Tetrakis(diethyldithiocarbamato-S,S')tellurium

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

8 Nov 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Version / remarks:

July, 2010

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Version / remarks:

December, 2015

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Name of test item (as cited by study report): Tellurium diethyldithiocarbamate
- Batch No.: 60700109
- Appearance: Light orange to yellow powder
- Purity: 99.19%
- Homogeneity: Homogeneous
- Water solubility: < 0.1 g/L
- Production date: 10 Jul 2016
- Expiry date: 10 Jul 2018 (re-test date)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
The test item was stored in a closed vessel dry at 16.6 - 20.4 °C.

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Due to the poor solubility of the test item, the test item was weighed directly into the test vessels.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant in D-67435 NW-Lachen-Speyerdorf.
- Pretreatment: Upon arrival in the test facility, the sludge was filtrated, washed with tap water 3 times and re-suspended in tap water. The activated sludge was aerated until usage in the test and fed daily with 50 mL synthetic sewage feed/L.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Hardness:

1.03 mmol/L (of the drinking water)

Test temperature:

19.2 - 21.2 °C

pH:

7.4 - 7.7

Conductivity:

242 µS/cm at 25 °C (of the drinking water)

Nominal and measured concentrations:

- Nominal concentrations: 0 (control), 1, 10, 100 and 1000 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass beakers
- Fill volume: 250 mL
- Aeration: Purified air, using Pasteur pipettes
- No. of vessels per concentration: 1 replicate for the 1, 10 and 100 mg/L treatments, 5 replicates for the 1000 mg/L treatment.
- No. of vessels per blank control: 2 replicates before and 2 after measuring positive control and test item, respectively.
- No. of vessels per positive control: 1
- Sludge concentration: The dry matter was determined as 2.64 mg suspended solids/L, giving a concentration of 1.32 g suspended solids/L in the test.
- Nutrients provided for bacteria: nutrient solutionwas provided, 16 mL/vessel.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water was used

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Measurements of conditions: The pH was measured at the end of the test in each vessel.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Nominal concentrations of reference substance: 5, 10, 20 and 40 mg/L.

PREPARATION OF THE TEST
On the day before the experiment, the inoculum was taken from its source, washed, aerated and the dry matter was determined. Volume was adapted to the desired content of dry matter. The nutrient solution was thawed and the sludge was fed with 50 mL/L sludge. On the day of the experiment, the dry matter was determined once more. The stock solution of the positive control was prepared.

PERFORMANCE OF TEST
In the blank control vessels, 16 mL nutrient solution was mixed with 234 mL water. The positive control vessels and the treatments were prepared by putting the appropriate amount of positive control solution respectively test item into the respective test vessel, adding 16 mL nutrient solution and water to reach a total volume of 250 mL. Then, 250 mL inoculum was added in 5 minute intervals and the mixtures were aerated.

EFFECT PARAMETERS MEASURED: oxygen consumption
After 3 hours, the content of the first vessel was poured in a 250 mL narrow-neck bottle and the respiration rate was determined by measurement of the O2-concentration over a period of max. 5 minutes. The vessels were measured likewise in 5 minute intervals.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

No respiration inhibition was observed after 3 hours exposure at any of the tested concentrations. See 'Any other information on materials and methods incl. tables'.

Results with reference substance (positive control):

The 3-hEC50 value of the reference substance 3,5-dichlorophenol was 8.3 mg/L (95% CI: 5.8 - 11.0 mg/L).

Reported statistics and error estimates:

The F-test was used to determine equality of variance. As equality of variance was not given, the WEIR test is used.

Table: O2-consumption, inhibition

Vessel No.	Content	Concentration in mg/L (nominal)	O2 consumption in mg/(L*min)	O2 consumption in mg/(L*h)	Inhibition in %	pH
1	Blank Control	0	0.6155	36.928	0	7.6
2	Blank Control	0	0.5950	35.700	0	7.6
3	Positive Control	5	0.4101	24.604	32.0	7.7
4	Positive Control	10	0.2513	15.079	58.3	7.7
5	Positive Control	20	0.1350	8.099	77.6	7.7
6	Positive Control	40	0.0702	4.214	88.4	7.7
7	Blank Control	0	0.6086	36.517	0	7.6
8	Blank Control	0	0.5939	35.633	0	7.6
*9-16	*	*	*	*	*	*
17	Test Item	1000	0.6017	36.103	0.3	7.4
18	Test Item	1000	0.6267	37.604	-3.9	7.5
19	Test Item	1000	0.5913	35.480	2.0	7.6
20	Test Item	1000	0.5898	35.390	2.2	7.6
21	Test Item	1000	0.5409	32.454	10.4	7.6
22	Test Item	100	0.5911	35.464	2.0	7.5
23	Test Item	10	0.5932	35.592	1.7	7.5
24	Test Item	1	0.5768	34.606	4.4	7.5
25	Blank Control	0	0.5986	35.918	0	7.5
26	Blank Control	0	0.6085	36.510	0	7.6

*Annotation: measurements in vessels 9 – 16 do not belong to this study.

ADDITIONAL EFFECT VALUES

- 3 -h NOEC: ≥ 1000 mg/L

Validity criteria fulfilled:

yes

Remarks:

See 'Any other information on materials and methods incl. tables'

Description of key information

The 3-h (EC50 value and) EC10 value is >1000 mg/L as observed in a respiration inhibition study with activated sludge of a predominantly domestic sewage.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The toxicity of the substance to microorganisms was investigated in an activated sludge respiration inhibition study according to OECD TG 209 and in compliance with GLP criteria (LAUS GmbH, 2017). In this study activated sludge from a predominantly domestic sewage was exposed to nominal test substance concentrations of 0 (control), 1, 10, 100 and 1000 mg/L for 3 hours. Test concentrations were not analytically verified. The effects on microorganisms was determined by measuring total respiration rates and comparing these to an unexposed control. No significant inhibition was observed after 3 hours up to 1000 mg/L. Based on these findings, the 3-h EC50 and EC10 values were determined at > 1000 mg/L.