2,6-Octadienal, 3,7-dimethyl-, acid-isomerized

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-07-13 to 2017-07-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2011

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2016

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0.625 - 1.25 - 2.50 - 5.00 - 10.0 mg/L (WAF)
- Sampling method: Separate replicates for each test item loading and control were prepared for the test item analysis at the beginning of the exposure with algae. The samples for the test item analysis after 72 hours were prepared at the start of the exposure with algae and incubated under test conditions.
- Sample storage conditions before analysis: All samples were stored at 6 ± 2 °C until sample preparation and at room temperature until the start of the analysis

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Water accomodated fractions WAF
- Method: An appropriate amount of the test item was directly pipetted into a glass bottle with an appropriate amount of dilution water for each loading. This dispersion was shaken for 24 hours with 20 rpm at room temperature. After a separation phase of 1 hour, the WAF was removed by siphoning (from the approximate centre of the flask) and used in the test.
- Test loading: 0.625 - 1.25 - 2.50 - 5.00 - 10.0 mg/L
- Controls: Six replicates (without test item) were exposed under the same conditions as the test loadings.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Strain: HINDAK, SAG 61.81
- Method of cultivation: Fresh stocks are prepared every month on Z-Agar. Light intensity amounted to 2567 - 5130 lux corresponding to 35-70 µE·m-2·s-1 for 24 hours per day.
- Culture medium: Nutrient medium Z

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

nominal: 0.24 mmol Ca+Mg/L

Test temperature:

22.0 – 23.0 °C

pH:

8.0 to 8.19 at test start and 8.31 to 9.42 at test end

Nominal and measured concentrations:

Nominal concentrations: 0.625 - 1.25 - 2.50 - 5.00 - 10.0 mg/L, and a control
Measured concentrations: 0.214, 0.816, 0.937, 2.34, 6.00 mg/L, and < LOQ (Measurement of two main constituents)

Details on test conditions:

TEST SYSTEM
- Test vessel: Sterile headspace flasks
- Type: closed
- Material, size, headspace, fill volume: 59 mL, with aluminium tops with PTFE seals fill with 59 mL test solution, no headspace
- Initial cells density: 6839 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes, As recommended in OECD TG 201

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: 24 hours/day light
- Light intensity and quality: Mean light intensity: 5852 lux (range: 5102 to 6451 lux)

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: fluorimeter
- Chlorophyll measurement: measured daily, excitation at 436 nm, emission at 685 nm.
- Other: Microscopic evaluation: carried out at the start and the end of the incubation period

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2

Range finding study
- Test concentrations: 100 - 10.0 - 1.00 mg/L
- Results used to determine the conditions for the definitive study: Growth Rate Inhibition at loading level of 100, 10.0 , 1.00 mg/L were 100%, 100% and -4%, respectively. Yield Inhibition at loading level of 100, 10.0 , 1.00 mg/L were 100%, 100% and -21%, respectively.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

6.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL20

Effect conc.:

5.08 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

4.09 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

2.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOELR

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

4.57 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

1.49 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Microscopic evaluation: no morphological abnormalities
- Physicochemical Data: pH-value, room temperature, light intensity were determined to be within the acceptable limits. The test media were clear throughout the exposure phase.

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50: most recent test: yield: 0.320 mg/L (95% CI: 0.242 - 0.341), growth rate 0.559mg/L (95% CI: 0.538 - 0.581)

Biological results:

The measured cell densities are reported below:

Nominal test item loading (mg/L)	Mean cell density (cells/mL)
	0 h	24 h	48h	72h
10	6839	4403	n.a.	n.a.
5	6839	16466	70408	295419
2.5	6839	26627	152445	619639
1.25	6839	32247	190268	619834
0.625	6839	28016	179165	674501
Control	6839	32514	248244	716831

Nominal test item loading (mg/L)	growth rate (/d)	Inhibition of growth rate (%)	Yield (cells/mL)	Inhibition of yield (%)
10	n.a.	100	n.a.	100
5	1.26	19	288580	59
2.5	1.5	3	612800	14
1.25	1.5	3	612995	14
0.625	1.53	1	1667662	6
Control	1.55		709992

Analytical results:

Measured concentrations of two main constituents and percent of the initial concentrations (WAF):

Nominal test item loading levels (WAF)	Meas. Cons. [mg/L]		%
	0 hours fresh medium	72 hours old medium
10.0	6.00	6.26	104
5.00	2.34	2.51	107
2.50	0.937	0.921	98
1.25	0.816	0.816	100
0.625	0.214	0.207	97
Control	< LOQ	< LOQ

The test item is sufficiently stable throughout the test.

Effect concentrations:

Influence of test item on the growth of algae ( based on nominal test item loadings):

	Growth Rate Inhibition Nominal test item loading[mg/L]
NOEL	2.50
LOEL	5.00
ErL10	4.09 (3.54 - 4.43)
ErL20	5.08 (4.95 - 5.31)
ErL50	6.90 (6.24 - 8.05)
	Yield Inhibition Nominal test item loading [mg/L]
NOEL	0.625
LOEL	1.25
EL10	1.49(<0.625 - 2.97)
EyL20	3.06 (2.51 - 3.70)
EyL50	4.57 (4.18 - 4.84)

Validity criteria fulfilled:

yes

Conclusions:

The EL50-values with 95% confidence intervals for inhibition of growth rate (ErL50) and yield (EyL50) after 72 hours were 6.90 (6.24 - 8.05) mg/L and 4.57 (4.18 - 4.84) mg/L, respectively. The EL10-values with 95% confidence intervals for inhibition of growth rate (ErL10) and yield (EyL10) after 72 hours were 4.09 (3.54 - 4.43) mg/L and 1.49 (< 0.625 - 2.97) mg/L, respectively. The NOEL-values for inhibition of growth rate and yield after 72 hours were 2.50 mg/L and 0.625 mg/L, respectively.

Executive summary:

The toxicity of test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201. The study was conducted under static conditions in a closed system without headspace with an initial cell density of 6839 cells/mL. Five water accommodated fractions (WAF) with the nominal test item loadings 0.625 - 1.25 - 2.50 - 5.00 - 10.0 mg/L (factor 2) were prepared with dilution water and shaken for 24 hours (20 rpm, room temperature). Three replicates were tested for each test item loading and six replicates for the control. The environmental conditions were within the acceptable limits.

The test media were clear throughout the test period. The concentrations of the test item in all test loadings and the control were analytically verified by GC-MS analysis of the two main constituents at the start and the end of exposure.The measured concentrations of the two main constituents of the test item at the end of the exposure were in the range of 97 to 107% of the initial measured concentrations. This means, that the test item was stable during the exposure. All effect values given are based on the nominal test item loadings.

The EL50-values with 95% confidence intervals for inhibition of growth rate (ErL50) and yield (EyL50) after 72 hours were 6.90 (6.24 - 8.05) mg/L and 4.57 (4.18 - 4.84) mg/L, respectively. The EL10-values with 95% confidence intervals for inhibition of growth rate (ErL10) and yield (EyL10) after 72 hours were 4.09 (3.54 - 4.43) mg/L and 1.49 (< 0.625 - 2.97) mg/L, respectively. The NOEL-values for inhibition of growth rate and yield after 72 hours were 2.50 mg/L and 0.625 mg/L, respectively.

Description of key information

For this endpoint one test is available.The toxicity of test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201. The test was performed using 5 WAF's.

The EL50-values for inhibition of growth rate (ErL50) after 72 hours was 6.90 mg/L. The EL10-values for inhibition of growth rate (ErL10) after 72 hours was 4.09 mg/L. The NOEL-value for inhibition of growth rate after 72 hours was 2.50 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

6.9 mg/L

EC10 or NOEC for freshwater algae:

4.09 mg/L

Additional information

For this endpoint only one test is available. The toxicity of test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201. The study was conducted under static conditions in a closed system without headspace with an initial cell density of 6839 cells/mL. Five water accommodated fractions (WAF) with the nominal test item loadings 0.625 - 1.25 - 2.50 - 5.00 - 10.0 mg/L (factor 2) were prepared with dilution water and shaken for 24 hours (20 rpm, room temperature). Three replicates were tested for each test item loading and six replicates for the control. The environmental conditions were within the acceptable limits.

The test media were clear throughout the test period. The concentrations of the test item in all test loadings and the control were analytically verified by GC-MS analysis of the two main constituents at the start and the end of exposure. The measured concentrations of the two main constituents of the test item at the end of the exposure were in the range of 97 to 107% of the initial measured concentrations. This means, that the test item was stable during the exposure. All effect values given are based on the nominal test item loadings.

The EL50-values with 95% confidence intervals for inhibition of growth rate (ErL50) and yield (EyL50) after 72 hours were 6.90 (6.24 - 8.05) mg/L and 4.57 (4.18 - 4.84) mg/L, respectively. The EL10-values with 95% confidence intervals for inhibition of growth rate (ErL10) and yield (EyL10) after 72 hours were 4.09 (3.54 - 4.43) mg/L and 1.49 (< 0.625 - 2.97) mg/L, respectively. The NOEL-values for inhibition of growth rate and yield after 72 hours were 2.50 mg/L and 0.625 mg/L, respectively.