Chromium tris((2-ethylhexanoate)

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:

3 April 2017 - 12 July 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Range-finder test:
The test soluitions were prepared in OECD modified medium by water accomodated fractions (WAF) at 3 loading rates equivalent to: 10, 100 and 1 000 mg test item/L. A control was set up with Itest medium only. There were 3 replicates for each treatement and 6 for the control, inoculated with about 5 000 algal cells per millilitres.
The test was performed in a thermostatic chamber maintained at 23°C +/- 2°C under continuous illumination (at about 8 000 lux). Algae were maintained suspended under continuous orbital stirring.
Algae biomass was measured every day in each flask using an electronix particle counter.
pH was recorded at thebeginning and the end of the test.

Definitive test:
Besed on the results of the range-finder, concentrations were prepared in OECD medium by water accomodated fractions (WAF) at 7 loading rates equivalent to: 25; 50; 100; 200; 400, 800 and 1600 mg test item/L. A control was set up with ISO test medium only. There were 3 replicates for each treatment and 6 for the control, inoculated with about 10 000 algae cells per millilitres..
The test was performed in a thermostatic chamber maintained at 23°C +/- 2°C under continuous illumination (at about 8 000 lux). Algae were maintained suspended under continuous orbital stirring.
Algae biomass was measured every day in each flask using an electronix particle counter.
pH was recorded at thebeginning and the end of the test.

Test solution analysis:
The test item quantification was performed according to a validated analytical method to measure the concentration of the test item at the start and the end of the test.
Test item solution and control were sampled (approximately 50 mL) and transferred to analyse the same day.

Vehicle:

no

Details on test solutions:

Since the test item is a poorly soluble substance under the test conditions, test solutions were prepared by water accommodated fractions (WAF) approach according to OECD monograph No. 23. WAFs were prepared individually. Measured quantities of test item were added directly to test medium and mixed for 48 hours to achieve an equilibrated concentration of dissolved and dispersed or emulsified components in the aqueous phase. Following cessation of mixing and a period of settling (to allow phase separation) the aqueous phase was drawn off for testing.

Test organisms (species):

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

Details on test organisms:

The algal stock culture was provided by the CCAP (Culture Collection of Algae and Protozoa), reference CCAP 278/4.The Pseudokirchneriella subcapitata algal stock culture was maintained on sloped agar tubes at 4°C and regularly transferred to fresh medium at the laboratory.
A culture was prepared from the stock culture and maintained in an exponential growth by successive transfers every 3 to 4 days.

Test type:

static

Water media type:

other: reconstituted test water

Remarks:

OECD modified medium in accordance with ISO 14442 standard

Limit test:

no

Total exposure duration:

72 h

Test temperature:

Range-finder test: 22.6 - 23.3°C
Definitive test: 23.4 - 23.8°C

pH:

Range-finder test: 7.64 - 8.41
Definitive test: 7.33 - 9.13

Nominal and measured concentrations:

nominal: 25, 50, 100, 200, 400, 800 and 1600 mg/L of test substance

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 600 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 600 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield rate

Details on results:

The study is valid since the growth multiplication factor in the control within the 72-hour test period was higher than 16 (actual values: 349 in the range-finder and 199 in the definitive test), the coefficient of variation of the average specific growth rates in the control during the whole test period was less than 7% (actual values: 3,56 in the range-finder and 0,95 in the definitive test) and the mean coefficient of variation for section-by-section specific growth rates (days 0-
1, 1-2 and 2-3) in the control was less than 35% (actual values: 9,89 in the range-finder and 20,87 in the definitive test).

Results with reference substance (positive control):

The last algae growth inhibition test performed with the reference item Potassium dichromate (20 March 2017) gave an EC50(0-72h) = 1.22 mg/L [0.96 – 1.48], indicating that the algae sensitivity is correct (within the accepted interval of 0.65 to 1.73 mg/L fixed by the International Standard NF EN ISO 8692 from Mai 2012 as mentioned in the OECD Guideline).

Validity criteria fulfilled:

yes

Conclusions:

Under the experimental conditions of the test conducted under OECD 201 guideline, the EC50-72h was estimated to be > 1 600 mg test item.L-1 based on growth rate and the EC50-72h was estimated to be > 1 600 mg test item.L-1 based on yield rate for the Pseudokirchneriella subcapitata.

Description of key information

Under the experimental conditions of the test conducted under OECD 201 guideline, the EC50-72h was estimated to be > 1 600 mg test item.L-1 based on growth rate and  the EC50-72h was estimated to be > 1 600 mg test item.L-1 based on yield rate for the Pseudokirchneriella subcapitata.

Key value for chemical safety assessment

EC50 for freshwater algae:

1 600 mg/L