Sodium O,O-diisopropyl dithiophosphate

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08.10.2012 - 19.12.2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

GLP compliance:

yes (incl. QA statement)

Remarks:

Chemical analysis not conducted under GLP

Test material

Test material information

Constituent 1

Reference substance name:

Sodium O,O-diisobutyl dithiophosphate

EC Number:

258-508-5

EC Name:

Sodium O,O-diisobutyl dithiophosphate

Cas Number:

53378-51-1

Molecular formula:

C8H18NaO2PS2

IUPAC Name:

Sodium O,O-diisobutyl phosphorodithioate

Test material form:

other: 51 % w/w solution in water, stabilized with X % NaOH

Details on test material:

- Substance type: Liquid
- Physical state: Light brown liquid

Specific details on test material used for the study:

Details on properties of test material:
PHYSICO-CHEMICAL PROPERTIES:
- Boiling point: 107 °C
- Water solubility (under test conditions): > 1000 g/L
- pH 12-14
- log Pow: 1.67

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: (Nominal) 0 (control); 20; 50; 100; 200; 500; 1,000 and 2,000 mg/L
- Sampling method: Samples were collected at test start, every 24 hours and at the end of the test for chemical analysis of the test product. Duplicate samples of 15 mL were collected in 20-mL plastic vials for later analysis. Only one of these samples were analysed. The spare samples were discarded after sponsor approved the report.
- Sample storage conditions before analysis: at - 20 ˚C ± 2.0˚C

Test solutions

Vehicle:

no

Details on test solutions:

A stock solution of 2,400 mg/L was prepared by weighing out 2,400 mg of the test product and dissolving it in 1 L of algal test medium. pH in the stock solutions was 9.3 and was therefore adjusted to 8.2 by adding 4 droplets of 1 M HCl. The test solutions were prepared by diluting the appropriate amounts of stock solution in algal test medium.
The test product was tested at the following nominal concentrations: 0 (control); 20; 50; 100; 200; 500; 1,000 and 2,000 mg/L.

Test organisms

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
Clone: NIVA, CHL 1
The alga Pseudokirchnerella subcapitata is cultured at DHI under the test conditions prior to the start of the test. Algae from this culture were used in the study.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

23.2 ± 0.0˚C

pH:

8.0-8.1 at the beginning and 7.8-10.2 at the termination of the test.

Nominal and measured concentrations:

The results from the analysis showed a measured IBP1-Na concentration of 88-102% of the estimated nominal concentration of IBP1-Na. As the tested concentraions were maintained within ± 20% of the nominal concentrations, the statistical calculaiton were based on the nominal concentrations.

Details on test conditions:

TEST SYSTEM
- Material, size, headspace, fill volume: 250 mL glass flasks with wide neck, containing 100 mL of test solution

- Renewal rate of test solution (frequency/flow rate):
- Initial cells density:
- Control end cells density:
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6 (flasks with algae but no test product) + a blank of each concentration ( flasks with the test product but no algae)
Furthermore, one flask of the control and one flask of each test concentration without algae were used to cellect samples for chemical analysis.

OTHER TEST CONDITIONS
- Adjustment of pH: Test media: from 9.3 to 8.2 by adding 1 M HCl
- Photoperiod: 72 hours
- Light intensity and quality: fluorescent light with an intensity of approx 60-120 μmol x m-2 x sec-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Beckman Coulter Multisizer and in-vivo fluorescence, Turner TD-700 Laboratory Fluorometer

TEST CONCENTRATIONS
- Test concentrations (nominal): 0 (control); 20; 50; 100; 200; 500; 1,000 and 2,000 mg/L.

Reference substance (positive control):

yes

Remarks:

K2Cr2O7, CAS no 7778-50-9

Results and discussion

Effect concentrations

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

261 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Remarks on result:

other: 245-278

Details on results:

- Exponential growth in the control (for algal test): yes

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50: 1.09 mg/L

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

Growth rate = 1.9/day (> 1.4/day). Variation coefficient of control growth rates = 1.4 (< 5%). Mean varion coefficen = 13.4% (<35%). Increase of pH > 1.5 unit from start to end for control, not considered significant. EC50 for ref. sub. = 1.09 (0.65-1.73)

Conclusions:

ErC50(72h) of the test substance, sodium O,O-diisobutyl dithiophosphate, CAS No. 53378-51-1 is 261 mg/L for Pseudokirchneriella subcapitata.
Remark: the test solution contains NaOH due to the production method.