Octadecanoic acid, C16-18-alkyl esters

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 Apr - 24 Apr 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study with acceptable restrictions (The highest test concentration was slightly turbid which probably has affected the outcome of this study).

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Reference 2

Reference Type:

secondary source

Title:

National Industrial Chemicals Notification and Assessment Scheme - Full Public Report - [trade name]

Author:

Australian Government - Department of Health and Ageing NICNAS

Year:

1999

Bibliographic source:

File No.: NA/655

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

Test guideline 3

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2-octyldodecyl isooctadecanoate

EC Number:

298-361-4

EC Name:

2-octyldodecyl isooctadecanoate

Cas Number:

93803-87-3

Molecular formula:

C38H76O2

IUPAC Name:

2-octyldodecyl isooctadecanoate

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Two solutions were prepared at nominal concentrations of 10 and 100 mL respectively in order to achieve maximum exposure concentrations. These solutions were stirred for approx. 21 h, stabilized for 4 h and separated using a separation funnel afterwards. After preparation, volumes of 50 mL were added to each replicate of the respective test concentration.
- Eluate: no
- Differential loading: no
- Controls: yes, test medium control
- Evidence of undissolved material: The separated solutions were slightly turbid.

Test organisms

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: CCAP 278/4
- Source: Laboratory culture
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from pure culture on agar. The suspensions were continuously aerated and exposed to light (4000-9000 lux) in a climate room at a temperature of 23 ± 2 °C.

ACCLIMATION
- Acclimation period: 4 d before the start of the test, cells from the algal stock culture were inoculated in a culture medium at a cell density of 2x10^4 cells/mL.
- Culturing media and conditions (same as test or not): same as test

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Hardness:

24 mg CaCO3/L

Test temperature:

20 - 22 °C

pH:

8.3 - 8.5

Nominal and measured concentrations:

nominal: 0, 10 and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size: all-glass, 100 mL
- Aeration: continuously shaking
- Initial cells density: 1x10^4 cells/mL
- Control end cells density: 47.5 x 10^4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- Other: One vessel of each test concentration without algae.

GROWTH MEDIUM
- Standard medium used: yes (according to ISO guideline)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water purified by reverse osmosis and then passed over activated carbon and ion-exchange cartridges.
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continuously illuminated
- Light intensity and quality: TLD-lamps of 18 Watt yielding 6000 - 6500 lux.

EFFECT PARAMETERS MEASURED: growth rate (every 24 h)
- Determination of cell concentrations: At the beginning of the test, cells were counted by microscope using a counting chamber. Thereafter, cell densities were determined by spectrophotometric measurement of samples at 720 nm using a Lambda Spectrophotometer (Perkin-Elmer, Illinois, USA), with a cuvette of 5 cm path-length. Algal medium was used as blank and the extra replicates as background for the treated solutions.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10x

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Water Accommodated Fraction (WAF)

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Water Accommodated Fraction (WAF)

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: Test solution at nominal 100 mg/L was slightly turbid.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50: 1.7 mg/L based on growth rate reduction (95% CL: 1.1 - 2.8 mg/L)

Any other information on results incl. tables

Cell growth was inhibited significantly (31.2%) at nominal 100 mg/L, while cell growth was not affected at nominal 10 mg/L. This significant effect is probably related to the turbid test solution which adsorbed a fraction of light needed for algal cell growth. Since both test concentrations are above water solubility it can be concluded that both the EC 50 and the NOEC exceed the maximum possible water solubility of the test substance.

Table 1: Percentage reduction of growth rate at different time intervals.

Concentration of test substance:	Cell growth inhibition (0-72 h):		Growth rate [cells/mL/h-1]
	Area (mean)	Inhibition [%]	mean µ1	Reduction [%]
blank	894.41	--	0.05360	--
10 mg/L	855.12	4.4	0.05204	2.9
100 mg/L	615.50	31.2	0.05140	4.1