Fatty acids, C8-10, oxybis(2-hydroxy-3,1-propanediyl) esters

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:

17 - 20 Jul 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

adopted March 23, 2006, corrected July 28, 2011

GLP compliance:

yes (incl. QA statement)

Remarks:

13. Mar 2017, Hess. Ministerium für Umwelt, Klimaschutz, Landwirtschaft und Verbraucherschutz, Wiesbaden, Germany

Analytical monitoring:

yes

Details on sampling:

- Concentrations: control and 6.25, 12.2, 25, 50, 100 mg/L loading rate
- Sampling method: samples of the freshly prepared test medium and at the end of the test (after 72 h) were taken.
- Sample storage conditions before analysis: stored in a refrigerator (4 ± 4 °C)

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Before test start each concentration was prepared separately by suspending test substance in adequate amounts of test water. The test media with nominal loading rates of 100, 50, 25, 12.5 and 6.25 were prepared by mixing 99.9, 50.2, 25.2, 12.0 and 12.7 mg test item into 999, 1004, 1008, 960, 2032 mL test water and stirring for 23.5 hours. Then, non-dissolved fractions of the test item were separated from the test media by membrane filtration (0.45 µm cellulose acetate filter). The filtrates were used as test media. The test media were prepared under sterile conditions avoiding bacteria growth.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: Strain No. 61.81 SAG
- Source (laboratory, culture collection): laboratory culture; original source: "Sammlung von Algenkulturen, Albrecht-von-Haller-Institut für Pflanzenwissen-schaften, Universität Göttingen", Göttingen, Germany.
- Age of inoculum (at test initiation): Cells were taken from an exponentially growing pre-culture, which was set up 4 days prior to the test start under the same conditions as in the test
- Method of cultivation: For this test the sterile algae culture was used to avoid bacteria growth

ACCLIMATION
- Culturing media and conditions (same as test or not): same as in test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

0.24 mmol/L as CaCO3.

Test temperature:

23.5 - 24.1 °C

pH:

8.0 at test start
9.0 to 9.6 at test end

Nominal and measured concentrations:

Nominal loading rates (WAF): 0 (Control), 6.25, 12.2, 25, 50, 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks (50 mL nominal volume)
- Type: covered with sterile caps
- Fill volume: 50 mL
- Initial cells density: 5000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted Water (OECD Medium)

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continuous illumination
- Light intensity and quality: 5530 to 6680 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometrical measurement after 24, 48 and 72 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WAF (nominal loading)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WAF (nominal loading)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WAF (nominal loading)

Basis for effect:

growth rate

Details on results:

The exposure concentration was considered stable over the test period based on TOC analyses (100% of initial TOC after 72 h). Therefore all reported results refer to nominal loading rates.
- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: The lowest concentrations showed a significant effect on algae for yield and growth rate. However according to the OECD guideline 201 definition of LOEC and NOEC: LOEC is the lowest tested concentration at which the substance is observed to have a statistically significant reducing effect on growth (at p < 0.05) when compared with the control, within a given exposure time. However, all test concentrations above the LOEC must have a harmful effect equal to or greater than those observed at the LOEC.”
Due to the natural biological variation in algal growth, the slight inhibition for growth rate calculated for the lowest loading rate (7 %) was not deemed to be treatment related.

Results with reference substance (positive control):

ECr50 (72 h): 1.02 mg test item/L (tested in January 2018)

Table 1; Growth rates and percentage inhibition after 72 h

Nominal loading rate [mg test item/L]	Growth rate 0-72 h [1/day]	Inhibition [%]
Control	1.754	--
6.25	1.631	7.0*
12.5	1.786	-1.8
25	1.776	-1.3
50	1.787	-1.9
100	1.765	-0.7

(*) significant difference was not considered for the determination of LOEC and NOEC, due to the OECD definition of LOEC

 Table 2: Results for the Determination of the Carbon Content of the Test Item in the Test Samples

Sample Description nominal loading rate [mg test item/L]	TOC [mg Carbon/L]*	RSD [%]
Control	n.a.	n.a.
6.25	n.a.	n.a.
12.5	4.85	7
25	7.84	7
50	9.49	2
100	23.36	2

*mean value of all measured samples per treatment group

RSD: relative standard deviation per treatment group

Table 3: Validity criteria for OECD 201.

Criterion from the guideline	Outcome	Validity criterion fulfilled
The biomass in the control cultures should have increased exponentially by a factor of at least 16 within the 72-hour test period.	193.6-fold increase	yes
The mean coefficient of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3, for 72-hour tests) in the control cultures must not exceed 35%	8.6%	yes
The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures must not exceed 7% in tests with Pseudokirchneriella subcapitata and Desmodesmus subspicatus. For other less frequently tested species, the value should not exceed 10%.	2.0%	yes

 

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Description of key information

ErL50 (72 h) >100 mg/L (WAF, nominal loading rate), Pseudokirchneriella subcapitata (OECD 201)

ErL10 (72 h) >100 mg/L (WAF, nominal loading rate), Pseudokirchneriella subcapitata (OECD 201)

Additional information

The study investigated toxic effects of Fatty acids, C8-10, oxybis(2-hydroxy-3,1-propanediyl) esters (CAS 92044-91-2) to aquatic algae according to OECD 201 (GLP). The test was conducted with Pseudokirchneriella subcapitata as test organism. The algae were exposed to water accommodated fractions (WAF) with nominal loading rates of 6.25, 12.2, 25, 50, 100 mg/L and a control. The stability of the test substance in the test medium was analytically verified by TOC analysis. The recovery was 100% of initial TOC after 72 h, thus the test substance concentration was considered stable. At test termination after 72 h an ErL50 (72 h) >100 mg/L WAF (nominal loading rate) was determined. The ErL10 (72 h) was > 100 mg/L WAF (nominal loading rate).