Reaction mass of dodecyl methacrylate and tridecyl methacrylate

Endpoint summary

Additional information

No experimental aquatic toxicity data are available for the target substance Reaction mass of dodecyl methacrylate and tridecyl methacrylate.

A short-term toxicity study in fish conducted with the structurally related Isotridecyl methacrylate is available as well as a long-term toxicity to aquatic invertebrates and a toxicity study to aquatic algae which were conducted with the structurally related source substance Dodecyl methacrylate. Toxicity studies to microorganism were conducted with Methacrylic acid methyl ester 13.6 and Dodecyl methacrylate. A detailed justification for read-across is attached to IUCLID section 13.

 

Summary

Water solubility of Reaction mass of dodecyl methacrylate and tridecyl methacrylate is extremely low (< 1 µg/L). No toxicity to aquatic organisms was observed in the range of water solubility in short-term and long-term tests conducted with closely related source substances. Therefore, the derivation of a meaningful PNEC is not feasible.

 

Hypothesis for the analogue approach

The read-across hypothesis relies on the close structural similarity between the source substances Isotridecyl methacrylate, Methacrylic acid methyl ester 13.6 and Dodecyl methacrylate and the target substance Reaction mass of dodecyl methacrylate and tridecyl 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 substances Isotridecyl methacrylate, Methacrylic acid methyl ester 13.6 and Dodecyl methacrylate predict the ecotoxicological properties of the target substance Reaction mass of dodecyl methacrylate and tridecyl methacrylate.

 

Based on the available data, including physicochemical data (water solubility and log Kow), the read-across strategy is supported by close structural analogy of the substances.

 

Ecotoxicological 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 ecotoxicity studies conducted with the source substances 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 Reaction mass of dodecyl methacrylate and tridecyl methacrylate is an ester of Methacrylic acid and mainly linear C12 / C13 alcohols. The source substances Isotridecyl methacrylate, Methacrylic acid methyl ester 13.6 and Dodecyl methacrylate are comparable to the target substance with respect to chain length. But Isotridecyl methacrylate contains mainly branched alkyl chains.

 

Structural differences:

There are only minor differences in alkyl chain length between the target and the source substances, which are not considered relevant for aquatic toxicity. The source substance Isotridecyl methacrylate contains mainly branched alkyl chains. This also is not considered to underestimate ecotoxicity.

 

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

An OECD 203 guideline GLP study with nominal test concentrations above 10000 mg/L showed no toxicity to Danio rerio. Therefore, it appears that saturated solutions of Isotridecyl methacrylate are non-toxic to fish.

 

Long-term toxicity to aquatic invertebrates

The 21-day-chronic toxicity of dodecyl methacrylate to Daphnia magna STRAUS was studied under semi static conditions according to OECD guideline 211. Daphnids were exposed to dodecyl methacrylate at a limit concentration of 10 µg/L (nominal).

This concentration is higher than the solubility in water (< 1 µg/L) but has, nevertheless, been chosen with regard to the feasibility of

attaining appropriate and detectable test concentrations at 10 µg/L.

10 test organisms, individually held were used for the limit concentration and control. At test start they were 2 to 24 hours old. The test method was semi-static. Test solutions were renewed daily.

Concentrations of dodecyl methacrylate in the stock solution, limit concentration and control of fresh (0 h) and old (24 h) media were determined via HPLC. Samples were taken and analysed on days 0, 7, 16, 20 (fresh media) and on days 1, 8, 17, 21 (old media). The test item concentrations decreased within 24 h. All effect values were given based on the time weighted mean measured concentration for the limit concentration of 5.73 µg/L.

The average number of juveniles per parent in the control group was 85 after 21 days. The reproductive output at the limit concentration was not statistically significant reduced compared to the control (One Way Analysis of Variance, p < 0.05).

The coefficient of variation around the mean number of living offspring produced per parent in the control group was 5.02 % and shows very small variances between the control replicates.

No winter eggs, males, ephippia, stillborn juveniles and aborted eggs occurred in control or test groups.

The mean day of release of first brood was 9 in the control group and the limit concentration. There was no difference between the two groups. At the limit concentration and the control group 4 broods were released during the test period.

The intrinsic rates of natural increase (IR) of the surviving parent animals accounting for generation time and offspring numbers were used for calculation of population growth. The mean IR of the surviving daphnids of the limit concentration was compared to the control by One Way Analysis of Variances (p < 0.05). There was no statistically significant difference. The intrinsic rate was comparable for the control and limit concentration.

The no observed effect concentration (NOEC) after 21 days based on reproduction capacity is the tested limit concentration of 5.73

µg/L. No statistically significant test item related effects were observed at the limit concentration when compared to the control

group. No immobilisation of parent animals occurred in the control or test group.

Water quality parameters as pH-value, dissolved oxygen, water hardness and temperature were determined to be within the acceptable limits.

In order to prove the validity of the test system and test conditions at the testing facility, an acute immobilisation test according to DIN 38412 L11 was carried out with potassium dichromate as reference item once per month. The EC50 of the reference item at 1.84 mg/L after 24 hours was within the validity range of 1.0 to 2.5 mg/L according to DIN 38412 L30.

 

The 21 day LC50/EC50based on reproduction/immobilisation was greater than 5.73 µg/L (mean measured concentration). The 21-day NOEC based on reproduction/immobilisation was 5.73µg/L (mean measured concentration). Production of offspring in the treated groups indicated that Dodecyl methacrylate did not have an effect on the reproduction at concentrations greater than 5.73 µg/L.

 

Toxicity to aquatic algae

There is one study available with acceptable reliability: Dodecyl methacrylate did not cause any inhibiting effects to Desmodesmus subspicatus after 72 h when tested at a concentration of 10 µg/l. The test concentration was approx. 10-fold higher than the water solubility (technical reasons) setting some limitation to the validity of the study.

The test concentration was chosen because it was sufficiently high above the LoQ (1 µg/l) to be measurable, with the consequence that it had to be approx. 10 fold higher than the limit of solubility.

 

Toxicity to microorganisms

In a 5 d toxicity study according to OECD Guideline 209 the cultures of activated sludge were exposed to Dodecyl methacrylate at concentrations of 100, 200 and 500 mg/L. Due to low solubility the substance was tested emulsified.

No inhibition of respirometric activity in any of the tested concentrations. LC0 (bacteria): > 500 mg/L.

 

In a 3 h toxicity study according to OECD Guideline 209 the cultures of activated sludge were exposed to Methacrylic acid methyl ester 13.6 at a concentration of 10000 mg/L. The EC10 (3 h) was > 10000 mg/L. Therefore, it can be concluded that the test substance Methacrylic acid methyl ester 13.6 is non-toxic to bacteria.