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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

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:
For details and justification of read-across please refer to the attached report in section 13 of IUCLID.
Reason / purpose for cross-reference:
read-across source
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Filtrate of nominal 100 mg test item/L
Basis for effect:
growth rate
Remarks on result:
not determinable because of methodological limitations
Remarks:
Concentration must be below LOD of 0.01 mg/L though a supersatured solution of the test item was prepared.
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Filtrate of nominal 100 mg test item/L
Basis for effect:
growth rate
Remarks on result:
not determinable because of methodological limitations
Remarks:
Concentration must be below LOD of 0.01 mg/L though a supersatured solution of the test item was prepared.
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Filtrate of nominal 100 mg test item/L
Basis for effect:
growth rate
Remarks on result:
not determinable because of methodological limitations
Remarks:
Concentration must be below LOD of 0.01 mg/L though a supersatured solution of the test item was prepared.
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Filtrate of nominal 100 mg test item/L
Basis for effect:
other: Yield
Remarks on result:
not determinable because of methodological limitations
Remarks:
Concentration must be below LOD of 0.01 mg/L though a supersatured solution of the test item was prepared.
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Filtrate of nominal 100 mg test item/L
Basis for effect:
other: Yield
Remarks on result:
not determinable because of methodological limitations
Remarks:
Concentration must be below LOD of 0.01 mg/L though a supersatured solution of the test item was prepared.
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Filtrate of nominal 100 mg test item/L
Basis for effect:
other: Yield
Remarks on result:
not determinable because of methodological limitations
Remarks:
Concentration must be below LOD of 0.01 mg/L though a supersatured solution of the test item was prepared.
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): No. The microscopic examination of the shape of the algal cells after 72 hours of test duration did not show any difference between the algae that had been growing up to a filtrate of 100 mg test item/L and the algal cells in the control. Thus, the shape of the algal cells was not obviously affected up to the highest concentration tested.
- Unusual cell shape: No
- Colour differences: No
- Flocculation: No
- Adherence to test vessels: No
- Aggregation of algal cells: 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: The water solubility of test item was indicated to be low (< 0.51 mg/L) and when preparing the fresh media, particles were floating on the surface or were lying on the bottom of the flask. Therefore, a filtrate of 100 mg test item/L representing the highest test concentration and dilutions of 1:3, 1:9, 1:27 and 1:81 of this filtrate, and a control were tested. The preparation of the test solution was conducted according to the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (OECD 23).
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- ErC50: 0.963 mg test item/L (95 % C.I.: 0.927 - 1.001 mg test item/L)
Reported statistics and error estimates:
Based on the calculated cell densities, the 72 hours ErC50 and the 72 hours EyC50 could not be calculated by a statistical analysis due to the lack of effects and were therefore determined directly from the raw data. For the determination of the 72 hours LOEC and the 72 hours NOEC, the calculated growth rates and yields at each test concentration were tested for significant differences compared to the control values by Dunnett's t- test.
The software used to perform the statistical analysis was ToxRat Professional, Version 3.2.1, ToxRat® Solutions GmbH.

Biological results:

The EC50, EC20 and EC10 for yield and growth rate were estimated to be greater than the highest test concentration of the filtrate of 100 mg test item/L, which, however, could not be quantified analytically as the content was below the limit of detection. The NOEC was determined to be at least the filtrate of 100 mg test item/L. The LOEC was estimated to be greater than the filtrate of 100 mg test item/L. Therefore, no toxicity towards the test organism up to the limit of solubility was detected for the test item.

Analytical results:

The quantification of the test item 5′-O-[bis(4-methoxyphenyl)phenylmethyl]-2′-deoxythymidine, 3′-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] in the test samples was performed using liquid chromatography with UV detection. The chosen analytical method was the most sensitive method applicable. The concentrations of the test item were analysed in the duplicate test media samples from all test concentrations (filtrate of the test item stock solution and its dilutions) and the duplicate control samples from all sampling times. No substance was detected in any sample (see Table 1), concluding that the maximum soluble amount of the test item must be below the Limit of Detection (LOD) of the method (0.01 mg test item/L).

 

Validity Criteria of the Study

Cell Density
Increase in Control Cultures:


226.8-fold increase within 72 hours and thus, the validity criterion was met.

Coefficient of Variation of Sectional (Daily) Growth Rates in Control Cultures:



14.7 % and thus, the validity criterion was met.

Coefficient of Variation of Average Growth between Control Replicates:



1.2 % and thus, the validity criterion was met.

 

 

Table 1. Summary of Analytical Results

 

Sample Description

% of

RSD

[mg test item/L]

nominal1

[%]

n

Control

n.a.

n.a.

4

Dilution 1:81

<LOD

n.a.

4

Dilution 1:27

<LOD

n.a.

4

Dilution 1:9

<LOD

n.a.

4

Dilution 1:3

<LOD

n.a.

4

Filtrate of 100

<LOD

n.a.

4

 

 

 

 

 

1mean value of all measured samples per treatment group
RSD: relative standard deviation per treatment group
n: number of analysed samples
n.a.: not applicable

LOD: 0.01 mg/L

Validity criteria fulfilled:
yes
Conclusions:
No effect on the growth or yield of Pseudokirchneriella subcapitata was observed up to the limit of water solubility of the test substance.
The analytical verification could not determine a measured concentration as the concentration of the test item was too low. Although a saturated solution was prepared by stirring for 48 h. The substance is hardly soluble and the limit of detection was 0.01 mg/L.
Executive summary:

In a 72-hour acute toxicity study, the cultures of Pseudokirchneriella subcapitata (KORSHIKOV), Strain No. 61.81 SAG were exposed to 5′-O-[bis(4-methoxyphenyl)phenylmethyl]-2′-deoxythymidine, 3′-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] at nominal concentrations of 100, 33, 11, 3.7 and 1.2 mg test item/L under static conditions in accordance with the OECD guideline 201.  No effect was observed up to the limit of water solubility of the test substance. The EC50, EC20 and EC10 for yield and growth rate were estimated to be greater than the highest test concentration of the filtrate of 100 mg test item/L, which, however, could not be quantified analytically as the content was below the limit of detection. The NOEC was determined to be at least the filtrate of 100 mg test item/L. The LOEC was estimated to be greater than the filtrate of 100 mg test item/L. Therefore, no toxicity towards the test organism up to the limit of solubility was detected for the test item. The analytical verification of the concentrations was below the LOD of 0.01 mg test item/L.

 

This toxicity study is classified as acceptable guideline requirements for Freshwater Alga and Cyanobacteria, Growth Inhibition Test with P. subcapitata.

 

Results Synopsis

 

Test Organism: of Pseudokirchneriella subcapitata (KORSHIKOV), Strain No. 61.81 SAG

Test Type (Flowthrough, Static, Static Renewal): Static

 

Parameter

Yield
[mg test item/L]

Growth rate
[mg test item/L]

72-hour EC50

>Filtrate of nominal 100 mg/L

>Filtrate of nominal 100 mg/L

95 % conf. interval

n.d.

n.d.

 

 

 

72-hour EC20

>Filtrate of nominal 100 mg/L

>Filtrate of nominal 100 mg/L

95 % conf. interval

n.d.

n.d.

 

 

 

72-hour EC10

>Filtrate of nominal 100 mg/L

>Filtrate of nominal 100 mg/L

95 % conf. interval

n.d.

n.d.

 

 

 

72-hour NOEC

≥Filtrate of nominal 100 mg/L

≥Filtrate of nominal 100 mg/L

72-hour LOEC

>Filtrate of nominal 100 mg/L

>Filtrate of nominal 100 mg/L

n.d. = not determinable

 

Endpoint(s) Effected: Growth rate, Yield

 

This information is used in a read-across approach in the assessment of the target substance.For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Description of key information

No effect on the growth or yield of Pseudokirchneriella subcapitata was observed up to the limit of water solubility of the test substance in a growth inhibition test conducted according to OECD guideline 201 and under GLP.

The analytical verification could not determine a measured concentration as the concentration of the test item was too low. Although a saturated solution was prepared by stirring for 48 h. The substance is hardly soluble and the limit of detection was 0.01 mg/L.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Key value for chemical safety assessment

Additional information