was observed. White test item remnants were evident in eye or conjuncitval sac of the animal 1 -48 hours after treatment. No corrosion of the cornea was observed at any of the reading times.

The mean score for corneal opacity, iris, redness and chemiosis of the conjunctivae were not calculated because the animal was sacrificed for ethical reasons after the 48 -hour reading.

Interpretation of results:

Category 1 (irreversible effects on the eye) based on GHS criteria

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irreversible damage)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

For the assessment of skin irritation potential the following studies are taken into account:

-      an equivalent to OECD 430 trancutanous electrical resistance corrosivity in vitro study of the target substance DIMAPDO

-      an OECD 404 primary dermal irritation study in vivo of the source substance N-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50 (w/w %).

-      an additional OECD 404 primary dermal irritation in vivo study similar of the source substance Stearic acid 3-(dimethylaminopropyl)amide

No experimental data on the target substane DIMAPDO are available for the endpoint eye irritation. However, a study was conducted with the source substance N-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50. A justification for read-across is attached to IUCLID section 13.

 

Skin Irritation

The skin corrosivity potential of DIMAPDO was assessed using the Transcutaneous Electrical Resistance Assay (TER) equivalent to OECD guideline 430. After 24 hours application of the test material and the positive/negative control substances to the epidermal surface of three skin discs each the following TERs were recorded:

 

DIMAPDO: 16.33 ± 2.5 kΩ

Positive control disc, Hydrochloric acid (approximately 36%): 820.9 Ω

Negative control disc, Sterile distilled water: 23.8 kΩ

 

Test materials that give a mean electrical resistance of 5 kΩ or less are considered likely to be corrosive in vivo. Therefore DIMAPDO was considered not to have the potential to be corrosive to skin in vivo under the conditions of the test.

 

An in vivo primary dermal irritation study is available for the structurally similar source substanceN-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50 (w/w %).According to OECD Guideline 404, adopted 24 April 2002, and EU Method B.4, May 2008, 3 adult New Zealand white rabbits (1 male, 2 females) were dermally exposed to 0.5 g of N-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50 (w/w %; moistened with 0.5 mL water) to 6.25 cm² skin surface. Animals then were observed for 10 days. Irritation was scored by the method of the numerical scoring system listed in the Commission Regulation (EC) No 440/2008, B.4.

One hour after test item exposure a very slight erythema (grade 1) was observed in the first treated female and in the male which progressed into a well-defined erythema (grade 2) at the 24-hour reading and persisted well-defined or very slight up to the 72-hour reading in both animals. A very light swelling was recorded in the first treated female 24 and 48 hours after removal of the dressing. Scaling was present on the skin of the male on day 7. In this study, C18/C22 is classified as not irritating to rabbit skin according the criteria of CLP, EU GHS (Regulation (EC) No 1272/2008).

 

Also the second source substancestearic acid 3-(dimethylaminopropyl)amide has no irritation potentialas demonstrated by the following study:

In a primary dermal irritation study according to OECD Guideline 404, adopted 24 April 2002, and EU Method B.4, May 2008, 3 young adult New Zealand white rabbit of one sex were dermally exposed to 0.5 g of Stearic acid 3-(dimethylaminopropyl)amide (100% a.i) to 6 cm² skin surface. The first animal was subsequently exposed for 3 minutes, 1 and 4 hours. Two further animals were exposed for 4 hours. Animals then were observed for 7 (animal #1) or 14 days (animals #2, #3). 

 

In animal 1, no signs of skin reactions were recorded after removing the patch applied for 3 minutes and 1 hour in the observations carried out after removing the patches. After the 4 hours exposure to the test item, very slight oedema (grade 1) was observed one hour after removing the patch. Skin reactions observed in this animal during the observations made 24 and 48 hours after removing the patch were slight erythema (grade 2) and very slight edema (grade 1). After 72 hours, there was very slight erythema and very slight edema (grade 1) that was fully reversible within 7 days.

 

In animals 2 and 3, very slight edema (grade 1) and very slight erythema (grade 1) were observed 1 h after patch removal. At the 24, 48 and 72 h observations slight erythema (grade 2) and very slight or slight edema (grade 1 - 2) were noted. Scaliness was seen in these two animals after 7 days. The skin irritation resolved within 15 days.

The means of the erythema and edema evaluations at 24, 48 and 72 hours for the three animals after a four-hour exposure were 1.6, 2 and 2 (erythema) and 1, 1.3 and 1 (edema).

 

In this study, Stearic acid 3-(dimethylaminopropyl)amide is classified as not irritating to rabbit skin according the criteria of CLP, EU GHS (Regulation (EC) No 1272/2008).

 

 

Eye Irritation 

In a primary eye irritation study according to OECD 405, 0.1 g of the source substance N-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50 (w/w %) was instilled into the conjunctival sac of the left eye of one young adult female New Zealand White rabbit for 48 hours. The animal then was observed for 48 hours.  The eye was washed with physiological saline at 24 and 48 hours. Irritation was scored by the method of Commission Directive 2001/59/EC of August 06, 2001.

 

A slight opacity of the cornea affecting the whole area was noted in the treated femael at the 24-hour reading and progressed into moderate at the 48-hour evaluation. The light reflex was absent 24 to 48 hours after test item instillation. Moderate reddening and obvious swelling (chemosis) of the conjunctivae were noted 1 hour after treatment which progressed into marked reddening and marked swelling at the 24- and 48-hour reading. The sclerae of the animal were moderately reddened at the 1-hour observation and were not assessable 24 to 48 hours after treatment due to swelling of the conjunctivae. Moderate ocular discharge was noted 1 to 48 hours after test item exposure. Blood was noted in the eye of the animal at the 48-hour evaluation. The treated female showed uneven head and severe signs of pain during the examination of the eye at the 48-hour reading and was therefore sacrificed immediately thereafter.

 

In this study, N-[3-(dimethylamino)propyl]stearamide (C18) and N-[3-(dimethylamino)propyl] docosanamide (C22) 50:50 (w/w % is classified as "R41 - Risk of serious damage to eye" (eye irritant category 1).

 

Respiratory irritation

No data on the respiratory irritation of DIMAPDO are available.

 

There are no data gaps for the endpoint irritation/corrosion. No human information is available for this endpoint. However, there is no reason to believe that these results would not be applicable to humans.

 

Justification for classification or non-classification

Based on the available data DIMAPDO does not need to be classified as irritating to the skin but as irreversible effects to the eye (Category 1) and labelled with H318 (Causes serious eye damage) according to regulation (EC) 1272/2008.