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EC number: 202-327-6 | CAS number: 94-36-0
Endpoint summary
Administrative data
Description of key information
Additional information
Relative to photolysis, three data are available concerning the potential phototransformation of Dibenzoyl peroxide. Nevertheless, no information is available in order to evaluate the relevance of these data. Based on these data, Dibenzoyl peroxyde may decompose due to photolysis. Consequently, in order to reach a conclusion concerning the degradation potential of Dibenzoyl peroxyde via photolysis, an experimental test has to be performed. Nevertheless, this information was not considered as crucial in order to assess the environmental risk of the substance. Therefore, no test is proposed at the moment in order to cover this issue.
The preliminary hydrolysis study showed that at pH 4, 7 and 9 and 50±0.5ºC, more than 50% hydrolysis had occurred after 2.4 hours, equivalent to a half-life of less than 1 day under environmental conditions (25°C). Benzoic acid, the expected main degradation product, was present in the hydrolysed solutions at each test pH. Dibenzoyl peroxide was thus determined to be hydrolytically unstable under acidic, neutral and basic conditions.
Consequently, when released into water, Dibenzoyl peroxide will rapidly be transformed into benzoic acid due to its instability. Nevertheless, the hazard assessment of this peroxide in water is not based on its degradation products in water (and particularly on the data relative to benzoic acid) because the half-life of parent substance is not sufficiently low to avoid toxic effects on the aquatic compartment organisms caused by the parent substance.
According to a new result of ready biodegradation obtained (Van Ginkel, 2015), 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 all 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).
Conducting a study on bioaccumulation is scientifically not justified, because of the following:
1) Toxicokinetic results indicate that there is no risk of bioaccumulation of neither Dibenzoyl peroxide nor benzoic acid (see section 7.1.1 “Basic Toxicokinetics”).
Benzoyl peroxide is rapidly converted to benzoic acid in the skin of both animals and humans.Absorption of the benzoic acid occurs as benzoate through the blood vessels in the dermis. This metabolite enters the blood circulation and is rapidly cleared through the kidney (Nacht, S. et al, 1981; Yeung, D., et al, 1983; Morsches, B. and Holzmann, H., 1982; Wepierre, J., et al, 1986). Topically applied benzoyl peroxide penetrates unchanged through the stratum corneum or follicular openings of excised human skin and is converted metabolically to benzoic acid within the skin (Nacht S. et al, 1981). A study in rhesus monkeys in vivo showed that this benzoic acid is systemically absorbed as benzoate and rapidly excreted in the urine in an unchanged form, without being conjugated to hippuric acid, as would be predicted to occur following oral administration.
2) A computer simulation via EPI Suite TM (using an experimental log Kow of 3.2, coming from the Klimisch-1 -rated study (2009), see section 4.7 “Partition coefficient”) resulted in a BCF for dibenzoyl peroxide equal to 60 L/kg wet-wt, which is far below the trigger value of BCF = 500 for classification with respect to chronic aquatic toxicity (see attached EPI Suite TM printout file).
Bioaccumulation Estimates (BCFBAF v3.00):
Log BCF from regression-based method = 1.778 (BCF = 60.03 L/kg wet-wt)
Log Biotransformation Half-life (HL) = -0.5728 days (HL = 0.2674 days)
Log BCF Arnot-Gobas method (upper trophic) = 1.823 (BCF = 66.58)
Log BAF Arnot-Gobas method (upper trophic) = 1.823 (BAF = 66.59)
log Kow used: 3.20 (user entered)
Based on the available information it is therefore proposed that the study on bioaccumulation of Dibenzoyl peroxide and its degradation substance can be waived, which is in accordance to the intention of the REACH regulation to minimize animal consumption by conducting unnecessary vertebrate studies.
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