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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:

03/09/04 - 26/10/05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

See "Principles of method"

Principles of method if other than guideline:

The pH in the range-finding test and the two limit tests increased above a value of 9.0 and/or with more than 1.5 units.

Evaluation: The observed increase was due to the fact that test vessels were completely closed and consequently gas exchange was reduced in comparison to normal open systems. Increasing the NaHC03 concentration in the medium prevented an increase in pH of more than 1.5 units but could not maintain the value below 9.0.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether

EC Number:

609-858-6

Cas Number:

406-78-0

Molecular formula:

C4H3F7O

IUPAC Name:

1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether

Test material form:

liquid

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

During the final limit test duplicate samples were taken from the blank-control and the limit concentration. Samples were transferred to headspace-vials that were immediately closed.

Test solutions

Vehicle:

no

Details on test solutions:

Preparation of test solutions for the range-finding test started with weighed amounts of test substance that were quantitatively added to volumetric flasks to provide test solutions of nominally 10 and 100 mg/l. The test solutions were magnetically stirred for 2-5 minutes. Care was taken that during preparation as little as possible evaporation occurred (weighing and preparation in closed vessels which already contained a small volume of test medium, short preparation period). The lower test concentrations were prepared by dilution of the test solution of 10 mg/I.

Test organisms

Test organisms (species):

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

Details on test organisms:

This system is an unicellular algal species sensitive to toxic substances in the aquatic ecosystem and has been selected as an internationally accepted species.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

24 h

Test conditions

Test temperature:

21-25°C, constant within 2°C

pH:

6.0-9.0, preferably not varying by more than 1.5 unit

Nominal and measured concentrations:

Range-finding test: 0, 0.1, 1.0, 10 or 100 mg/I (nominal) (nominal 10 mg/l = 1.0 mg/l measured, nominal 100 mg/l = 14.6 mg/l measured)
First limit test: 0 or 147 mg/l (nominal) which was equivalent to 0 and 8.7 mg/l, respectively (TWA measured concentration).
Final limit test: 0 or 257 mg/l (nominal) at start of test this was equivalent to 0 and 213 mg/l (measured), respecitvely. The TWA for the duration of the test was 0 and 24 mg/l (measured)

Details on test conditions:

Test duration: 72 hours
Test type: Static
Test vessels: 100 ml, all-glass, containing 75 ml of test solution, airtight closed with a screw cap.
Medium: M2
Cell density: An initial cell density of 1 x 10^4 cells/ml.
Illumination: Continuously using TLD-lamps of the type 'Cool-white' of 30 Watt, with a light intensity within the range of 67 to 82 µE.m^-2.s^-1
Incubation: Vessels were distributed at random in the incubator. During incubation the algal cells were kept in suspension by continuous shaking.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 24 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 213 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

Range-finding test: No biologically significant effects were observed on algal growth inhibttion and growth rate reduction up to a nominal test concentration of 100 mg/I. Samples taken from nominal 10 and
100 mg/I were analysed, which showed mean start concentrations of 1.0 and 14.6 mg/I, respectively. These concentrations decreased by approximately 80 to 90% below initial during the test period despite the fact that test vessels were air tightly closed. All test conditions were maintained within the limits prescribed by the protocol, except for the pH that increased above 9.0, which was likely to be caused by the fact that test vessels were closed.

Due to the extreme volatile character of the test substance, it was not possible to start at the intended nominal concentration with the method of preparation used in the present range-finding test and to keep concentrations stable during exposure. Therefore, it was decided to adapt the preparation procedure for the final test as to be able to start at an actual exposure concentration close to 100 mg/I. For this purpose, an amount of 100 µI was pipetted directly into 1 liter (nominal 147 mg/I) of stirring algal growth medium. The vessel was immediately closed and the content magnetically stirred for 1 minute. Immediately thereafter, individual replicate vessels were filled with test solution, algae were added, samples were taken and the incubation started in completely closed vessels. All within the shortest time possible.

First limit test
Measured test substance concentrations: Analysis at the start of the test showed a mean measured concentration of 57 mg/I in samples taken from nominally 147 mg/I. The measured concentration decreased to 6.3 mg/I after 24 hours and to 2.1 mg/I after 72 hours of exposure. The Time Weight Average (TWA) concentration was calculated to correspond to 8. 7 mg/I.

Mean cell densities, Inhibition of cell growth and reduction of growth rate: No significant differences were recorded between the values for cell growth or growth rate between the limit test concentration and the blank-control. However, as the initial measured concentration was only 57 mg/I, and thus still not at the required 100 mg/I, it was decided to perform a second limit test. In the second limit test a higher nominal concentration was prepared as to be able to start the test at the required minimum concentration of 100 mg/I. All test conditions were maintained within the limits prescribed by the protocol, except for the pH
that increased with more than 1.5 units to a value of 10.4 at the end of the test. The pH increase was probably caused by the fact that test vessels were closed hampering the CO2 exchange.

Final limit test
Measured test substance concentrations
Analysis at the start of the test showed a mean measured concentration of 213 mg/I in samples taken from nominally 257 mg/I. Hence, this time a much higher recovery was achieved in the samples taken at the start of exposure. The measured concentration decreased to 13 mg/I after 24 hours and to 6.3 mg/I after 72 hours of exposure. The Time Weight Average (TWA) concentration was calculated to correspond to 24 mg/I.

Inhibition of cell growth and reduction of growth rate
No significant differences were recorded between the values for cell growth or growth rate between the test concentration and the blank-control.

Effect parameters
Parameter Concentration (mg/I)
ASAHIKLIN AE-3000
Measured TWA (mg/l
NOEC (biomass) 24
72h-EC50 (biomass) >24
NOEC (growth rate) 24
72h-EC (growth rate) >24

The pH was within the limits prescribed by the protocol (6.0-9.0, preferably not varying by more than 1.5 unit) at the start of exposure, but exceeded the upper limit at the end of the test due to the fact that test vessels were airtight closed. The temperature of the test medium was 22.8°C at the start of the test. During the exposure period the temperature measured in the incubator was maintained between 22.1 and 23.6°C. Temperature remained within the limits prescribed by the protocol (21-25°C, constant within 2°C).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The EC50 (growth rate) for 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether was determined to be >213 mg/l (initial) and >24 mg/l (TWA measured) and the NOEC (growth rate) 213 mg/l (initial) and 24 mg/l (TWA measured).

Executive summary:

The toxicity of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether to algae was determined in a 72 -hour algal growth inhibition study undertaken in accordance with OECD TG 201. The EC50 (growth rate) for 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether was determined to be >213 mg/l (initial) and >24 mg/l (TWA measured) and the NOEC (growth rate) 213 mg/l (initial) and 24 mg/l (TWA measured).