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Except a fish study which was performed in order to confirm the Read-Across approach between 1,4-bis(tert-butylperoxyisopropyl)benzene and 1,3-bis[1-(tert-butylperoxy)-1-methylethyl]benzene (see document attached to IUCLID), there is no data on 1,4-bis[1-(tert-butylperoxy)-1-methylethyl]benzene. Based on this read-across, one key study is available for each of the following endpoints:

Short term Toxicity to Fish:

The acute toxicity of 1,4-bis(tert-butylperoxyisopropyl)benzene to zebra fish has been investigated according to OECD 203 guideline in a GLP study. As no effect was observed during the preliminary test, a definitive limit-test at 100 mg/L was conducted and gave a 96-Hour LC50 of greater than 100% v/v saturated solution. The No Observed Effect Concentration was 100% v/v saturated solution. To conclude, this study showed no toxic effects at saturation.

Short term Toxicity to Aquatic invertebrates:

[1,3(or 1,4)-Phenylenebis(1-methylethylidene)]bis[tert-butyl]peroxide was not found to be acutely toxic to Daphnia magna when dispersed in water at a nominal loading rate of 1.0 mg/L equivalent to an initial mean measured concentration of 0.0219 mg/L. Consequently, the 48-hour EC50 value for [1,3(or 1,4)-Phenylenebis(1-methylethylidene)]bis[tert-butyl]peroxide could not be calculated but must be >1.0 mg/L (>0.0219 mg/L). The “no observed effect loading rate” was 1.0 mg/L (0.0219 mg/L as initial mean measured concentration).


Short term Toxicity to freshwater algae:

The acute toxicity of [1,3(or 1,4)-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide was evaluated with Pseudokirschneriella subcapitata in a study performed in accordance with OECD testing guideline 201 and GLP requirements.

The algae were exposed to nominal test concentrations of 1 mg/L under static conditions during 72 hours. The mean measured concentrations were not maintained between 80 and 120 % of nominal. The test substance was not found to be acutely toxic to Pseudokirchneriella subcapitata at a nominal loading rate of 1.0 mg/L, equivalent to an initial mean measured concentration of 0.0471 mg/L.


Toxicity to microorganisms: in order to predict effects of chemicals in the environment and in biological wastewater treatment plants, an activated sludge respiration inhibition test was performed on 1,3-bis[1-(tert-butylperoxy)-1-methylethyl]benzene according to OECD 209 guideline and GLP requirements. The test substance was not soluble in water and therefore the activated sludge was exposed to bis (tert-butyl peroxy isopropyl)benzene adsorbed onto silica gel at a concentration of 1 g/L. By this exposure no effect was recorded indicating that the obtained distribution of 1,3-bis[1-(tert-butylperoxy) -1-methylethyl]benzene in the water system did not inhibit the activated sludge.


To summarize, no effect of 1,4-bis(tert-butylperoxyisopropyl)benzene was observed up to its water solubility limit.

According to claimed uses of 1,4-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide aquatic compartment exposure is likely. At the moment no data is available for characterizing 1,4-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide long-term effects on organisms inhabiting aquatic compartment. Risk assessment demonstrated that there is no risk for those organisms using the PNEC derived based upon acute data, however a long-term test on aquatic invertebrates was proposed with an analogous substance (CAS 25155-25-3). As soon as this test on CAS 25155-25-3 is available, the REACH dossier will be updated.