Polysulfides, bis[3-(triethoxysilyl)propyl]

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:

2009-09-03 to 2009-09-03

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

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling method: 46ul of the test substance which corresponds to 50 mg, was pipetted below the surface of the Milli-RO water and stirred briefly to mix (5 minutes). Synthetic sewage was subsequently feed and sludge added (final volume 500 ml) and the test was initiated. A loading rate of 100 mg/l was tested in duplicate.

- Sample storage conditions before analysis: Test substance stored at room temperature in the dark

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Pretreatment: The sludge was coarsely sieved to remove large particles. The sludge was then washed by centrifuging at 1000 g for 10 minutes. The supernatent was decanted and replaced with ISO-medium. The washing step was performed three times. Small amount of the sludge was weighed and dried overnight at ca. 105 C to determine the amount of suspended solids.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2°C

pH:

7.4

Dissolved oxygen:

46 ul of test substance, Milli-RO water, synthetic sewage feed (16 ml) and activated sludge (200 ml) were mixed and made up to 500 ml with Milli-RO water in a 1 L bottle. The mixture was aerated during the contact time, using a pipette as an aeration device.

Details on test conditions:

TEST SYSTEM
- Test vessel: All glass, approximately 300 ml oxygen bottles and 1 L test bottles

- Type (delete if not applicable): open

- Aeration: Strong aeration with clean, oil-free air

- Type of flow-through (e.g. peristaltic or proportional diluter): peristaltic

- No. of organisms per vessel: Number of micro-organisms was determined as the amount of mixed liquor suspended solids (MLSS) per litre of test medium.

- Biomass loading rate: 100 mg/l


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap-water was purified by reverse osmosis (Mill-RO) and subsequently passed over activated carbon and ion-exchange cartridges (Mill-Q).

Reference substance (positive control):

yes

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid? Yes

Reported statistics and error estimates:

Regression line: Y = 43.61 X + 9.02

Table 2: Study plan

Flask	Test Substance (µL)	Synthetic sewage feed (mL)	Stock sol. R 0.5 g/l (mL)	Activated sludge (ml)	Made up to 500 ml with Mill-RO water	Exposure time (h)	Conc/ loading rate (mg/L)
C start R	-	16	-	200	+	8.00 – 11.00	0
R1	-	16	5.0	200	+	8.15 – 11.15	5.0
R2	-	16	12	200	+	8.30 – 11.30	12
R3	-	16	30	200	+	8.45 – 11.45	30
C end R	-	16	--	200	+	9.00 – 12.00	0
C start T	-	16	-	200	+	9.45 – 12.45	0
T1	46 (=50 mg)	16	-	200	+	10.00 – 13.00	100
T2	46 (=50 mg)	16	-	200	+	10.15 – 13.15	100
C end T	-	16	-	200	+	10.30 – 13.30	0

C: Control

R: Reference substance, 3,5-dichlorophenol

T: Test substance, Bis[3-(triethoxysilyl)propyl]polysulfides

Table 3: Controls (C) and Bis[3-(triethoxysilyl)propyl]polysulfides (T): pH, oxygen concentration, oxygen consumption and percentage inhibition of the respiration rate

Flask	loading rate (mg/l)	Oxygen conc. At the start (~mg O2/l)	Oxygen consumption (mg O2/l/h)	% Respiration rate	pH
C start T	0	7.4	29	-	8.2
C end T	0	7.9	28	-	8.3
T1	100	5.3	29	-2^1	8.1
T2	100	7.1	30	-5^1	8.2

¹: Negative values indicate stimulation of the respiration rate sludge. The values are considered not significant

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiratory inhibition test value EC50 exceeding a loading rate of 100 mg/L has been determined for Bis[3-(triethoxysilyl)propyl]polysulfides in a test conducted according to OECD 209. The result is considered reliable.

Description of key information

ASRI 3-hour EC₅₀: >100 mg/l (loading rate) (activated sludge respiration inhibition, OECD 209). Organisms were likely predominantly exposed to the parent test substance

Additional information

An activated sludge respiration inhibition 3-hour EC₅₀ value of >100 mg/l (loading rate) was determined for the substance in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. This indicates that the test substance was not toxic to waste water (activated sludge) bacteria at a loading rate of 100 mg/l. This study was chosen as the key study as it uses a more standard methodology than that used in the supporting study.

For the supporting study, a bacterial growth inhibition 16-hour EL₁₀ value of >10 g/l (>10,000 mg/l) (nominal) was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.