Dibutyltin oxide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Aug - Sept 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

other: EC guideline 92/69/EEC

Qualifier:

according to guideline

Guideline:

other: Schering Method No. TXME. 656.2

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

- Concentrations: A suspension with a nominal loading of 100 mg di-n-butyltin oxide/l was stirred for 24 hours; The following diluations were used as further concentrations 1:2, 1:4, and 1:8

The substance concentrations was calculated on the basis of the molecular formula. The concentration of a separately prepared saturated solution was confirmed by ICP/MS analysis of tin.

Vehicle:

not specified

Details on test solutions:

For the stock solution, 100 mg of di-n-butyltin oxide were suspended in 1000 ml deminerlised water under constant stirring for approximately 24 hours. Thereafter, the suspension was filtered through a glassfibre filter. Aliquots of the solution were diluted 1:8, 1:4, and 1:2 with demineralized water to prepare the appropriate test concentrations.

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Solution 1:
160 mg potassium dihydrogenphosphate
8 mg ferrous (III) chloride x 6 H2O
10 mg titriplex III x 2 H2O
19 mg boric acid
42 mg manganese chloride x 4 H2O
dissolved in 100 ml demineralized water

Solution 2:
30 mg zinc chloride
15 mg cobalt chloride x 6 H2O
70 mg sodium molybdate x 2 H2O
dissolved in 100 ml demineralized water and thereafter 1:10 diluted

Solution 3:
10 mg copper chloride x 2 H2O
dissolved in 100 ml demineralized water and thereafter 1:10 diluted

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Green algae

- Source (laboratory, culture collection): Sammlung von Algenkulturen, Universitat Gottingen

- Method of cultivation: 10 ml of the concentrated nutrient solution were added to the 80 ml demineralized water. 10 ml of the inoculum were added. The pre-culture was incubated in triplicate for 72 hours in an incubator shaker apparatus. Thereafter the cell concentration of the algae was measured. The fastest growing culture of the three was used as a stock for inoculation. This stock was diluted to approximately 100000 cells per ml with demineralized water, ready to be used as inoculum.

Test type:

not specified

Water media type:

freshwater

Total exposure duration:

72 h

Post exposure observation period:

No further information required.

Hardness:

No information available.

Test temperature:

23 °C

pH:

7.7 to 8.2

Dissolved oxygen:

No information available.

Salinity:

No information available.

Nominal and measured concentrations:

0, 0.2, 0.4, 0.8 and 1.6 mg/L

Details on test conditions:

TEST SYSTEM

- Control end cells density: 269317 cells/ml
- No. of organisms per vessel: Range of means = 31880 to 39230 cells/ml at 24 hours; 141067 to 187800 cells/ml at 72 hours
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Detailed composition if non-standard medium was used:

NUTRIENT SOLUTION
Solution A:
572 mg boric acid
44 mg zinc sulphate x 7 H2O
16 mg copper sulphate x 5 H2O
12 mg cobalt nitrate x 6 H2O
3 mg ammonium molybdate x 4 H2O

Solution B:
200 mg ferric chloride x 6 H2O
225 mg titriplex III

Solution C:
147 mg calcium chloride x 2 H2O

Solution D:
9400 mg potassium nitrate
950 mg magnesium sulphate x 7 H2O
565 mg potassium dihydrogenphosphate

5 ml of solution A, B, and C were added to solution D and filled up to 6 l with demineralized water

TEST MEDIUM / WATER PARAMETERS

- Total organic carbon: 0.79 mg TOC corresponding to 2.05 mg di-n-butyltin oxide/l

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Coulter Counter - measured after 24, 48, and 72 hours of incubation

Reference substance (positive control):

not specified

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 1.6 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 1.6 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

Di-n-butyltin oxide had an inhibitory effect on the growth of the algae at all chosen concentrations. The inhibition was already observed after 24 hours. However, it did not show a concentration dependence and did not exceed 40% and 20 % for biomass integral and growth rate, even after 72 hours. Therefore the observed effects were regarded as not being substance-related.

Reported statistics and error estimates:

The percentage inhibition of the cell growth at each substance concentration was calculated as the difference between the area under the control growth curve and the area under the growth curve at each test substance concentration.

Concentrations of di-n-butyltin oxide (mg/l)	Inhibition in percent
	Biomass (integral)	Growth Rate
0	0	0
0.2	24.74	12.02
0.4	29.56	12.66
0.8	39.61	19.9
1.6	26.29	13.26

Validity criteria fulfilled:

not specified

Conclusions:

The observed reduction of growth of the algae during di-n-butyltin oxide exposure was not very prominent and showed no concentration-dependence. It was therefore interpreted as not being substance-related. The biomass and growth rate could not be calculated. Consequently, according to the author, a saturated solution of di-n-butyltin oxide is not toxic to the green algae.

Executive summary:

Di-n-butyltin oxide was incubated in an aqueous solution including nutrients with an algae population of Scendesmus subspicatus for a test duration of 72 hours. The increase in biomass and growth rate of each concentration were compared to those of the controls, and the inhibition was calculated. The observed reduction in growth was not prominent and showed no concentration-dependence. It was therefore interpreted as not being substance-related. the biomass and growth rates could not be calculated. A saturated solution of di-n-butyltin oxide is not toxic to the green algae Scenedesmus subspicatus.

Description of key information

The following study has been submitted to address the toxicity to algae and cyanobacteria endpoint:

 

Steger-Hartmann T (1999). Growth inhibition test of di-n-butyltin oxide (ZK 26385) on the green algae Scenedesmus subspicatus. Testing laboratory: Schering AG, Experimentelle Toxikologie, D-13342 Berlin, Germany. Report no.: IC28. Owner company: Schering AG, Experimentelle Toxikologie, Berlin, Germany. Study number: TXST19980234. Report date: 1999-02-17. The EC50 was found to be 1.6 mg/L.

 

The study has been allocated a Klimisch score of 2 and is the key study for this endpoint.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.6 mg/L

Additional information

Steger-Hartmann T (1999) was provided as the key study for the endpoint. The study was performed in accordance with the OECD Guideline 201. The study was therefore assigned a reliability score of 2 and considered adequate for the assessment of the toxicity of the test material to algae. Di-n-butyltin oxide was incubated in an aqueous solution including nutrients with an algae population of Scendesmus subspicatus for a test duration of 72 hours. The increase in biomass and growth rate of each concentration were compared to those of the controls, and the inhibition was calculated. The observed reduction in growth was not prominent and showed no concentration-dependence. It was therefore interpreted as not being substance-related. The biomass and growth rates could not be calculated. A saturated solution of di-n-butyltin oxide is not toxic to the green algae Scenedesmus subspicatus.