O,O,O-tris(2(or 4)-C9-10-isoalkylphenyl) phosphorothioate

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: short-term

Type of information:

experimental study

Adequacy of study:

other information

Study period:

2002

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

GLP guideline study with analytical monitoring. The study was terminated after an exposure time of only 10 days. The regulatorily relevant endpoint was survival. Additionally, body weight was evaluated.

Qualifier:

according to guideline

Guideline:

OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)

Deviations:

yes

Remarks:

The study was terminated after 10 d.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature at about 20 °C, away from direct sunlight

Analytical monitoring:

yes

Details on sampling:

- Sampling interval: At test start and at test end
- Sample storage before analysis: The application solution samples were stored deep-frozen and protected from light until analysis was performed. The water, pore water and sediment samples were worked up and stored in a refrigerator until analysis was performed.

Vehicle:

yes

Details on sediment and application:

PREPARATION OF SPIKED SEDIMENT
- Method of mixing: According to guideline
- Details of spiking: No aqueous application solution could be prepared for the dosage of the test item due to the limited water solubility of the test item. However, the test item was completely soluble in the organic solvent acetone at the required concentrations. Thus, the test item was dissolved and diluted in acetone and applied to a portion of sand. The application solution for the highest test item concentration was prepared by dissolving 445 mg of the test item completely in acetone. The volume of the application solution was made up to 50 mL with acetone resulting in a test item concentration of 8.9 mg/mL acetone. Aliquots of this application solution were diluted with acetone to obtain the application solutions for the lower test concentrations. The resulting concentrations of the test item in the application solutions were 0.56, 1.11, 2.23, 4.45 and 8.9 mg/mL. The application solutions were prepared one day before spiking the sediment. For spiking the sediment, the volume of 1.0 mL of the corresponding application solution was applied to 10 g sand in a glass flask. The solvent acetone was completely evaporated by a stream of nitrogen at room temperature under a hood for 2 hours. To the 10 g sand/test item mixture 120 g of the wet sediment was weighed into the glass flask. For a better mixing procedure of the spiked sediment 10 mL of the test water were added. This spiked sediment was intensely shaken by hand and then mixed in the closed glass flasks on a roller mixer for 2.5 hours. Afterwards the sediment was filled into the test beakers. The sediment of the solvent control was prepared like the spiked sediments incorporating the same amount of acetone to the sand, but without the test item. To the sediment of the control 10 g of sand was added accordingly, but without acetone or test item.
- Equilibration time: The vessels were prepared seven days before inserting of the test animals, and were incubated under the test conditions to reach equilibrium between sediment and aqueous phases (pore water and overlying water) in the water-sediment systems.

Test organisms (species):

Chironomus riparius

Details on test organisms:

TEST ORGANISM
- Common name: Midge
- Source: Novartis Crop Protection AG, CH-4002 Basel, Switzerland
- Age of animals at beginning of exposure: 2 - 3 days
- Feeding during test: Yes
- Food type: TetraMin
- Amount: 23 mg/vessel (on days 0, 3, 5), 47 mg/vessel on day 7

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

artificial sediment

Limit test:

no

Duration:

10 d

Exposure phase:

total exposure duration

Hardness:

3.4 - 4.0 mmol/L

Test temperature:

18.7 - 20.3°C

pH:

7.5 - 8.3

Dissolved oxygen:

5.6 - 8.6 mg/L

Ammonia:

0.44 - 3.05 mg/L

Nominal and measured concentrations:

Nominal sediment concentrations: 6.3, 12.5, 25, 50 and 100 mg/kg dw
Sediment concentrations (initial): 4.6 (calculated), 9.1 (calculated), 17.4 (measured), 36.5 (calculated) and 77.1 (measured) mg/kg dw

Details on test conditions:

TEST SYSTEM
- Test container: Glass beakers (600 mL, approximately 8 cm in diameter), covered with watch-glasses
- Preparation of the test vessels: The mixed wet sediment was filled into each test beaker, resulting in a layer of approximately 2 cm depth. The amount of 130 g wet sediment corresponded to approximately 89 g dry sediment. Then 240 mL test water were poured into the beakers, resulting in a water column of 5.5 cm depth. The water was filled up very slowly, taking care not to disturb the sediment. The sediment surface was covered by a plastic plate, which floated as the water was poured onto it. After filling the vessels with water, the plastic plate was removed. The water level was marked outside on the test vessel. Water levels did not change by more than 10% during the test period. If necessary, purified water was filled up to the normal water level. The vessels were prepared seven days before inserting of the test animals, and were incubated under the test conditions to reach equilibrium between sediment and aqueous phases (pore water and overlying water) in the water-sediment systems.

EXPOSURE REGIME
- No. of organisms per container: 20
- No. of replicates per treatment group: 4
- No. of replicates per control / vehicle control: 4
- Type and preparation of food: TetraMin, finely ground and suspended in test water

OVERLYING WATER CHARACTERISTCS
- Type of water: Reconstituted water according to guideline ("M7-medium") with an initial pH of 7.9 ± 0.3. In purified (deionized) water analytical grade salts and additives were added to obtain the needed concentrations.

CHARACTERIZATION OF ARTIFICIAL SEDIMENT
- Composition (if artificial substrate): According to guideline
- Method of preparation (if artificial substrate): According to guideline
- Maturation of artificial substrate (if any): yes

OTHER TEST CONDITIONS
- Light conditions: A 16-hours light to 8-hours darkness photoperiod with a 30 minute transition period between light and darkness. Light intensity at light period within the range of approximately 790-948 Lux (measured approximately at water surfaces of the test beakers).

EFFECT PARAMETERS MEASURED: Mortality, weight

VEHICLE CONTROL PERFORMED: yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Key result

Duration:

10 d

Dose descriptor:

EC50

Effect conc.:

> 100 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Key result

Duration:

10 d

Dose descriptor:

NOEC

Effect conc.:

50 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: body weight

Key result

Duration:

10 d

Dose descriptor:

LOEC

Effect conc.:

100 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: body weight

Key result

Duration:

10 d

Dose descriptor:

EC50

Effect conc.:

> 100 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: body weight

Details on results:

Survival:
At the highest test concentration the mean survival rate was still 90%, and no visual abnormalities in the larvae were recorded.


Body dry weight:
At the highest test concentration the mean dry weight was statistically significantly reduced to 79% of the mean dry weight of the larvae in the solvent control (Williams-test, a = 0.05, one-sided smaller).

Nominal test concentration (mg/kg dry sediment)	No. Larvae tested (per replicate)	No of survining larvae in replicate				% survival (mean)
		1	2	3	4
Control	20	19	19	18	17	91.3
Solvent control	20	17	16	19	18	87.5
6.3	20	14	20	17	20	88.8
12.5	20	18	16	19	19	90
25	20	19	18	17	17	88.8
50	20	19	18	16	17	87.5
100	20	19	17	17	19	90

Description of key information

The short-term study on Chironomus riparius did not reveal any toxic effec on the survival rate. Therefore, EC50 values could not be calculated.

Additional information

A study according to OECD draft guideline 218 (Feb. 2001) was conducted to elucidate the toxicity of the compound to larvae of Chironomus riparius (RCC 2003). Two endpoints (survival rate and body weight) were evaluated after a 10 d exposure period.  

According to ECHA’s guidance on information requirements and chemical safety assessment R.7b – Endpoint specific guidance the standardized test methods envisage an exposure period of at least 10 days for short-term and 28 days for long-term tests. Endpoints studied in sediment toxicity tests should be of ecological relevance. For long-term tests the sub-lethal endpoints reproduction, growth and emergence are most relevant. For short-term tests survival is the normal endpoint to be considered.

In the present study, the regulatorily relevant endpoint survival, did not reveal any toxic effects after the 10 d exposure period. At the highest test concentration the mean survival rate was still 90% and no visual abnormalities of the larvae were recorded. In case of body weight, the highest test concentration of 100 mg/kg dw (nominal) revealed a slight but statistically significant decrease.