Dibenzoyl peroxide

Endpoint summary

Additional information

The ready biodegradability of Benzoyl peroxide was evaluated in a study performed in accordance with OECD testing guideline 301 C by Ministry of International Trade and Industry of Japan. The maximum level of biodegradation was 100 % in 21 days (based on HPLC analysis). Therefore, according to these results, Benzoyl peroxide is considered as readily biodegradable. Nevertheless this result has to be taken with caution because no sufficient information are given in order to evaluate the validity of the study.

Another ready biodegradability test was performed which allowed the measurement of the biodegradability in an aerobic aqueous medium was performed according to OECD 301B in order to check the validity of the aforementioned data. Since 56% of biodegradation was reached after 28 days in the closed bottle, Dibenzoyl perozide could not be classified as readily biodegradable.

Nevertheless, the threshold of readily biodegradability was almost achieved. On the other hand, this result is quite different from the result obtained by the Ministry of Japan trade and Industry ("Ministry of International Trade and Industry, Japan / K4 SS / Biodegradation in water: screening tests"). Consequently, other tests have been carried out in order to reach a conclusion concerning the ready biodegradability of the substance.

A new study was performed to assess the ready biodegradability of the test item according to the OECD guideline 301 D “Ready biodegradability – Closed Bottle Test” (GRL, 2010).Under the test conditions, the biodegradation of benzoyl peroxide reached 68 % of the ThOD at the end of the test (28 days), but this level was not obtained within a 10 days window.

Another test was performed according to OECD guideline 301 D and in compliance with the OECD principles of GLP (Van Ginkel, 2015).The presence of Dibenzoyl peroxide did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. Dibenzoyl peroxide was biodegraded by 71% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved in a period of approximately 10 days immediately following the attainment of 10% biodegradation. All the validity criteria have been fulfilled and thus the study is considered as valid.

As a conclusion, Dibenzoyl peroxide should be classified as readily biodegradable.

In addition, the PEC/PNEC ratio for water, sediment and soil compartments obtained in the exposure assessment of the substance are below 1. Therefore, simulation testing on ultimate degradation in surface water (OECD 309), sediment simulation testing (OECD 308) and soil simulation testing (OECD 307) are waived in accordance with column 2 of Annex IX chapter 9.2 of Regulation EC 1907/2006.

As mentioned in the REACH guidance on information requirements and chemical safety assessment Chapter R.11 on PBT/vPvB assessment (Version 2.0, November 2014, Figure R.11-3), there is no reason to perform further biodegradation tests for the PBT/vPvB assessment when a substance is readily biodegradable. The conclusion is that Dibenzoyl peroxide does not fulfil the criteria for Persistence (P).

In addition, Dibenzoyl peroxide was determined to be hydrolytically unstable under acidic, neutral and basic conditions, with a half-life of less than 1 day under environmental conditions (25°C). Benzoic acid, the main breakdown product present in the hydrolysed solutions at each test pH is known to be readily biodegradable as it is used as reference substance during screening tests for ready biodegradability.
According to 67/5848 EEC regulation, a substance can be considered as readily biodegradable if there is scientific evidence showing that the substance of interest can degraded (biotic and abiotic degradation) in the aquatic environment up to 70% in 28 days. Based upon the aforementioned information, we can safely assume that the substance is degraded during this cut-off period. Besides, abiotic degradation will involve the formation of benzoic acid, which is readily biodegradable.