Bis(tributyltin) oxide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

4-8 January 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-1 (Fish Acute Toxicity Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

A 500 ml sampling was taken of the control, solvent control and test levels 1 and 2. Test levels 3, 4 and 5 were sampled at 100 ml. Butyltin fortifications were prepared at 1.0, 10 and 25 µg/L in 500, 100 and 100 mL of aquatic test water, respectively, for tetrabutyltin, dibutyltin and monobutyltin. For tributyltin, the fortification levels were 12.4, 4.95 and 0.495 µg/L for day 0 sampling and 24.7, 9.89 and 0.989 µg/L for the 96 hour sampling.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Controls: Solvent control was 0.05 ml of acetone in 1.978 L of dilution water = 0.025 ml/L
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Acetone

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout (Oncorhynchus mykiss)
- Source: The fish (lot #3889) were reared at ABC Laboratories from eggs and milt obtained from Mt. Lassen Trout Farms of Red Bluff, CA on July 14, 1989. The developing embryos and larval fry were cultured In ABC well water.
- Length at study initiation (length definition, mean, range and SD): Mean standard length = 46 mm (± 4.6 mm)
- Weight at study initiation (mean and range, SD): Mean weight = 1.4 g ( ± 0.41 g)
- Type of food: Food for the fish consisted of newly hatched brine shrimp nauplii and salmon Starter. The Brine shrimp (Artemia) cyets were purchased from Ocean Star International, Inc. of Snowville, Utah and the salmon starter from Zeigler Brothers, Inc. of Gardners, PA. When fish were placed in the acclimation conditions, food was withheld.

ACCLIMATION
- Acclimation: Approximately 48 hours before the initiation of the test, 150 fish were removed from the living stream culture tank and placed in the temperature acclimation unit in ABC soft blended water. During this time, the fish were held without food. At study initiation 20 fish were impartially selected from the acclimated fish to be used as a representative sample for weight and length data. These fish were set aside 1 to 2 at a time during the process of adding the fish to the test aquaria until all 20 had been collected.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

44 mg/L (40-50 mg/L as CaCO3)

Test temperature:

11.1 to 12.2 (mean 11.6) °C

pH:

7.9-8.1 (Approximately 8.0)

Dissolved oxygen:

9.3 - 9.7 mg/L

Nominal and measured concentrations:

Nominal concentrations 1.5, 3.0, 6.0, 12, and 24 µg/L total TBTO

Details on test conditions:

TEST SYSTEM
- Material, size, headspace, fill volume: 30.5 cm tall by 26.8 cm wide by 29.7 cm long. Average water depth in the chambers was set at 19.1 cm by means of a PVC stand pipe drain. Therefore, the average volume of each test chamber was 26.8 cm x 29.7 cm x 19.1 cm = 15,200 cc = 15,200 ml = 15.2 L
- Aeration: Not artificially aerated
- Type of flow-through: proportional diluter
- Renewal rate of test solution (frequency/flow rate): The diluter delivered 1.0 litre of test solution or control water to each 15.2 litre replicate chamber at an average rate of 140 times per day over the course of the study. This flow rate resulted in the equivalent of 9.2 test volume additions per chamber per day. Each chamber underwent a 95% volume replacement approximately every 8 hours. At a mean weight of 1.4 g per fish, 10 fish per chamber weighed 14 g. The flow through biomass loading level was 0.1 g of fish/L/day.
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- Biomass loading rate: The test specimen density will be no greater than 1 gram of fish per litre of solution/water passing through a test chamber in 24 hours. The loading density will not exceed 10 g/L at any given time.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The study was performed in ABC soft blended water. Soft blended dilution water is a mixture of reverse osmosis (R.O.) and well water to achieve a final hardness (as CaCO3) of ~40-48 mg/L.
- Total organic carbon: <1.0 mg/L
- Particulate matter: 0.0 mg/L
- Alkalinity: 52 mg/L CaCO3 in control dilution water
- Conductivity: 120 µS in control dilution water
- Culture medium different from test medium: During late September and early October, 1989 some of the juvenile fry were transferred to the living stream culture tank which contained ABC soft blended water. The remainder of the lot were left in the ABC well water culture tank.
- Intervals of water quality measurement: Water chemistry parameters were measured at 0, 48 and 96 hours and were within the specified limits for conducting aquatic toxicity tests.

OTHER TEST CONDITIONS
- Photoperiod: 16 hour daylight period
- Light intensity: The test system lighting consisted of both fluorescent and Incandescent lights set on a 16 hour daylight photoperiod. During the first half hour of the photoperiod (6:00 a.m. to 6:30 a.m.) the incandescent lights became progressively brighter in a simulated dawn transition period, When the incandescent lights reached full intensity (6:30 a.m.), the fluorescent lights came on and remained on throughout the day. At 9:30 p.m. the fluorescent lights were turned off and a half hour simulated dusk period began. During this transition to darkness, the incandescent lights gradually became dimmer until 10:00 p.m. when they were completely turned off. From 10:00 p.m. till 6:00 a.m. the test system lights were off.

TEST CONCENTRATIONS
- Range finding study: A 96-hour preliminary range-finding study was conducted with the tributyltin oxide sample from December 29, 1989 to January 2, 1990.
- Test concentrations: Nominal tributyltin oxide concentrations were 1.5 and 6.0 µg/L based on total TBTO product. Both concentrations were comprised of a Single test chamber to which five fish were added at Initiation.
- Results used to determine the conditions for the definitive study: No effects were observed in the lower concentration, but 3 of the 5 fish exhibited sublethal effects in the higher concentration. No mortality occurred in either concentration during the test.

Reference substance (positive control):

not specified

Duration:

24 h

Dose descriptor:

LC50

Effect conc.:

7.5 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

mortality (fish)

Remarks on result:

other: >3.9 95% CL, mortality occurred in only once concentration and <63%

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

5.6 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

mortality (fish)

Remarks on result:

other: 3.9 and 7.9 95% CL

Duration:

72 h

Dose descriptor:

LC50

Effect conc.:

2.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

mortality (fish)

Remarks on result:

other: 2.1 and 3.9 95% CL

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

2.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

mortality (fish)

Remarks on result:

other: 2.1 and 3.9 95% CL

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

7.2 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

other: equilibrium loss

Remarks on result:

other: >3.9 95% CL

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

5.6 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

other: equilibrium loss

Remarks on result:

other: 3.9 and 7.9 95% CL

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

other: equilibrium loss

Remarks on result:

other: 2.1 and 3.9 95% CL

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

2.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin

Basis for effect:

other: equilibrium loss

Remarks on result:

other: 2.1 and 3.9 95% CL

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

1 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin from tributyltin

Basis for effect:

other: mortlaity and sublethal effects

Duration:

96 h

Dose descriptor:

LOEC

Effect conc.:

2.1 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Remarks:

tin from tributyltin

Basis for effect:

other: mortality and sublethal effects

Details on results:

- Behavioural abnormalities: Sublethal effects noted included quiescence, fish resting on bottom of test chambers, and loss of equilibrium
- Mortality of control: 0

Reported statistics and error estimates:

Statistical analysis of the mean measured concentration of tin (Sn) from tributyltin vs. effect (mortality and/or equilibrium loss) was obtained by employing a computerized LC50 program developed by Stephan et al. (1978). This program calculated the LC50 and EC50 statistics and their 95 percent confidence limits using the binomial, moving average and probit tests. In this study, however, only the binomial test resulted in LC50, and EC50 values. Both the moving average and probit methods require partial mortality (and/or equilibrium loss for EC50) in at least two test levels for LC50/EC50 calculations, which did not occur during this study. All calculations were performed on an IBM PC-XT or compatible Computer.

Stephan, C. E. , K. A. Busch, R. Smith, J. Burke and R. W. Andrew. 1978. A Computer program for calculating an LCJQ. U. S. Environmental Protection Agency, Duluth, Minnesota, pre-publication manuscript, August, 1978.

Sublethal observations / clinical signs:

Based on the lack of mortality and sublethal effects the highest no-observed effect concentration (NOEC) by test termination was 1.0 µg/L Sn from tributyltin. The lowest observed effect concentration (LOEC) was 2.1 µg/L Sn.

Validity criteria fulfilled:

not specified

Conclusions:

Mortality was 100% in the 2 highest test levels (3.9 and 7.9 ug/L tin) after 96 hours of testing. Using the mean measured concentrations of tin from tributyltin, the 96 hour LC50 and EC50 were both 2.9 ug/L tin. The LC50 was based on mortality and the EC50 on mortality and equilibirum loss. Sublethal behavioural responses observed during the study included quiescence, fish resting on the chamber bottoms, and loss of equilibrium. Based on the lack of mortality and sublethal effects, the 96 hour NOEC was 1.0 µg/L tin from tributyltin, and the LOEC was 2.1 µg/L. The slope of the 96 hour mortality and equilibrium loss dose-response line was 17.

Executive summary:

A 96 -hour acute flow-through toxicity study of bis(tri-n-butyltin)oxide to rainbow trout was conducted following GLP regulations and according to the method: EPA OPP 72-1 (Fish Acute Toxicity Test). Using the mean measured concentrations of tin from tributyltin, the 96 hour LC50 and EC50 were both 2.9 µg/L tin. The LC50 was based on mortality and the EC50 on mortality and equilibrium loss. Sublethal behavioural responses observed during the study included quiescence, fish resting on the chamber bottoms, and loss of equilibrium. Based on the lack of mortality and sublethal effects, the 96 hour NOEC was 1.0 µg/L tin from tributyltin, and the LOEC was 2.1 µg/L. The slope of the 96 hour mortality and equilibrium loss dose-response line was 17.

Description of key information

A 96 -hour acute flow-through toxicity study of bis(tri-n-butyltin)oxide to rainbow trout was conducted following GLP regulations and according to the method: EPA OPP 72-1 (Fish Acute Toxicity Test). Using the mean measured concentrations of tin from tributyltin, the 96 hour LC50 and EC50 were both 2.9 µg/L tin. The LC50 was based on mortality and the EC50 on mortality and equilibrium loss. Sublethal behavioural responses observed during the study included quiescence, fish resting on the chamber bottoms, and loss of equilibrium. Based on the lack of mortality and sublethal effects, the 96 hour NOEC was 1.0 µg/L tin from tributyltin, and the LOEC was 2.1 µg/L. The slope of the 96 hour mortality and equilibrium loss dose-response line was 17.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

2.9 µg/L

Additional information

The key study, Cohle, P., and Lochhaas, C. (1990), was performed in compliance with GLP and in line with EPA OPP 72-1 (Fish Acute Toxicity Test). The study was considered adequate for assessment and was assigned a reliability score of 1.