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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:

25 January 2018 to 18 March 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Reliable experimental study following OECD 201 guidelines (2006) and EC No. 761/2009 Method C.3 adopted 2009 and GLP standards.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2006

Deviations:

yes

Remarks:

During range finding test the lux dropped below the study plan range of 4440 and 8880 but did not impact the outcome of the test.

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

yes

Remarks:

During range finding test the lux dropped below the study plan range of 4440 and 8880 but did not impact the outcome of the test.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

The test substance is listed as ATHC, acetyl trihexyl citrate (CAS # 24817-92-3). The test substance is a pale yellow slightly viscous liquid with 99.4% purity. The test substance was obtained from the Sponsor, Vertellus Holdings LLC and stored at room temperature in the dark.

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

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

Details on test organisms:

The test was carried out using Pseudokirchneriella subcapitata strain CCAP 278/4. Liquid cultures of Pseudokirchneriella subcapitata were obtained from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland. Master cultures were maintained in the laboratory by the periodic replenishment of culture medium. The master cultures were maintained in the laboratory under constant agitation by orbital shaker (100 to 150 rpm) and constant illumination at 24 ±1 °C.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

24 °C ± 1 °C

pH:

7.6 – 8.0

Nominal and measured concentrations:

A saturated solution was prepared by stirring an excess (50 mg/L) of test item in culture medium for a period of 24 hours prior to removing any undissolved test item present by filtration through a 0.2 gm Sartorius Sartopore filter (first approximate 2 liters discarded in order to pre-condition the filter) to give a saturated solution of the test item.

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % v/v saturated solution.

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

100% v/v saturated solution prepared from a test solution with a loading rate of 50 mg/L.

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 50 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

Test solution prepared with a loading rate of 50 mg/L resulting in a 100% v/v saturation solution.

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

100 other: % v/v saturated solution.

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

100% v/v saturated solution prepared from a test solution with a loading rate of 50 mg/L.

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

50 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

Test solution prepared with a loading rate of 50 mg/L resulting in a 100% v/v saturation solution.

Results with reference substance (positive control):

The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Validity criteria fulfilled:

yes

Remarks:

Cell concentrations of control increased by a factor of 63 after 72 h (protocol ≥ factor of 16); mean of coeff. of variation for growth rates control 12% (protocol ≤ 35%); coeff.of var.of avg. sp. growth rate in rep.control cultures 3% (protocol ≤ 7%).

Conclusions:

The test substance did not cause a reduction of growth in the algal cultures (test units) exposed to any test concentration of the test item for 72 h; therefore, there were no toxic or inhibitory effects at saturation. The 72-h EC50, 72-h EC20, and 72-h EC10 (based on growth rate) were each reported as > 100% v/v saturated solution; the corresponding 72-h EL50, 72-h EL20 and 72-h EL10 (based on growth rate) were each reported as > 50 mg/L (based on the nominal loading rate).

Description of key information

The key study was a static acute toxicity test on the effects of the substance on the freshwater unicellular green alga, Pseudokirchneriella subcapitata following OECD Guideline 201. The test substance did not cause a reduction of growth in the algal cultures (test units) exposed to any test concentration of the test item for 72 h; therefore, there were no toxic or inhibitory effects at saturation.  The 72-h EC50, 72-h EC20, and 72-h EC10 (based on growth rate) were each reported as > 100% v/v saturated solution; the corresponding 72-h EL50, 72-h EL20 and 72-h EL10 (based on growth rate) were each reported as > 50 mg/L (based on the nominal loading rate).

 

 

 

Key value for chemical safety assessment

EC50 for freshwater algae:

50 mg/L

EC10 or NOEC for freshwater algae:

50 mg/L