Bis(α,α-dimethylbenzyl) peroxide

Short-term toxicity to fish

Description of key information

Dicumyl peroxide showed no effects up to maximal water soluble concentrations.

Additional information

Data on acute toxicity towards fish gave different results based on the fact if solvents were used to prepare stock solution for testing or not. Water solubility of dicumyl peroxide has been determined to be 0.43 mg/L.

In a 96-h acute toxicity study, medaka fisch (Oryzias latipes) were exposed to dicumyl peroxide under semi-static conditions. The test concentrations were prepared using rather high concentrations of solvent and were verified by HPLC analysis. The 96-h LC₅₀ was 0.469 mg/L, slightly above normal water solubility. No mortality has been observed at concentrations of 0.386 mg/L. As the test was performed with solvent the result cannot be regarded as valid for classification and labeling purposes.

Other studies on acute fish toxicity were performed without analytical monitoring.

One of these studies was conducted in accordance with Japanese Industrial Standard JIS K 0102-1986-71 Testing methods for industrial waste water. The 48 h LC₅₀ was determined to be 4.2 mg/L (nominal). The reliability of the study was considered not to be assignable, due to missing information on preparation of test solution and analytical monitoring.

A further study was conducted in accordance with the accepted OECD test guideline 203: fish, acute toxicity test (1984). The LC₅₀ of 108.45 mg/L (95% CL = 80.51-146.07 mg/L) calculated in the report should be used with care as there was no true concentration effect relationship. Test solutions of 10 and 21 mg/L have been prepared by using an acetonic stock solution (max. concentration 100 µL/L), while the higher concentration were obtained by direct addition of substance. Afterwards the solutions were stirred for 24 h. During the test, the substance remained visible at the surface of the test media as a fine layer of solids at all test concentrations. Effects may be caused either by exposure to the concentrations of test substance dissolved in water or via contact or ingestion of particles of the test substance.

However, the import result for classification and labelling purpose is that even with solvent no mortality was observed up to 10 mg/L (in both tests only 1 of 10 animals died at this concentration). In the main test 50 % died at 21 mg/L after 96 h.

In conclusion, data from acute toxicity testing towards fish can be interpreted in a weight of evidence that dicumyl peroxide showed no effects up to maximal water soluble concentrations. This is in line with a recent study on acute toxicity towards daphnia, where no effects were observed in water accommodated fraction (test solution prepared without solvent, but reaching maximal water solubility).