Phosphorothioic acid, O,O-bis(2-methylpropyl) ester, sodium salt (1:1)

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:

19 June - 11 July 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Also according to GLP principles.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Test guideline 3

Qualifier:

according to guideline

Guideline:

ISO 6341 (Water quality - Determination of the Inhibition of the Mobility of Daphnia magna Straus (Cladocera, Crustacea))

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Sodium O,O-diisobutyl phosphorothioate

EC Number:

610-992-2

Cas Number:

53378-52-2

Molecular formula:

C8 H18 O3 P S . Na

IUPAC Name:

Sodium O,O-diisobutyl phosphorothioate

Test material form:

other: grease-like solid

Specific details on test material used for the study:

- Name of test material (as cited in study report): S10783
- Name: Sodium diisobutyl monothiophoshate
- CAS: 53378-52-2
- Molecular formula: C8H18O3PS.Na
- Molecular weight: 248.26
- Storage condition of test material: not indicated in the study report
- Purity: 70%

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations (final test):
Control, 10, 22, 46, 100 and 200 mg/L
- Sampling method:
Samples for possible analysis were taken from all test concentrations and the control according to the schedule below.
Frequency at t=0 h and t=48 h
Volume 1 ml from the approximate centre of the test vessels

- Sample storage conditions before analysis: Samples were stored in a freezer until analysis

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
Preparation of test solutions started with a loading rate of 100 mg/l for the combined limit/range-finding test and a loading rate of 220 mg/l for the final test. A short period of vigorous stirring was applied to dissolve the test substance in the test medium. The lower test concentrations were prepared by subsequent dilutions of the 100 and 220 mg/l concentrations, respectively, in test medium. The final test solutions were all clear and colourless.
- Controls: Test medium without test substance or other additives
- Evidence of undissolved material (e.g. precipitate, surface film, etc): None

Test organisms

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 (mean and range, SD): With newborn daphnids, i.e. less than 3 days old
- Method of breeding: Acyclical parthenogenesis under specified breeding conditions.
- Feeding during test: None

ACCLIMATION
- Acclimation period: Culture conditions same as test conditions, no acclimation required
- Acclimation conditions (same as test or not): Yes
- Type and amount of food: Suspension of fresh water algae
- Feeding frequency: Daily
- Health during acclimation (any mortality observed): Daphnids to be used in the test did not show signs of stress such as mortality >20%, presence of males, ephippia or discoloured animals and there no delay in the production of the first brood.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

Hardness:

180 mg/L expressed as CaCO3

Test temperature:

19.6 - 20.9°C

pH:

6.0 - 8.5

Dissolved oxygen:

≥3 mg/L at the end of the test

Nominal and measured concentrations:

Nominal conc.: 0, 10, 22, 46, 100, 220 mg/L

Measured conc.:
At 0 h = 0.0003043 (0), 7.66 (10), 21.8 (22), 51.2 (46), 101 (100) and 222 (220) mg/L
At 48 h = <0.000014 (0), 10.3 (10), 21.7 (22), 44.9 (46), 107 (100) and 240 (220) mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass vessel
- Aeration: None
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water purified by Reverse Osmosis
- Culture medium different from test medium: No
- Intervals of water quality measurement: pH and dissolved oxigen measured at the beginning and at the end of the test, for all concentrations and the control.

OTHER TEST CONDITIONS
- Photoperiod: 16 h photoperiod daily

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Immobility (including mortality) at 24 hours and at 48 hours.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: approximately 2
- Range finding study
- Test concentrations: 0.10, 1.0, 10, 100 mg/L
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Effect concentrations 2

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

53 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 43-68

Details on results:

No immobilisation observed in the control

Analysis of the samples taken at the start of the final test showed that the initial concentrations were in agreement with nominal (99-111%) at nominally 22 mg/l and higher. These concentrations remained stable during the test period (88-108% of initial at the end of the test). The lowest test concentration of 10 mg/l was slightly lower at the start (77-82% of nominal), but again in agreement with nominal at the end of the test period (103% of nominal). Given these results, the effect parameters were based on nominal test concentrations.

Results with reference substance (positive control):

The actual responses in this reference test with K2Cr2O7 were just outside (below) the ranges of the expected historical responses at the different concentrations, i.e. a 48h-EC50 between 0.3 and 1.0 mg/l. Hence, the sensitivity of this batch of D. magna was slightly higher when compared to the historical data collected at NOTOX.
The 24h-EC50 was 0.49 mg/l with a 95% confidence interval between 0.45 and 0.55 mg/l.
The 48h-EC50 was 0.28 mg/l with a 95% confidence interval between 0.14 and 0.65 mg/l.

Any other information on results incl. tables

Acute immobilisation of daphnids after 24 and 48 hours in the final test

Concentration S-10783 (mg/l)	Vessel number	Number Daphnia exposed	Response at 24 h		Response at 48 h
			number	Total %	number	Total %
control	A B C D	5 5 5 5	0 0 0 0	0	0 0 0 0	0
10	A B C D	5 5 5 5	0 [2] 0 [2] 0 [4] 0	0	0 0 0 0	0
22	A B C D	5 5 5 5	0 0 [1] 0 [2] 0 [1]	0	1 0 0 1	10
46	A B C D	5 5 5 5	0 [3] 0 [4] 0 [4] 0 [3]	0	1 [3] 1 [4] 0 [5] 1 [4]	15
100	A B C D	5 5 5 5	0 [5] 0 [5] 0 [5] 0 [5]	0	5 [4] 5 [5] 4 [4] 5 [4]	95
220	A B C D	5 5 5 5	3 [5] 2 [5] 0 [5] 0 [5]	25	5 5 [3] 5 [1] 5	100

[ ]: number of daphnids observed trapped at the surface of the test solutions. These organisms were reimmersed into the respective solutions before recording of mobility.

Concentrations of the test substance in test medium - final test
			Concentration
Time of sampling [hours]	Date of sampling [dd-mm-yy]	Date of analysis^1[dd-mm-yy]	Nominal [mg/l]	Analysed [mg/l]	Relative to nominal [%]	Relative to initial [%]
0	09/07/2012	19/07/2012	0	0.0003043	n.a.
			0^2	0.0002393	n.a.
			10	7.66	77
			10^2	8.19	82
			22	21.8	99
			46	51.2	111
			100	101	101
			220	222	101
48	11/07/2012	19/07/2012	0	<0.00001^4	n.a.
			10	10.3	103	130^5
			22	21.7	99	100
			46	44.9	98	88
			100	107	107	106
			220	240	109	108

1) Samples were stored in the freezer (≤ -15°C) until the day of analysis.

2) Reserve sample.

3) A small response in the blank sample, maximum contribution to the 10 mg/l samples is 0.004% based on the response

4) Response smaller then lowest standard taking a dilution factor into account.

5) Relative to the mean concentration of corresponding t=0 samples

n.a.) Not applicable.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present study the test material did not induce acute immobilisation of Daphnia magna at 10 mg/L after 48 hours of exposure (NOEC). The 48h-EC50 was 53 mg/L (95% confidence interval between 43 and 68 mg/L).

Executive summary:

The toxicity of S-10783 to aquatic invertebrates was assessed according to OECD TG 202 and GLP principles. Nominal exposure concentrations were the following: control, 10, 22, 46, 100, 220 mg/L.

The NOEC was 10 mg/L and the EC50 was 53 mg/L (as nominal concentrations).

All criteria for acceptability of the test were met and the present toxicity study is classified as reliable without restrictions according to the OECD guideline No. 202.