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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
2018-01-26
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
QSAR prediction
Qualifier:
according to
Guideline:
other: REACH guidance on QSARs R.6, May 2008
Deviations:
no
Principles of method if other than guideline:
See attached QPRF.
GLP compliance:
no
Remarks:
(not relevant)
Specific details on test material used for the study:
- SMILES: O=C(OCc(cccc1)c1)c(cccc2)c2
- CHEM: Benzoic acid, phenylmethyl ester
- MOL FOR: C14 H12 O2
- MOL WT: 212.25
- log Kow : 3.536 (EPISuite, kowwin v1.68 estimate)
- Water solubility : 34.85 mg/L (EPISuite, WSkowwin v1.43 estimate)
Details on sampling:
Not applicable
Details on test solutions:
Not applicable
Details on test organisms:
None
Total exposure duration:
96 h
Post exposure observation period:
Not applicable
Hardness:
Not applicable
Test temperature:
Not applicable
pH:
Not applicable
Dissolved oxygen:
Not applicable
Salinity:
Not applicable
Nominal and measured concentrations:
Not applicable
Details on test conditions:
Not applicable
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
2.117 mg/L
Remarks on result:
other: ECOSAR Class: esters
Details on results:
Validity of model:
1. Defined Endpoint: Toxicity to aquatic algae.
2. Unambigous algorithm: Linear regression QSAR; Log 96h-EC50 (mmol/L) = -0.6993 (log Kow) + 0.4715. To convert the EC50 from mmol/L to mg/L, multiply by the molecular weight.
3. Applicability domain: applicable to chemicals with log Kow less than 6.4 and molecular weight less than 1000 g/mol. The model can be suitable to estimate toxicity for the following esters: Acetates, Benzoates, Dicarboxylic aliphatics and Phthalates derived from aliphatic alcohols and phenols.
4. Statistical characteristics: N = 20 + 6 and the coefficient of determination R² = 0.8581.
5. Mechanistic interpretation: related to the partitioning of the substance from water into the organisms lipid phase.

Adequacy of prediction: the substance falls within the applicability domain described above and therefore the predicted value can be considered reliable.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
N = 20 + 6 and the coefficient of determination R² = 0.8581.

None

Validity criteria fulfilled:
yes
Conclusions:
The substance was predicted to have an EC50 of 2.117 mg/L to green algae after 96h of exposure.
Executive summary:

Toxicity to green algae was estimated using the ECOSAR v1.11 QSAR model available from the U.S. EPA.

The predicted 96h-EC50 was 2.117 mg/L (ECOSAR Class: Esters). This value was calculated from an estimated log Kow value (3.536) and the following linear regression:

Log 96h-EC50 (mmol/L) = -0.6993 (log Kow) + 0.4715.

The substance falls within the applicability domain of the model. Therefore, the prediction can be considered reliable for acute toxicity (96h-EC50) to algae.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-09-11 to 2017-11-16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
GLP study performed according to OECD Guideline No. 201. All validity criteria were fulfilled.
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Remarks:
signed on January 10, 2017
Specific details on test material used for the study:
None
Analytical monitoring:
yes
Details on sampling:
Samples for analysis were taken from the control, the solvent control and all test concentrations (from a replicate of each test concentration without algae dedicated exclusively to chemical analyses) at the start and the end of the test. Concentration of dissolved organic material was checked by analysis of Total Organic Carbon (TOC) in the control medium and the WAFs. TOC analysis was not performed in compliance with the OECD GLP principles but was adapted to fit the specific parameters of the test item, in accordance with ISO 17025.
Vehicle:
yes
Remarks:
Acetone
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The study was carried out using WAFs (Water Accommodated Fractions). The WAFs were prepared under closed conditions and by slow-stirring. After having tried different methods for the preparation of the WAFs in the preliminary study, the protocol described hereafter has been selected for the final test.
The mixing vessels were cylindrical glass bottles sealed with screw caps and fitted with a drain port near the bottom for drawing off the WAFs. The volume of each mixing vessel was approximately 1 L. A magnetic stirring bar was placed in each mixing vessel completely filled with test water (with a minimum of headspace). The loading rates of the test item were weighed in glass vials and resuspended in acetone. Then the loading rates of the test item/vehicle were vortexed to obtain homogeneous suspensions, and thereafter a specific volume (corresponding to a (limit) solvent concentration of 100 mg.L-1, as recommended in OECD guidance on testing and assessment No. 23) of each preparation was carefully added to the surface of test water contained in the mixing vessels that were closed immediately. The mixing was initiated with the vortex in the centre extending maximally around 10% vessel depth from the top to the bottom of the vessel. After 22 hours of gentle stirring in the dark at room temperature, the WAFs were allowed to stand for at least 1 hour before use. The first 100 mL were removed via the drain port. Then the WAFs were directly added into test flasks containing a fixed amount of inoculum (5.10^3 cells.mL-1 per vessel) that were immediately sealed after filling with a minimum of headspace. At the start of the test, the solution was observed to be clear and colourless.

- Controls: Test water without test substance but treated in the same way as the test substance solutions (WAFs).
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Museum National d’Histoire Naturelle - 12, rue Buffon, Case N°19 -75005 PARIS, bred in the Laboratoires des Pyrénées et des Landes under standardised conditions according to the test guidelines.
- Stock culture: Algae stock cultures were started by inoculating growth medium (=test water) with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light in a climate room at a temperature of 23 ± 2 °C.
- Pre-culture: 2 to 4 days before the start of the test, cells from the algal stock culture were inoculated in test water at a cell density of 1 x 10^4 cells/mL. The pre-culture was maintained under the same conditions as used in the test. The cell density was measured immediately before use.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
None
Post exposure observation period:
None
Hardness:
No data
Test temperature:
between 22.9 - 23-8 °C throughout the test (average value: 23.7°C)
pH:
Start(t=0 h): 8.16 to 8.26
End (t=72 h): 8.8.40 to 9.74
Dissolved oxygen:
No data
Salinity:
No data
Conductivity:
no data
Nominal and measured concentrations:
Nominal concentrations: 1.0, 3.2, 10.0, 32.0 and 100.0 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 100 mL, all-glass closed flasks with ground glass stopper, completely filled with test solution with minimum headspace.
Each test vessel was uniquely identified with study code, replicate number, date of experimentation and treatment group.
- Initial cells density: An initial cell density of 5.10^3 cells.mL-1 using the exponentially growing pre-culture.
- Replicates: 6 controls, 6 solvent controls and 3 replicates of each loading rate for counting. Moreover, a replicate of each treatment without algae was prepared for chemical analyses.

GROWTH MEDIUM
- Standard medium used: Yes; Original medium of OECD TG 201. Since the test was performed in sealed conditions, additional sodium bicarbonate was added to test water (for all treatments and inoculum suspension): 7 mL of NaHCO3 was added to the sterilised water during test water reconstitution (instead of 1 mL) to obtain a final concentration of 350 mg.L-1, according to the study plan.

OTHER TEST CONDITIONS
- Sterile test conditions: Yes
- Photoperiod: Continuous illumination
- Light intensity and quality: Continuous illumination with a light intensity of 4,440-8,880 lux and did not vary more than ± 15% from the average light intensity over the incubation area.

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: Cell numbers were counted daily by microscope using a counting chamber.
- Other:
- pH: At the start and the end of the test in one vessel per concentration and the control (same vessel at t=0h and t=72h).
- Temperature of Medium: Measured continuously in the growth chamber, over the study period.
- Light Intensity: Light intensity was measured once (t=0 h) during the test at 5 positions distributed over the experimental area at the surface of the test media.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.16
- Results used to determine the conditions for the definitive study: Based on the results of a range-finding test, test solutions used in the definitive test were prepared to obtain the following loading rates: 1.0, 3.2, 10.0, 32.0 and 100.0 mg/L
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
34.352 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% conf. limits: 28.110 - 39.763 mg/L
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
19.735 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% conf. limits: 0.268 - 26.826
Duration:
72 h
Dose descriptor:
EL20
Effect conc.:
45.464 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% conf. limits: 39.192 - 50.803 mg/L
Duration:
72 h
Dose descriptor:
EL20
Effect conc.:
24.977 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% conf. limits: 2.082 - 31.604 mg/L
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
77.722 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% conf. limits: 72.205 - 83.219 mg/L
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
39.197 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% conf. limits: 30.747 - 147.380
Details on results:
See above
Results with reference substance (positive control):
On August 21, 2017 (most recent test), the 72h-EC50 was 1.457 mg.L-1 for the parameter growth rate. Hence, the sensitivity of this batch of Pseudokirchneriella subcapitata was consistent with the level proposed by the ISO 8692 (6) (expected 72h-EC50: 0.92 mg.L-1 to 1.46 mg.L-1).
Reported statistics and error estimates:
The evaluation of the effects was based on the nominal WAFs concentrations (nominal loading values). The software ToxRat® Professional was used for the determination of the effective concentrations.

Table 6.1.5/1: pH-values during the final test

 

Nominal concentration(mg test item.L-1)*

Control

Solvent Control

1.0

3.2

10.0

32.0

100.0

Start t=0h

8.21

8.23

8.16

8.26

8.18

8.23

8.23

End t=72h

9.80

9.65

9.63

9.74

9.53

9.42

8.40

 * WAF prepared at the given loading rate.

Table 6.1.5/2: Algal cell densities during the final test (expressed as density of algal cells/mL x 104)

 

Replicate

Nominal concentration

 (mg test item.L-1)

Control(without solvent)

Control(with solvent)

1.0

3.2

10.0

32.0

100.0

t=24h

1

5.2

4.4

2.8

4.8

2.8

3.6

2.0

2

5.6

4.4

2.4

4.0

3.2

2.8

2.4

3

4.8

4.4

4.4

5.6

4.8

2.0

2.0

4

6.4

4.0

 

 

 

 

 

5

4.0

4.8

 

 

 

 

 

6

4.4

4.4

 

 

 

 

 

Mean

5.1

4.4

3.2

4.8

3.6

2.8

2.1

Std. Dev.

0.86

0.25

1.06

0.80

1.06

0.80

0.23

% Inh.

-

-

16.2

-3.6

10.4

22.0

33.4

t=48h

1

21.6

20.0

21.6

15.2

14.0

9.2

2.0

2

25.2

18.8

16.4

16.0

15.6

13.6

1.6

3

18.0

25.6

22.0

19.2

15.6

11.2

1.2

4

19.2

16.0

 

 

 

 

 

5

15.6

22.4

 

 

 

 

 

6

18.8

25.6

 

 

 

 

 

Mean

19.7

21.4

20.0

16.8

15.1

11.3

1.6

Std. Dev.

3.30

3.85

3.12

2.12

0.92

2.20

0.40

% Inh.

-

-

1.7

6.2

9.0

16.9

69.5

t=72h

1

91.6

87.2

76.8

83.2

74.4

58.4

4.0

2

78.8

99.2

66.8

67.2

88.0

56.0

2.4

3

76.4

90.0

89.6

68.0

85.6

59.2

2.8

4

82.8

91.2

 

 

 

 

 

5

72.0

78.0

 

 

 

 

 

6

83.6

84.8

 

 

 

 

 

Mean

80.9

88.4

77.7

72.8

82.7

57.9

3.1

Std. Dev.

6.77

7.07

11.43

9.02

7.26

1.67

0.83

% Inh.

-

-

2.6

3.8

1.3

8.1

65.4

% Inh.

-

-

0.9

2.1

-0.4

6.5

64.8

* WAF prepared at the given loading rate.

At test start 5000 algal cells/mL were incubated; 6 replicates of the controls, 6 replicates of the solvent controls and 3 replicates of each test loading rate.

Std. Dev.: standard deviation.

 

Validity criteria of the study

- Cell density in Controls: 177-fold increase within 72 hours. The specific growth rate was determined at 1.72 day-1, so greater than 0.92 day-1.

- Coefficient of Variation:

1. The mean coefficient of variation for section-by-section specific growth rates in the control cultures was of 25.0%.

2. The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures was of 1.5%.

Thus the validity criteria were respected in this study.

 

Analytical results

Concentration of dissolved organic material in the controls and the WAFs was checked by TOC analysis at the start and at the end of the test.

The analytical results of this test revealed that TOC analysis was not specific enough to separate organic carbon related to the solvent from the one of the test item, and that TOC content in WAFs was maintained around ± 30-40%. Nevertheless, the test item presence in WAFs was proportional to the tested loading rates given the algal growth inhibition observed in the final test and the analytical test results (TOC content) without solvent during the range-finding test. Thus, we consider that this point does not interfere with the conclusion of the study.

It should be noted that a WAF is by definition a complex mixture for which the individual concentration of each constituent differs due to its properties (e.g. solubility, adsorption, volatilisation, bioaccumulation…). Due to these differences, interactions between certain constituents of the mixture may occur and affect the behaviour of a given constituent which consequently would not react in the same way that if it was alone in the mixture.Therefore, and since the test item was a UVCB substance, the results were based on the nominal loading rates.

 

Table 6.1.5/3: Concentrations of the test item in test water - Results of the determination of TOC analysis (mg.L-1) - Final test.

Nominal concentration*

(mg test item.L-1)

Start (t=0h)

End

(t=72h)

Control

0.52

0.93

Solvent Control

20.00

14.30

1.0

22.20

16.30

3.2

22.00

15.90

10.0

21.50

15.40

32.0

19.30

12.00

100.0

20.40

14.90

* WAF prepared at the given loading rate.

Physico-chemical parameter values throughout the test

- The results of measurement of pH are presented in Table 6.1.5/1. Although the pH level in the control varied more than 1.5 units at the end of the test (1.59 units of difference) this was not considered to have affected the integrity of the study. The cause of the pH increases in the controls and test concentrations was certainly due to the substantial algal growth in conjunction with closed conditions used in the test, despite the addition of more sodium bicarbonate.

- The temperature in the incubator was situated between 22.9 and 23.8°C throughout the test (average value: 23.7°C), and complied with the requirements as laid down in the study plan (23°C ± 2°C, constant within 2°C).

- The mean light intensity was of 5037 lux (range: 4731-5491 lux), which remained within the ranges prescribed by the study plan (range: 4440-8880 lux and shall not vary more than ± 15% from the average light intensity over the incubation area).

Validity criteria fulfilled:
yes
Conclusions:
Under the experimental conditions and based on nominal concentrations, the 72-hour EL50 for the parameters growth rate and yield were determined to be 77.722 mg.L-1 and 39.197 mg.L-1, respectively. The 72-hour EL10 for growth rate was 34.352 mg L-1 and for yield was 19.735 mg.L-1.
Executive summary:

A study was performed to assess the test item ELEMI RESINOID for its ability to generate toxic effects on the unicellular algal species Pseudokirchneriella subcapitata. The method followed was designed to be compliant with OECD Guideline for Testing of Chemicals No. 201, referenced as Method C.3 of Commission Regulation No. 440/2008 amended by Commission Regulation (EU) 2016/266(2) and with the “Guidance document on aquatic toxicity testing of difficult substances and mixtures” (OECD No. 23).

Following a preliminary range-finding test, algal cells were exposed to Water Accommodated Fractions (WAFs) of the test item over a range of nominal loading values of 1.0, 3.2, 10.0, 32.0 and 100.0 mg/L and to a control. The inhibition of growth in relation to control cultures was determined over a test period of 72 hours, and thus over several algal generations.Concentration of dissolved organic material in the controls and the WAFs was checked by TOC analysis at the start and the end of the test.

 

The analytical results of this test revealed that TOC analysis was not specific enough to separate organic carbon related to the solvent from the one of the test item, and that TOC content in WAFs was maintained around ± 30-40%. Nevertheless, the test item presence in WAFs was proportional to the tested loading rates given the algal growth inhibition observed in the final test and the analytical test results (TOC content) without solvent during the range-finding. Therefore, we consider that this point does not interfere with the conclusion of the study.

After 72 hours of exposure, the ErLx and EyLx values were as follows:

Parameter

Growth rate (mg.L-1)

Yield (mg.L-1)

72-hour EL10

34.352

19.735

95% conf. limits

28.110 – 39.763

0.268 – 26.828

 

 

 

72-hour EL20

45.464

24.977

95% conf. limits

39.192 – 50.803

2.082 – 31.604

 

 

 

72-hour EL50

77.722

39.197

95% conf. limits

72.205 – 83.219

30.747 – 147.380

 

Under the experimental conditions and based on nominal concentrations, the 72-hour EL50 for the parameters growth rate and yield were determined to be 77.722 mg.L-1 and 39.197 mg.L-1, respectively. The 72-hour EL10 for growth rate was 34.352 mg L-1 and for yield was 19.735 mg.L-1.

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:
A read-across from a study performed on the analogue substance Resinoid of Canarium luzonicum (Burseraceae) obtained from the exudate by cyclohexane extraction was performed for that endpoint. The registered substance (target) and the source substance are natural extracts belonging to the group of Natural Complex Substances (NCS): UVCB sub-type 3, where the source is biological, and the process is refinement (ECHA Guidance on Identification and naming of substances under REACH, version 2.1 – May 2017, Section 4.3.1 and EFEO/IFRA Guidelines on substance identification and sameness of natural complex substances (NCS) under REACH and CLP, version of August 5, 2015).
The source and the registered substances have the same botanical origin. Indeed, they are both Resinoid of Canarium luzonicum (Burseraceae) obtained from the exudate. They have the same related EC and CAS numbers as well as the same EC description. Overall, they both have the same main constituents in similar concentrations, based on their respective SIP (except the presence of the residual sovent in the registered substance). Based on these similarities, the target and the source substances are expected to show similar ecotoxicological behaviour. Therefore, we consider as reliable the read across from the source substance dossier to this dossier.
Reason / purpose:
read-across source
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
34.352 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% conf. limits: 28.110 - 39.763 mg/L
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
19.735 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% conf. limits: 0.268 - 26.826
Duration:
72 h
Dose descriptor:
EL20
Effect conc.:
45.464 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% conf. limits: 39.192 - 50.803 mg/L
Duration:
72 h
Dose descriptor:
EL20
Effect conc.:
24.977 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% conf. limits: 2.082 - 31.604 mg/L
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
77.722 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% conf. limits: 72.205 - 83.219 mg/L
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
39.197 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% conf. limits: 30.747 - 147.380
Details on results:
See above
Results with reference substance (positive control):
On August 21, 2017 (most recent test), the 72h-EC50 was 1.457 mg.L-1 for the parameter growth rate. Hence, the sensitivity of this batch of Pseudokirchneriella subcapitata was consistent with the level proposed by the ISO 8692 (6) (expected 72h-EC50: 0.92 mg.L-1 to 1.46 mg.L-1).
Reported statistics and error estimates:
The evaluation of the effects was based on the nominal WAFs concentrations (nominal loading values). The software ToxRat® Professional was used for the determination of the effective concentrations.

Table 6.1.5/1: pH-values during the final test

 

Nominal concentration(mg test item.L-1)*

Control

Solvent Control

1.0

3.2

10.0

32.0

100.0

Start t=0h

8.21

8.23

8.16

8.26

8.18

8.23

8.23

End t=72h

9.80

9.65

9.63

9.74

9.53

9.42

8.40

 * WAF prepared at the given loading rate.

Table 6.1.5/2: Algal cell densities during the final test (expressed as density of algal cells/mL x 104)

 

Replicate

Nominal concentration

 (mg test item.L-1)

Control(without solvent)

Control(with solvent)

1.0

3.2

10.0

32.0

100.0

t=24h

1

5.2

4.4

2.8

4.8

2.8

3.6

2.0

2

5.6

4.4

2.4

4.0

3.2

2.8

2.4

3

4.8

4.4

4.4

5.6

4.8

2.0

2.0

4

6.4

4.0

 

 

 

 

 

5

4.0

4.8

 

 

 

 

 

6

4.4

4.4

 

 

 

 

 

Mean

5.1

4.4

3.2

4.8

3.6

2.8

2.1

Std. Dev.

0.86

0.25

1.06

0.80

1.06

0.80

0.23

% Inh.

-

-

16.2

-3.6

10.4

22.0

33.4

t=48h

1

21.6

20.0

21.6

15.2

14.0

9.2

2.0

2

25.2

18.8

16.4

16.0

15.6

13.6

1.6

3

18.0

25.6

22.0

19.2

15.6

11.2

1.2

4

19.2

16.0

 

 

 

 

 

5

15.6

22.4

 

 

 

 

 

6

18.8

25.6

 

 

 

 

 

Mean

19.7

21.4

20.0

16.8

15.1

11.3

1.6

Std. Dev.

3.30

3.85

3.12

2.12

0.92

2.20

0.40

% Inh.

-

-

1.7

6.2

9.0

16.9

69.5

t=72h

1

91.6

87.2

76.8

83.2

74.4

58.4

4.0

2

78.8

99.2

66.8

67.2

88.0

56.0

2.4

3

76.4

90.0

89.6

68.0

85.6

59.2

2.8

4

82.8

91.2

 

 

 

 

 

5

72.0

78.0

 

 

 

 

 

6

83.6

84.8

 

 

 

 

 

Mean

80.9

88.4

77.7

72.8

82.7

57.9

3.1

Std. Dev.

6.77

7.07

11.43

9.02

7.26

1.67

0.83

% Inh.

-

-

2.6

3.8

1.3

8.1

65.4

% Inh.

-

-

0.9

2.1

-0.4

6.5

64.8

* WAF prepared at the given loading rate.

At test start 5000 algal cells/mL were incubated; 6 replicates of the controls, 6 replicates of the solvent controls and 3 replicates of each test loading rate.

Std. Dev.: standard deviation.

 

Validity criteria of the study

- Cell density in Controls: 177-fold increase within 72 hours. The specific growth rate was determined at 1.72 day-1, so greater than 0.92 day-1.

- Coefficient of Variation:

1. The mean coefficient of variation for section-by-section specific growth rates in the control cultures was of 25.0%.

2. The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures was of 1.5%.

Thus the validity criteria were respected in this study.

 

Analytical results

Concentration of dissolved organic material in the controls and the WAFs was checked by TOC analysis at the start and at the end of the test.

The analytical results of this test revealed that TOC analysis was not specific enough to separate organic carbon related to the solvent from the one of the test item, and that TOC content in WAFs was maintained around ± 30-40%. Nevertheless, the test item presence in WAFs was proportional to the tested loading rates given the algal growth inhibition observed in the final test and the analytical test results (TOC content) without solvent during the range-finding test. Thus, we consider that this point does not interfere with the conclusion of the study.

It should be noted that a WAF is by definition a complex mixture for which the individual concentration of each constituent differs due to its properties (e.g. solubility, adsorption, volatilisation, bioaccumulation…). Due to these differences, interactions between certain constituents of the mixture may occur and affect the behaviour of a given constituent which consequently would not react in the same way that if it was alone in the mixture.Therefore, and since the test item was a UVCB substance, the results were based on the nominal loading rates.

 

Table 6.1.5/3: Concentrations of the test item in test water - Results of the determination of TOC analysis (mg.L-1) - Final test.

Nominal concentration*

(mg test item.L-1)

Start (t=0h)

End

(t=72h)

Control

0.52

0.93

Solvent Control

20.00

14.30

1.0

22.20

16.30

3.2

22.00

15.90

10.0

21.50

15.40

32.0

19.30

12.00

100.0

20.40

14.90

* WAF prepared at the given loading rate.

Physico-chemical parameter values throughout the test

- The results of measurement of pH are presented in Table 6.1.5/1. Although the pH level in the control varied more than 1.5 units at the end of the test (1.59 units of difference) this was not considered to have affected the integrity of the study. The cause of the pH increases in the controls and test concentrations was certainly due to the substantial algal growth in conjunction with closed conditions used in the test, despite the addition of more sodium bicarbonate.

- The temperature in the incubator was situated between 22.9 and 23.8°C throughout the test (average value: 23.7°C), and complied with the requirements as laid down in the study plan (23°C ± 2°C, constant within 2°C).

- The mean light intensity was of 5037 lux (range: 4731-5491 lux), which remained within the ranges prescribed by the study plan (range: 4440-8880 lux and shall not vary more than ± 15% from the average light intensity over the incubation area).

Validity criteria fulfilled:
yes
Conclusions:
Under the experimental conditions and based on nominal concentrations, the 72-hour EL50 for the parameters growth rate and yield were determined to be 77.722 mg.L-1 and 39.197 mg.L-1, respectively. The 72-hour EL10 for growth rate was 34.352 mg L-1 and for yield was 19.735 mg.L-1.
Executive summary:

A study was performed to assess the test item ELEMI RESINOID for its ability to generate toxic effects on the unicellular algal species Pseudokirchneriella subcapitata. The method followed was designed to be compliant with OECD Guideline for Testing of Chemicals No. 201, referenced as Method C.3 of Commission Regulation No. 440/2008 amended by Commission Regulation (EU) 2016/266(2) and with the “Guidance document on aquatic toxicity testing of difficult substances and mixtures” (OECD No. 23).

Following a preliminary range-finding test, algal cells were exposed to Water Accommodated Fractions (WAFs) of the test item over a range of nominal loading values of 1.0, 3.2, 10.0, 32.0 and 100.0 mg/L and to a control. The inhibition of growth in relation to control cultures was determined over a test period of 72 hours, and thus over several algal generations.Concentration of dissolved organic material in the controls and the WAFs was checked by TOC analysis at the start and the end of the test.

 

The analytical results of this test revealed that TOC analysis was not specific enough to separate organic carbon related to the solvent from the one of the test item, and that TOC content in WAFs was maintained around ± 30-40%. Nevertheless, the test item presence in WAFs was proportional to the tested loading rates given the algal growth inhibition observed in the final test and the analytical test results (TOC content) without solvent during the range-finding. Therefore, we consider that this point does not interfere with the conclusion of the study.

After 72 hours of exposure, the ErLx and EyLx values were as follows:

Parameter

Growth rate (mg.L-1)

Yield (mg.L-1)

72-hour EL10

34.352

19.735

95% conf. limits

28.110 – 39.763

0.268 – 26.828

 

 

 

72-hour EL20

45.464

24.977

95% conf. limits

39.192 – 50.803

2.082 – 31.604

 

 

 

72-hour EL50

77.722

39.197

95% conf. limits

72.205 – 83.219

30.747 – 147.380

 

Under the experimental conditions and based on nominal concentrations, the 72-hour EL50 for the parameters growth rate and yield were determined to be 77.722 mg.L-1 and 39.197 mg.L-1, respectively. The 72-hour EL10 for growth rate was 34.352 mg L-1 and for yield was 19.735 mg.L-1.

All validity criteria of the study were fulfilled. The result of this study performed on an analogue is used for the registered substance.

Description of key information

For that endpoint, the 96h-EC50 for the registered substance has been determined to be 2.117 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
2.117 mg/L

Additional information

For that endpoint, a study on the registered substance "Resinoid of Canarium luzonicum (Burseraceae) obtained from the exudate by benzyl benzoate extraction" was not available. Therefore, in order to fulfill that endpoint, the following studies were available:

- One experimental study performed on the analogue substance "Resinoid of Canarium luzonicum (Burseraceae) obtained from the exudate by cyclohexane extraction". In this study, the toxic effect of the test item to the unicellular algal species Pseudokirchneriella subcapitata was investigated in a static limit test using Water Accommodated Fractions. The method followed was designed to be compliant with OECD 201 guideline and with the “Guidance document on aquatic toxicity testing of difficult substances and mixtures” (OECD No. 23). Under the experimental conditions and based on nominal concentrations, the 72-hour EL50 for the parameters growth rate and yield were determined to be 77.722 mg.L-1 and 39.197 mg.L-1, respectively. The 72-hour EL10 for growth rate was 34.352 mg L-1 and for yield was 19.735 mg.L-1. This study has been reviewed and it respected the requirements of the guideline. The validity criteria were successful. This study was therefore considered reliable.

- One QSAR prediction on benzyl benzoate, the major constituent of the registered substance which represents 45 to 55% according to the SIP. To estimate the toxicity of benzyl benzoate to green algae, the QSAR model used was ECOSAR v1.11 from EPISUITE software. The 96h-EC50 for benzyl benzoate was found to be 2.117 mg/L.

The EC50 predicted for benzyl benzoate was more conservative than the result from the read-across on the analogue substance. Therefore, the toxicity value of benzyl benzoate was selected as the key value for the registered substance, as a conservative approach for that endpoint.