Fatty acids, C16-18

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

14 Mar - 17 Mar 2000

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

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Melting point: 63 °C
- Boiling point: 351 °C
- Water solubility: 0.82 mg/L (at 25 °C)
- log Pow: 5.64

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 10 mg/L (nominal concentration)
- Sampling method: same volume of test water was sampled by each test vessel and mixed in each group at the test initiation and after exposure.
- Sample storage conditions before analysis: analysis was conducted immediately after sampling, no storage

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: a stock solution (100 mg/L) was prepared with test substance, growth medium and dispersant. Stock solution was diluted with filter sterilized growth medium up to the concentration, and then filter sterilized.
- Controls: dilution water with/withour vehicle
- Chemical name of vehicle: HCO-50
- Concentration of vehicle in test medium: stock solution: 1000 mg/L, final test solution: 100 mg/L
- Evidence of undissolved material: test water was colurless and no precipitate was observed.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: alga
- Strain: ATCC-22662
- Source: American Type Culture Collection
- Age of inoculum: < 3 days
- Method of cultivation: on a rotary shaker

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions: same as test
- Any deformed or abnormal cells observed: not observed

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

22.0 - 23.0 °C (23 ± 2 °C )

pH:

at the initiation: 7.5 - 7.6
at the end: 8.4 - 9.1

Nominal and measured concentrations:

nominal concentration: 10.0 mg/L
meaured concentration: 0 hour: 0.9 mg/L, 72 hour: < 0.8 mg/L (under detection limit)

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 mL Erlenmeyer flask capped with air-permeable stoppers
- Type: open
- Material, fill volume: glass, 100mL
- Initial cells density: 10000 cells/mL
- Control end cells density: 1884000 ± 59400 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

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuously
- Light intensity and quality: 4000 - 5000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter; 24, 48, 72 hours

TEST CONCENTRATIONS
- Justification for using less concentrations than requested by guideline: 10 mg/L is the highest concentration to be dissolved uniformly with sorvent (100 mg/L)
- Range finding study: performed
- Test concentrations: 100 mg/L
- Results used to determine the conditions for the definitive study: EbC50: > 100 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate (reagent grade)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.9 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 0.9 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.9 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 0.9 mg/L

Nominal / measured:

meas. (initial)

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: 0.52 mg/L

Reported statistics and error estimates:

F & t-test

Table 1: Growth inhibition of Selenastrum capricornutum

Initial Measured Concentration (mg/L)	Biomass	Growth rate
	Inhibition (%)	Inhibition (%)
Control	-	-
Dispersant control	-0.05	-0.31
0.9	-3.36	-1.51

Description of key information

No effects up to the limit of water solubility are expected.

Additional information

Studies are available for some pure homologue members of the fatty acid category. In addition some studies are available for certain fatty acid mixtures. Generally it could be stated that toxicity of fatty acids to aquatic organisms increases with increasing chain length up to the water solubility limit at a chain length of C12. For longer chains no effects at saturation are observed.

For the mixture under discussion here no study on algae is available. Thus a read-across is prepared to a study conducted with the pure homologue C16 (CAS 57 -10 -3), one of the main components of the mixture. For the other main constituent, stearic acid, no test on algae is available.

For the evaluation of the mixture only studies available for pure homologues which were determined as key were chosen for read-across.

Fatty acid homologue	EC50for growth rate (as reported in the study)	Water solubility*	Test design and species	Reference
C16 - CAS 57-10-3 palmitic acid	> 0.9 mg/L (initial mean measured)	< 0.05 at 20 °C	72 h, static, Pseudokirchneriella subcapitata	NITE, 2003b

* see category justification

Palmitic acid (C16: CAS 57 -10 -3) was tested on Pseudokirchneriella subcapitata as well under OECD 201 in a GLP-study (NITE, 2003b). One test substance concentration was used (10 mg/L nominal, corresponding to 0.9 mg/L initial mean measured), which was above the reported water solubility limit for this substance (< 0.05 mg/L according to the category justification). As no effects could be observed at this test concentration, the EC50 for growth rate is reported to be above 0.9 mg/L (initial mean measured).

From the reported results of the test available for the fatty acid homologue C16 no adverse effects of the considered fatty acid mixture are expected on algae. In the cited test no effects up to the water solubility limits of the pure homologues were reported. Thus for the considered fatty acid mixture no effects within the range of water solubility is expected.