Castor oil, ester with glycerol

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions (no purity)

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Direct dispersion in culture medium. A 640 mg/L stock solution was prepared in culture medium and serial dilutions produced the required test concentrations.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Green algae
- Strain: CCAP 276/20

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

24 °C

pH:

at test start 8.0
at test end 7.5 - 10.3

Dissolved oxygen:

Medium was air-saturated at test start.

Nominal and measured concentrations:

Nominal: 20, 40, 80, 160 and 320 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: conical flasks
- Type (delete if not applicable): closed (loosely stoppered)
- Material, size, headspace, fill volume: size: 250 mL, fill volume: 100 mL
- Shaking: Orbital shaker, 100 rpm
- Initial cells density of control: 2.17E04 cells/mL
- Control end cells density: 7.99E05 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes, AAP medium according to guideline

- Intervals of water quality measurement: pH of each vessel was measured at test start and test end

OTHER TEST CONDITIONS
- Photoperiod: continuous light
- Light intensity and quality: approx. 7000 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Cell densities were determined at 0, 24, 48 and 72 h.
- Determination of cell concentrations: Cell counting using a Haemocytometer

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2x

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

86 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

75 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- The results of the test solution analysis showed an increasing carbon concentration with increasing nominal test concentration. The results also showed that there was no significant change in carbon concentration observed over the 72 h exposure period and this was taken to demonstrate the stability of the test preparations employed during the period of exposure.

OBSERVATION OF ABNORMALITIES
- Colour differences: Colourless cells at 160 and 320 mg/L
- Aggregation of algal cells: yes, at 160 and 320 mg/L
- Observation of pH-shift: The pH values of the control and test cultures changed from 8.0 at test start to 7.5 to 10.3 at test end. This effect is considered to be due to the large numbers of algal cells in the log phase of growth respiring oxygen and producing carbonates and bicarbonates as part of photosynthesis which in solution give alkaline conditions. This effect is not considered to affect the integrity of the study given that the cell density of the control cultures increased by a factor 03 37 during the test.

Reported statistics and error estimates:

Statistical analysis using a Students t-test was carried out on the area under the growth curve data for the control and all test concentrations. There were no statistically significant differences (P ≥ 0.05) between the control and 20 mg/L test concentration, however all other test concentrations were significantly different (P < 0.05), and therefore the NOEC is given as 20 mg/L.

Table 1: Inhibition of Growth from the Exposure of S. subspicatus to the test substance for 72 h

Nominal Concentration (mg/L)	Area under curve at 72 h	% Inhibition	Growth rate (0-24 h)	% Inhibition
Control	1.70E07	-	0.051	-
20	1.72E07	+1	0.053	+4
40	1.37E07	19	0.043	16
80	9.18E06	46	0.019	63
160	4.79E05	97	0.000	100
320	-7.64E04	100	-0.005	110

Table 2: Results from Total Organic Carbon (TOC) Analysis

Samples	Nominal Concentration (mg/L)	Concentration of TOC corrected for control (mg C/L)
0 h	20	11.75
	40	24.19
	80	50.21
	160	100.95
	320	194.65
72 h	20	10.30
	40	21.66
	80	46.11
	160	86.60
	320	191.37

Description of key information

The study was conducted according to OECD 201.

NOEC (72h) = 20 mg/L (algal growth rate and biomass)

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

20 mg/L

Additional information

The study with Castor oil, ester with glycerol (CAS 68459-67-6) was performed according to OECD 201 (GLP compliance not specified) under static conditions using the freshwater algaeDesmodesmus subspicatusas test organism. The algae were exposed to nominal concentrations of 0, 20, 40, 80, 160 and 320 mg/L over a period of 72h. The test concentrations were prepared by direct dispersion in culture medium. 320 mg of test material was dispersed in culture medium and the volume adjusted to 500 ml to give a 640 mg/L stock solution. Serial dilutions made from this stock solution were made to produce 320, 160, 80 and 40 mg/L stock solutions. 150 ml of the 40, 80, 160, 320 and 640 mg/L stock solutions were mixed with 150 ml algal suspension to give the required test concentrations of 20, 40, 80, 160 and 320 mg/L The stability of the test substance was verified by TOC analysis. Based on the algal growth a NOEC (72 h) of 20 mg/L was determined. Algal growth rate and biomass were reduced at test concentrations > 20 mg/L. The reported effect concentrations are higher than the determined water solubility of the test substance (WS:<0.6µg - 10 mg/L at pH 6.3). Thus detrimental effects are not expected up to the limit of water solubility of Castor oil, ester with glycerol (CAS 68459-67-6).