Bis(tributyltin) oxide

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March 2 1990-March 23 1990

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.

Qualifier:

no guideline followed

Principles of method if other than guideline:

First instar Daphnia were exposed to five nominal concentrations of 0.13, 0.25, 0.5, 1.0 and 2.0 µg/L tributyltinoxide (0.05, 0.10, 0.20, 0.40 and 0.80 µg/L of tin) for 21-days and observed for toxicity.

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Control, Solvent Control (acetone), 0.13, 0.25, 0.50, 1.0 and 2.0 µg/L
- Sampling method: 500 to 750ml samples taken on days 0, 7, 14, 21
- Sample storage conditions before analysis: Acidified with 2ml of concentration HCl

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Dissolved in acetone
- Eluate: Acetone + bis(tributyltin) oxide
- Controls: Pure, and solvent controls
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Solvent, acetone
- Evidence of undissolved material (e.g. precipitate, surface film, etc): None

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain/clone: First instar
- Source: In-house culture
- Age of parental stock (mean and range, SD): Culture maintained since 1977
- Age at study initiation: Neonates (<24-hours old)
- Feeding during test: The test daphnids were uniformly fed an equal volume per test chamber of an algal Suspension (Selenastrum capricomutiim) once daily providing at least 8.0 x 10^7 cells/400 mL to each replicate on each solution renewal day of the study.
Daphnids in each chamber were supplemented at least on each renewal day with a Suspension of trout chow and yeast giving a final suspended solids concentration of at least 2.5 mg/L.

ACCLIMATION
- Acclimation period: <24 hours old. All daphnids were cultured and tested in a temperature controlled area at 20 ± 2°C. The lighting was 40-80 footcandles on a 16-hour daylight photoperiod, with 30-minute dawn and dusk transition periods.
- Acclimation conditions (same as test or not): Same as test
- Type and amount of food: Same as that provided in the study
- Health during acclimation (any mortality observed): Good

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

No

Hardness:

160 and 180 mg/L as CaCO3

Test temperature:

19-21 °C

pH:

7.9 to 8.4 (new solutions)
7.7 to 8.2 (old solutions)

Dissolved oxygen:

The dissolved oxygen concentrations of the new solutions ranged from 7.4 to 8.5 mg/L representing 85 and 98% Saturation at 20°C.
The dissolved oxygen concentrations of the old solutions ranged from 5.2 to 7.9 mg/L, representing 63 and 91% Saturation at 20°C.

Nominal and measured concentrations:

Nominal Test Concentrations as tin (Sn): Control, Solvent Control (acetone) 0.050, 0.10, 0.20, 0.40 and 0.80 µg/L
Nean Measured Test Concentrations as Sn: 0.05, 0.08, 0.14, 0.26 and (see results for discussion) 0.52 µg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 1L glass jars
- Type : open
- Material, size, headspace, fill volume: Glass, 400mL fill volume
- Aeration: No
- Renewal rate of test solution: All solutions were renewed on Monday, Wednesday and Friday.
- 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: Hard blended (artificial) water
- Total organic carbon: <1.0 ppm
- Particulate matter: 0.2 ppm
- Metals: Below detection limits
- Pesticides: Below detection limits
- Chlorine: Not measured
- Alkalinity: 174-202 mg/L as CaCO3
- Conductivity: 300 to 311 uMHOS/cm
- Culture medium different from test medium: No
- Intervals of water quality measurement: Weekly

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 8 hours light: 16 hours dark
- Light intensity: 40 to 80 footcandles

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Survival, growth, reproduction

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY: A range finding study was performed, the concentrations used for the deifinitive test were based on these results, however no details of the range finding study were reported.

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

0.12 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.08 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

0.14 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

other: MATC

Effect conc.:

0.11 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element

Basis for effect:

mortality

Details on results:

- Mortality of parent animals: Significant differences from controls (see table below)
- No. of offspring produced per day per female: Not significantly impacted by bis(tributyltin) oxide
- Body length and weight of parent animals: Not significantly impacted by bis(tributyltin) oxide
- Type and number of behavioural abnormalities: Erratic swimming, surfacing and bottoming
- Time to first brood release or time to hatch: Not significantly impacted by bis(tributyltin) oxide
- Brood size: Not significantly impacted by bis(tributyltin) oxide
- Effect concentrations exceeding solubility of substance in test medium: None

Results with reference substance (positive control):

N/A

Reported statistics and error estimates:

Survival data were analyzed using frequency analysis comparing each test concentration to the control. This analysis was coupled with a one-tailed Fisher's exact test and the chi-square statistic to determine those concentrations exhibiting a response significantly less than that of the control. Control and solvent control responses were pooled if a t-test showed no significant difference.
Reproduction data were analyzed by a one-way analysis of variance (ANOVA) procedure appropriate for a nested experimental design similar to that described by McClave et al.. A Dunnett's one-tailed multiple means comparison procedure was used to determine those exposure levels exhibiting responses significantly different than that of the control. When a t-test between the control and solvent control indicated no significant difference, all controls were pooled for that measured parameter.

Table 1: Survival, adult reproduction day, length in time to first brood, and adult length for Daphnia exposed to bis(tributyltin) oxide

Nominal Concentration (µg/L)	Mean 21-day survival (%)	Adult reproductive days (mean)	Length in time to first brood	Mean adult length
Control	95	4.8	7	3.59
Solvent control	100	5.0	7	3.63
Pooled controls	98	4.9	7	3.61
0.13	95	4.7	7	3.59
0.25	90	4.2	7	3.57
0.50	45*	3.5**	7**	3.32**
1.0	0*	2.7**	7**	--
2.0	0*	0**	--	--

* Significantly different from controls

* Not statistically analysed due to significance of mortality endpoint

Validity criteria fulfilled:

not specified

Conclusions:

Statistical analysis of survival, reproduction, length of time to first brood and adult length identified 0.08 µg/L as a no-effect concentration (NOEC) for tributyltin. The lowest-effected concentration (LOEC) for tributyltin was identified as 0.14 µg/L. All instar produced during the study were observed to be normal.
From the results of the daphnid survival, reproduction, length of time to first brood and adult length, the MATC calculated as the geometric mean of the NOEC (0.08 µg/L) and LOEC (0.14 µg/L) was 0.11 µg/L. The calculated EC50 after 21 days was 0.12 µg/L with a dose-response slope of 5.6.
The measured tributyltin (as Sn) concentrations ranged from 65 to 100 percent of expected nominal. The lowest values were for the 0.26 and 0.52 µg/L test concentrations. Since the measured test concentrations remained consistent for the duration of the study, the results derived from these values accurately represent the toxicity of tributyltin to Daphnia magna.

Executive summary:

Subject: "Chronic Toxicity of Biß(Tributyltin)Oxide to Daphnia magna", ABC Draft Report Number 38310

Test Material: Bis(Tributyltin)Oxide (CAS #56-35-9) 100% A.I.

Nominal Test Concentrations as Whole Product: Control, Solvent Control (acetone), 0.13, 0.25, 0.50, 1.0 and 2.0 µg/L

Nominal Test Concentrations as tin (Sn): Control, Solvent Control (acetone) 0.050, 0.10, 0.20, 0.40 and 0.80 µg/L

Mean Measured Test Concentrations as Sn: 0.05, 0.08, 0.14, 0.26 and 0.52 µg/L

Temperature Range: 19-21 °C

Dissolved Oxygen Range: 5.2-8.5 mg/L

pH Range: 7.7-8.4

Photoperiod: 8 hour light, 16 hour dark

Dilution Water: 160-174 mg/L (hardness), 174-202 mg/L (alkalinity), 7.5-7-7 (pH), 300-311 µMhos/cm (conductivity)

Experimental Test Dates: Initiation - March 2, 1990; Termination - March 23, 1990

Length of Study: 21-Days

Results: 21-Day EC50 = 0.12 µg/L as Sn (95% C.I. = 0.11 - 0.15 µg/L); 21-Day NOEC =0.08 µg/L as Sn; 21-Day LOEC =0.14 µg/L as Sn; 21-Day Dose-Response Slope =5.6; 21-Day MATC =0.11 µg/L

Test Species: Daphnia magna (Source: ABC Laboratories in-house culture)

Age of Organisms at Study Initiation: Neonates (<24-hours old)

Description of key information

First instar Daphnia were exposed to five nominal concentrations of 0.13, 0.25, 0.5, 1.0 and 2.0 µg/L tributyltinoxide (0.05, 0.10, 0.20, 0.40 and 0.80 µg/L of tin) for 21-days and observed for toxicity. Statistical analysis of survival, reproduction, length of time to first brood and adult length identified 0.08 µg/L as a no-effect concentration (NOEC) for tributyltin in a 21 day toxicity study with Daphnia magna (first instar). The lowest-effected concentration (LOEC) for tributyltin was identified as 0.14 µg/L. All instar produced during the study were observed to be normal.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.08 µg/L

Additional information

The key study, Lochhaas, C. (1990), though not performed to a standardised guideline, was performed to good scientific principles and in compliance with GLP. The study was considered reliable with acceptable restrictions and deemed adequate for assessment. The study was assigned a reliability score of 2.