Tall oil, potassium salt

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

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)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Remarks:

by HPLC-MS

Details on sampling:

Samples were taken from the control and each test group at 0 hours and from the pooled replicates at 72 hours for quantitative analysis. All samples were taken for immediate analysis. A set of duplicate (reserve) samples was taken at 0 and 72 hours occasion from the additional flasks and stored frozen for further analysis if necessary.

Vehicle:

yes

Remarks:

water

Details on test solutions:

Nominal amounts of test item (5.0, 16, 50, 160 and 500 mg) were each separately added to the surface of 5 liters of culture medium to give the 1.0, 3.2, 10, 32 and 100 mg/L loading rates respectively. After the addition of the test item, the culture medium was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixtures allowed to stand for 1 hour. Microscopic observations made on the WAFs indicated that a significant amount of dispersed test item was present in the water column and hence it was considered justifiable to remove the dispersed material by filtering the WAFs through a glass wool plug (2 to 4 cm in length) and one piece of filter paper. A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. A glass wool plug was inserted into the opposite end of the tubing and the Water Soluble Fraction (WSF)∗ removed by mid-depth siphoning (the first 75 to 100 mL discarded) before passing through a filter paper to give the 1.0, 3.2, 10, 32 and 100 mg/L loading rate WSF. Microscopic observations of the WSFs were performed after filtering and showed no micro-dispersions of test item to be present.
An aliquot (1000 mL) of each of the loading rate WSFs was separately inoculated with algal suspension (7.0 mL) to give the required test concentrations of 1.0, 3.2, 10, 32 and 100 mg/L loading rate WSF. Each test concentration was inverted several times to ensure the algal suspension was fully mixed before dispensing into test vessels.

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

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

24 ±1ºC

pH:

7.5 to 8.8

Nominal and measured concentrations:

Nominal: 0, 1, 3.2, 10, 32 and 100 mg/L
Measured: 0, 0.527, 1.37, 4.33, 10.9 and 33.1 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

76 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, the EL50 and NOEL for growth rate were determined to be 76 mg/L and 10 mg/L loading rate WAF.

Executive summary:

The effect of the test substance on the growth of the alga Pseudokirchneriella subcapitata was assessed according to OECD Guideline 201 and EU Method C.3 under GLP conditions. Due to the low aqueous solubility and complex nature of the test substance, the test medium was prepared as a water accommodated fraction (WAF). The algal cells were exposed to WAFs of the test substance over a range of nominal loading rates of 0, 1, 3.2, 10, 32 and 100 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 25 ± 2°C. Analysis of the test concentrations at the start revealed measured test concentrations to range from 0.28 and 38 mg/L which varied up to 0.53 to 33 mg/L at 72 hours. Under the conditions of this study, the EL50 and NOEL for growth rate were determined to be 76 mg/L and 10 mg/L loading rate WAF (Hull, 2019).

Key value for chemical safety assessment

EC50 for freshwater algae:

76 mg/L

EC10 or NOEC for freshwater algae:

10 mg/L

Additional information

The effect of the test substance on the growth of the alga Pseudokirchneriella subcapitata was assessed according to OECD Guideline 201 and EU Method C.3 under GLP conditions. Due to the low aqueous solubility and complex nature of the test substance, the test medium was prepared as a water accommodated fraction (WAF). The algal cells were exposed to WAFs of the test substance over a range of nominal loading rates of 0, 1, 3.2, 10, 32 and 100 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 25 ± 2°C. Analysis of the test concentrations at the start revealed measured test concentrations to range from 0.28 and 38 mg/L which varied up to 0.53 to 33 mg/L at 72 hours. Under the conditions of this study, the EL50 and NOEL for growth rate were determined to be 76 mg/L and 10 mg/L loading rate WAF (Hull, 2019).