Decanoic 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:

24 May - 27 May 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

calculation of results based on nominal values despite >20% deviation from measured values

GLP compliance:

yes

Remarks:

according to the Japanese GLP Standard

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Vapour pressure: 1 mm at 125 °C
- Water solubility: < 1 mg/L
- log Pow: 4.09

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0, 1.8, 3.2, 5.6, 10 and 18 mg/L (nominal)
- Sampling method: At study initiation: test solution for analytic was separately prepared, since the volume was > 5% of test water in vessels. After exposure: test solution was sampled directly from each test vessel.
- Sample storage conditions before analysis: Analysis was conducted immediately after sampling, no storage.

Vehicle:

yes

Details on test solutions:

- Method: The test substance was dissolved in vehicle, and this stock solution was diluted in dilution water and stirred for 1 hour.
- Controls: dilution water with/without vehicle
- Chemical name of vehicle: dimethylformamide
- Concentration of vehicle in test medium: 0.1 mL/L
- Evidence of undissolved material: not observed

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: alga
- Strain: ATCC22662
- Source: American Type Culture Collection
- Age of inoculum: within 72 hours
- Method of cultivation: on rotary shaker (100 rpm)

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions: same as test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

23.7 - 23.8 °C (23 ± 2 °C)

pH:

at the initiation: 7.6 - 7.8
at the end: 7.4 - 7.6

Nominal and measured concentrations:

nominal concentration: 1.8, 3.2, 5.6, 10, 18 mg/L
measured concentration: at test initiation: 1.8, 3.0, 5.9, 8.9, 16 mg/L
at test end (percent of nominal): 0.52 (29%), 1.2 (38%), 3.2 (57%), 6.0 (60%), 14 (78%) mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL Erlenmeyer flask with an air-permeable stopper
- Type: open
- Material, fill volume: glass, 100 mL
- Initial cells density: 10000 cells/mL
- Control end cells density: 2620000 ± 130000 cells/mL
- 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
- Source/preparation of dilution water: not stated
- Intervals of water quality measurement: pH (0 and 72 hours), temperature, light intensity and number of revolutions (0, 24, 48, 72 hours) were determined.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: not adjusted
- Photoperiod: continuously
- Light intensity and quality: 4300 - 5000 lux


EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: electronic particle counter; 24, 48, 72 hours

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8
- Range finding study: performed
- Test concentrations: 2.0 and 20 mg/L
- Results used to determine the conditions for the definitive study: 2.0 mg/L: growth inhibition was not observed, 20 mg/L: 93 % growth inhibition was observed

Reference substance (positive control):

yes

Remarks:

potassium dichromate (reagent grade)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

15 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 14 - 17 mg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

3.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

5.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 5.5 - 6.3 mg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1.8 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
- EbC50: 0.44 mg/L

Reported statistics and error estimates:

Barlett, Probit and Dunnett test

Table 1: Cell density of Selenastrum capricornutum after treatment with decanoic acid

Loading Rate  (mg/L)	Areal Mean Measured Conc. (mg/L)	Cell Densities (cells/mL)
			0 Hour	24 Hour	48 Hour	72 Hour
Control	-	Mean	10000	65300	407000	2620000
		SD	0	5600	12000	130000
Solvent Control	-	Mean	1000	66900	411000	2550000
		SD	0	3200	14000	190000
1.8	2.12	Mean	1000	64000	392000	2630000
		SD	0	7200	8000	60000
3.2		Mean	1000	54000	321000	2090000
		SD	0	3400	23000	50000
5.6		Mean	1000	46800	239000	1260000
		SD	0	1700	10000	80000
10		Mean	1000	33000	128000	465000
		SD	0	1900	8000	18000
18		Mean	1000	23100	47000	99700
		SD	0	1200	3500	6800

Table 2: Growth inhibition of Selenastrum capricortum after treatment with decanoic acid

Nominal concentration (mg/L)	Inhibition (%) Biomass	Inhibition (%) Growth rate
Control	0	0
Solvent Control	1.7	1.5
1.8	0.6	-0.7
3.2	20.4	0.9
5.6	49.3	10.9
10	79.0	28.3
18	94.6	60.4

Description of key information

ErC50 (72 h) = 15 mg/L (nominal, growth rate, OECD 201)

NOErC (72 h) = 3.2 mg/L (nominal, growth rate, OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:

15 mg/L

EC10 or NOEC for freshwater algae:

3.2 mg/L

Additional information

One study investigating the toxicity of decanoic acid (CAS 334-48-5) to freshwater algae is available.

The study (1999) was conducted according to OECD 201 and GLP. The test organism Pseudokirchneriella subcapitata was exposed to 5 nominal test item concentrations of 0 (control), 1.8, 3.2, 5.6, 10, 18 mg/L for 72 h. The substance was dissolved in dimethylformamide and monitored during the experiment by GC-MS analysis. While recoveries of the test item concentrations were above 80% of nominal at the start of the experiment, they decreased to 29 – 78% of the nominal values at the end of the experiment. The test showed growth rate inhibitions and resulted to an ErC50 (72 h) of 15 mg/L and an NOEC (72 h) of 3.2 mg/L (nominal).