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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Not specified
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
no guideline followed
Principles of method if other than guideline:
Determination of butyl tin compounds in the fish samples was carried out by the method in Tsuda T. et al. (1987a) Bioconcentration and metabolism of phenyl tin chlorides in carp. Wat. Res. 21: 949-953

While not to current guidelines the paper describes a robust bioconcentration study with carp. Consistent exposure was maintained in a flow through system which exposed carp to the test compound for 14 days. Measurements were taken in fish tissue and test water on days 0, 1, 3, 7, 10 and 14.
The data is not normalized from the lipid content, but at the time the study was performed it was not standard practice to normalise to a 5% lipid content as it is now. There are a number of items missing from the current TG, in the existing study, but it is considered the data shows a robust exposure.
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
- The concentration of chemical in water was sampled at 1, 3, 7, 10, and 14 days.


Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
An aqueous stock solution of 1 µg/mL was diluted continuously 150 times with dechlorinated tap water and supplied to aquarua tanks containing 15 fish. During the test, the flow rate and temperature of the test water were maintained at 300 mL/min and 22 ± 1 °C, respectively. The measured concentrations of the test material (experiment days 3, 14) in the test tanks was 0.0065 ± 0.0004 µg/L (mean +/- SD) (range: 0.0060-0.0070 µg/mlL.
Test organisms (species):
Cyprinus carpio
Details on test organisms:
TEST ORGANISM
- Common name: Carp
- Strain: Cyprinus carpio
- Source: Purchased from the Nango Suisan Center (Shiga Prefecture, Japan)
- Length at study initiation (length definition, mean, range and SD): 9.5-11.5 cm in body length
- Weight at study initiation (mean and range, SD): weighed 20.0-27.5 g; lipid content of the muscle was 0.70-0.83% (n=5) by Folch method
- Feeding during test: Fish were not fed during the exposure period

Butyl tin compounds were not detected in the carp before exposure to chemicals, but inorganic tin was detected in the range of 0.02-0.03 ug/g as SN4+ in the muscle.
Route of exposure:
aqueous
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
14 d
Test temperature:
22 ± 1°C
Details on test conditions:
An aqueous stock solution of 1 µg/mL were diluted continuously 150 times with dechlorinated tap water and added to aquaria containing 15 fish. During the test, the flow rate was mainiated at 300 mL/min.
Nominal and measured concentrations:
0.0065 µg/mL (measured)
Reference substance (positive control):
no
Details on estimation of bioconcentration:
BASIS INFORMATION
- Measured/calculated logPow: (Octanol:Water=1) = 0.09 ± 0.01; (Octanol:Water=1:10) = 2.2 ± 0.05
OECD Guidelines for Testing of Chemicals (1981) is not applicable to the measurement of Pow for dissociative chemicals such as butyl tin chlorides. BuSnCl3 was measured three times by a flask shaking method according to this guideline.

BCF was calculated by the following equation: concentration of chemical in fish / concentration of chemical in water

The concentration of chemical in water at each sampling time (1, 3, 7, 10, and 14 days) was used for the calculation of BCF.
Key result
Type:
other: LogBCF
Value:
0.3 dimensionless
Basis:
other: Muscle
Key result
Type:
other: LogBCF
Value:
2.1 dimensionless
Basis:
other: Liver
Key result
Type:
other: LogBCF
Value:
1.7 dimensionless
Basis:
other: Kidney
Key result
Type:
other: LogBCF
Value:
2.1 dimensionless
Basis:
other: Gall Bladder
Reported statistics:
The values of log BCF were higher in the viscera than in the muscle
Validity criteria fulfilled:
not applicable
Conclusions:
The log BCF values for the test material were determined to be 0.3 (muscle), 2.1 (liver), 1.7 (kidney) and 2.1 (gall bladder) in carp.
Executive summary:

The log BCF values for the test material were determined to be 0.3 (muscle), 2.1 (liver), 1.7 (kidney) and 2.1 (gall bladder) in carp. The test was performed in a continuous flow system using a method reported in Tsuda T. et al. (1987a) Bioconcentration nd metabolism of phenyl tin chlorides in carp. Wat. Res. 21: 949-953. Based on those results one can consider that the test material is not bioaccumulative.

Description of key information

Tsuda (1988)

The log BCF values for the test material were determined to be 0.3 (muscle), 2.1 (liver), 1.7 (kidney) and 2.1 (gall bladder) in carp. Based on the results one can consider that the test material is not bioaccumulative.

Key value for chemical safety assessment

BCF (aquatic species):
126 dimensionless

Additional information

Tsuda (1988)

This study was selected as the key study since it is a reliable study on the registered substance itself. While not to current guidelines the paper describes a robust bioconcentration study with carp. Consistent exposure was maintained in a flow through system which exposed carp to the test compound for 14 days. Measurements were taken in fish tissue and test water on days 0, 1, 3, 7, 10 and 14. LogBCF values are reported for muscle, liver, kidney and gall bladder – 0.3, 2.1, 1.7 and 2.1, respectively. As a conservative approach the worst case logBCF has been used to approximate the BCF in whole fish, namely logBCF = 2.1 for liver and gall bladder; BCF = 126.  Although this is an approximated BCF value, considering the value is very low and far from regulatory cut-off values for bioaccumulation set out in Annex XIII of REACH (2000 for a bioaccumulative substance or 5000 for a very bioaccumulative substance), it is considered robust and applicable for use in assessing the bioaccumulation potential of the substance.  

Data that are available on analogue substances was also considered in a weight of evidence approach. The following data were considered and suports the conclusion that the registered substance will not bioaccumulate.

Read-across to DBTO, CAS: 818-08-6 (1989)

The bioaccumulation of the test material was investigated following Kanpogyo No. 5, Yakuhatsu No. 615 and 49 Kikyoku No. 392 guidelines.

Common carp were exposed to the test material at 50 and 500 ppb (w/v) for 8 weeks. Analysis of the test fish and test water was performed using an atomic absorption photometer.

Bio concentration factor at 50 ppb (w/v) ranged from < 0.7 to 18 L/kg and at 500 ppb (w/v) ranged from < 7.1 to 69 L/kg.

Read-across to TTBT, CAS: 1461-25-2 (1991)

The bioaccumulation of the test material was investigated in accordance with the standardised guideline OECD 305C and other Japanese guidelines, under GLP conditions.

Common carp were exposed to the test material at 5.0 and 0.5 µg/L for 12 weeks in a continuous flow-through system. Analysis of the test fish and test water was performed using GC-MS.

Relationships between BCF and exposure period were investigated. Based on these figures, it is appeared to reach to equilibrium by Week 12. Concentration of test material in common carp is factor 38 – 97 L/kg for Group 1 and factor 127 – 310 L/kg for Group 2.

Read-across to DOTE, CAS: 15571-58-1, Bouwman (2010)

Fish bioconcentration test in rainbow trout with Dioctyltin bis(2-ethylhexyl thioglycolate).

The study procedure described in this report was based on the OECD guideline No. 305, 1996.In addition, the procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.13, 2008.

The batch of Dioctyltin bis(2-ethylhexyl thioglycolate) used was a colourless liquid with a purity of 97.5 area %. Water solubility was indicated to be below 0.1 mg/L. Stock solutions for the bioconcentration test were prepared in acetone and dosed via a computer-controlled system consisting of micro-dispensers into a mixing flask separately from the medium supply. Medium was supplied via a flow meter at a flow rate of 10 L/h. In the mixing flask the dosed stock volumeand the dilution water were mixed under continuous stirring at a ratio of 1 : 10,000. The final target concentrations were 0.25 and 2.5 µg/L (based on water solubility and detection limits of the analytical methods used).

At the start of the Bioconcentration test 58 fish per concentration were exposed to the target concentrations of 0.25 and 2.5 µg Dioctyltin bis(2-ethylhexyl thioglycolate) per litre and 42 fish were exposed to a control. The uptake phase lasted for 30 days, during which samples were taken from the test medium and from the fish.

Analyses were based on both dioctyltin (DOT) and monooctyltin (MOT). Results were based onDOT, due to the fact that MOT-concentrations were below the Limit Of Quantification (LOQ) for the target concentration of 0.25 µg/L. The mean concentrations of DOT were 0.19 ± 0.048 µg/l and 2.6 t 0.35 µg/L at target concentrations of 0.25 and 2.5 µg/L, respectively. The measured concentrations varied within the ± 20 % window of the mean concentration at the target concentration of 2.5 µg/L but not at the target concentration of 0.25 µg/L.

Analyses of the concentrations of both DOT and MOT in fish tissues during the 30-day uptakephase showed measured concentrations that were always below the Limit of Quantification, i.e.< 0.25 mg/kg.

Since the concentrations of both DOT and MOT in fish were constantly below the LOQ duringthe uptake phase, a depuration phase was not considered to be significant. Therefore, the bioconcentration test was terminated after 30 days of exposure. In addition to the analytical work already performed on tin species, fish samples taken after 30 days of exposure were analysed on total tin.

The mean BCF-values based on dioctyltin at target concentrations of 0.25 and 2.5 µg/L were1294 and 99, respectively. The mean BCF-values based on total tin at target concentrations of 0.25 and 2.5 µg/L were 178 and 58, respectively.

The high value found at the target concentration of 0.25 µg/L was in fact due to the analytical methodology limit, which could not be further improved.

Based on the result found for the highest target concentration of 2.5 µg/L, the BCF is at leastless than 100 and therefore the substance does not bioconcentrate.

Read across to DMTC, CAS: 753-73-1, Ishi (1982) In Hall and Pinkey, (1985)

In a literature source with limited detail, the bioaccumulation of the test material was examined in a static saltwater study using algae. The BCF for dimethyltin dichloride is reported to be 1.6 - 5.9.

Read across to DMTC, CAS: 753-73-1, Hadjispyrou et al., (2001)

The bioaccumulation of dimethyltin dichloride was examined in a 24 hour static saltwater study using juvenuile Artemia franciscana.

The BCF factor of dimethyltin dichloride is reported to be 50 at 10 mg Sn/L to 6 at 100 mg Sn/L.

Read across to DBTC, CAS: 683-18-1, Tsuda et al (1986)

Bioconcentration factors (BCF) by round crucian carp and partition coefficients between n-octanol and water (Pow) were measured for dibutyltin dichloride. Log Pow was 0.97. Results were reported as log BCF: muscle = 1.08; vertebra = 1.66; liver =  2.13; and kidney = 1.78, which corresponds to BCF values of: muscle = 12; vertebra = 46; liver =  135; and kidney = 60.

Read across to DBTC, CAS: 683-18-1, Tsuda et al (1988)

Bioconcentration factors (as log BCF) by carp (Cyprinus carpio)and partition coefficients between n-octanol and water (Pow) were measured for dibutyltin dichloride.

Log Powwas 0.05. Results were reported as log BCF: muscle = -0.9; gall bladder = 0.9; liver = 1.0; and kidney = 0.7.

QSAR Prediction

The bioaccumulation of the test material was calculated using BCFBAF v3.01, 2000 U.S. Environmental Protection Agency.

Given that the substance is within the molecular weight range of the training set compounds, the prediction is considered to be acceptable.

The bioconcentration factor of the test material was estimated to be 3.162 L/kg (wet-wt)

Summary

A whole body BCF value of 126 for carp is quoted as the key value for the CSR. This value is taken from Tsuda et al (1988). While not to current guidelines the paper describes a robust bioconcentration study with carp. Consistent exposure was maintained in a flow through system which exposed carp to the test compound for 14 days. Measurements were taken in fish tissue and test water on days 0, 1, 3, 7, 10 and 14. LogBCF values are reported for muscle, liver, kidney and gall bladder – 0.3, 2.1, 1.7 and 2.1, respectively. As a conservative approach the worst case logBCF has been used to approximate the BCF in whole fish, namely logBCF = 2.1 for liver and gall bladder; BCF = 126. Although this is an approximated BCF value, considering the value is very low and far from regulatory cut-off values for bioaccumulation set out in Annex XIII of REACH (2000 for a bioaccumulative substance or 5000 for a very bioaccumulative substance), the Registrant considers it robust and applicable for use in assessing the bioaccumulation potential of MBTC.  

In addition to supplement the existing data and to help alleviate any concerns regarding bioaccumulation additional data on other organotin substances have been included to support the non bioaccumulative conclusion for MBTC.