4-methylpent-3-en-2-one

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:

July 14 to July 17, 2008

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

Temperature was above 25 °C with a maximum of 27 °C.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Duplicate samples from the freshly prepared test media (containing algae) of all test concentrations and from the control were taken at the start of the test.For the determination of the stability of the test item under the test conditions and of the maintenance of the test item concentrations during the test period, adequate volumes of the freshly prepared test media of all test concentrations and the control were incubated during test period under the same conditions as in the actual test (but without algae) and from these test media duplicate samples were taken at the end of the test period (after the 72 hours test period).

The concentrations of the test item mesityl oxide were analysed in the duplicate test media samples from the test concentrations of nominal 32 and 100 mg/L from both sampling times (0 and 72 hours). From the control samples only one of the duplicate samples was analysed from each of both sampling times.

Vehicle:

yes

Details on test solutions:

The test item Mesityl Oxide is expected to be volatile. To keep the test item concentrations during the preparation of the test solutions, during the course of the biological incubation and in the analytical part as constant as possible, the test vessels containing the test media were only opened as often and as long as necessary during the whole period of the study. All samples were treated in the same way, also the samples for chemical analysis.The test medium of the highest test concentration was prepared by dissolving 35.15 µL test item into 350 mL culture medium by intense stirring for 10 minutes. This test medium was prepared a second time to have enough volume to prepare the test media of the other desired test concentrations. Therefore adequate volumes of this test medium were diluted with test water. All test media were prepared just before introduction of the algae (= start of the test).

Test organisms (species):

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

Details on test organisms:

Species: Pseudokirchneriella subcapitata, Strain No. 61.81 SAG
Origin: The algae were supplied by the "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttingen", 37073 Göttingen, Germany.
Breeding Conditions: The algae were cultivated in the laboratories of IBACON under standardised conditions according to the test guidelines.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

The temperature was measured daily in an Erlenmeyer flask filled with water and incubated under the same conditions as the test flasks. Water temperature was: 23 °C

pH:

Was measured in all test item concentrations and the control at the start and the end of the test. pH was: 7.0 at test start and 10.0 at test end

Nominal and measured concentrations:

100, 32, 10, 3.2 and 1.0 mg test item/L and a control

Details on test conditions:

The light intensity was measured once during the test at 6 positions distributed over the experimental area at the surface of the test media.Mean light intensity:7242 Lux (range: 7070 - 7440 Lux)

Pre-experiments were performed to determine the solubility of the test item in test water and to select suitable methods for the preparation of a stock solution and the dosage of the test item into the test media.

Range-Finding Test: For the determination of the test concentrations a range-finding test was performed. However, according to the Commission Directive 92/69/EEC concentrations in excess of nominal 100 mg test item/L were not tested.The solubility pre-experiments and the range-finding test were not performed in compliance with the GLP-Regulations and are excluded from the Statement of Compliance in the final report, but the raw data of these tests will be archived under the project number of the present study.

Introduction of Algae: The test was started (0 hours) by inoculation of a biomass of 3500 algal cells per mL test medium. According to the 201 cell concentration recommended for Pseudokirchneriella is 5*103 to 5*104. What is the impact in terms of study relevance?? These cells were taken from an exponentially growing pre-culture, which was set up 3 days prior to the start of the test under the same conditions as in the test.
Replicates: The test was performed with three replicates per test concentration and six replicates in the control. A volume of 60 mL algal suspension per replicate was continuously stirred by magnetic stirrers in Erlenmeyer flasks of 50 mL volume. The flasks were closed with a conical stopper and incubated in a water bath.
Blanks: Additionally, one replicate of each test concentration and of the control was prepared without algae to provide a "blank" for the spectrophotometrical measurements. The additional replicates were incubated under the same conditions as described above. The blank values were subtracted from the absorption measured in the samples containing algae in order to eliminate absorption caused by test item.
Exposure Time: 72 hours

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

61.56 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

The microscopic examination of the shape of the algal cells after 72 hours of test duration did not show any difference between the algae that had been growing at a nominal test concentration of 100 mg test item/L and the algal cells in the control. Thus, the shape of the algal cells was not obviously affected up to this test concentration, the highest concentration tested.

Validity criteria fulfilled:

yes

Conclusions:

EC50-72h > 100 mg/L

Executive summary:

The 72-hours EC₅₀for the parameter growth rate and yield could not be determined by statistical analysis due to the lack of effects. Therefore the 72-hours EC₅₀for both parameters was determined to be > 100 mg test item/L (the highest concentration tested). The 72-hours EC₁₀could only be calculated for the parameter growth rate and is 61.56 mg/L. The 72-hours EC₁₀for the parameter growth ratewas determined to be > 100 mg/L.

The 72-hours NOEC was determined to be 32 mg test item/L. The 72-hours LOEC was determined to be 100 mg test item/L. The NOEC and the LOEC are the same for growth rate and yield and were calculated based on nominal test concentrations.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

32 mg/L

Additional information

The acute toxicity of mesityl oxide to algae has been investigated according to OECD 201. The 72-hours EC₅₀ for the parameter growth rate and yield could not be determined by statistical analysis due to the lack of effects. Therefore the 72-hours EC₅₀ for both parameters was determined to be > 100 mg test item/L (the highest concentration tested). The 72-hours EC₁₀ could only be calculated for the parameter growth rate and is 61.56 mg/L. The 72-hours EC₁₀ for the parameter growth ratewas determined to be > 100 mg/L.

The 72-hours NOEC was determined to be 32 mg test item/L. The 72-hours LOEC was determined to be 100 mg test item/L. The NOEC and the LOEC are the same for growth rate and yield and were calculated based on nominal test concentrations.