Bis(tributyltin) oxide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Range finding - July 14 to 18 1989; Definitive test - July 28 to August 1 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Experiment performed under GLP conditions, but not according to standardised guidelines. Analytical verification of test concentrations performed, but resulted in an abornally high recovery of nominal concentrations

Qualifier:

no guideline followed

Principles of method if other than guideline:

A flow-through saltwater toxicity test was conducted at the Gulf Coast Research Laboratory (GCRL) in Ocean Springs, Mississippi, to determine the acute effect of bis(tributyltin) oxide on the Eastern Oyster (Crassostrea virginica Gmelin). The criteria of effect was reduced shell growth in treatment oysters compared to shell growth of the control oysters. Results of the test are reported as the 96-hour median effectlve concentration (EC50), the no observed effect concentration (NOEC) and the lowest observed effect concentration (LOEC). Chemical analysis of all test media utilized n-pentyl derivatization followed by gas chromatography/flame photometric detection.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Control, 160, 266, 442, 737 and 1228 ng (Sn)/L.
- Sampling method: 200 ml of water sampled from one replicate below water surface and away from aquaria sides at least weekly
- Sample storage conditions before analysis: Analysed immediately

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Stock solutions were prepared by serial dilution from a primary stock which contained 126.2 mg TBTO in 250 mL of dimethylformamide (DMF).
- Eluate: Water+DMF+TBTO
- Controls: pure and solvent
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Dimethylformamide (DMF)
- Concentration of vehicle in test medium (stock solution and final test solution): 0.01388 ml/L
- Evidence of undissolved material (e.g. precipitate, surface film, etc): None

Test organisms (species):

other aquatic mollusc: Crassostrea virginica

Details on test organisms:

TEST ORGANISM
- Common name: Eastern oyster
- Source: Aquacultural Research Corporation, Dennis, MA
- Weight at study initiation (mean and range, SD): 0.74 g wet weight
- Valve height at study initiation, for shell deposition study (mean and range, SD): 28.1 ± 2.2 mm umbo to distal edge length (range 24 to 32)
- Peripheral shell growth removed prior to test initiation: Yes

ACCLIMATION
- Acclimation period: 48 hours
- Acclimation conditions (same as test or not): Yes
- Health during acclimation (any mortality observed): Good

Test type:

flow-through

Water media type:

saltwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

No

Hardness:

Not reported

Test temperature:

27 to 28°C

pH:

7.8 to 8.1

Dissolved oxygen:

≥ 6.1 mg/L (or ≥ 87 % saturation)

Salinity:

11 to 12 ppt

Nominal and measured concentrations:

Measured (nominal) concentrations: N.D. (Control). N.D. (Solvent Control), 49.1 (160), 88.8 (266), 16A (442), 313 (737), and 673 (1228) ng (Sn)/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 20L polycarbonate aquaria
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: Polycarbonate, 13.3L fill volume
- Aeration: Via flow-through
- Type of flow-through (e.g. peristaltic or proportional diluter): Proportional diluter
- Renewal rate of test solution (frequency/flow rate): 30L/hour
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates):2
- No. of vessels per vehicle control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Mississippi Sound adjacent to GCRL
- Total organic carbon: 7.83 to 11.3 mg/L
- Metals: At or below detection limit, execpt iron and nickel
- Pesticides: Below detection limit
- Culture medium different from test medium: No
- Intervals of water quality measurement: Weekly

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 hour light:8 hour dark
- Light intensity: Fluorescent

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Shell deposition

A range finding study was reportedly performed, however no details are provided in the reporting of the study

Reference substance (positive control):

not specified

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

129 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

other: shell deposition

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

49.1 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

other: shell deposition

Duration:

96 h

Dose descriptor:

LOEC

Effect conc.:

88.8 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

other: shell deposition

Details on results:

- Behavioural abnormalities: None reported
- Other biological observations: Shell deposition (see table below)
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: None

Results with reference substance (positive control):

N/A

Reported statistics and error estimates:

Shell growth of oysters in the seawater control and solvent control were compared by a Student's t-test to determine if there were any solvent effects. Differences in shell growth between the pooled controls and TBTO-exposed oysters were determined by analysis of variance (ANOVA) followed by Williams (1972) multiple comparison test to identify those concentrations producing effects statistically greater than the control at a confidence level of 95 percent.

Table 1: New shell growth of the eastern oyster exposed to TBTO for 96 hours under continuous flow-through conditions

Mean measured concentration (ng SN/L, ppt)	Mean new shell growth, mm (SD)
Control	1.03 (0.43)
Solvent control	1.40 (1.04)
49.1	1.02 (0.87)
88.8	0.70 (0.44)*
164	0.50 (0.43)*
313	0.28 (0.25)*
673	0.64 (0.47)*

* significantly different from control

Validity criteria fulfilled:

not applicable

Conclusions:

Eastern Oysters demonstrated reductions in shell deposition at concentrations >88.8 ng Sn as bis(tributlytin) oxide per litre of seawater. The 96-hour EC50 was 129 ng (Sn)/L based on new shell growth in comparison to the test controls. The LOEC was 88.8 ng (Sn)/L. and the NOEC was 49.1 ng (Sn)/L.

Executive summary:

Bis(tributyltin) oxide; CAS No. 56-35-9; 97.5 percent bis(tributyltin) oxide (39.3 percent elemental tin) containing 0.089 percent dibutyltin oxide (DBTO), 0.09 percent Chloride, and 2.3A percent other tin compounds as reported by M&T Chemicals, Inc. An analysis for purity on September 11, 1989 by the Analytical Chemistry Sectlon of GCRL indicated 97.9 percent bis(tributyltin) oxide, 1.0 percent dibutyltin dichloride and 1.05 percent tetrabutyltin.

Natural Unfiltered Seawater amended with sea salts to 12 ppt salinity; test temperature range of 27 to 28°C.

Oysters averaged 28.1±2.2 mm umbo to distal edge length (range 2A to to 32 mm) and 0.7A g wet weight and appeared in good physical condition at initiation of task 3.

The 96-hour EC50 was 129 ng (Sn)/L; the NOEC was 49.1 ng (Sn)/L; and the LOEC was 88.8 ng (Sn)/L.

Description of key information

A flow-through saltwater toxicity test was conducted to determine the acute effect of bis(tributyltin) oxide on the Eastern Oyster (Crassostrea virginica Gmelin (reduced shell growth). Reductions in shell deposition at concentrations >88.8 ng Sn as bis(tributlytin) oxide per litre of seawater. The 96-hour EC50 was 129 ng (Sn)/L based on new shell growth in comparison to the test controls. The LOEC was 88.8 ng (Sn)/L. and the NOEC was 49.1 ng (Sn)/L.

Key value for chemical safety assessment

Marine water invertebrates

Marine water invertebrates

Effect concentration:

129 ng/L

Additional information

The key study, Walker, W.W. (1990), though not conducted to a standardised guideline, the study was performed in line with good scientific principles and in compliance with GLP. The study was assigned a reliability score of 2 and considered adequate for assessment.