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Long-term toxicity to fish

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Description of key information

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

Key value for chemical safety assessment

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. The Substance is not readily biodegradable; however, metabolites were predicted by the model CATALOGIC 301C (OASIS Catalogic v5.13.1). The model predicted 128 metabolites, identifying 37 metabolites as relevant degradation products in terms of PBT/vPvB assessment, with an estimated quantity of ≥ 0.1% (for details see ‘Attached background material’ of the respective Endpoint Study Record in IUCLID Ch. 5.2.1). 26 of these metabolites are not readily biodegradable (< 60% after 28 d, based on BOD), but all of these 37 metabolites have a log Kow < 3; therefore, a significant bioaccumulation potential is not expected. Therefore, it can be concluded that none of these degradation products is potentially PBT/vPvB.

Step 2: The substance does not produce an alert for protein binding in the schemes by OECD and OASIS (OECD QSAR Toolbox v4.3.1; see Chapter 2.5 of the updated Read-Across Justification), which is an indication of the absence of elevated toxicity. According to the modified classification scheme of Verhaar, the mode of action of the Substance is less inert (Class 2). Therefore, it can be concluded that the Substance has no specific mode of action 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 as well as the structurally similar substance TMDC (CAS 65962-45-0). The available information of the two substances are described and discussed in the updated Read-Across-Justification.

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 have been assessed from studies with the Substance itself. Information on the long-term toxicity to fish are not available.

Fish are not the most sensitive aquatic trophic level (96-h LC50 > 100 mg/L, pH-adjusted test solutions). 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 are provided in 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 (including alkylamines) with less inert compounds (e.g. polar narcosis; 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 (pH-adjusted test solution; source: Oryzias latipes, OECD 203; NITE, 2002, report no. NMMP/E00/4090), 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 PBT nor vPvB. The Substance is not readily biodegradable and should therefore be considered as persistent (P) or very persistent (vP) from a precautionary point of view. However, the Substance is not bioaccumulative (B) nor very bioaccumulative (vB) based on the low log Kow (log Kow < 3, see IUCLID Chapter 4.7) and the available experimental data (BCF < 60 L/kg, NITE 2002, report no. A010200). 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, DMDC is officially not classified. However, it is self-classified as STOT-RE. Identified target organs are skeletal muscle and liver. Hence, the substance fulfills the T-criterion. 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.

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.