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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
The substance has a similar structure and similar phys-chem properties. Therefore it is likely that the toxicology of the substance is similar.
Reason / purpose:
read-across source
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
2.7 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 2.0 - 3.5 mg/L
Key result
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
4.6 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 3.7 - 5.6 mg/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
13 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 11 - 15 mg/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
1.3 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no
- Unusual cell shape: no
- Colour differences: no
- Flocculation: no
- Adherence to test vessels: no
- Aggregation of algal cells: no
- Other: no
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no
Reported statistics and error estimates:
Parameters of probit analysis (growth rate)
---------------------------------------
Computation runs: 7
Slope b: 1.9166
Intercept a: -2.11697
Variance of b: 1.4806
Goodness of Fit
Chi²: 0.1046
Degrees of freedom: 10
p(Chi²): 1.0000
Log EC50: 1.1046
SE Log EC50: 0.2642
g-Criterion: 0.0209
Residual Variance (Chi²/df): 0.0105
r²: 0.9600
F: 237.1530
p(F) (df: 1;10): 0.0000
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the present study with Pseudokirchneriella subcapitata, Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid inhibited growth rate and yield of this fresh water algae species significantly at a time weighted average concentration of 4.2 mg/L.
The EC50 for growth rate inhibition (72h-ErC50) was 13 mg/L (95% confidence interval ranging from 11 to 15 mg/l).
The EC50 for yield inhibition (72h-EyC50) was 3.1 mg/L (95% confidence interval ranging from 2.0 to 3.3 mg/L).
The 72h-NOEC for growth rate inhibition was 1.3 mg/L. The 72h-EC10 for yield inhibiton was 1.2 mg/L.



Executive summary:

Pseudokirchneriella subcapitata, Fresh Water Algal Growth Inhibition Test with Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid.

The study procedures described in this report were based on the OECD guideline No. 201, 2006; Annex 5 corrected 28 July 2011. In addition, the procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.3, 2008; Amended by EC No. 761/2009 and the ISO International Standard 8692, 2012.

The batch of Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid tested was a clear yellowish liquid with a purity of 97.6 % and not completely soluble at the loading rate initially prepared.

A final test was performed based on the results of a preceding combined limit/range-finding test. Preparation of test solutions started with a nominal concentration of 100 mg/l applying a 2 -day period of magnetic stirring followed by an one-hour settlement period. The aqueous Water Soluble Fraction (WSF) was siphoned off. The pH of the WSF was adjusted from 5.8 to 6.5 using 1 M NaOH. This solution was used as the highest test concentration. The lower test concentrations were prepared by subsequent dilutions of the WSF in test medium. The final test solutions were all clear and colourless.

Six replicates of exponentially growing algal cultures were exposed to a control, whereas three replicates per concentration were exposed to nominally 0.10, 0.32, 1.0, 3.2, 10, 32 and 100% of the WSF. The initial cell density was 10E4 cells/ml and the total exposure period was 72 hours. Samples for analytical confirmation of actual exposure concentrations were taken at the start, after 24 and 72 hours of exposure.

The concentrations measured in the samples taken from the solutions containing 0.10 and 0.32% of the WSF prepared at 100 mg/l were below the Limit Of Quantification (LOQ was 0.5 mg/l) at all sample occasions. The actual concentration at the start of the test in the vessels containing 1.0, 3.2, 10, 32 and 100% of the WSF prepared at 100 mg/l were 0.74, 2.9, 9.7, 32 and 111 mg/l, respectively. These concentrations did not remain stable during the exposure period (21 -52% of the initial at the end of the rest). The Time Weighted Average (TWA) exposure concentrations were calculated to correspond to 0.42, 1.3, 4.2, 23 and 93 mg/l. The two lowest test concentrations that were below LOQ and the 0.42 mg/l concentration were not needed for determination of the effect parameters.

The study met the acceptability criteria prescribed by the protocol and was considered valid.

Effect parameters based on growth rate:

NOErC 1.3 mg/L

ErC10 2.7 mg/L (95% confidence interval 2.0 - 3.5 mg/L)

ErC20 4.6 mg/L (95% confidence interval 3.7 - 5.6 mg/L)

ErC50 13 mg/L (95% confidence interval 11 - 15 mg/L)

Effect parameters based on yield:

NOEyC 1.3 mg/L

EyC10 1.2 mg/L (95% confidence interval 1.0 - 1.3 mg/L)

EyC20 1.6 mg/L (95% confidence interval 1.5 - 1.8 mg/L)

EyC50 3.1 mg/L (95% confidence interval 2.0 - 3.3 mg/L)

Description of key information

An algae test with 2 -hexyldecanoic acid is not available. The toxicity of the similar substance Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid was assessed in a fresh water algal groth inhibition test with Pseudokirchnerella subcapitata according to OECD guideline 201. The ErC10 of 2.7 mg/L (95% CL 2.0 – 3.5 mg/L), NOErC of 1.3 mg/L and the  ErC50 of 13 mg/L (95% CL 11 – 15 mg/L) after 72 hours of exposure can be considered reliable without restrictions.

Key value for chemical safety assessment

EC50 for freshwater algae:
13 mg/L
EC10 or NOEC for freshwater algae:
1.3 mg/L

Additional information

An algae test with 2 -hexyldecanoic acid is not available. Toxicity in freshwater algae Pseudokirchneriella subcapitata with the similar substance Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid was tested according to OECD guideline No. 201. The study met the acceptability criteria and was conducted GLP compliant, therefore considered reliable without restrictions.

A supporting study with 2 -decyltetradecanoic acid was performed according to OECD guideline No. 201 and in compliance with GLP. In this study 2 -decyltetradecanoic acid was found to not inhibit the growth of the freshwater green alga Pseudokirchneriella subcapitata after 72 hours. No effects were found up to the maximum water solubility level (estimated ≤ 0.9 µg/L), which is below the nominal loading level of 10 mg/L. Therefore, no effects were found in the range of water solubility of the test item.