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EC number: 230-241-9 | CAS number: 6976-93-8
Endpoint summary
Administrative data
Description of key information
The lowest aquatic toxicity value for MTMA is the 96 h LC50 of 48.7 mg/L, based on the short-term toxicity study in Danio rerio obtained by read-across to ETMA. This value will be used to derive the PNECs.
Additional information
No experimental data on MTMA are available for the assessment of ecotoxicity. However, studies are available for the source substance ETMA. A detailed justification for read-across is attached to IUCLID section 13.
Hypothesis for the analogue approach
The read-across hypothesis relies on the close structural similarity between the source substance ETMA and the target substance MTMA, differing only by one CH2-group. 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 ETMA predicts the toxicological properties of the target substance MTMA. This read-across is used for the endpoints biodegradation, short-term toxicity to fish, short-term toxicity to aquatic invertebrates, toxicity to algae, toxicity to microorganisms, acute dermal toxicity, skin irritation, eye irritation, sensitisation, and in vitro genotoxicity (bacterial reverse mutation assay).
Based on the available data, including physicochemical data (water solubility and log Kow) and QSAR predictions of aquatic toxicity, the read-across strategy is supported by close structural analogy and similar toxicological profile of the substances.
Toxicological 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 toxicity 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.
Common assessment elements for analogue approaches:
AE A.1 Characterisation of source and target substances
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 highly pure mono-constituent substances. They do not contain impurities, which would be of toxicological concern.
The target substance MTMA is an ester of Methacrylic acid and 2-Methoxyethanol. It is produced by esterification of Methacrylic acid and 2-Methoxyethanol.
The source substance ETMA is an ester of Methacrylic acid and 2-Ethoxyethanol. It is produced by esterification of Methacrylic acid and 2-Ethoxyethanol. ETMA is different to MTMA in only one CH2-group.
AE A.2 Link of structural similarities and structural differences with the proposed prediction
The target substance MTMA differs from the source substance ETMA by one CH2-group. The physicochemical properties (water solubility and log Kow) are, however, very similar. Thus, a comparable bioavailability can be expected. Additionally, QSAR estimations for aquatic toxicity are available for MTMA and ETMA, which further support the read-across for the aquatic endpoints.
Target substance: MTMA |
Source substance: ETMA |
|
Substance type |
Mono-constituent |
Mono-constituent |
IUPAC name |
2-Propenoic acid, 2-methyl-, 2-methoxyethyl ester |
2-Propenoic acid, 2-methyl-, 2-ethoxyethyl ester |
EC name |
2-methoxyethyl methacrylate |
2-ethoxyethyl methacrylate |
EC number |
230-241-9 |
219-135-3 |
CAS number |
6976-93-8 |
2370-63-0 |
Molecular weight |
144.2 g/mol |
158.2 g/mol |
Log Kow |
1.3 at 23.3°C
(OECD Guideline 117/EU Method A.8; HPLC method) |
1.8 at 23.3°C
(OECD Guideline 117/EU Method A.8; HPLC method) |
Water solubility |
31.33 g/L (pH 7.6) at 20°C
(OECD Guideline 105/EU Method A.6; flask method) |
17.05 g/L (pH 5.3) at 20°C
(OECD Guideline 105/EU Method A.6; flask method) |
AE A.3 Impact of impurities on the prediction
Both, the target substance and the source substance, are highly pure mono-constituent substances.
They do not contain impurities, which would be of toxicological concern.
AE A.4 Consistency of properties in the data matrix
Although no experimental data on aquatic toxicity are available for the target substance MTMA, QSAR estimations have been performed for both, the target and the source substance. The results of the QSAR estimations demonstrate, that the effects levels of the target and source substance can be expected to be in the same order of magnitude, and thus, in addition to structural similarity and comparable key physicochemical properties, additionally support the read-across hypothesis.
AE A.5 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 selected key studies are adequate for classification and labelling and for risk assessment purposes.
Data availability
Short-term toxicity to fish
No experimental data are available for the target substance MTMA. However, a short-term toxicity study in fish according to OECD Guideline 203 conducted with the structurally related substance ETMA resulted in a 96 h LC50 of 48.7 mg/L (nominal).
LC50 values of 81.76 mg/L for MTMA and 39.67 mg/L for ETMA were predicted using ECOSAR V1.11. This supports the hypothesis, that effect levels in the same order of magnitude can be expected for the target and source substance. Thus, the result obtained with the source substance ETMA can be used as surrogate date for the target substance MTMA.
Short-term toxicity to invertebrates
No experimental data are available for the target substance MTMA. However, a short-term toxicity study in Daphnia conducted with the structurally related substance ETMA resulted in a 48 h EC50 of 170 mg/L (95% c.i. 130-230 mg/L) (measured initial concentrations).
LC50 values of 62.3 mg/L for MTMA and 30.97 mg/L for ETMA were predicted using ECOSAR V1.11. This supports the hypothesis, that effect levels in the same order of magnitude can be expected for the target and source substance. Thus, the result obtained with the source substance ETMA can be used as surrogate date for the target substance MTMA.
Toxicity to algae
No experimental data are available for the target substance MTMA.
However, a toxicity study in Pseudokirchneriella subcapitata according to OECD Guideline 201 conducted with the structurally related substance ETMA resulted in NOEC, EC10 and EC50 values based on growth rate of 4.0 mg/L, 22.0 mg/L and >184.2 mg/L (initial measured concentrations), respectively.
EC50 values of 0.367 mg/L for MTMA and 0.295 mg/L for ETMA were predicted using ECOSAR V1.11. Although the QSAR highly overestimates toxicity to algae, it is nevertheless used as supporting information. Since the QSAR results of both substances are in the same order of magnitude, the result obtained with the source substance ETMA can be used as surrogate date for the target substance MTMA.
Toxicity to microorganisms
No experimental data are available for the target substance MTMA.
In a 3 h Respiration Inhibition Test according to OECD Guideline 209, activated sludge obtained from a municipal treatment plant was exposed to ETMA at nominal concentrations of 10, 32, 100, 320 and 1000 mg/L under static conditions. The EC10 of ETMA based on respiration inhibition of activated sludge is 72.8 mg/L.
Based on close structural similarity and a similar ecotoxicological profile as demonstrated with QSAR estimations for fish, daphnia and algae, it can be reasonably assumed, that the results obtained with the source substance ETMA are adequate to predict toxicity to microorganisms of the target substance MTMA.
Based on the QSAR estimations for toxicity to fish, daphnia and algae, the source substance ETMA was identified as a worst case. Thus, the available experimental results obtained in the short-term toxicity studies with ETMA can be used to predict the aquatic toxicity potential of MTMA without applying additional safety factors.
In conclusion, the lowest aquatic toxicity value for MTMA is the 96 h LC50 of 48.7 mg/L, based on the short-term toxicity study in Danio rerio obtained by read-across to ETMA. This value will be used to derive the PNECs.
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