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Diss Factsheets

Administrative data

Description of key information

Isobutyl acrylate is a potential skin sensitiser.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Referenceopen allclose all

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
26 Oct 2005 - 15 Nov 2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes
Type of study:
mouse local lymph node assay (LLNA)
Specific details on test material used for the study:
- Name of test material: Butyl acrylate
- Physical state: liquid
- Batch reference number: CTL Bottle No 281910, 30010013680
- CTL test substance reference number: Y03526/002
- Expiration date of the lot/batch: November 2005 (reanalysed February 2006)
- Storage condition of test material: Ambient temperature in the dark
Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan Interfauna UK Limited, UK
- Strain: CBA/Ca/Ola/Hsd
- Diet (ad libitum): Diet (RM1), supplied by Special Diet Services Limited, UK
- Water (ad libitum): Mains water
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±3
- Humidity (%): 30-70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light):12/12
Vehicle:
acetone/olive oil (4:1 v/v)
Concentration:
1, 2.5, 5, 10 or 25 % w/v
No. of animals per dose:
4
Details on study design:
RANGE FINDING TESTS:
A preliminary sighting study was conducted on one animal per dose group for 2.5, 10 and 50 % w/v concentrations to determine the acceptable toxicity and lymph node activation levels. MAIN STUDY
Groups of four female mice were used for the main LLNA study. Approximately 25μL of a 1, 2.5, 5, 10 or 25 % w/v preparation of the test substance in acetone in olive oil (4:1) was applied, using a variable volume micro-pipette, to the dorsal surface of each ear. A vehicle control group was similarly treated using acetone in olive oil (4:1) alone. The procedure was repeated daily for 3 consecutive days.
Three days after the third application, all the animals were injected, via the tail vein, with
approximately 250μl of phosphate buffered saline (PBS) containing 20 μCi of a 2.0 Ci/mmol specific activity 3H-methyl thymidine. Approximately 5 hours later, the animals were humanely killed by inhalation of halothane vapour followed by cervical dislocation. The draining auricular lymph nodes were removed from each animal and, together with the nodes from the other animals in the group, were placed in a container of PBS.
A single cell suspension was prepared by mechanical disaggregation of lymph nodes through 200-mesh stainless steel gauze. The cell suspensions were then washed three times by centrifugation with approximately 10ml of PBS. Approximately 3mL of 5% w/v trichloroacetic acid (TCA) was added and, after overnight precipitation at 4°C, the samples were pelleted by centrifugation and the supernatant was discarded. The cells were then resuspended in approximately 1mL of TCA. The lymph node suspensions were transferred to scintillation vials and 10ml of scintillant (Optiphase) was added prior to β-scintillation counting using a Packard Tri-Carb 3100TR Liquid Scintillation Counter.

Clinical observations: Animals were checked at least once daily for signs of systemic toxicity.
Bodyweights: The bodyweight of each animal was recorded prior to dosing on day 1 and prior to injection of 3H-methyl thymidine on day 6 for LLNA study mice or prior to termination for sighting study mice.

Positive control study: Approximately 25μL of a 5%, 10% or 25% w/v preparation of hexylcinnamaldehyde in acetone in olive oil was applied, and a vehicle control group was similarly treated using acetone in olive oil alone (4:1).

Data evaluation:
The results are expressed as disintegrations per minute (dpm) value per lymph node for each group. The activity of each test group is then divided by the activity of the vehicle control group to give a test:control ratio known as the stimulation index (SI), for each concentration. The criterion for a positive response is that one or more concentrations of the test substance should elicit a 3-fold or greater increase in isotope incorporation relative to the vehicle control group.

EC3 calculations
The estimated concentration of the test substance required to produce a 3-fold increase in the draining lymph node cell proliferative activity was calculated (EC3).
The EC3 value was derived by interpolating between two points on the Stimulation Index (SI) axis, one immediately above and the other immediately below the SI value of 3 (vehicle-treated control values [SI=1] not being used for the latter). Where the data points lying immediately above and below the SI value of three have the co-ordinates a (the concentration giving the SI immediately above 3), b (the SI of a), c (the concentration giving the SI immediately below 3) and d (the SI of c), the EC3 value was calculated using the following equation: EC3 = [(3-d)/(b-d)] x (a-c) + c
The quantity applied per square centimetre was derived from this value, assuming that the area of the mouse ear is 1cm2 and that 1 μL is equivalent to 1 mg.
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Positive control results:
The application of hexylcinnamaldehyde at concentrations of 5%, 10% and 25% w/v in acetone in olive oil (4:1) resulted in a greater than 3-fold increase in isotope incorporation at the 10 and 25 % w/v concentrations. Therefore, hexylcinnamaldehyde was shown to be a skin sensitiser, confirming the validity of the protocol used for the study.
Key result
Parameter:
EC3
Value:
11.2
Parameter:
SI
Value:
8.7
Test group / Remarks:
25 % (w/v)
Parameter:
SI
Value:
2.5
Test group / Remarks:
10 % (w/v)
Parameter:
SI
Value:
1.4
Test group / Remarks:
5 % (w/v)
Cellular proliferation data / Observations:
DETAILS ON STIMULATION INDEX CALCULATION
The application of the test substance at concentrations of 1, 2.5, 5, 10 and 25 % w/v in acetone in olive oil (4:1) resulted in an increase in isotope incorporation which was greater than 3-fold at the 25 % w/v concentration.

EC3 CALCULATION
The concentration giving rise to a 3 fold increase in lymphocyte proliferation (EC3) was calculated to be 11.2 % w/v (2800 μg/cm2), indicative of a sensitiser of weak potency.

Concentration of

test substance

(% w/v)

Number of lymph

nodes assayed

Disintegrations

per minute

(dpm)

dpm per

lymph node

Test : control

ratio (SI)

0 (vehicle only)

8

5964

746

N/A

1

8

4722

590

0.8

2.5

8

7956

995

1.3

5

8

8213

1027

1.4

10

8

15161

1895

2.5

25

8

51892

6487

8.7

EC3

Calculated to be 11.2 % (2800 µg/cm2)

N/A- not applicable

Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
ANALOGUE APPROACH JUSTIFICATION
For read-across justification please refer to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Key result
Parameter:
EC3
Value:
11.2
Parameter:
SI
Value:
8.7
Test group / Remarks:
25 % (w/v)
Parameter:
SI
Value:
2.5
Test group / Remarks:
10 % (w/v)
Parameter:
SI
Value:
1.4
Test group / Remarks:
5 % (w/v)
Cellular proliferation data / Observations:
DETAILS ON STIMULATION INDEX CALCULATION
The application of the test substance at concentrations of 1, 2.5, 5, 10 and 25 % w/v in acetone in olive oil (4:1) resulted in an increase in isotope incorporation which was greater than 3-fold at the 25 % w/v concentration.

EC3 CALCULATION
The concentration giving rise to a 3 fold increase in lymphocyte proliferation (EC3) was calculated to be 11.2 % w/v (2800 μg/cm2), indicative of a sensitiser of weak potency.
Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

There are no experimental data on the sensitization potential of isobutyl acrylate available. The structural analogue n-butyl acrylate on the other hand has been investigated in depth. Thus, an assessment of the potential skin sensitising properties of isobutyl acrylate by read-across was made.

N-butyl acrylate was investigated in a Local Lymphnode Assay conducted according to OECD guideline 429 and GLP regulations (BAMM, 2006). The application of the test substance at concentrations of 1, 2.5, 5, 10, or 25 % w/v in acetone : olive oil (4:1) resulted in an increase in isotope incorporation which was greater than 3-fold at the 25 % w/v concentration. Consequently, the test substance was shown to be a potential skin sensitiser. The concentration giving rise to a 3 fold increase in lymphocyte proliferation (EC3) was calculated to be 11.2 % w/v (2800 μg/cm2), indicative of a sensitiser of weak potency.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available
Additional information:

There is no information available on the potential for isobutyl acrylate to produce respiratory sensitisation in animals.

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No 1272/2008

The available data on skin sensitisation are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. Based on the available data, the substance is considered to be classified for skin sensitisation, Cat. 1B, H317 under Regulation (EC) No 1272/2008, as amended for the fifteenth time in Regulation (EU) 2020/1182.