Triethoxy(2,4,4-trimethylpentyl)silane

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The study was conducted according to an appropriate OECD test guideline. It was not compliant with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 (Bioconcentration: Flow-through Fish Test)

GLP compliance:

no

Radiolabelling:

yes

Details on sampling:

Water was removed from the aquaria using 32-oz glass amber bottles, by submerging the bottle to approximately one-third depth of the water column, and allowing 500 ml of water to enter. Liquid Scintillation Counting carried out on triplicate 10-ml samples.
Fish were sampled one fish from each aquarium and treated as whole fish samples. On days 28 and 56 of the uptake phase, three additional fish, one from each aquarium in both control and treated levels, were pooled and dissected into fillet/edible and viscera/non edible. Fish were processed and homogenised. Triplicate analysis of samples using sample combustion followed by Liquid Scintillation Counting.

Details on preparation of test solutions, spiked fish food or sediment:

Stock solutions in acetone prepared.
High treatment: 10 000 mg/l
Low treatment: 1000 mg/l
Stock solutions were poured into a graduated cylinder directly hooked up to the Hamilton injector.

Test organisms (species):

Cyprinus carpio

Details on test organisms:

TEST ORGANISM
- Common name: Carp

- Source: Osage Catfisheries, Inc., in Osage Beach, Missouri.

- Length at study initiation (length definition, mean, range and SD): 98 ±5.9 mm

- Weight at study initiation (mean and range, SD): 28.7 ±6.0 g

- Weight at termination (mean and range, SD): High treatment level: 44.5 ±4.0 g; Low treatment group 53.0 ±9.5 g

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

56 d

Total depuration duration:

14 d

Test temperature:

24 - 25 °C

pH:

High treatment 7.4 - 8.1; Low treatment 7.6 - 8.1

Dissolved oxygen:

High treatment 5.3 - 8.0 mg/l saturation; Low treatment 5.0 - 8.0 mg/l

Details on test conditions:

TEST SYSTEM
- Test vessel: 70-L glass aquaria

- Type: closed

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

- Renewal rate of test solution (frequency/flow rate): 904-905 ml/minute/aquarium

- No. of organisms per vessel: Nine groups of 20 fish

- No. of vessels per concentration (replicates): Three

- No. of vessels per control / vehicle control (replicates): Three

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Aerated hard-blended water

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: Nominal: 0.6, 1.3, 2.5, 5.0, 10 mg/l

- Results used to determine the conditions for the definitive study: no effects

Nominal and measured concentrations:

Nominal water concentrations: 1 mg/l; 0.1 mg/l

Mean measured water concentrations: 0.166 mg/l (±0.037); 0.0141 mg/l (±0.00339)

Reference substance (positive control):

no

Details on estimation of bioconcentration:

A nonlinear two-compartment kinetic modelling computer program (BIOFAC) was used to analyse the uptake/depuration whole fish data.

Key result

Type:

BCF

Value:

1 670 dimensionless

Basis:

whole body w.w.

Calculation basis:

kinetic

Remarks on result:

other: ±143

Remarks:

Conc.in environment / dose:0.166 mg/l

Key result

Type:

BCF

Value:

1 980 dimensionless

Basis:

whole body w.w.

Calculation basis:

kinetic

Remarks on result:

other: ±318

Remarks:

Conc.in environment / dose:0.0141 mg/l

Type:

BCF

Value:

1 450 dimensionless

Basis:

whole body w.w.

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:0.166 mg/l

Type:

BCF

Value:

1 890 dimensionless

Basis:

whole body w.w.

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:0.0141 mg/l

Key result

Parameter:

other: DT 50 (high treatment)

Depuration time (DT):

5.71 d

Key result

Parameter:

other: DT 50 low treatment

Depuration time (DT):

3.01 d

Details on kinetic parameters:

- Uptake rate constant (k1): High treatment: 203 (±13.5) mg/kg fish/mg/L water/day; Low treatment: 456 (±54.0) mg/kg fish/mg/L water/day
- Depuration (loss) rate constant (k2): High treatment: 0.121 (± 0.0065) day-1; Low treatment: 0.230 ( High treatment:0.0248) day-1
T (50%) for clearance, Day: High treatment: 5.71 (± 0.307); Low treatment: 3.01 (± 0.325)

Details on results:

High treatment tissue concentrations ranged from 134 to 1940 for whole fish. Low treatment tissues concentrations ranged from 2.13 to 30.2 mg/l for whole fish.

Table 1: Bioconcentration factors at different time points and concentrations in water

	Duration of exposure (days)	0	0.17	1	3	7	14	21	28	35	42	49	56
High concentration level	Concentration in the water(mg/l)	0.148	0.152	0.155	0.119	0.219	0.197	0.164	0.188	0.180	0.119	0.158	0.193
	Concentration infish (mg/kg)	N/A	10.9	45.2	101	205	302	209	226	282	208	212	272
	Bioconcentration factor	-	72.7	297	701	1290	1830	1270	1350	1670	1270	1300	1640
Low concentration level	Concentration in the water(mg/l)	0.0166	0.0152	0.0165	0.0164	0.0152	0.0149	0.0136	0.0122	0.0139	0.0107	0.0087	0.0159
	Concentration infish (mg/kg)	N/A	2.13	9.07	19.4	28.7	30.2	28.5	26.8	26.3	22.4	22.5	27.5
	Bioconcentration factor	-	134	563	1200	1790	1910	1840	1770	1770	1540	1610	1940

 

 Table 2: Depuration

	Days	1	3	7	10	14
High concentration level	Concentration in the water(mg/l)	<MQL	<MQL	<MQL	<MQL	<MQL
	Concentration infish (mg/kg)	228	154	150	110	67.7
	Bioconcentration factor	-	-	-	-	-
Low concentration level	Concentration in the water(mg/l)	<MQL	<MQL	<MQL	<MQL	<MQL
	Concentration infish (mg/kg)	20.7	16.7	11.6	10.6	7.35
	Bioconcentration factor	-	-	-	-	-

 

Validity criteria fulfilled:

yes

Conclusions:

BCFss values of 1450 (0.166 mg/l) and 1890 (0.0141 mg/l) and BCFk values of 1670 (0.166 mg/l) and 1980 (0.0141 mg/l) were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Bioaccumulation: aquatic / sediment: BCFss 1450 (0.166 mg/l) and 1890 (0.0141 mg/l); BCFk 1670 ±143 (0.166 mg/l) and 1980 ±318 (0.0141 mg/l), read-across from a structurally-related substance. A value of 2298 (1980 + 318) is used in the exposure assessment as a worst case. The silanol hydrolysis product has a low potential for bioaccumulation.

Key value for chemical safety assessment

BCF (aquatic species):

2 298 dimensionless

Additional information

Steady-state BCF (BCFss) values of 1450 (0.166 mg/l) and 1890 (0.0141 mg/l), and kinetic BCF (BCFk) values of 1670 ±143 (0.166 mg/l) and 1980±318 (0.0141 mg/l) have been read-across from a structurally-related substance, triethoxyoctylsilane (CAS 2943-75-1). The registration substance and the read across substance have similar hydrolysis half-lives (43 hours and approximately 30 hours at 20-25°C and pH 7 respectively) and similar log K_ow values (> 6.5 (supporting study 6.1) and 6.41 respectively). Both substances are triethoxysilanes containing a single silicon centre with three -OEt groups. The substances have one C8 alkyl side-chain bound to silicon which is branched (iso octyl) and linear (n-octyl) for the target and source substances respectively.

The target substance hydrolyses moderately (half-life 43 hoursat 20-25°C and pH 7) and the hydrolysis products have low log K_ow values and thus have low potential for bioaccumulation