Docosanoic acid

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:

01 June - 04 June 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes

Remarks:

According to Japanese GLP standard

Analytical monitoring:

yes

Details on sampling:

- Sampling method: Test water was directly sampled by each vessel.
- Sample storage conditions before analysis: No storage before analysis.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test item was mixed with HCO-40 at 80 °C. Test medium was added to prepare stock solution (250 mg/L) at room temperature.
- Controls: Blank control and vehicle control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): HCO-40
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): 20000 mg/L in stock solution and 100 mg/L in final test solution

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: ATCC22662
- Source (laboratory, culture collection): Incorporated Administrative Agency, National Institute for Environmental Studies, Tsukuba, Japan
- Age of inoculum (at test initiation): About 72 hours
- Method of cultivation: On a shaker (100 rpm)

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions (same as test or not): Same as test

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

22.5 - 23.4 °C

pH:

at the initiaion: 7.9 - 8.2
at the end of the study: 9.8 - 10.2

Nominal and measured concentrations:

Nominal concentration: 5 mg/L
Measured concentration: 4.59 mg/L at 0 hour and 3.7 mg/L at 72 hour

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 mL Erlenmeyer flask
- Type (delete if not applicable): closed with air-permeable stopper
- Material, fill volume: Glass, 100 mL
- Initial cells density: 10000 cells/mL
- Control end cells density: 2689200± 78100 cells/mL in control and 2715900 ± 35100 cells/mL in solvent control
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: Same as test

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: Continuously
- Light intensity and quality: 4000 - 5000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter

TEST CONCENTRATIONS
- Range finding study: Performed
- Test concentrations: 5 mg/L
- Results used to determine the conditions for the definitive study:
Growth rate compared to control was 99% in solvent control and 93% in 5 mg/L.
Growth rate compared to solvent control was 94% in 5 mg/L.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50: 0.41 mg/L

Reported statistics and error estimates:

Student's t-test, subsequent to F test for homogeneity of variances for NOEC.

Table 1. Measured concentration

Nominal Conc. (mg/L)	Measured Concentration (mg/L) (Percent of nominal)
	0 Hour	72 Hour
Control	<0.06	<0.06
Solvent control	<0.06	<0.06
5	4.59 (92)	3.70 (74)

The concentration of test substance was not maintained within 20% of nominal concentration. However, the results were calculated based on nominal concentration, since the water solubility of the substance is actually lower than 0.1 mg/L and the solubility of the substance was increased within this test by using a vehicle. Generally, it can be stated that no effects could be observed within the range of water solubility.

Table 2. Percent growth inhibition of Selenastrum capricornutum

Nominal Concentration (mg/L)	Biomass	Growth rate (24-72 h)
	Inhibition (%)	Inhibition (%)
Control	-	-
Solv. Cont	-	-
5	- 12.7	- 1.7

Validity criteria fulfilled:

yes

Description of key information

No toxicity effects up to the limit of water solubility

Additional information

One study is available on the toxicity of docosanoic acid (CAS 112-85-6) on algae.

The 72 h test was conducted according to OECD 201 and in accordance with GLP requirements. Algae (Selenastrum capricornutum) were exposed to docosanoic acid under static conditions in a limit test by using a solvent. The ErC50 (72 h) and the NOEC for growth rate were determined to be > 5.0 mg/L and ≥ 5.0 mg/L, respectively, based on nominal concentrations. Based on measured concentrations for the test concentration 5 mg/L a value of 4.59 mg/L was determined at the start of the exposure and 3.7 mg/L after 72 h. Thus no effects could be observed within the range of water solubility, which is determined to be 0.016 mg/L.

Based on the results of this study it can be concluded that no toxic effects of docosanoic acid on algae are expected up to the limit of water solubility.