2-Propenoic acid, 2-methyl-, C11-14-isoalkyl esters, C13-rich

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

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 physicochemical, ecotoxicological and toxicological properties because
• they are manufactured from similar or identical precursors under similar conditions
• they share structural similarities with common functional groups: methacrylate esters
• the metabolism pathway leads to comparable products (methacrylic acid and medium chain alcohol).

Therefore, read-across from the existing physicochemical, ecotoxicity and toxicity studies on the source substances is considered as an appropriate adaptation to the standard information requirements of REACH regulation

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

Radiolabelling:

no

Vehicle:

no

Test organisms (species):

other: Danio rerio

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Test temperature:

24 +/- 1°C

Type:

BCF

Value:

37 dimensionless

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

1.5 h

Elimination:

yes

Parameter:

other: DT95

Depuration time (DT):

6 h

Conclusions:

The BCF was calculated to be 37 for both test concentrations. Therefore the substance has low potential for bioaccumulation and the criteria for classification is not fulfilled.

Description of key information

An experimental study on the structural analogue 2 -Ethylhexyl methacrylate (log Kow > 4) of bioconcentration of the substance, according to OECD guideline 305 demonstrates that a rapid metabolisation occurs, this depuration prevents any significant accumulation. The measured BCF is 37.

Key value for chemical safety assessment

BCF (aquatic species):

37 dimensionless

Additional information

No experimental data on Isotridecyl methacrylate are available for the assessment of bioaccumulation potential. However, a study isavailable for the source substance 2-Ethylhexyl methacrylate. A detailed justification for read-across is attached to IUCLID section 13.

 

An experimental study on the structural analogue 2-Ethylhexyl methacrylate (log Kow = 4.95) of bioconcentration of the substance, according to OECD guideline 305 demonstrates that a rapid metabolism occurs, this depuration prevents any significant accumulation. The measured BCF is 37.

This result is representative for the target substance, although there are differences in physicochemical properties (log Kow of the target substance > 6.5, and water solubility < 1 µg/L; log Kow of the source substance 4.95 and water solubility 3.1 mg/L). Rapid metabolism of the target substance by unspecific esterases is expected to occur, thus, bioaccumulation potential is judged to be low.

 

Hypothesis for the analogue approach

The read-across hypothesis relies on the close structural similarity between the source substance 2-Ethylhexyl methacrylate and the target substance Isotridecyl methacrylate. This read-across hypothesis corresponds to scenario 2 - different compounds have qualitatively similar properties - of the read-across assessment framework i.e. properties of the target substance are predicted to be quantitatively equal to those of the source substance. Namely, the structurally similar source substance 2-Ethylhexyl methacrylate predicts the environmental fate properties of the target substance Isotridecyl methacrylate.

 

Experimental data are summarised in the data matrix; robust study summaries are included in the Technical Dossier in the respective sections.

 

Therefore, read-across from the existing studies conducted with the source substance 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 detailed justification for the proposed read-across approach is attached to Iuclid section 13.

 

1. Identity and characterisation of the source substance

 

There is close structural similarity between the source and the target substances and the identity and characterisation of these substances is unambiguous thereby giving a high level of confidence in the validity of the read across.

The target and source substances are manufactured from similar compounds by esterification of methacrylic acid with the corresponding fatty alcohol. Typical trace impurities are water and the corresponding alcohols as well as < 1 % methacrylic acid, which are not of toxicological concern.

The carbon chain length distribution of the resulting mix of long-chain aliphatic methacrylate esters mirrors the chain length distribution of the alcohol(s) used.

 

2. Link of structural similarities and differences with the proposed prediction

Structural similarities:

The target substance Isotridecyl methacrylate is an ester of Methacrylic acid and branched C12-C18 alcohols. The source substance 2-Ethylhexyl methacrylate contains branched alkyl chains as well, though it contains shorter C-chains (C8).

 

Structural differences:

There are differences in alkyl chain length between the target and the source substances.

The source substance 2-Ethylhexyl methacrylate can be expected to have a slightly higher bioavailability due to lower molecular weight compared to the target substance.

The physicochemical properties (low water solubility and high log Kow) are, however, quite similar. Thus, no large differences in bioavailability are expected.

 

Reliability and adequacy of the source data

All available studies have been conducted according to OECD guidelines and have been assigned a reliability of 1 or 2 as documented in the data matrix (see detailed justification for read-across attached to Iuclid section 13).

 

Overall, the study design of the respective source studies is adequate and reliable for the purpose of this read-across. The results of the study are adequate for classification and labelling and for risk assessment purposes.

 

Data availability

In a valid guideline study the bioaccumulation factor BCF of 2-Ethylhexyl methacrylate was tested in a bioconcentration study according to OECD Guideline 305 with Danio rerio at nominal concentrations of 0.06 and 0.3 mg/L under flow through conditions. Based on a range finding experiment which indicates fast metabolism, the uptake phase was scheduled for 26 hours, the depuration phase for 30 hours.

The steady state BCF was calculated to be 35 and 34 hours for the low and high test concentration, respectively. From the kinetic rates the BCF of 2-Ethylhexyl methacrylate was calculated to be 37 for both test concentrations.

Therefore, 2-Ethylhexyl methacrylate has low potential for bioaccumulation and the criteria for classification is not fulfilled.