S-(3-(triethoxysilyl)propyl)octanethioate

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

Study period:

27 May - 30 Sep 2003

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

other: "Method for Testing the Degree of Accumulation of Chemical Substances in Fish Body" stipulated in the "Testing Methods for New Chemical Substances" (July 13, 1974, Revised October 8, 1998, No. 5, Planning and Coordination Bureau, Environment Agency; No. 6

GLP compliance:

yes

Radiolabelling:

no

Details on sampling:

- Sampling intervals/frequency for test organisms: Analysis of test fish was performed five times at each level in duration of exposure. Four fish were taken out at each sampling time and divided into two groups, then both were analyzed individually. Analysis of control fish was performed before the experimental starting and after the experimental completion. Four fish were taken out at each sampling time and divided into two groups, and then each was analyzed individually. In addition, two fish were taken out and three groups (two fish per group) were used for measurement of lipid contents.

- Sampling intervals/frequency for test medium samples: The test water of each level was analyzed once before first analysis of test fish and at the same time as analysis of test fish thereafter using atomic absorption spectrophotometry (AA) analysis.

Vehicle:

yes

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

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test item and HCO-20 and HCO-40 (each 10 times amount of test item) were mixed and kneaded. An ion-exchanged water was added to the mixture to prepare a 1000 mg/L stock solution (Level 1) and 100 mg/L (Level 2), respectively.
- Controls: HCO-20 and HCO-40 were dissolved in ion-exchanged water to prepare a 10 g/L stock solution.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): HCO-20 and HCO-40 (hydrogenated castor oil)

Test organisms (species):

Cyprinus carpio

Details on test organisms:

TEST ORGANISM
- Common name: Carp
- Source: Kurume Laboratory Chemicals Evaluation and Research Institute, Japan
- Lot No.: TFC-030224-IV
- Age at study initiation: Yearling fish
- Length at study initiation: 5.8-10.2 cm
- Weight at study initiation: mean 2.020 g
- Feeding during test: yes (Feed for fry of carp; Composition: Protein content = 43%, Lipid content = 3%; Manufacturer: Nippon Formula Feed Mfg. Co., Ltd.; Feeding amount: Amount corresponding to about 2% of total body weight was fed twice a day in halves). Fish were starved 24 h prior to sampling.

ACCLIMATION
- Acclimation period and conditions: After rearing, the fish were transferred to an acclimatizing aquarium and acclimatized there after the external disinfection. The fish showing any abnormalities during this period were removed and the remainders were reared for 35 days in a flow-through system at the temperature of 25 ± 2 °C. The fish were transferred to test tanks and reared at the same temperature in the flow-through system for 25 days, following an external disinfection.

DISINFECTION
The external disinfection in the acclimitising aquarium was carried out in an aqueous solution containing 50 mg/L oxytetracycline hydrochloride and 7 g/L sodium chloride for 24 h. The second disinfection in the test tanks was carried out twice in an aqueous solution containing 20 mg/L ELBAZIU and 7 g/L sodium chloride for 24 h.

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

60 d

Test temperature:

Level 1: 25.3 - 25.8 °C
Level 2: 25.3 - 25.8 °C
Control: 25.1 - 25.4 °C

pH:

Level 1: 7.7 - 8.1
Level 2: 7.6 - 8.2
Control: 7.7 - 8.2

Dissolved oxygen:

Level 1: 7.3 - 8.0 mg/L
Level 2: 7.6 - 8.1 mg/L
Control: 7.7 - 8.1 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass tank
- Size: 100 L
- Renewal rate of test solution: flow rate 2 mL/min for stock solution, 800 mL/min for dilution water
- No. of organisms per vessel: 37 at Levels 1 and 2, 12 in control

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Groundwater from the premises of the Kurume Laboratory
- Holding medium different from test medium: no
- Intervals of test medium replacement: renewal every 8-16 hours

OTHER TEST CONDITIONS
- Photoperiod: 14 h/day
- Light intensity: artificial light of white fluorescent lamp

Nominal and measured concentrations:

Level 1: 2.5 mg/L
Level 2: 0.25 mg/L

Reference substance (positive control):

no

Lipid content:

2.84 %

Time point:

start of exposure

Lipid content:

3.2 %

Time point:

end of exposure

Type:

BCF

Value:

20 dimensionless

Basis:

other: 2-5 g tissue

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:2.5 mg/L (dose)

Details on results:

No abnormality in behaviour or appearance was observed during the study period

The BCFs of the test item ranged from 11 to 25 at Level 1 and not more than 80 at Level 2 (Table 1). Because the variation of BCFs (average value) after 32, 46 and 60 days from the initiation of exposure were within ± 20% of the average for these days’ BCFs, it is evaluated that a steady state was reached. The BCF (steady state) was calculated to be 20 at Level 1 on the basis of these results. Because the test item in all test fish at the last three successive analysis was not more than minimum determination limit of test item, BCF at steady state was not calculated. However, because all BCF were less than 100 (Table 1), it was evaluated that a steady-state was reached within 60th day. The depuration after the uptake phase of 60 days was not evaluated.

Chemical analysis of the test item in test water showed that the test species were continuously exposed to the desired concentrations (Table 2).

Table 1: BCFs of test substance

Level (dose)	After 10 days	After 18 days	After 32 days	After 46 days	After 60 days
1 (2.5 mg/L)	20 14 (17)	15 11 (13)	16 21 (18)	19 25 (22)	19 19 (19)
2  (0.25 mg/L)	=80 =80	=80 =80	=80 =80	=80 =80	=80 =80

( ): average value

Table 2: Measured concentrations of the test item in water in mg/L

Level	After 3 days	After 10 days	After 18 days	After 32 days	After 46 days	After 60 days	Average (standard deviation)
1	2.53	2.14	2.61	2.42	2.55	2.43	2.45 (0.168)
2	0.198	0.176	0.231	0.196	0.238	0.255	0.216 (0.0302)

Conclusions:

Y-15099 has a low potential for bioaccumulation in animal tissues.

Executive summary:

This study examined the bioconcentration of Y-15099. The fish Cyprinus carpio (carp) was exposed to 0.25 and 2.5 mg/L of the test substance for 60 days. Uptake of the test substance was very slow. The steady-state was reached after approx. 32 days. Based on the results at steady-state the BCF was calculated to be 20 at a test concentration of 2.5 mg/L (Level 1). The BCF could not be calculated at Level 2 concentration of 0.25 mg/L since the test item in all test fish at the last three successive analysis was not more that minimum determination limit of the test item. However, because all BCFs were less than 100, it was evaluated that a steady-state was reached within 60th day. Chemical analysis of the test item in test water showed that the test species were continuously exposed to the desired concentrations. In deviation to the guideline, the depuration of the test substance after uptake was not assessed. The results of this study indicate that there is a low potential for Y-15099 to bioaccumulate in animal tissues as indicated by the very low BCF determined for fish.

Description of key information

BCF: 20

Key value for chemical safety assessment

BCF (aquatic species):

20 dimensionless

Additional information

A GLP study according to the OECD Guideline 305 was performed to assess the bioaccumulation of Y-15099 (Yakata, 2003). The carp Cyprinus carpio was exposed to the test substance in concentrations of 0.25 (Level 2) and 2.5 mg/L (Level 1) for 60 days. In contrast to the OECD Guideline, the depuration of the substance after the uptake was not evaluated. A steady-state was reached after approx. 32 days indicating a slow uptake of the substance. Based on the results at steady-state the BCF was calculated to be 20 at a test concentration of 2.5 mg/L. The BCF could not be calculated at Level 2 concentration of 0.25 mg/L since the test item in all test fish at the last three successive analysis was not more that minimum determination limit of the test item. However, because all BCFs were less than 100, it was evaluated that a steady-state was reached within 60th day. Chemical analysis of the test item in test water showed that the test species were continuously exposed to the desired concentrations. The results of this study indicate that there is a low potential for Y-15099 to bioaccumulate in animal tissues as indicated by the very low BCF determined for fish.

Since the substance Y-15099 is hydrolytically unstable, the hydrolysis products also need to be taken into account for the assessment. They were already assessed in this bioaccumulation study. The low bioaccumulation potential for the hydrolysis products ethanol and silanetriol, (3-mercaptopropyl)- is supported by a log Kow < 3. The third hydrolysis product octanoic acid with a log Kow of 3.05 (Hansch et al., 1995) might has a low potential to bioaccumulate, but a supporting QSAR calculation resulted in a BCF of 83.64 L/kg wet weight indicating a low potential for bioaccumulation (Müller, 2012).

References: Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants.,: American Chemical Society., 1995.