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Administrative data

Description of key information

Skin irritation/corrosion

in vitro EpiDerm skin irritation assay (OECD Guideline 439): non irritant

Eye irritation: A weight of evidence approach was used to address the endpoint of eye irritation

read-across (OECD QSAR Toolbox v4.1): The substance is predicted 'highly irritative to the eye'. It lies within the applicability domain of this model and is based on consistent data.

QSAR prediction (QSAR model 'Eye irritation/corrosion by BfR'): The substance is predicted to be 'irritating or corrosive to the eye'.

Key value for chemical safety assessment

Skin irritation / corrosion

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

Eye irritation

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Skin irritation/corrosion

In the key in vitro study (KS_RHE EpiDerm skin irritation assay_in vitro_2017) methyl 2-hydroxyisobutyrate was evaluated for skin irritation potential in an non-GLP in vitro EpiDerm skin irritation assay (MatTek Corporation; Ashland, MA) according to OECD Guideline 439. The EpiDerm tissue model consists of normal, human-derived epidermal keratinocytes that are cultured to form a multilayered, differentiated model of human epidermis. In this assay, methyl 2-hydroxyisobutyrate was topically applied to the EpiDerm tissue for 60 minutes, followed by a 42-hour post-exposure recovery. Following recovery, the cell viability was measured in treated and control tissues using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay and the data reported as a percentage of the mean of negative control. A test chemical was considered to possess skin irritation potential (Cat. 1 or 2) if the relative cell viability was less than or equal to 50%. In this study, Dulbecco’s Phosphate Buffered Saline (DPBS) and 1% TRITON™ X-100 served as the negative and positive controls, respectively.

The mean relative cell viability of methyl 2-hydroxyisobutyrate- and positive control-treated tissues were 98.1% and 3.2% (i.e. ≤ 50%), respectively, therefore, methyl 2-hydroxyisobutyrate was interpreted as a non-irritant (Cat. NC) in the EpiDerm irritation assay.

In a supporting in vivo primary skin irritation study (SS_Skin irritation study_in ivo_rabbit_1993) methyl 2-hydroxyisobutyrate was assessed in accordance with the OECD Guideline 404 (1981).

Briefly, methyl 2-hydroxyisobutyrate was topically applied to the back skin (circular area of about 6 cm2) of 3 Japanese white rabbits for 4 hrs, and the skin was macroscopically examined over time after completion of exposure. No evidence of skin irritation was observed in any of the 3 rabbits in the initial examination 30-60 min after completion of the exposure to methyl 2 -hydroxyisobutyrate and in the subsequent examination period completed 168 hrs later.

The primary irritation index (P.I.I.) was determined to be 0.0 based on findings obtained 30-60 min, 24 hrs, and 72 hrs after termination of exposure to methyl 2-hydroxyisobutyrate, indicating that it causes no primary skin irritation.

Eye irritation

Read-across on eye irritation potential of methyl 2-hydroxyisobutyrate was performed using the OECD QSAR Toolbox (version 4.1). The substance is predicted 'highly irritative to the eye'. It lies within the applicability domain of this model and is based on consistent data. Three of the analogues ( Propyl L-lactate CAS 53651-69-7, Polysolvan O CAS 7397-62-8 and 3-Hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropanoate CAS 1115-20 -4) used for the prediction induced irreversible effects to the eye in rabbits or in the ex vivo Enucleated Eye Test with chicken eyes (CEET).

In addition eye irritation potential of methyl 2-hydroxyisobutyrate was predicted with the QSAR model 'Eye irritation/corrosion by BfR'. It is predicted to be 'irritating or corrosive to the eye'.

Justification for classification or non-classification

Skin irritation/corrosion

The substance methyl 2-hydroxyisobutyrate was assessed in the in vitro EpiDerm skin irritation assay as non irritating. This finding is supported by an skin irritation study according to OECD Guideline 404. Therefore, methyl 2 -hydroxyisobutyrate is not classified as skin irritant in accordance to Regulation (EC) No 1272/2008 (CLP Regulation).

Eye irritation

In a weight of evidence QSAR approach the substance was predicted to to be 'highly eye irritating'. Therefore it is concluded that the test item does meet the criteria for classification as eye irritant Cat. 1 (Eye Dam. 1, H318: Causes serious eye damage) according to Regulation (EC) No 1272/2008 (CLP Regulation).

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