((4S,4aR,7S,7aR)-4,7-dimethylhexahydrocyclopenta[c]pyran-1(3H)-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:

November 2020 to May 2021

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)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch Number CH-DA-01-18

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

In order to determine an appropriate test preparation method, an assessment was made of the material's behaviour in deionised water. A 1000 mg/L stock was prepared in deionised water and the resulting mixture was then stirred for one hour, left to settle for a further hour and its behaviour assessed. As the material was observed to be poorly soluble, it was stirred again for approximately 19 hours, left to settle for a further hour and its behaviour was reassessed.

The material was observed to be poorly soluble so was prepared by Water Accommodated Fractions (WAF). Test material stocks were individually prepared by weighing out an appropriate amount of test material, adding UD EPA culture medium and stirring for approximately 20 hours. The stocks were then left to settle for 1 our and the mid column stock was siphoned off, taking care to avoid siphoning of any undissolved material. Test material stocks were prepared for the range finding test.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
-Strain: 278/4
-Source (laboratory, culture collection): SAMS Limited
-Method of cultivation: Pre-cultures in the exponential growth phase were then prepared from stock laboratory cultures by inoculating autoclaved freshwater at 120 oC for 15 minutes with nutrient medium 2 to 4 days before test commencement. The pre-culture flasks were incubated at approximately 21-24 oC under constant illumination and were used as the inoculum source for subsequent toxicity tests.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21-24 +/- 2 oC

pH:

7.5 +/- 0.1

Nominal and measured concentrations:

1, 3.2, 10, 32, 100, 320 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
-Test vessel: 100 mL borosilicate glass conical flasks
-Material, size, headspace, fill volume: 50 mL of test medium
-Initial cells density: 5 x 10^3 cells per millilitre
-No. vessels per concentration (replicates): 3
-No. vessels per control (replicates): 6

GROWTH MEDIUM
-Standard medium used

TEST MEDIUM / WATER PARAMETERS
-Source/preparation of dilution water: Purified water treated by reverse osmosis followed by electro-deionisation

OTHER TESTS CONDITIONS
-Adjusment of pH: pH of the culture medium was adjusted, if required, by adding 1M HCl or NaOH to give a pH of 7.5 +/- 0.1.
-Photoperiod: Continuous
-Light intensity and quality: Light intensity values (4440 to 8880 Ix) were measured daily during the test.

EFFECT PARAMETERS MEASURED
-Determination of cell concentrations: Fluorimeter; haemocytometer, Sedgewick-Rafter chamber

TEST CONCENTRATIONS
-Range finding study
-Test concentration 1, 10, 100 and 1000 mg/L
-Results used to determine the conditions for the definitive study.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

51.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

70.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

173 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

Exponential growth was observed in the control for the algal test. No abnormalities were reported and no observations were noted that may have caused a difference between the measured and nominal values. The effect concentrations did not exceed the solubility of the substance in the test medium.

Results with reference substance (positive control):

The results for the reference substance are valid with an EC50 of 1.7 after 72 hours.

Validity criteria fulfilled:

yes

Conclusions:

Dihydronepetalactone exhibited a 72h EC(r)50 value of 51.2 mg/L.

Executive summary:

A short-term toxicity study to determine the aquatic toxicity of dihydronepetalactone to freshwater unicellular algae (Pseudokirchneriella subcapitata) was determined by a GLP compliant study performed in accordance with OECD 201 test guideline.

In order to determine the concentrations to be used in the definitive test a range finding study was performed over 72h to determine the appropriate concentrations at which growth rate effects were observed was conducted.  Dihydronepetalactone was characterised as poorly water soluble and was therefore prepared by Water Accommodated Fractions (WAF).

 

The concentration range used in the definitive study was 1, 3.2, 10, 32, 100, 320 and 1000 mg/L.

 

The 72h EC50 for dihydronepetalactone was 51.2 mg/L.  

Description of key information

A short-term toxicity study to determine the aquatic toxicity of dihydronepetalactone to freshwater unicellular algae (Pseudokirchneriella subcapitata) was determined by a GLP compliant study performed in accordance with OECD 201 test guideline.

In order to determine the concentrations to be used in the definitive test a range finding study was performed over 72h to determine the appropriate concentrations at which growth rate effects were observed was conducted.  Dihydronepetalactone was characterised as poorly water soluble and was therefore prepared by Water Accommodated Fractions (WAF).

The concentration range used in the definitive study was 1, 3.2, 10, 32, 100, 320 and 1000 mg/L.

The 72h EC50 for dihydronepetalactone was 51.2 mg/L.  

Key value for chemical safety assessment

EC50 for freshwater algae:

51.2 mg/L