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Short-term toxicity to fish

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Description of key information

LC50 (96 h) > 137.2 mg/L for Oryzias latipes (OECD 203), recalculated value

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
137.2 mg/L

Additional information

For short-term toxicity to fish, one GLP-study with 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione, trisodium salt (TMT, CAS No. 17766-26-6) and one GLP-study with 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione (TMT-H3,CAS No. 638-16-4) as read across of a surrogate substance are available and were considered to be reliable.

This read across approach is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. "Grouping of substance and read across approach" and is explained within the read across justification attached in IUCLID section 13. TMT-H3 is the acidic form of 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione. Except for different cations (hydrogen vs sodium), the anion of both the source and target substance have an identical structure. Since dissociation of the sodium salt under environmental conditions (pH 4 -9) yields the same ionic species as the acidic form of the substance, this read across can be considered as justified.

The first study (87-0025-DGO) was carried out according to OECD guideline 203 with TMT 60 as test substance (87-0025-DGO. The exposure of zebra fish (Brachydanio rerio) under semi-static conditions resulted in an LC50 (96 h) in the range from 560 to 1000 mg TMT 60/L (nominal). This corresponds to 324.8 to 580 mg/L anhydrous TMT. During the study period the pH of the test solutions reached critical values up to 11.1 (pH of test solutions rose with increasing concentrations). A further deficiency of the study includes the lack of an analytical analysis of the test solutions. This would have been beneficial since at each time point of medium renewal some particles were seen at the bottom of the test solutions containing the two highest test concentrations. It is recommended by OECD guideline 203, that the test has to be repeated with adjustment of pH “if there is evidence of marked change in the pH of the tank water after addition of the test substance”, but since a test with an adequate surrogate substance (TMT-H3) is available, it is not necessary to repeat the test.

Therefore a study with TMT-H3, which is the acidic form of TMT, is taken into account (2008-0206-FGO) for the chemical safety assessment of TMT. This read across study was conducted as limit test similar to OECD guideline 203 with analytical monitoring. Rice fish (Oryzias latipes) was exposed under semi static conditions, after 96 hours of exposure no mortality was observed. The measured pH values ranged from 6.1 to 7.9 during the test period. Hence, the LC50 (96 h) is above the test substance concentration of 100 mg/L nominal (102.4 mg/L geom. mean measured).

As aforementioned, with respect to the limitations of the study with TMT itself, the result for TMT-H3 (LC50 (96 h) > 100 mg/L) as a part of a read across approach was taken into account for further assessment. For this purpose the LC50 (96 h) value was recalculated to be > 137.2 mg TMT/L.

In addition to these studies two non-GLP short-term toxicity studies with fish are available. In the first study (77 -0017 -DKO) a LC0 of 930 mg/L for TMT (not further specified) was reported. However, the documentation of this study was very limited and was insufficient for assessement (Kl.4). The second non-GLP study was performed with TMT15 as test substance. As the documentation of the results are limited (insufficient for assessment - Kl.4) and the study is not owned by the registrant no endpoint study record is provided. The reported LC50 of TMT15 in this study is 191.1 mg/L corresponding to 28.7 mg/L anhydrous TMT. This result is is clearly below the values of all other studies. However, as the documentation was limited and the study was not performed according to GLP the results were considered to be less reliable.