Dimethyl itaconate

Long-term toxicity to aquatic invertebrates

Description of key information

Most sensitive aquatic organism group for long-term effects, endpoint reproduction, EC10 overwrites NOEC

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.3 mg/L

Additional information

On the basis of the available data, aquatic invertebrates were found to be the most sensitive aquatic organism group for long-term exposure.

The long-term primary consumer ecotoxicity of the submission item Dimethyl itaconate (CAS 617-52-7) to aquatic invertebrates (Daphnia magna) was measured in a GLP-compliant study (Harris 2014, Harlan Laboratories Report no. 41301814) using the “Daphnia magna Reproduction Test” compliant with EU Method C.20 (Commission Regulation (EC) No. 440/2008), OECD TG 211 (2012) and US EPA OCSPP (former OPPTS) 850.1300 (1996) protocols. The validity criteria were met and the experiment can be considered relevant and adequate for the endpoint. Therefore it is deemed conclusive and was rated „reliable without restrictions“, i.e. “Klimisch 1” according to the scale of Klimisch et al. (1997).

Ten replicates of one first instar larvae were exposed under semi-static conditions (renewal 3 times per week) for 21 days to the test item at nominal concentrations of 2.0, 4.0, 8.0, 16 and 32 mg/L. Analysis of the test preparations showed measured test concentrations in the fresh media to range from 63 to 98 % of nominal, and in the old or expired media to range from 5 to 83 % of nominal. Due to the nature of the data, time weighted average (TWA) concentration could not be determined for the nominal 32 mg/L concentration, but were 0.71, 1.9, 3.9 and 14 mg/L for the remaining treatments. These values correspond to 36, 48, 49 and 84 % of nominal.Thus the effects of the test item had to be assigned to the measured (TWA) concentrations. Because the percentage of test item biodegradation shows a clear trend to lower with increasing nominal concentrations it is concluded that metabolization after absorption by the test organisms (or adsorption to their surface) is the main reason for the test item concentration decline. The test animals were fed daily with a mixture of algal suspension and Tetramin® flake food suspension. On a daily basis the numbers of live and dead of the Parental (P1) generation, the numbers of live and dead Filial (F1) daphnids and the number of discarded unhatched eggs were counted. An assessment was also made of the general condition and size of the parental daphnids as compared with the controls. The number of daphnids with eggs or young in the brood pouch was determined daily.

Reproduction determined by the number of live young produced per adult was the most sensitive endpoint (for NOEC and EC10). The NOEC was the lowest treatment concentration of 0.71 mg/L and the LOEC was 1.9 mg/L, which gives an MATC (geometric mean of NOEC and LOEC) of 1.2 mg/L. According to the ECHA R.10 guidance (2008, p 11) “An EC10 for a long-term test which is obtained using an appropriate statistical method (usually regression analysis) will be used preferentially.” The EC10, calculated by interpolation to be 1.3 mg/L, represents thus the point of departure for the PNEC derivation from this study.

In conclusion the relevant endpoint for risk assessment from this study is the EC10 of 1.3 mg/L for long-term effects with a 95 % CL 0.87 to 1.7 mg/L. As in the same study the pre-test results indicated an LC50 of ca. 27 mg/L, the acute-to-chronic-ratio (ACR) is ca. 21 indicating an average steepness of the dose-effect curve. On the basis of this study alone no classification is indicated according to CLP (5th ATP of Regulation (EC) No 1272/2008 of the European Parliament and of the Council) as implementation of UN-GHS in the EU. It is known that the test material is subject to ready biodegradation by micro-organisms under non-sterile conditions. Eisner (2011, Harlan Laboratories study report no. D32045), found 90 % degradation until day 7 in a OECD TG 301 A study. Under the non-sterile conditions of this study the observed depletion of the test item can be attributed to bacterial biodegradation known to reach relevant levels in the time frame of the incubation periods (see section on biodegradation in water: screening tests).

Preference of EC10 over NOEC for PNEC derivation

As early as 1998 the OECD (STA 10) concluded that the NOEC (No-Observed-Effect-Concentration), as the main summary parameter of aquatic ecotoxicity tests, is inappropriate and should be phased out. It was recommended that the OECD should move towards a regression‐based estimation procedure. OECD repeated this statement in 2006 (STA 54). Similarly US EPA recommends the BMC (Benchmark concentration corresponding to the Effect Concentration ECx) instead NOEC since it reflects the shape of the dose-response curve, is not an artefact of the choice of experimental concentration, takes into account some variability in the test population and increases the minimum quality of an acceptable study (Reed et al. 2004). In fact there is a lot of uncertainty in the NOEC concept as this value can fail to be determined even at effects of more than 50 % if variability of data is high. It is therefore concluded to use the EC10 rather than the NOEC for the PNEC derivation.

• ECHA European Chemicals Agency (2008). Guidance on information requirements and chemical safety assessment Chapter R.10: Characterisation of dose [concentration]-response for environment. Guidance for the implementation of REACH. Self-published, Helsinki, Finland, in May. 65 p.
• Klimisch HJ, Andreae M, Tillmann U (1997). A Systematic Approach for Evaluating the Quality of Experimental Toxicological and Ecotoxicological Data. DOI 10.1006/rtph.1996.1076 PMID 9056496 Regul Toxicol Pharmacol 25:1-5.
• OECD Organisation for Economic Co-operation and Development (1998). Report of the OECD Workshop on Statistical Analysis of Aquatic Toxicity Data. Self-published on January 28th, Paris, France. Document reference ENV/MC/CHEM(98)18. Series of Testing and Assessment (STA) Number 10. 133 p.
• OECD Organisation for Economic Co-operation and Development (2006) Current Approaches in the Statistical Analysis of Ecotoxicity Data: A Guidance to Application. Self-published on May 09th, Paris, France. Document reference ENV/JM/MONO(2006)18. Series of Testing and Assessment (STA) Number 54. 147 p.
• Reed NR (lead person), Jenks C, Kwok E, Lim L (2004). Guidance for Benchmark Dose (BMD) Approach - Quantal data. Self-published by Medical Toxicology (MT) Branch, Department of Pesticide Regulation (DPR), California Environmental Protection Agency, Sacramento, CA, U.S.A. Document reference DPR MT-1 2004. 24 p.