[(3,7-dimethyl-6-octenyl)oxy]acetaldehyde

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From July 12, 2019 to October 29, 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

[(3,7-dimethyl-6-octenyl)oxy]acetaldehyde

EC Number:

231-324-2

EC Name:

[(3,7-dimethyl-6-octenyl)oxy]acetaldehyde

Cas Number:

7492-67-3

Molecular formula:

C12H22O2

IUPAC Name:

2-[(3,7-dimethyloct-6-en-1-yl)oxy]acetaldehyde

Test material form:

liquid

Specific details on test material used for the study:

Batch: VE00601569
Appearance: Colorless to pale yellow liquid
Expiration Date: January 12, 2020
Purity: 92.9% (sum of the two peaks)

Sampling and analysis

Analytical monitoring:

yes

Remarks:

GC-FID

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

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

Details on test organisms:

Strain No. 61.81 SAG, supplied by the Collection of Algal Cultures (SAG, Institute for Plant Physiology, University of Göttingen, 37073 Göttingen / Germany).

Study design

Test type:

static

Water media type:

other: The algae were cultivated and tested in synthetic test water (AAP Medium), prepared according to the test guidelines, but modified according to the International Standard ISO 14442 [2] as a closed test system was applied.

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

The test flasks were incubated in a temperature controlled orbital shaker (Multitron-Pro, Infors HT, Bottmingen/Switzerland) at a temperature of 21°C.

pH:

The pH was measured and recorded in each treatment at the start and end of the test.

Nominal and measured concentrations:

Dilutions tested: 1:2.2, 1:4.6, 1:10 and 1:22. Additionally, a control (test water without test item) was tested in parallel.

Details on test conditions:

The test flasks were positioned randomly and repositioned daily. They were continuously illuminated by LED light installed above the test flasks. The light intensity at the level of the test solutions was approximately 75 µE s-1 m-2 (range: 70 to 79 µE s-1 m-2 , measured at nine places in the experimental area).

Reference substance (positive control):

yes

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC10

Remarks:

95% Confidence Interval

Effect conc.:

15 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

EC20

Remarks:

95% Confidence Interval

Effect conc.:

17 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Key result

Duration:

72 h

Dose descriptor:

EC50

Remarks:

95% Confidence Interval

Effect conc.:

22 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 4

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

4.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 5

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

9.2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Results with reference substance (positive control):

For evaluation of the algal quality and experimental conditions, potassium dichromate is tested as a positive control twice a year to demonstrate satisfactory test conditions. The 72-hour EC50 for growth rate in the reference test IES Study Number 20190094 was 1.1 mg/L (May 2019) and showed that the sensitivity of the test system was within the range recommended by the guideline (72-hour EC50 for the growth rate 0.9-1.5 mg/L).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

A clear concentration-response relationship was observed for both biological endpoints growth rate and yield after the exposure period of 72 hours. A statistically significant inhibitory effect on the growth rate and yield of the algae was observed at the end of the test at the mean measured concentration of 9.2 mg/L and at all higher test concentrations.

Executive summary:

The impact of the test item CITRONELLYL OXYACETALDEHYDE on the growth of the freshwater green algal species Pseudokirchneriella subcapitata was investigated in a 72-hour static test according to the OECD Guideline 201 (2006, corrected 2011) and the Commission Regulation (EU) No 2016/266, C.3.

As the test item is a volatile substance, the test was performed using glass Erlenmeyer completely filled (without headspace) with test medium that were tightly sealed with glass stoppers to avoid losses of test item by evaporation (closed system).

As the test item is a liquid with low water solubility, the slow-stirring method (to avoid formation of micro-droplets) was applied for preparation of a saturated test item solution. For preparation of the highest concentration of test medium, the test item was carefully applied (pipetted) onto the surface of the test water at a loading rate of 100 mg/L. Thereafter slow-stirring was applied for 24 hours in a closed vessel.

After this treatment the lower part of the equilibrated test medium was carefully harvested from the stirring vessel through a tap at the bottom of the vessel. This equilibrated aqueous phase with a loading rate of 100 mg/L, containing dissolved test item only, was used as the highest concentration and was diluted with test water to obtain the dilutions 1:2.2, 1:4.6, 1:10 and 1:22. Additionally, a control (test water without test item) was tested in parallel.

The preparation of the test media was based on the OECD Guidance Document No. 23 on Aqueous-Phase Aquatic Toxicity Testing of Difficult Test Chemicals, 2019.

The daily measured concentrations of the test item CITRONELLYL OXYACETALDEHYDE in the test media are shown in the table below. The analytical measurements from test media at the start of the test shown the correct preparation of the test media, i.e. the theoretical spacing factor of 2.2 between the different test concentrations was met. Since the test item concentrations decreased over the test period, the mean measured concentrations were calculated as the time-weighted geometric mean of the concentrations measured at all sampling dates (0, 24, 48, and 72 hours).

Treatment / Dilution#	Analytically Measured Concentration of the Test Item [mg/L]				Mean Measured Concentration (Geometric Mean) [mg/L]
	0 Hours	24 Hours	48 Hours	72 Hours
1:22	2.52	2.36	1.43	0.624	1.6
1:10	5.03	5.03	4.33	3.06	4.4
1:4.6	10.1	9.85	8.88	8.08	9.2
1:2.2	20.7	19.9	17.6	18.1	19
Undiluted Test Medium*	40.4	41.7	43.7	39.6	42

*: Equilibrated test medium with a loading rate of 100 mg/L.

#: Dilutions of the equilibrated test medium with a loading rate of 100 mg/L.

The biological results are based on the mean measured test item concentrations.

A clear concentration-response relationship was observed for both biological endpoints growth rate and yield after the exposure period of 72 hours. A statistically significant inhibitory effect on the growth rate and yield of the algae was observed at the end of the test at the mean measured concentration of 9.2 mg/L and at all higher test concentrations.

Endpoint after 72 Hours	Growth Rate [mg/L]	Yield [mg/L]
EC10 (95% Confidence Interval)	15 (14-16)	5.9 (5.6-6.3)
EC20 (95% Confidence Interval)	17 (16-18)	7.6 (7.3-8.0)
EC50 (95% Confidence Interval)	22 (21-23)	12 (12.0-12.7)
NOEC	4.4	4.4
LOEC	9.2	9.2

Validity Criteria: The validity criteria for increase of biomass, mean coefficient of variation of the daily growth rates and coefficient of variation of the average specific growth rates were fulfilled for the control.