Reaction mass of disodium hexatitanium tridecaoxide and disodium trititanium heptaoxide

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Activated sludge from a real wastewater treatment plant in the Czech Republic was used for testing the toxicity of the NPs. The NPs were prepared in a commercial solution for machining. Generally it is assumed that the solution reduces the formation of large agglomerates of NPs. The stock solution was prepared for
each type of NP in a concentration of 25 g/L, mixed well and sonicated. The sample for measurement contained 96 mL of activated sludge (dry matter 1 g/L), 2 mL of the concentrated solution with NPs (final concentration 500 mg/L of NPs), and 2 mL of phosphate-buffered saline (PBS) and nutrients – acetate was
added at a concentration of 100 mg/L. The stock solution of NPs was subsequently diluted for final concentration of NPs 300 mg/L and 100 mg/L. The amount of solution with NPs added to the sample was the same. A control sample was prepared in the same way but instead of the solution of NPs a clear stabilized
solution (no NPs) was added into the sample of activated sludge.

GLP compliance:

not specified

Remarks:

There was no mention of GLP compliance in the paper given.

Test material

Test material information

Constituent 1

Reference substance name:

Titanium dioxide

EC Number:

236-675-5

EC Name:

Titanium dioxide

Cas Number:

51745-87-0

Molecular formula:

O2Ti

IUPAC Name:

Titanium dioxide

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

TiO2 NPs were supplied by ‘SkySpring Nanomaterials’, Inc., Houston, USA. The characteristics of the NPs are as follows: Titanium dioxide NPs (TiO2, anatase, 99.5%, Product #: 7910DL), size 10 – 25 nm, white nanopowder, specific surface area 50 – 150 m2 /g, morphology: flat texture of the surface with smooth edges

Sampling and analysis

Analytical monitoring:

not specified

Test organisms

Test organisms (species):

activated sludge

Details on inoculum:

A mixed culture of microorganisms of activated sludge from a real wastewater treatment plant in the Czech Republic was used for the experiments

Study design

Test type:

static

Total exposure duration:

40 h

Results and discussion

Effect concentrations

Duration:

40 h

Dose descriptor:

other: % maximum respiration

Effect conc.:

>= 100 - <= 500 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

Maximum respiration (%) for each concentration
Sample/Concentration of NPs 100 mg/L 300 mg/L 500 mg/L
Control (no NPs) 100 100 100
TiO2 66.7 86.8 100.4

Any other information on results incl. tables

The toxic effect of TiO2 NPs was observed using respirometric measurement, which showed the influence of the NPs on the cumulative oxygen consumption of the microorganisms in the activated sludge. The results of the respiration test showed that the toxic effect of NPs depends on their concentration. The TiO2 NPs at concentrations of 500 mg/L showed no decrease in the respiration of the microorganisms. The cumulative oxygen consumption is almost the same as in the control sample.

It was found that the lower concentration of TiO2 NPs has a greater toxic effect on the microorganisms. The maximum cumulative oxygen consumption is 100.4 % in the sample with a concentration of 500 mg/L of TiO2 NPs. When the lower concentration of 300 mg/L was used then the maximum respiration was reduced by 13.2 %. In the sample with the lowest tested concentration of 100 mg/L of TiO2 NPs respiration was reduced by 33.3 %.

Applicant's summary and conclusion

Conclusions:

The toxicity of NPs highly depends on their concentration. The results indicate that nanoparticles of TiO2 (500 mg/L) have almost no toxic effect on microorganisms in activated sludge. A reverse trend was observed in the samples with TiO2 NPs. The lower the concentration of TiO2 NPs (100 mg/L) the more
pronounced the decrease in respiration of microorganisms in the activated sludge.