Hexanoic acid, 2-ethyl-, C16-18-alkyl esters

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:

12 - 14 Jun 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions: The study is not performed under GLP conditions. No test substance monitoring is performed. No NOEC value is determined.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

no NOEC value is calculated

GLP compliance:

no

Remarks:

but performed according to ISO 17025

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Method: Test solutions are prepared in accordance with the OECD monography n°23. Aqueous algae test medium is saturated with the substance to be tested by dynamic contact setting with a known test substance amount. The preparation consists of 68 h of gentle agitation by magnetic stirring to obtain a vortex of about 1/3 (or less under some conditions) of the height between the top and the bottom of the flask, followed by 4 h of phase separation.The aqueous phase, containing the soluble substances is taken to perform the test. The test solution is identified to its loading rate (massic proportion of substance to be tested/ test medium mass introduced into the diphasic reactor) while operating the Water accomodated fraction (WAF). The implemented loaded ratio is : 0.11/1000.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Source: Microbiotests Inc., Venecoweg 19, 9810 Nazareth, Belgium (Batch No.: SC110112)
- Method of cultivation: The algae are maintained in culture in the laboratory by weekly subcultures.

ACCLIMATION
- Acclimation period: An inoculum is prepared by dispersion of algae into dilution water. The cell culture is acclimated for 4 days.
- Culturing media and conditions: same as test

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

23 ± 2 °C

pH:

8.0 - 8.1

Nominal and measured concentrations:

Nominal: 110 mg/L loading rate WAF

Details on test conditions:

TEST SYSTEM
- Test vessel: culture vial for spectrophotometric measurement
- Type: The vials are half-covered.
- Material: polyacrylate; Size: 35 mL
- Initial cells density: 5000 - 10000 cells/mL (confirmed by optical counting)
- Control end cells density: 395531 cells/ml (mean)
- No. of vessels per concentration: 6
- No. of vessels per control: 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to OECD guideline 201
- Culture medium different from test medium: no
- Intervals of water quality measurement: The pH of the control and the treatment is measured at the beginning and the pH of one vial is measured at the end of the test.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: continuous light
- Light intensity and quality: 8000 lux (spectra from 400 - 700 nm)
- The culture vials are placed onto a rotative stirrer (60 mvt/s).

EFFECT PARAMETERS MEASURED: Cell concentration was recorded after 24, 48 and 72 h test duration.
- Determination of cell concentrations: spectrophotometer
- Other: Microscopic examination of algal cells were performed at the end of the test.

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 110 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(WAF)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

> 110 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(WAF)

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control: yes
- Observation of abnormalities: No abnormalities were observed.
- Unusual cell shape: The microscopic examination of algae cells, at the end of the test, confirmed the organism identy and the normal shape of the cells (no fading).
- Any stimulation of growth found in any treatment: The growth rate of the treatment was slightly higher than the growth rate of the control.

Table 1: Cell concentrations measured in control and treatment and inhibition in treatment

Nominal concentration [mg/L]	replicate	Measured cell concentration [cells/mL]			Inhibition [%]
		24 h	48 h	72 h
control	1	41282	140728	376831	-
	2	29638	106910	391650
	3	32814	115378	368363
	4	32814	130197	413879
	5	32814	151368	422347
	6	27521	97383	400118
	mean	32814	123670	395531
110	1	39165	103029	398707	- 0.2
	2	38107	118906	461159	- 1.5
	3	55043	134784	419877	- 1.7
	4	37048	122082	465393	- 3.9
	5	33872	111497	423053	- 4.1
	6	34931	112555	475978	- 4.7
	mean	39694	117142	440695	-2.7 ± 1.8

Description of key information

No toxic effects up to the limit of water solubility (< 0.15 mg/L) for Pseudokirchneriella subcapitata (OECD 201)

Additional information

One study investigating toxicity of Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) to freshwater algae is available. The non GLP study was conducted under static conditions according to OECD guideline 201 using Pseudokirchneriella subcapitata as test organism (Bouillon, 2012). A 110 mg/L loading rate WAF was tested in a limit test. No NOEC calculation was performed. No growth inhibition was observed in the treatment throughout the test period of 72 h. Hence, the 72 h-EL10 and EL50 is determined to be > 100 mg/L based on the nominal test concentration.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within the CSR.