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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

The intrinsic properties of 1-methylimidazole indicate that significant and relevant long-term effects on fish will not occur (NOEC > 1 mg/L).

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Dose descriptor:
Effect concentration:
> 1 mg/L

Additional information

The information requirements will be fulfilled using a weight-of-evidence approach based on the scheme provided in REACH Guidance Document R.7b (v4.0, ECHA, 2017: Figure R.7.8-2) and in accordance with Annex XI Section 1.2.


Step 1: The structure as well as the physico-chemical properties of the substance are clearly identified. Although the substance is not readily biodegradable it is not considered persistent (P) nor very persistent (vP) as the results of an enhanced degradation test indicate that it will degrade in significant amounts over time. ECHA Guidance on information requirements and chemical safety assessment (v3.0, June 2017), Chapter R.11.4.1 specifies that “Constituents, impurities and additives should normally be considered relevant for the PBT/vPvB assessment when they are present in concentration of ≥ 0.1% (w/w)” […] “Similar arguments apply to relevant transformation/degradation products”. In order to identify the relevant degradation products of 1-methylimidazole as a standard information requirement according to Column 1, Section 9.2.3. of Annex IX to REACH and for purposes of an assessment of potential PBT/vPvB properties, the metabolites were modelled using CATALOGIC 301C v11.16 (OASIS CATALOGIC v5.14.1.5). Overall, the model calculated 22 metabolites identifying 9 metabolites as relevant degradation products in terms of PBT/vPvB assessment, with an estimated quantity of ≥0.1% (equivalent to quantity setting in OASIS CATALOGIC: ≥ 0.001 [mol/mol parent]). Based on modelled data relevant degradation products present in concentration of ≥ 0.1% (equivalent to quantity setting in OASIS CATALOGIC: ≥0.001 [mol/mol parent]) do neither fulfil the PBT criteria (not PBT) nor the vPvB criteria (not vPvB) (see IUCLID Ch. 2.3).


Step 2: The substance does not produce an alert for protein binding in the schemes by OECD and OASIS (OECD QSAR Toolbox v4.4; see document under ‘Attached background material’ in IUCLID Ch. 6.1.2 - ACR approach), which is an indication of the absence of elevated toxicity. According to the acute toxicity MOA of OASIS the substance is unspecified reactive. By ECOSAR the substance was classified as Imidazole. According to Verhaar the substance’s toxicity mode of action was classified as narcosis or baseline toxicity (Class 1). Therefore, it can be concluded that the substance has a mode of action similar to narcotic substances and critical long-term effects are not to be expected.


Step 3 and 4: No experimental data are available on the long-term toxicity to fish for the substance itself.


Step 4a/b: Reliable QSAR predictions or in-vitro results for long-term toxicity to fish are not available.


Step 5: Acute and long-term toxicity for the aquatic environment, as well as supporting information have been taken from studies with the substance itself. Information on the long-term toxicity to fish are not available. Fish are the most sensitive aquatic trophic level (96-h LC50 > 100 < 215mg/L). The substance is neither acutely nor chronically hazardous to the aquatic environment according to the CLP-Regulation (EC) No 1272/2008. The long-term toxicity to fish is derived using the Acute-to-Chronic (ACR) approach. The detailed description as well as the result of the ACR approach will be provided in the update of the IUCLID as part of IUCLID Chapter 6.1.2. The ACR approach is an important method to predict acceptable no-effect values (NOEC) from acute toxicity data (LC50, EC50). The method is valuable for the risk assessment of chemical substances, which has been successfully assessed for several chemicals, including organic substances with a narcotic mode of action (modified acute aquatic toxicity classification of Verhaar) to which the substance belongs (May et al., 2016; Kienzler et al., 2016; ECETOC, 2003). Based on these three publications, a conservative ACR of 100 was selected which covers at least 90% of all organic chemicals; therefore, the derived NOEC can be regarded as reliable and sufficiently protective. Based on the available 96-h LC50 of > 100 mg/L (Leuciscus idus, DIN 38412; BASF AG, 1989, report no. 10F0163/895106) a NOEC for the long-term toxicity to fish of > 1 mg/L was derived. The available short-term as well as the long-term toxicity data do not lead to a classification of the substance as chronically hazardous to the aquatic environment following the CLP-Regulation (EC) No 1272/2008.

With regard to the PBT assessment, further testing is also not required as the substance is not considered persistent (P) nor very persistent (vP) as the results of an enhanced degradation test indicate that it will degrade in significant amounts over time. The substance is also neither bioaccumulative (B) nor very bioaccumulative (vB). Based on low log D values (pH 5 = -0.655; pH 7 = -0.029; pH 9 = 0.096; see IUCLID Chapter 4.7) and the substance’s low n-octanol/water partition coefficient of -0.19 for the uncharged molecule (25°C; BASF AG, 1989; 104547/01), accumulation in organisms is not to be expected. The available short-term as well as the long-term toxicity data for the three trophic levels (fish, aquatic invertebrates and algae) do not indicate a concern for a high sensitivity of aquatic organisms. In addition, the substance holds no relevant classification. Therefore, further testing does not seem justified and long-term toxicity testing on fish should therefore not be carried out to avoid unnecessary testing on vertebrate animals. Avoiding unnecessary testing of vertebrate animals is also in line with the REACH regulation, which states in §25 that testing on vertebrate animal shall be undertaken as a last resort. This is further supported by the EU Directive on the protection of animals used for scientific purposes (EU, 2010) and the EURL ECVAM strategy to replace, reduce and refine the use of fish in aquatic toxicity and bioaccumulation testing (EURL ECVAM, 2014).   


Step 6: The intrinsic properties of the substance indicate that significant and relevant long-term effects on fish will not occur. The substance has no specific mode of action and does not produce structural alerts for relevant effects. The derived NOEC of > 1 mg/L indicates that long-term effects on fish are not to be expected. In addition, the substance degrades in significant amounts over time and will therefore be removed from the aquatic environment; thus, reducing the exposure of the aquatic environment. Therefore, and in accordance with REACH Regulation 1907/2006, Annex XI, Section 1.2, further testing on vertebrate animals will be omitted for reasons of animal welfare. The Registrant will not perform a long-term toxicity test on fish.