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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The determination of the growth inhibition of the freshwater algae Pseudokirchneriella subcapitata exposed to the test item TERT-AMYL PEROXIDE for duration of 72 hours was assessed according to the OECD Guideline 201 in a GLP study. The results were as follows (extrapolated concentrations as geometric mean between measured initial and final abiotic values): 
ErC50-72h = 1.2 mg/L (growth rate)
ErC10-72h = 0.38 mg/L (grpwth rate)
This value is supported with the ErC50 value determined with the analogue substance 1,1,3,3-Tetramethylbutyl hydro peroxide: ErC50-72h=5.6 mg/L (Geometric Measured Means), which indicates that both substances are "Toxic" to algae.
 

Key value for chemical safety assessment

EC50 for freshwater algae:
1.2 mg/L
EC10 or NOEC for freshwater algae:
0.38 mg/L

Additional information

Two studies are mentioned for this endpoint. The first one was performed with the registered substance and the second, which is used as supporting study, with the analogue substance 1,1,3,3-Tetramethylbutyl hydro peroxide.

The determination of the growth inhibition of the freshwater algae Pseudokirchneriella subcapitata exposed to the test item TERT-AMYL PEROXIDE for duration of 72 hours was assessed according to the OECD Guideline 201 in a GLP study. Algae were exposed to 0.4 to 25 mg/L of TERT-AMYL PEROXIDE dissolved in dilution water. The toxic effect measured during the assay was the inhibition of cellular multiplication over a time period of 72 hours.

The concentrations of test item causing a 50% reduction in biomass (EbC50) and in growth rate (ErC50) were estimated as well as the concentrations of test item causing a 10% reduction in biomass (EbC10)and in growth rate (ErC10). The results were as follows (extrapolated concentrations as geometric mean between measured initial and final abiotic values):

 

ErC50-72h = 1.2 mg/L

ErC10-72h = 0.38 mg/L

 

EbC50-72h = 0.66 mg/L

EbC10-72h = 0.23 mg/L

 

In order to predict the effects of 1,1,3,3-Tetramethylbutyl hydro peroxide in an aquatic environment, an Algal Growth Inhibition test was conducted in accordance with OECD test guidelines and with the OECD Principles of Good Laboratory Practice.  

 

The toxicity of the test chemical to an exponentially growing culture of P. subcapitata was determined in a sealed system over an exposure period of 72 hours. Nominal loading concentrations of 0.35, 1.12, 3.58, 11.5 and 36.0 mg/L were tested. For the highest 3 concentrations a statistically significant effect in growth rate in comparison to the control was found.

The ErC10(72h) was calculated as 2.9 mg/L (Growth rate). The ErC50(72h) was calculated as 5.6 mg/L. (Growth rate Geometric Measured Means).

 

The NOEC was determined as 2.0 mg/L (Growth rate Geometric Measured Means).

 

Values are reported as geometric means of measured concentrations in parallel replicates during the test without test organisms. Analytical measurements in the actual replicates were conducted however due to the reactive (oxidising) nature of the test chemical. The test chemical was degraded in the test replicates containing algal growth and was therefore not measurable.

 

The following quality criteria have been met in the present study:

 

·        The cell density of the controls increased at least a factor 16 within 72 hours. .

·        The coefficient of variation of average specific growth rates during the whole test period in the replicate control cultures did not exceed 7% (See Table 4 a).

·        The ErC50value of the reference compound, potassium dichro­mate, was in the  range of 0.25-2.0 mg/L (Documented as part of GLP laboratory maintenance). 

·          The mean coefficient of variation for section-by-section specific growth rates in the control did not exceed 35 %

·          The validity criteria for the analytical method were met.

 

The following criterion was not met:

 

·          The test concentration did not stay within 80 and 120 % of the nominal concentrations. Geometric means of the measured concentrations were therefore used for endpoint calculations.

 

 Chemical analyses showed that the concentration of the test chemical steadily decreased during the test duration and was not maintained at > 80% of the nominal concentration. For this reason geometric means of the measured concentrations were calculated and used for expressing of the endpoints.