Octanoic acid, 2-phenoxyethyl ester

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04 - 11 May 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling method: Water samples (2 mL) were taken from the centre of the test vessel in
test 1 (static limiit test) at (I) 0 h and 48 h in
test 2: (semi-static limit test) at 0 h and 24 h fresh (from the freshly prepared solutions) and at 24 h and 48 h old (from 24 h old solution)
- Sample storage conditions before analysis: Samples were stored in a freezer until analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
Rrange finding test: a stock solution with a a loading rate of 100 mg/L was prepared. The stock solution was stirred for 48 h (magnetic stirring) followed by a stabilisation period of ~ 24 h. The resulting solution was clear and colourless with a floating layer. The water soluble fraction was syphoned off and the test concentrations were prepared by subsequent dilutions of the saturated solution.

Limit tests (test 1 and test 2): a stock solution with a a loading rate of 100 mg/L was prepared. The pH was set to 6 before the stock solution was stirred for 24 h (magnetic stirring) followed by a stabilisation period of ~ 24 h. The resulting solution was clear and colourless with a floating layer.The water soluble fraction (WSF) was syphoned off and filtered through a glass fibre filter. The pH was re-adjusted from 6.4 to 6.0.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Source: in-house laboratory culture with a known history
- Age at study initiation: < 24 h
- Method of breeding: 250 newborn daphnids (< 3 d) were placed in a culture vessel containing 5 L medium (M7). After 7 d cultivation half of the medium was renewed twice a week. Daphnids were fed daily with a suspension of fresh water algae.
- Feeding during test: no
-other: Daphnids originated from a healthy stock (2nd to 5th brood), showing no signs of stress, such as mortality > 20%, presence of males, ephippia or discoloured animals. Additionally, there was no delay in the production of the first brood.

Test type:

other: static and semi-static tests

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

not specified

Test temperature:

19.4 - 20.1 °C (test 1: static limit test)
19.4 - 20.0 °C (test 2: semi-static limit test)

pH:

6.0 -6.7 (test 1: static limit test)
6.0 -6.7 (test 2: semi-static limit test)

Dissolved oxygen:

8.4 - 8.9 mg/L (test 1: static limit test)
8.9 - 9.2 mg/L (test 2: semi-static limit test)

Nominal and measured concentrations:

Nominal:
Test 1: static limit test:100 mg/L loading rate filtered test solution
Test 2: semi-static limit test: 100 mg/L loading rate filtered test solution

Measured:
Test 1: static limit test: 0.72 mg/L (initial), < detection limit after 48 h;
Test 2: semi-static limit test: 1.5 mg/L (0 h fresh), 0.974 mg/L (24 h fresh), 0.292 mg/L (24 h old), 0.129 mg/L (48 h old)

Details on test conditions:

TEST SYSTEM
Test 1: static limit test
Test 2: semi-static limit test:
- Test vessel: 100 mL vessel (Daphnids were separated from a possbile floating layer by a net)
- Material: all-glass; Fill volume: 80 mL
- Renewal rate of test solution: every 24 h ( in semi-static limit test)
- No. of organisms per vessel: 5
- No. of vessels per concentration: 4
- No. of vessels per control: 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: M7 medium
- Intervals of water quality measurement: Dissolved oxygen and pH were measured at the beginning and at the end of the test. Temperature was measured continuously in a temperature control vessel, beginning at the start of the test.

OTHER TEST CONDITIONS
- Adjustment of pH: adjusted to pH 6.0
- Photoperiod: 16 h illumination

EFFECT PARAMETERS MEASURED: Immobility was recorded after 24 and 48 h.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Range finding study:
- Test concentrations: 100 mg/L loading rate syphoned test solution, dilutions containing 0.1, 1.0 and 10% of the syphoned test solution
- Results used to determine the conditions for the definitive study:
The test resulted in 50% immobility of the daphnids at the 100 mg/L loading rate, which could be explained by a floating layer present in these test vessels.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.51 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: filtered saturated solution

Basis for effect:

mobility

Remarks on result:

other: Test 2: semi-static limit test

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: filtered saturated solution

Basis for effect:

mobility

Remarks on result:

other: Test 2: semi-static limit test

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.72 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

other: filtered saturated solution

Basis for effect:

mobility

Remarks on result:

other: Test 1: static limit test

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: As in the static limit test the measured concentrations decreased after 48h test duration below the detection level and as the EC50 in the semi-static limit test is above the average measured test concentration it can be concluded that the EC50 value will be above the solubility of the substance in the test medium.

Table 1: Incidence of immobility in the conducted tests

Nominal test concentration [mg/L]	Vessel	Number of Daphnia exposed	Response at 24 h		Response at 48 h
			number	Total %	number	Total %
Limit/range-finding test
control	1	5	0	0	0	0
	2	5	0		0
	3	5	0		0
	4	5	0		0
0.1	1	5	0	0	0	0
	2	5	0		0
1.0	1	5	0	0	0	0
	2	5	0		0
10	1	5	0	0	0	0
	2	5	0		0
100	1	5	2 (1)	35	2	50
	2	5	2 (2)		3 (1)
	3	5	2		2
	4	5	1 (3)		3 (1)
Static limit test
Control	1	5	0	5	0	5
	2	5	0		0
	3	5	0		0
	4	5	1		1
100	1	5	0	0	0	0
	2	5	0		0
	3	5	0		0
	4	5	0		0
Semi-static limit test
control	1	5	0	0	0	0
	2	5	0		0
	3	5	0		0
	4	5	0		0
100	1	5	0	5	2	35
	2	5	0		2
	3	5	0		0
	4	5	1		3

Between brackets: Number of Daphnia observed trapped at the surface of the test solutions. These organisms were reimmersed into the respective solutions before recording of mobility.

Table 2: Concentrations of the test substance in test medium

Loading rate [mg/L]	Measured concentration [mg/L]	Recovery [%]	Mean recovery [%]	Time of sampling [h]
Limit/range-finding test
0.200	0.178	89	92	initial
	0.190	95
50	45.9	92	102
	56.0	112
Static limit test
0	n.d.	-	-	0
100	0.716	-	-
0	n.d.	-	n.a.	48
100	n.d.	-	n.a.
Semi-static limit test
0	n.d.	-	-	0 (fresh)
100	1.50	-	-
0	n.d.	-	-	24 (old)
100	0.292	-	-
0	n.d.	-	-	24 (fresh)
100	0.974	-	-
0	n.d.	-	-	48 (old)
100	0.129*	-	-

n.d. = not determined

n.a. = not applicable

* = obtained by extrapolation of the calibration curve. Result is an estimate

Description of key information

No toxic effects on aquatic invertebrates up to the limit of water solubility

Additional information

The acute toxicity of 2-Phenoxyethyl octanoate (CAS No. 23511-73-1) to aquatic invertebrates was tested in a GLP guideline study following OECD 202. The study report comprises a static limit test (test 1) and a semi-static limit test (test 2). Based on the results of a range finding study the selected nominal test substance concentration in both tests was 100 mg/L. A saturated solution was prepared siphoning off the phase containing the water soluble fraction of the test material and subsequent filtering of the solution. The test vessels were equipped with a net preventing the contact of Daphnids with a possible floating layer of undissolved test solution. The tests were terminated after 48 hours, immobile Daphnids were observed in neither of the two tests. Thus an EC50 (48 h) >100 mg/L based on the nominal test substance concentration was reported. Based on the mean measured concentrations an EC50 (48 h)> 72 mg/L was determined in test 1 (static test) and EC50 (48 h) > 0.51 mg/L was determined in test 2 (semi-static limit test).

Therefore of 2-Phenoxyethyl octanoate is considered not acutely toxic to aquatic invertebrates up to the limit of water solubility.