Tin dioxide

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 16th march 2012 to 16th April 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study in compliance with international recognized guidelines

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material:
2012-000203
- Expiration date of the lot/batch:
07/02/2013, W0167
- Purity test date:
> 99.9%, 23/01/2011



INFORMATION ON NANOMATERIALS
- Chemical Composition:
Tin Dioxide
- Density:
6.936 g/cm³
- Particle size & distribution:
10-100 nm; 78
- Specific surface area: 7.4293 ± 0.0132 m²/g

Analytical monitoring:

not specified

Details on sampling:

The sludge was used one day after collection. it was settled for about 10 minutes and the uppor layer with finer solids decanted. before starting the test, it was washed three times with chlorine free tap water by centrifugation (10 min at 3000 rpm). After centrifuging, the supernatant was decanted and discarded and the sludge was resuspended in chlorine free tap water. this procedure was repeated twice.

Vehicle:

no

Details on test solutions:

Test mixtures containing water, synthetic wastewater and the test item were prepared to obtain different nominal concentrations of the test item. All test item concentrations, 1000, 100 and 10 mg/L were weighted directly into the test vessels.
The test items 1000 and 100 mg/L were performed with a final volume of 500 mL whereas 10 mg/L test item concentration was performed with a final volume of 1000 ml.
the abiotic control was prepared with the highest test item concentration water and synthetic wastewater.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge from the minucipal wastewater treatment plant of Pforzheim, Germany, collected from the aeration tank, was used as the inocolum for the test.

Test type:

static

Water media type:

freshwater

Total exposure duration:

3 h

Post exposure observation period:

no data

Hardness:

no data, composition according to the guideline.

Test temperature:

17.8 - 21.7°C ( measured during O2 determination at 30 min and 3 h after start of respiration)

pH:

7.38 - 8.13

Dissolved oxygen:

no data, the study determines the consumption of oxygen see "details on test condistions"

Salinity:

no data, composition according to the guideline.

Nominal and measured concentrations:

A range finding test was performed with concentrations from 10, 100 and 1000 mg/L in a limit test design. The highest concentration of 1000 mg/L was tested in three replicates whereas 10 and 100 mg/L were tested in one replicate.
Since no toxic effect were observed in the range-finding test which was performed in a limit test design, no further experimental testing was necessary

Details on test conditions:

Synthetic wastewater and the corresponding test solutions wre filled up with water to a final volume of approximately 250 ml for the test item concentrations 100 and 1000 mg/L and up to 500 ml for the 10 mg/l test item concentration.

The reference assay with different concentrations (e.g. 2,5,10 and 25 mg/l) was set up in the same way as the test item concentration 1000 and 100 mg/L. The abiotic control was performed without microbial inocolum but with the highest test item concentration and filled up with water to a final volume of 250 ml. The blank control was set up in the same way as the test item concentrations 1000 and 100 mg/l but without test item.

Aeration was performed for some minutes to saturate the solution with O2 above 60-70%. At T0= h 250ml of microbial inocolum were added except the 10 mg/l test item concentration which was inoculated with 500 ml.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorphenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The coefficient of variation of the control for total oxygen uptake were 8% and 3% after 30 min and 3h respectively and did not exceed 30%.

Results with reference substance (positive control):

four concentration of 3,5-dichlorophenol as toxic reference were also tested to demonstrate the sensitivity of the test system.
The EC50 for 3,5-Dichlorophenol (DCP) was determined to be in a range of 10 to 25 mg/L after 30 min and 5 mg/L after 3 hours. These values were whithin the recommended range of 2 to 25 mg/L.

Reported statistics and error estimates:

The NOAEC was determined using the t-Test pooled. P-values below 0.05 showed statistically significant differences to the control. A test for normality was performed.

Validity criteria fulfilled:

yes

Conclusions:

The effect of the test item on microrganisms of an aerobic treatment plant was tested using the activated sludge respiration test.
The test item tin dioxide had no toxic effects on the oxygen uptake at the highest concentration tested (1000 mg/l). Hence, the EC50 of tin dioxide is > 1000 mg/l and the NOAEC is 1000 mg/l.