Registration Dossier

Administrative data

Description of key information

Skin sensitisation:

The test substance was found in in vivo as well as in vitro studies to have a sensitising effect on the skin.

Respiratory sensitisation:

There are valid human data available for the assessment of the respiratory sensitisation potential of the test item. Based on Human field and cross-sectional studies with serial examinations there is clear evidence that the substance is a respiratory irritant, but there is no convincing evidence that the test substance has a potential to induce respiratory sensitization (Please refer to Brubaker et al., 1979, reliability score: 2, details see section 7.10.5 Exposure related observations in Humans)






Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
GLP compliance:
no
Type of study:
mouse local lymph node assay (LLNA)
Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 7 - 12 weeks
Vehicle:
acetone/olive oil (4:1 v/v)
Concentration:
0.5; 1.0; 2.5; 5.0; 10.0%
No. of animals per dose:
a minimum of 4 animals
Parameter:
SI
Remarks on result:
other: Vehicle (Acetone : olive oil): 1 Test material:  0.5%: 1.3 1.0%: 1.1 2.5%: 3.5 5.0%: 7.0 10.0%: 13.9
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: Vehicle: 463 Test material: 0.5%: 597 1.0%: 486 2.5%: 1626 5.0%: 3223 10.0%: 6417

EC3: 2.2% (EC3 value derived by linear interpolation);

EC3: 2.3% (EC3 values derived by log-linear extrapolation).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

Skin Sensitisation

There are valid in vivo data available for the assessment of the skin sensitisation potential of the test item.

The skin sensitizing potential of the test item (analytical purity 99%) was assessed in the radioactive Murine Local Lymph Node Assay according to GLP and OECD 429 (Wright et al., 2001/Ryan et al., 2007). The assay simulates the induction phase for skin sensitization in mice and determines the response of the auricular lymph nodes on repeated application of the test substance to the dorsal skin of the ears. Groups of 4 female CBA/Ca mice each were treated with 25μL per ear of 0.5, 1.0, 2.5, 5, or 10% of the test substance in acetone/olive oil 4:1 to the dorsum of each ear for three consecutive days. A stimulation index (increase in 3HTdR incorporation compared to control values) of 1.3, 1.1, 3.5, 7.0, or 13.9 was recorded for concentrations of the test material (0.5, 1.0, 2.5, 5, or 10% in acetone/olive oil 4:1). Due to an EC3 value of 2.2%, the test material was considered to be a moderate sensitizer in the Murine Local Lymph Node Assay under the test conditions chosen.  

In the Allied Corp study, the test substance was evaluated for dermal sensitization in 15 female Hartley guinea pigs by maximization test. Induction consisted of 3 pairs of 0.1 mL intradermal injections flanking the dorsal midline upon the clipped shoulder area, the respective twin injections including a 1 and 5% v/v solution in distilled water (a first challenge application of DMAPA was applied as 1% (v/v) solution in distilled water, in a second challenge application of DMAPA was applied as 5% (v/v) solution in distilled water; unspecified pretest concentration that produces neither local or systemic reactions), a 1 and 5% v/v solution in Freunds Complete Adjuvant (FCA), and FCA alone. Following the 7-day induction, 48-hour challenge was administered with a 0.3 mL topical application of 1% solution in distilled water under occluded patch covering the entire test area. A second 48-hour challenge was performed 21 days later with a 0.3 mL topical application of 5% solution and another of vehicle alone, each on either side of the dorsal midline to cover triplet test sites. After induction with 5% test item positive reaction were observed in 93% (14/15) of the test animals, relative to 0% response (0/6) in the vehicle/FCA control group. Due to a responding rate of 93% at 5% intradermal induction dose, the test material was considered to be a moderate sensitizer in the Guinea pig maximization test under the test conditions chosen.  

In a second GPMT study from Hazleton, the delayed contact hypersensivity of test substance was also evaluated in Guinea pigs according to OECD N°406 guideline and in compliance with GLP. The induction phase has been realized both by intradermal route on day 1 (test substance 0.25 % in water) and by cutaneous route on day 9 (test substance 5 % in water) in 2 groups of guinea pigs. The challenge phase was realized on day 22 by cutaneous application of test substance 1 % in water; the cutaneous reactions were scored 6, 24 and 48 hours after the challenge phase. Scratch marks on application site were observed 6 hours (n=3), 24 hours (n=6) and 48 hours (n=5) after challenge but only 3 and 2 animals showed a very slight erythema at 6 and 24 hours respectively. 48 hours after challenge phase, no erythema was observed in any treated group animals. The negative response obtained in this study was probably due to the lower test substance concentration at intradermal induction (0.25% compared to 1-5% in the Allied Corp study).  

In a third GPMT study from Covance (according to GLP and "EPA OPPTS 870.2600 Skin Sensitization/EU Methods B.6) male guinea pigs received 0.1 -mL intradermal injections of 0.1% DMAPA at the medial sites. Anterior sites were injected with 0.1 -mL of a 1:1 dilution of Freund´s complete adjuvant (FCA), while posterior sites received 0.1 -mL of 0.1% suspensions of DMAPA mixed 1:1 with FCA. Control animals were injected with sterile water. On day 8, the animals in the test and control groups received a topical induction application. A 5% w/v mixture of the test material in sterile water or control was applied to saturation and placed over the six intradermal injection sites. Patches were overwrapped and 48h later the wrappings were removed. On day 22, the animals received a challenge dose. The test material mixture (1% w/v DMAPA) was applied to saturation and placed at a native site of each animal for 24h. A second challenge dose was conducted 15 days after the initial challenge application. A new native site was selected on the animals in the test group and on ten new control animals. Each animal in the test and additional irritation control groups received an application of 1 % w/v mixture DMAPA in sterile water. In those study conditions, DMAPA (1% w/v in sterile water) is considered to be a skin sensitizer in this test system based on the number of animals in the test group that exhibited sensitization reactions at the second challenge phase (9/20).

The test substance was also tested positive in the Buehler test from Huntsman (PH 424 -TX-004 -92, 1992) conducted according to the OECD Guideline 406 (Skin Sensitization) in guinea pig (Hartley). The Buehler test using 5 animals per sex per dose group was conducted with test substance concentrations level in ethanol/acetone of 10% (v/v) for induction, 3.0% (v/v) at challenge and 1.0% (v/v) rechallenge. The minimal irritating concentration for induction and the maximal non irritating concentration for challenge/rechallenge were determined in a range-finding study (4 animals per sex per dose group, concentration levels of 1.0, 10, 25 and 50%). The test substance was applied epicutaneously (occlusive patch) on days 1 to 3 (6 hours per day; the control group received the vehicle only) for induction, on day 29 for challenge and on day 37 for rechallenge. 55% (11/20; 0% in the negative control group) of test animals showed positive reactions 24 hours after challenge (with 3.0% test substance concentration) and 35% 48 hours thereafter (5% in the negative control group). At rechallenge (with 1.0% test substance concentration), a positive reaction was still observable in 20% and 40% of test animals, respectively 24 and 48 hours after test substance application. 100% of test animals treated with the positive control reacted 24 and 48 hours after treatment.

In a non-guideline study (BASF XI/206) guinea pigs were treated with 50% solution of DMAPA in ethanol (epicutanous application) once followed by application of 10% solution of test material (9x). Treated animals showed sanguineous scabs and scarring on the application site. A second application of 1% solution of DMAPA after 13 days induced no skin sensitisation.

In an in vitro study, 27 pre- and pro-haptens including DMAPA were tested using the direct peptide reactivity assay similar to OECD TG 442C. Furthermore, a combination of results from this DPRA assay with results from KeratinoSens assay and h-CLAT assay were used in a 2 out of 3 weight of evidance (WoE) approach to identify the skin sensitization potential.The 2 out of 3 WoE approach identified DMAPA as a positive skin sensitizer (Urbisch et al 2016).  In the evaluation scheme used any two of three test results determine the overall classification, i.e. any two positive test results drive the prediction of a sensitizer, while any two negative test results drive the prediction of a test substance to be a non-sensitizer. In another in vitro study, the SENS-IS test protokol makes use of a 3D reconstructed human skin model (Episkin) as a test system and measures the expression of a large panel of genes relevant to skin sensitization. Here, DMAPA was identified as a moderate skin sensitizer (Cottrez et al 2016).

Based on the results of the LLNA of Wright et al. (2001) / Ryan et al. (2007) as well as the GPMT study of Allied Corp (1984)/Covance 2000 and the Buehler test performed by Huntsman (1992) the test substance is classified as a moderate sensitizer. This result was supported by in vitro assays. 


Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No 1272/2008
The available experimental test data are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. The substance is already listed in Annex VI to Regulation (EC) No 1272/2008 and classified as Skin Sens. Cat. 1 (H317, "May cause an allergic skin reaction"). This classification is supported by the presented data. There is no indication that the substance may cause sensitization to the respiratory system by inhalation as supported by Human data and OECD QSAR toolbox.