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Short-term toxicity to fish

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Description of key information

Both main constituents of the submission substance (BHMT and HMD) were assessed separately for acute fish toxicity. HMD proved to be of very low acute toxicity to fish with an LC50 (96 h) of 1825 mg/L. For BHMT the determined LC50 (48 h) was 76 mg/L, but the alkaline properties of the test item were not taken into account and toxicity due to alkaline pH is likely. However, this conservative value is taken as decisive for acute fish toxicity of the submission substance.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
76 mg/L

Additional information

Both main constituents of the submission substance (BHMT and HMD) were assessed separately for acute fish toxicity.

The study on HMD (according to OECD 203, reliability category 2) with fathead minnow (Pimephales promelas) resulted in a LC50 (96 h) of 1825 mg/L (95% CI = 1237-2461 mg/L; Probit analysis). No effects were observed up to a nominal concentration of 1000 mg/L. Very high concentrations up to 10 000 mg/L have been tested and pH of the stock solution was adjusted to pH 8-8.5. No analytical verification of test item concentration were performed, however the HMD-fraction of the submission substance has been shown to be completely stable under similar testing conditions in the invertebrates toxicity test (IUCLID section 6.1.3, KS_Rhodia_Harlan_D54670_2012_Short-term toxicity to aquatic invertebrates).

The study on BHMT with Golden ide (Leuciscus idus melanotus) was performed similar to OECD 203 (48 hour exposure, compliant to GLP, reliability category 2). Ten animals were exposed to various concentrations of the test substance in water (static test design).

After evaluation of the results with a "Probit"-method, the following toxicity data were obtained:

NOEC / LC0 (48h): 58 mg/L

LC50 (48 h): 76 mg/L

LC100 (48 h): 100 mg/L

No sublethal effects were observed. The alkaline properties of the test item were not taken into account and toxicity due to alkaline pH is likely. Thus, inherent toxicity of the test item is probably considerably lower and observed toxicity values may be taken as worst case and most probably overestimate toxicity of the test item.

However, the conservative effect value from BHMT is taken as decisive for acute fish toxicity of the submission substance.