3-(1-ethoxyethoxy)-3,7-dimethylocta-1,6-diene

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:

Jan - March 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study done to guideline, in compliance with GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, 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-(1-ethoxyethoxy)-3,7-dimethylocta-1,6-diene

EC Number:

255-138-6

EC Name:

3-(1-ethoxyethoxy)-3,7-dimethylocta-1,6-diene

Cas Number:

40910-49-4

Molecular formula:

C14H26O2

IUPAC Name:

1-[(3,7-dimethylocta-1,6-dien-3-yl)oxy]-1-ethoxyethane

Test material form:

gas under pressure: refrigerated liquefied gas

Details on test material:

Chemical name (IUPAC) 3-(1-ethoxyethoxy)-3,7-dimethylocta-1,6-diene
CAS Number 40910-49-4
EC number 255-138-6
Molecular formula C14H26O2
Molecular weight 226.40 g/mol

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

not specified

Test organisms

Test organisms (species):

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

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test conditions

Nominal and measured concentrations:

Nominal: 1.0, 3.2, 10, 32 and 100% of a water soluble fraction (saturated solution).
Initial measured concentrations: 0.18, 0.60, 2.4, 8.5 and 29 mg/l
Time-weighted average concentrations: 0.099, 0.13, 0.28, 2.0 and 6.7 mg/l

Details on test conditions:

The test item was known to be volatile and hence testing was conducted in sealed test vessels in order to minimize possible losses due to volatilization. In order to prevent inhibition of growth due to the restriction of gaseous exchange, additional sodium bicarbonate was added to the culture mediumto provide a source of carbon dioxide for algal growth.

Reference substance (positive control):

yes

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

12 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CL 9.6-16

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

2.3 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CL 1.6-2.9

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

3.3 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95% CL 2.5-4.2

Effect concentrations 4

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.85 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 95% CL 0.35-1.3

Effect concentrations 5

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.28 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

other: Inhibition of both growth rate and yield

Details on results:

During the exposure period the measured concentrations decreased to 1-30% of initial at the end of the test. The decrease in test concentrations may be related to one or more or a combination of factors, like for instance: photosensitivity of the test substance, adsorption of the test substance to algal cells, chemical instability of the test substance. Given these results, the EC50 was based on the TWA concentrations that were calculated as 0.099, 0.13, 0.28, 2.0 and 6.7 mg/l.

Results with reference substance (positive control):

A reference test was carried out to check the sensitivity of the test system used by WIL Research Europe to Potassium dichromate (Merck, Art. 1.04864, Batch K44879664). Closed test vessels were used as to mimic testing a volatile test article and results were compared with standard ‘open’ systems.
The EC50 for growth rate inhibition (72h-ERC50) was 1.3 mg/l with a 95% confidence interval ranging from 1.2 to 1.5 mg/l. The historical ranges for growth rate inhibition using standard ‘open’ systems range between 0.82 and 2.3 mg/l. Hence, the 72h-ERC50 for the present test in closed systems is within the historical range.
The EC50 for yield inhibition (72h-EYC50) was 0.50 mg/l with a 95% confidence interval ranging from 0.47 to 0.53 mg/l. The historical ranges for yield inhibition using standard ‘open’ systems lie between 0.43 and 1.1 mg/l. Hence, the 72h-EYC50 for the present test in closed systems was within range.
It was concluded that the sensitivity of algae exposed in closed test systems towards Potassium dichromate was not significantly different from the sensitivity of algae exposed in standard ‘open’ reference studies during the past years.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present study with Pseudokirchneriella subcapitata, Elintaal inhibited both growth rate and yield of this fresh water algae species significantly at TWA concentrations of 2.0 mg/l and higher.
The EC50 for growth rate inhibition (72h-ERC50) was 12 mg/l with a 95% confidence interval ranging from 9.6 to 16 mg/l. The corresponding EC10 was 2.3 mg/L (95% CL 1.6 to 2.9 mg/L).
The EC50 for yield inhibition (72h-EYC50) was 3.3 mg/l with a 95% confidence interval ranging from 2.5 to 4.2 mg/l. The corresponding EC10 was 0.85 mg/L (95% CL 0.35 to 1.3 mg/L).
The 72h-NOEC for inhibition of both growth rate and yield was 0.28 mg/l.

The preferred observational end point in this study is algal growth rate inhibition because it is not dependent on the test design (ECHA guidance Chapter R.7b v1.1) and classification shall be based on the ErC50 (EU CLP regulation No 1272/2008 and its adaption 286/2011). In terms of the NOEC and EC10 values, there is a preference for use of the EC10 value because it is derived from the dose response curve. In contrast the NOEC depends on the experimental design (e.g. the concentrations used in the test). Thus the 72-h EC50 of 12 mg/L and EC10 of 2.3 mg/L based on growth rate are used for classification purposes.