Dibenzoyl peroxide

Toxicity to aquatic algae and cyanobacteria

Key value for chemical safety assessment

EC50 for freshwater algae:

0.071 mg/L

EC10 or NOEC for freshwater algae:

0.02 mg/L

Additional information

Two experimental results were available in order to assess the toxicity of Dibenzoyl peroxide to aquatic freshwater algae. However, these results were considered as unreliable or difficult to evaluate due to the insufficient documentation or unsuitable test systems. As a consequence, a new test was performed according to EEC method C.1 (1984) and OECD Test Guideline 201(1984) and GLP criteria. These three studies are summarised below:

 

- K3 Supporting Study (methodological deficiencies): in order to predict effects of chemicals in an aquatic environment, the toxicity to freshwater algae was assessed. The algal toxicity was determined in the Algal Growth Inhibition test in accordance with OECD, EEC and ISO test guidelines and with Monograph 26 (1996). The test was performed according to the OECD Principles of Good Laboratory Practice. The guidelines were slightly modified to ensure good growth and pH control of the cultures. Test item dissolved in OECD medium at approximately 10 mg/l forms a solution with particles. Therefore water accommodated fraction's (WAF's) were tested, prepared from stirring a solution of 9.6 mg/l for 24 hours and then filtrated. From this solution the following dilutions were prepared and tested: 1:32 - 1:16 - 1:8 - 1:4 and 1:2. Chemical analyses were performed as NPOC (non-purgeable organic carbon). Based on the NPOC concentration determined at the beginning of the test after filtration, the test concentrations were calculated as indicative values. Based on these indicative values the toxicity of these WAF's to exponentially growingPseudokirchneriella subcapitatawas determined over an exposure period of 72 hours. The_EbC50and E_rC₅₀(0-72 h) values based on the indicative concentrations of the test compound forP. subcapitataare 0.44 mg/l (0.31-0.62 mg/l 95% confidence limits) and 0.83 mg/l (0.59-1.13 mg/I 95% confidence limits), respectively. The indicative NOEC determined from the results is 0.12 mg/l, the LOEC is 0.23 mg/l. 

- K4 Supporting Study (documentation insufficient for assessment): in another test the ECr50- 72h of Dibenzoyl peroxide was estimated at 0.44 mg/l (NIER, 2001).

 

- K1 Key Study: results are summarised in table below:

Algal growth inhibition assay

	Initial measured Dibenzoyl peroxide (mg/L)
Area under the growth curve
EbC50(72 h)	0.0422 [0.0230, 0.0661]
No observed effect concentration (NOEC)	0.02
Average specific growth rate
ErC50 (0 - 72 h)	0.0711 [0.0643, 0.0729]
No observed effect concentration (NOEC)	0.02
Yield
EyC50 (0 - 72 h)	0.0613 [0.0248, 0.0687]
No observed effect concentration (NOEC)	0.02

 [95% confidence limits]

Therefore, Dibenzoyl peroxide can be considered as very toxic to aquatic freshwater algae.