2-ethylhexyl (4-chloro-2-methylphenoxy)acetate

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25.11.2008 - 27.11.2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2-ethylhexyl (4-chloro-2-methylphenoxy)acetate

EC Number:

249-636-2

EC Name:

2-ethylhexyl (4-chloro-2-methylphenoxy)acetate

Cas Number:

29450-45-1

Molecular formula:

C17H25ClO3

IUPAC Name:

2-ethylhexyl (4-chloro-2-methylphenoxy)acetate

impurity 1

Reference substance name:

(4-chloro-2-methylphenoxy)acetic acid

EC Number:

202-360-6

EC Name:

(4-chloro-2-methylphenoxy)acetic acid

Cas Number:

94-74-6

Molecular formula:

C9H9ClO3

IUPAC Name:

(4-chloro-2-methylphenoxy)acetic acid

Test material form:

liquid

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Effect concentrations 2

Key result

Duration:

24 h

Dose descriptor:

EC0

Effect conc.:

>= 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Effect concentrations 3

Key result

Duration:

24 h

Dose descriptor:

EC100

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Effect concentrations 4

Key result

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 0.437 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Effect concentrations 5

Key result

Duration:

24 h

Dose descriptor:

EC0

Effect conc.:

>= 0.437 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Effect concentrations 6

Key result

Duration:

24 h

Dose descriptor:

EC100

Effect conc.:

> 0.437 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Effect concentrations 7

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Effect concentrations 8

Key result

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

>= 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Effect concentrations 9

Key result

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Effect concentrations 10

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.437 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Effect concentrations 11

Key result

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

>= 0.437 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Effect concentrations 12

Key result

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

> 0.437 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Any other information on results incl. tables

RESULTS AND DISCUSSION

THE PRELIMINARY TEST

According to the information from the Sponsor the test substance is insoluble in water (The test item description, Annex No 1 to contract No 23/PP/08). According to literature data the estimated limit of MCPA-2EH solubility is <0.17 mg/L and the ester is rapidly hydrolyzed. The test substance of low solubility should be tested up to the limit of solubility or at the concentration above the limit of solubility to ensure that the maximum soluble concentration has been obtained.

The preliminary test was performed in five concentrations: 0.10; 0.18; 0.32; 0.56 and 1.00 mg/L. In order to obtain each test concentration the same amount 0.1 mL of test item in acetone (solutions of certain concentrations). The time between test item addition into water and extraction into organic solvent (sample preparation for chemical analysis) was no longer than 30 min.

The analytical results obtained confirm the correct test item application. The detected contents of MCPA-2EH in test concentrations at the test beginning range 80.0 – 100.3 % of nominal.

 

Table 4. MCPA-2EH – Concentration of (4-chloro-2-methylphenoxy)acetic acid 2-ethylhexyl ester in the preliminary test

Nominal test item concentration [mg/L]	Mean concentration (n = 3) of MCPA-2EH measured in time [mg/L]
	t0	% of nominal concentration
Control with acetone	--
0.10	0.082	82.43
0.18	0.156	86.76
0.32	0.321	100.25
0.56	0.448	80.02
1.00	0.868	86.80

LOD = 0.05 mg/L
LOQ = 0.10 mg/L

 

Based on biological results obtained it was demonstrated that test item did not cause any immobilization at the tested range of concentrations (Table 5).

 

Table 5. MCPA-2EH – Daphnia magna acute immobilization test, the preliminary test

 

Concentration of test item [mg/L]	Number of tested organisms	Number of dead or immobilized								Total percentage of immobilized
		24 h				48 h
		Replicates
		A	B	C	D	A	B	C	D	24 h	48 h
Control	20	0	0	0	0	0	0	0	0	0	0
0.10	20	0	0	0	0	0	0	0	0	0	0
0.18	20	0	0	0	0	0	0	0	0	0	0
0.32	20	0	0	0	0	0	0	0	0	0	0
0.56	20	0	0	0	0	0	1	0	0	0	5
1.00	20	0	0	0	0	0	0	0	0	0	0

 

THE DEFINITIVE TEST

The definitive test was performed at one test substance concentration above the estimated limit of solubility in water. Acetone was used at 0.1 mL/L concentration as auxiliary substance to prepare the test concentration. Therefore, in the definitive test both standard control and control with acetone were conducted.

VALIDITY CRITERIA

The following validity criteria were met:

·        Mortality and immobilization ofDaphnia magnain control was 0 % (allowed 10% [1, 2]),

·        Concentration of dissolved oxygen was higher than 3 mg/L (should be kept at ≥3 mg/L).

DEVIATIONS FROM GUIDELINE

No deviations from Guideline occurred in the definitive test performed.

All validity criteria of the definitive test mentioned in both OECD Guideline No 202 and test

method EU C.2. were met.

ENDPOINTS

The acute toxicity ofMCPA-2EHforDaphnia magnawas studied in limit test at one test concentration 1.0 mg/L, i.e. above the estimated limit of solubility, to ensure the maximum stable concentration in water.

The contents ofMCPA-2EHwere chemically analyzed in the definitive test. The test substance was detected in the test concentration and the control with acetone at the beginning and the end of exposure (t0 and_t48).Results of concentration and stability measurements performed are presented in Table 6.

 

Table 6. MCPA-2EH – Concentration and stability of (4-chloro-2-methylphenoxy)acetic acid
2-ethylhexyl ester in the definitive test

Nominal test item concentration [mg/L]	Mean concentration (n = 3) of MCPA-2EH measured in time [mg/L]				Geometric mean of determined MCPA-2EH concentration [mg/L]
	t0	% of nominal concentration	t48	% of initial concentration
Control with acetone	<LOD	--	<LOD	--	--
1.0	0.885	88.50	0.216	24.41	0.437

 

In the sample collected at the start of the test the content of MCPA-2EH was 88.5 % of nominal. This confirms that the test item was correctly applied.

The test substance is not stable in the test concentration during 48 h of exposure. The content of test substance detected at the test end was 24.4 % of initial concentration.

The toxicity of MCPA-2EH forDaphnia magnawas assessed based on immobilization observations during the test.

In the test concentration 1.0 mg/L none of test organisms was immobile. In the control and the control with acetone no immobilization was observed.

The EC_xvalues were estimated based on nominal test item concentration, because the analytical results confirmed its correct application. The EC_xvalues are presented in Table 7. Median concentration causing immobilization of 50 % population (EC₅₀) after 48 hours of exposure is above 1.0 mg/L. The EC₀value after 48 h is equal or above 1.0 mg/L and_EC100is above 1.0 mg/L.

Based on the chemical analyses performed the content of MCPA-2EH is not stable in test conditions. Therefore, the geometric mean of measured test substance concentrations was calculated. The EC_xvalues were also determined based on the geometric mean Median concentration causing immobilization of 50 % population (EC₅₀) after 48 hours of exposure is above 0.437 mg/L. The EC₀value after 48 h is equal or above 0.437 mg/L and EC₁₀₀is above 0.437 mg/L.

Applicant's summary and conclusion

Executive summary:

The study was performed according to the OECD Guidelines for Testing of Chemicals No 202 (2004) and EU method C.2. as well as in compliance with Principles of GLP.

The aim of the study was evaluation of acute toxicity of test item for Daphnia magna and determination of EC₅₀, EC₀and EC₁₀₀values after 24 h and 48 h.

The test item was used in one concentration 1.0 mg/L (limit test). The content of test substance was determined at the beginning and at the end of exposure. The results of chemical analyses confirmed the correct application of test item. The detected substance is not stable in experiment conditions.

Taking into account the obtained results after 24 and 48 hours of exposure the EC50 value is above 1.0 mg/L, EC0 is equal or above 1.0 mg/L and EC100 is above 1.0 mg/L based on test item nominal concentrations.

Based on geometric mean of determined test substance concentrations the EC50 value is above 0.437 mg/L, EC0 is equal or above 0.437 mg/L and EC100 is above 0.437 mg/L.