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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The purpose of this study was to assess the toxicity of 1,1 -Dimethylpropyl 1-methoxycyclohexyl peroxide on the growth of Pseudokirchneriella subcapitata in a 72-hour test according to the OECD 201 Guideline and GLP requirements (Chastenet, 2016).

As the test item was suspected to be unstable in water (due to its chemical nature), tests solutions were prepared from dilutions of a saturated solution prepared using slow-stirring conditions described in the OECD 123 guideline.

The results are reported as growth rate and yield inhibitions. The concentrations that result in a 10 and 50% reduction in growth rate (72h-ErC10 and 72h-ErC50, respectively) and yield (72h-EyC10 and 72h-EyC50, respectively) were determined.

Chemical analysis of the test item showed the instability of the substance over the 72 -hour test period. Based on these results, the exposure concentrations were based on the geometric mean of measured concentrations. 72h-ErC10 and ErC50 were estimated to be 0.279 and 0.501 mg/L, respectively.

The definitive test met the validity criteria of the test guideline detailed as follows:

- The biomass in the control cultures increased exponentially by a factor of 63.6 within the 72-hour test period (required: at least 16-fold)

- The coefficient of variation of average specific growth rates during the whole test period in the control cultures was 2.5% (required: < 7%)

The following validity criteria of the test guideline was not respected:

- The mean coefficients of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3) in the control cultures were max 38.3% (required: < 35%)

Nevertheless, this deviation was considered to have not affected the outcome or the achievement of the study objectives and thus the results were considered as valid.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.501 mg/L
EC10 or NOEC for freshwater algae:
0.279 mg/L

Additional information