Titanium carbide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 500 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by sonication, particle size: 100-500 nm

Basis for effect:

mobility

Remarks on result:

other: 9 % effect at 500 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

1 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Remarks on result:

other: 6 % effect

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

2 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Remarks on result:

other: 9 % effect

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

5 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

10 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Details on results:

Test 1 - Sonicated TiO2 samples:
None of the experiments involving sonicated TiO2 showed mortality greater than 9%. The control showed 2% mortality. The highest mortality occurred at a concentration of 350 ppm. The highest and lowest concentrations (500 and 50 ppm, respectively) both had 9% mortality. The lowest mortality was seen at a concentration of 300 ppm, at which fatalities were similar to those in the control (2%). The slope did not differ significantly from zero; therefore, the LOEC and NOEC were incalculable.

Test 2 - Filtered (THF) samples:
Exposure to filtered TiO2 concentrations ranging from 0 to 10 ppm caused an increase in mortality with an increase in concentration.
Test solutions containing filtered and THF-treated TiO2 particles and test solutions containing filtered and deionized H2O-treated TiO2 particles showed no statistical difference in survivability. Adding THF to MHRW and evaporating it out of solution did not significantly affect survival of daphnids.

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

Mortality was analysed regarding concentration using a probit method analysis (U.S. EPA Probit Analysis Program, Ver 1.5; Environmental Monitoring Systems Laboratory, Cincinnati, OH, USA). This allowed the median LC50 to be calculated. Mean and variance also were calculated among treatments using analysis of variance (ANOVA; SigmaStat Software, Ver 3.10; Systat Software; Point Richmond, CA, USA).
The LOEC and NOEC were then calculated using Dunnett's test (Sigma Plot, Ver 9.0; Systat Software).

Validity criteria fulfilled:

not specified

Conclusions:

Test 1 - Sonicated TiO2 samples:
Reliable study according to US EPA 2024 test guideline. Less than 50% effect was observed at the highest test concentration (500 mg TiO2/L).
Test 2 - Filtered (THF) samples:
Results are not considered relevant for environmnetal exposure due to the dispersion treatment of TiO2 before the toxicity test.

Executive summary:

In a study according to U.S. EPA standard operating procedure 2024 the 48 hr acute toxicity of TiO2 to Daphnia magna was studied under static conditions. Daphnids were exposed to different TiO2 samples in two tests. TiO2 mixtures were prepared either by sonication or placement in tetrahydrofuran (THF) and filtration.  

 

The way the particles were prepared, however, impacted their toxicity. Exposure to concentrations of unfiltered, sonicated TiO2 powder that contained both micro- and nanoparticles did not cause mortality like that of the filtered nanoparticle solutions. Instead, solutions of sonicated TiO2 caused very few fatalities. Concentrations of TiO2 that were 25- and 30-fold greater than the concentrations that caused mortality in trials with filtered particles showed no difference in mortality from that of the control. Even concentrations as high as 500 ppm caused only 9% mortality. The transmission-electron micrograph (TEM) images of the solutions show that the particles in the filtered solutions are not clumped like those in the sonicated solutions. In the filtered TiO2 solution, only the smaller particles were retained in the aqueous solution (filter size, 200 nm), and the average particle diameter was 30 nm. In the sonicated TiO2 solution, however, all sizes of clumped particles remained, ranging from 100 to 500 nm in diameter. If Daphnia magna encounter an individual nanoparticle, the reactivity may be greater than that of a nanoparticle reacting with many others in larger clumps.

 

The results obtained with the filtered (THF) TiO2 samples are not considered relevant for environmental exposure due to the dispersion treatment of TiO2 before the toxicity test.

This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Justification for type of information:

Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach (see IUCLID section 13.2).

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

reference to same study

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- As nanoparticulate TiO2 did not show any toxic effects in the test the dissolved metal concentration was not determined.
- Aggregation increased mean particle diameter and much of the particle mass was present as larger aggregates (primary particle size distribution: 20.5 +/- 6.7 nm; major particle diameters observed in suspension: 687.5 nm).

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

EC50 values were calculated using the trimmed Spearman-Karber method.

Validity criteria fulfilled:

yes

Remarks:

all control survival was > 90 %

Conclusions:

Under the conditions of this test the EC50 was determined to be > 10 mg/L.

Executive summary:

The 48 hr acute toxicity of TiO2 nanoparticles (primary particle size distribution: 20.5 +/- 6.7 nm) to adult Daphnia pulex was studied under semi-static conditions.  Daphnids were exposed to 0 (control) and 10 mg/L nominal concentration. Immobilization were observed daily. Major particle diameters observed in suspension were 687.5 nm. The 48 hour EC₅₀ was > 10 mg/L (nominal concentration). 

 

The 48 hr NOEC based on immobilization was 10 mg/L (nominal concentration).

 

This information is used in a read-across approach in the assessment of the target substance. 

 

For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Justification for type of information:

Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach (see IUCLID section 13.2).

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

reference to same study

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- As nanoparticulate TiO2 did not show any toxic effects in the test the dissolved metal concentration was not determined.
- Aggregation increased mean particle diameter and much of the particle mass was present as larger aggregates (primary particle size distribution: 20.5 +/- 6.7 nm; major particle diameters observed in suspension: 687.5 nm).

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

EC50 values were calculated using the trimmed Spearman-Karber method.

Validity criteria fulfilled:

yes

Remarks:

all control survival was > 90 %

Conclusions:

Under the conditions of this test the EC50 was determined to be > 10 mg/L.

Executive summary:

The 48 hr acute toxicity of TiO2 nanoparticles (primary particle size distribution: 20.5 +/- 6.7 nm) to neonate Cerodaphnia dubia (< 24 h) was studied under semi-static conditions.  Cerodaphnids were exposed to 0 (control) and 10 mg/L nominal concentration. Major particle diameters observed in suspension were 687.5 nm. Immobilization was observed daily. 

 

The 48 hour EC₅₀ was > 10 mg/L (nominal concentration). 

The 48 hr NOEC based on immobilization was 10 mg/L (nominal concentration).

 

This information is used in a read-acorss approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

 

 

Reference 4

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Microscopic examinations of daphnids following exposure to TiO2 suspensions showed that the daphnids filtered the TiO2 particles, passing it to the gut.

Results with reference substance (positive control):

Not applicable.

Validity criteria fulfilled:

not specified

Conclusions:

Reliable study according to OECD 202 test guideline. Less than 50% effect was observed at the highest test concentration (1000 mg TiO2/L).

Executive summary:

In a study according to OECD Guideline 202 the 48 hr acute toxicity of TiO2 to Daphnia magna was studied under static conditions. Daphnids were exposed to 1000 mg/L TiO2 (nominal concentration) in two replicates and immobilization was observed. The 48 hour EC₅₀was > 1000 mg/L. 

 

Microscopic examinations of daphnids following exposure to TiO2 suspensions showed that the daphnids filtered the TiO2 particles, passing it to the gut.

 

Based on the results of this study, TiO2 would  be classified as non-toxic to Daphnia magna in accordance with the GHS classification system.

 

 

This information is used in a read-across approach in the assessment of the target substance. For justification of read-acorss please refer to the attached read-across approach report (see IUCLID seciont 13).

 

Reference 5

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

reference to same study

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

fine TiO2 (particle size 380 nm)

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

sub-pigmentary TiO2 (particle size 140 nm)

Basis for effect:

mobility

Details on results:

48-h exposure of daphnids to fine or ultrafine TiO2 particle nominal concentrations of 0, 0.1, 1.0, 10, and 100 mg/L resulted in 0, 0, 0, 10, and 10% or 0, 0, 0, 10, and 0% immobility, respectively.

Results with reference substance (positive control):

Not applicable.

Validity criteria fulfilled:

yes

Remarks:

All water quality parameters were within acceptable limits

Conclusions:

Reliable study according to OECD 202 test guideline. All water quality parameters were within acceptable limits during the exposure (however no data on water characteristics reported). Only one test chamber per concentration tested. Less than 50% effect was observed at the highest test concentration (100 mg TiO2/L).

Executive summary:

Fine TiO2 (380 nm) and ultrafine TiO2 (140 nm) was tested in an acute toxicity study using Daphnia magna as test organisms. The tests was conducted in accordance with OECD Guideline 202. The test substance were used at nominal test concentrations of 0 (control), 0.1, 1.0, 10, 100 mg TiO2/L. Daphnids were exposed for 48 h.

 

The 48-h EC50 for both fine and ultrafine TiO2 were determined to be > 100 mg/L.

This information is used in a read-across approach in the assessment of the target substance. For justification of read-acorss please refer to the attached read-across report (see IUCLID section 13).

Reference 6

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Key result

Duration:

7 d

Dose descriptor:

LC50

Effect conc.:

0.979 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 95 % CL: 0.707-1.355 mg/L

Key result

Duration:

7 d

Dose descriptor:

LC50

Effect conc.:

< 0.272 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

In addition to the experiments in soft water, a second experiment in tab water was conducted. The LC50 of Ti under this conditions was determined to be greater than the highest concentration tested (3.15 mg/L).

Validity criteria fulfilled:

not specified

Conclusions:

The 7-d LC50 of Ti (element) to Hyalella azteca was determined to be 0.979 mg Ti/L (nominal) or <0.272 mg Ti/L (measured).

Executive summary:

The toxicity of all atomically stable metals in the periodic table was determined in one-week toxicity tests conducted using the freshwater amphipod Hyalella azteca.

Instead of testing one or a few metals at a broad concentration range, a high amount of substances were tested simultaneously at one concentration only (either the maximum concentration of interest, or a concentration close to the predicted toxic threshold) in the first experiment. Depending on whether mortality was observed the concentration of each substance was then either increased or decreased in the next experiment. This procedure was repeated until the toxic range was covered for each substance, or until the substance was demonstrated to cause less than 50% mortality at the highest concentration of interest.

The number of test concentrations was reduced from the usual 10, 18, 32, 56, 100 logarithmic series to 10, 32, 100.

This provided a less precise estimate of the LC50, but allowed determination of LC50s for a much larger number of metals within a shorter time frame.

The 7-d LC50 of Ti (element) to Hyalella azteca in soft water was determined to be 0.979 mg Ti/L (nominal) or <0.272 mg Ti/L (measured).

 

This information is used in a read-across approach in the assessment of the target usbstance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 7

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

ca. 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

No toxicity could be observed up to 20,000 mg/L (incubation in the dark).

Validity criteria fulfilled:

not specified

Conclusions:

20,000 mg nano TiO2/L induced no mortility in T. platyrus

Executive summary:

The 48-h toxicity of nano TiO2 (25 -70 nm) to T. platyrus was investigated according to Standard Operational Procedures of Thamnotoxkit F TM magna (1995). 20,000 mg nano TiO2/L induced no mortality.

This information is used in a readacross approach in the assessment of the target substance. For justification o f read-across please refer to the attached read-across report (see IUCLID section 13). 

 

Reference 8

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Key result

Duration:

48 h

Dose descriptor:

other: EC60

Effect conc.:

ca. 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

20,000 mg nano TiO2/L induced 60% mortality. No toxicity could be observed at lower levels (incubation in the dark).
However, preliminary investigations (data not reported) demonstrated that illumination (8000 lux, cold white fluorescent lamp) during the test increased toxicity of nano TiO2 for daphnids about 30%.

Validity criteria fulfilled:

not specified

Conclusions:

20,000 mg nano TiO2/L induced 60% mortality. No toxicity could be observed at lower levels (incubation in the dark).

Executive summary:

The 48-h toxicity of nano TiO2 (25 -70 nm) to Daphnia magna was investigated according to Standard Operational Procedures of Daphtoxkit F TM magna (1996).

20,000 mg nano TiO2/L induced 60% mortality. No toxicity could be observed at lower levels (incubation in the dark).

This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 9

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 1) Lecane hamata

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

15.6 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

morphology

Remarks on result:

other: 1) Lecane hamata, 95% CI: 9.1 - 22.0 mg/l

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 2) Lecane luna

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

11.9 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mortality

Remarks on result:

other: 2) Lecane luna, 95 % Cl: 7.0 - 18.1 mg/l

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

< 5 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 3) Lecane quadridentata

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

8.5

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 3) Lecane quadridentata, 95% CI: 2.26 - 15.8 mg/l

Validity criteria fulfilled:

not specified

Conclusions:

The 48-h LC50 for Lecane hamata, Lecane luna, and Lecane quadridentata are 15.6 mg Ti/L, 11.9 mg Ti/L and 8.5 mg Ti/L, respectively.

Executive summary:

The authors investigated the influence of Ti (speciation not specified) to neonate females of three rotifer species.

24 h prior to the start of the experiments asexual eggs of three rotifer species Lecane hamata, Lecane luna, and Lecane quadridentata

 

This information is used in a read across approah in the assesssment of the target substance. For justification of read-across please refer to the attached read-across report (See IUCLID section 13). 

were collected from ovigerous asexual females grown at 25 °C in Petri dishes with EPA medium (U.S. EPA, 1985). The eggs were hatched by exposing them to 25 °C and continuous light for 24h. For the experiment 24-well polystyrene plates were used. Ten neonate females per well were exposed to the test titanium (adsorption standard solution) for total duration of 48h (endpoint mortility). The test volume per well is 0.5 ml. Exact test concentrations were not reported. The 48-h LC50 (nominal concentrations) for Lecane hamata, Lecane luna, and Lecane quadridentata are 15.6 mg Ti/L, 11.9 mg Ti/L and 8.5 mg Ti/L, respectively, demonstrating different susceptibility to the test chemical.

Reference 10

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: particle size: 50-150 nm

Details on results:

- Toxic effects could not be observed, probably due to rapid aggregation and/or coagulation of TiO2 nanoparticles (aggregation/coagulation was confirmed by analytical measurements).
- Dilution experiments demonstrate that formation of larger particles and settling of the lager particles under normal gravitation or centrifugation occurred to a greater extent in natural (pond) water than in ultrapure (Milli-Q) water.

Validity criteria fulfilled:

not applicable

Conclusions:

TiO2 nanoparticle (50-150 nm) are not toxic to Chydorus sphaericus under the conditions of the Chydotox test (EC50 (48 h) > 100 mg TiO2/L).

Executive summary:

The toxicity of TiO2 nanoparticles (50 -150 nm) at 100 mg/L to Chydorus sphaericus was tested in a Chydotox test. Invertebrates were exposed to the test chemical for a total duration of 48 h without feeding. Moartility counts were conducted at t=0h and t=48h. During the test TiO2 nanoparticles aggregated and were present in form of relatively large particles.

Under the conditions of the Chydotox test no mortality was observed. 

This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 11

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Duration:

24 h

Dose descriptor:

NOEC

Effect conc.:

8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: Experiment 2 - examination of concentration- and exposure time-related toxicities

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: Experiment 2 - examination of concentration- and exposure time-related toxicities

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

3.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: 95%, CI: 5.3–2.3; experiment 2 - examination of concentration- and exposure time-related toxicities

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.73 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: 95%, CI: 0.78–0.68; experiment 2 - examination of concentration- and exposure time-related toxicities

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.24 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: 95%, CI: 0.22–0.26; recalculation of 96-h EC50 based on findings of experiment 3

Details on results:

Experiment 1 - particle size dependency of TiO2 toxicity:
- No immobilisation after 24 and 48 h in test suspensions of ~100 nm and ~200 nm (test concentration: 2 mg/L)
- ~100 nm:
* 72 h: 66 % immobilisation
* 96 h: 100 % immobilisation
- ~200 nm:
* 72 h: 3 % immobilisation
* 96 h: 57 % immobilisation

Experiment 2 - Time and dose dependency of nTiO2 toxicity and dissipation
- Tendency for nTiO2 to form agglomerates and bind to organic and inorganic surfaces => dissipation from the water phase (see Experiment 3)

Experiment 3 - nTiO2 dissipation from medium and photographic monitoring
- Fast decline of measurable nTiO2 concentrations at all nominal concentrations
- Faster dissipation from the water phase with higher initial concentrations compared to lower concentrations

Experiment 4 - daphnia molting
a) Mechanism of toxicity – biological surface coating
- High tendency of nTiO2 to bind to organic surfaces => steadily growing layer of TiO2 on daphnids within the 96-h exposure period (= “biological surface coating”; TiO2 identified by SEM-EDX images)
- Visible within the first 24 h of exposure; complete disappearance with the first molting (shedding of shell)
- Biological surface coating reoccurred within 1 h after the first molting and continued steadily during the 96-h exposure period..
- Highest adhesion to filtering apparatus showed this particle adhesion phenomenon to a greater extent

b) Mechanism of toxicity – molting inhibition
- All animals (age ≤ 6 h at test start) completed the first molting within 36 h; no substantial differences between control and test animals (2 mg/L nTiO2,~100 nm)
- Control animals: second molting occurred in 100%, between 66 and 78 h after the start of the test
- Test animals: delay in molting and significantly (p = 0.0065) lower molting success of only 10%.

Reported statistics and error estimates:

Statistical analyses were carried out using the statistical software package R (version 2.10.1.). EC50 values were calculated using the drc package. Because the data from the size and molting experiments were not normally distributed, two sided Wilcoxon rank tests were performed, and a difference was considered to be statistically significant at p-values <0.05.

Validity criteria fulfilled:

yes

Conclusions:

No effects on daphnids at all concentrations tested after standard exposure duration of 48-h.

Executive summary:

A test according to OECD 202 was conducted with suspensions of non-nanosize TiO2 (~200 nm) and nanosize TiO2 (~ 100 nm) in order to investigate the effects on Daphnia magna in four different experiments. Experiments were conducted beyond the standard exposure duration of 48 h and effects were also investigated after 72h and 96 h.

 

In experiment 1 size-related toxicity of TiO2 was investigated. The test suspensions of ~200 nm and ~100 nm in mean diameter were applied at a single concentration of 2 mg/L for a total exposure duration of 96 h.

No immobilisation occurred after 24 and 48 h in both test suspensions of ~100 nm and ~200 nm. However, after 72 h and 96 h nanosize TiO2 particles (~ 100 nm) had a significantly higher effects on daphnids (66 % and 100 % immobilisation after 72 h and 96 h, respectively) compared to the ~200 nm suspension (3 % and 57 % immobilisation after 72 h and 96 h, respectively).

 

In experiment 2 concentration- and exposure time-related toxicities were evaluated. In this experiment the ~100 nm nano-TiO2 test suspension was used at concentrations of 0 (control), 0.5, 1, 2, 4 and 8 mg/L. Daphnids were exposed for up to 96 h.

No toxicity was observed at standard test durations at all test concentrations. Thus, the 48-h NOEC is 8 mg/L nano-TiO2. However, toxicity increases with increasing exposure duration. The calculated 72-h and 96-h EC50 values were 3.8 mg/L (95%; CI: 5.3–2.3) and 0.73 mg/L (95%; CI: 0.78–0.68), respectively.

Experiment 3 (see below) revealed the tendency for nano-TiO2 to form agglomerates and bind to organic and inorganic surfaces, resulting in dissipation from the water phase. Thus, the authors calculated time weighted average (TWA) values in the aqueous phase and recalculated the 96-h EC50 value of nano-TiO2 to be 0.24 mg/L (95%; CI: 0.22–0.26), based on measured aqueous-phase concentrations.

 

In the third experiment (experiment 3) the dissipation of nano-TiO2 from medium was investigated by analytical measurement accompanied by photographic monitoring. In this experiment the substance was again tested at concentrations of 0.5, 1, 2, 4, 8 mg/L. Triplicate samples from each concentration were taken after 0, 1, 2, 3, 6, 12, 24, 48, 72 and 96 h and were analyzed for the Ti concentration.

This experiment could demonstrate the tendency for nano-TiO2 to form agglomerates and bind to organic and inorganic surfaces, thus resulting in dissipation of TiO2 from the water phase. Measurable nano-TiO2 concentrations decline fast at all nominal concentrations, however, dissipation from the water phase with higher initial concentrations is faster than compared to lower initial concentrations.

 

In experiment 4 effects of nano-TiO2 (concentration: 2 mg/L) on molting daphnia were determined. The exposure period was 96 h.

Nano-TiO2 has a high tendency to bind to organic surfaces which results in steadily growing layers of TiO2 on the daphnids within the 96-h exposure period (= “biological surface coating”; TiO2 identified by SEM-EDX images). This biological surface coat completely disappeared with the first molting (shedding of shell) but reoccurred within 1 h after the first molting and continued steadily during the 96-h exposure period, causing a delay in molting and significantly (p = 0.0065) lower molting success of only 10% compared to the control.

This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 12

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

disregarded due to major methodological deficiencies

Justification for type of information:

For details and justification of read-across please refer to the report attached in section 13 of IUCLID.

Reason / purpose for cross-reference:

reference to same study

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

mainly anatase, particle-size 25 nm; non-illuminated

Basis for effect:

mortality

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

100 % anatase, particle size 100 nm, non-illuminated

Basis for effect:

mortality

Details on results:

In the control (illuminated), maximally 10% of the daphnids were immobilized at the end of the test.

Phototoxic effects have repeatedly been observed and reported for TiO2. As this effect is not known for TiC the results regarding ecotoxiclogical effects on daphnids from illuminated TiO2 solutions are not reported for the REACH registration of TiC.

Validity criteria fulfilled:

yes

Remarks:

Less than 10 % immobilization in control vessels.

Conclusions:

No clear concentration-effect dependence.

Executive summary:

The effects of nanoscale TiO2 particle (25 nm and 100 nm) on Daphnia magna was investigated in a 48 -h experiment according to OECD 202. TiO2 was used at nominal concentrations of 0, 1, 1.5, 2, 2.5 and 3 mg TiO2/l. Actual concentration were not verified by measurements.

A clear concentration-effect dependence could not be observed.

This information is used ina read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 13

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

No information on form of Ti added, confounding effect of acid in AAS standard. Various concentrations were not tested in the same batch. Justification for read-across: Due to similar or lower transformation/dissolution results for titanium carbide (the target substance) than titanium (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Qualifier:

no guideline followed

Principles of method if other than guideline:

The toxicity of all atomically stable metals in the periodic table was determined in one-week toxicity tests conducted using the freshwater amphipod Hyalella azteca.
Instead of testing one or a few metals at a broad concentration range, a high amount of substances were tested simultaneously at one concentration only (either the maximum concentration of interest, or a concentration close to the predicted toxic threshold) in the first experiment. Depending on whether mortality was observed the concentration of each substance was then either increased or decreased in the next experiment. This procedure was repeated until the toxic range was covered for each substance, or until the substance was demonstrated to cause less than 50% mortality at the highest concentration of interest.
The number of test concentrations was reduced from the usual 10, 18, 32, 56, 100 logarithmic series to 10, 32, 100.
This provided a less precise estimate of the LC50, but allowed determination of LC50s for a much larger number of metals within a shorter time frame.

GLP compliance:

not specified

Analytical monitoring:

yes

Details on test solutions:

Diluted tap water: 10% tap water, 90% Milli-Q deionized water (0.25 mg/l DOC).

Test organisms (species):

other: Hyalella azteca

Details on test organisms:

TEST ORGANISM
- Common name: Hyalella
- Source: Valens Conservation Area (ON, Canada, 1985)
- Age at study initiation (mean and range, SD): 1-11 days
- Method of breeding: cultured as described in Borgmann et al.
- Feeding during test: yes
- Food type: Tetra-Min fish food flakes
- Amount: 2.5 mg at the beginning of the test and additional food (2.5 mg) was provided midweek.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Hardness:

measured hardness: 18 mg/l
carbonate alkalinity: 14 mg/l

Test temperature:

24 - 25 °C

pH:

7.37 - 8.27

Dissolved oxygen:

7 - 10 mg/l

Salinity:

Not applicable.

Nominal and measured concentrations:

Nominal: not reported
Measured dissolved concentrations (by ICP-MS): not reported

Details on test conditions:

TEST SYSTEM
- Test vessel: 500-ml polyethylene cups (snap-top specimen containers)
- Fill volume: 400 ml
- Aeration: no
- No. of organisms per vessel: 15
- No. of vessels per concentration (replicates): 2-5
- No. of vessels per control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- soft water consisting of 10% tap water (Lake ontario) and 90% Milli-Qt (Millipore, Bedford, MA, USA) deionized water

OTHER TEST CONDITIONS
- Photoperiod: 16:8 light/dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

Reference substance (positive control):

no

Key result

Duration:

7 d

Dose descriptor:

LC50

Effect conc.:

0.979 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 95 % CL: 0.707-1.355 mg/L

Key result

Duration:

7 d

Dose descriptor:

LC50

Effect conc.:

< 0.272 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

In addition to the experiments in soft water, a second experiment in tab water was conducted. The LC50 of Ti under this conditions was determined to be greater than the highest concentration tested (3.15 mg/L).

Validity criteria fulfilled:

not specified

Conclusions:

The 7-d LC50 of Ti (element) to Hyalella azteca was determined to be 0.979 mg Ti/L (nominal) or <0.272 mg Ti/L (measured).

Executive summary:

The toxicity of all atomically stable metals in the periodic table was determined in one-week toxicity tests conducted using the freshwater amphipod Hyalella azteca.

Instead of testing one or a few metals at a broad concentration range, a high amount of substances were tested simultaneously at one concentration only (either the maximum concentration of interest, or a concentration close to the predicted toxic threshold) in the first experiment. Depending on whether mortality was observed the concentration of each substance was then either increased or decreased in the next experiment. This procedure was repeated until the toxic range was covered for each substance, or until the substance was demonstrated to cause less than 50% mortality at the highest concentration of interest.

The number of test concentrations was reduced from the usual 10, 18, 32, 56, 100 logarithmic series to 10, 32, 100.

This provided a less precise estimate of the LC50, but allowed determination of LC50s for a much larger number of metals within a shorter time frame.

The 7-d LC50 of Ti (element) to Hyalella azteca in soft water was determined to be 0.979 mg Ti/L (nominal) or <0.272 mg Ti/L (measured).

Reference 14

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

OECD guideline study without detailed documentation. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Principles of method if other than guideline:

In addition to the standrad test duration of 48 h investigations for daphnia toxicity were made after 72h and 96h.

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
From the nTiO2 powder additive free, size homogenized, stable suspensions were obtained by stirred media milling (PM2, Bühler AG, Switzerland) followed by centrifugation to remove residual coarse material.
Size distributions in undiluted, monodisperse stock suspensions showing average diameters of ~100 nm and ~200 nm were determined by dynamic light scattering (Delsa™ Nano C, Beckman Coulter, Krefeld) prior to each experiment (Table 1). Suspensions used were shown to be stable for over a month with a size variation of the average diameter below ± 5 %.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Source: Eurofins-GAB laboratories (Niefern-Oeschelbronn, Germany)
- Age at study initiation: < 24 h
- Method of breeding:
* Permanent culture in M4 medium, renewed three times a week
* 20±1°C
* Light:dark photoperiod = 16:8 h
* Feeding: green algae Desmodesmus sp. on a daily basis
- Feeding during test: no; hoewver, due to prolonged expsosure duration (96 h) neonates were fed algae with an equivalent of about 6 µg C per individual for 90 min prior to the test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Salinity:

not applicable

Nominal and measured concentrations:

Experiment 1 - investigation of TiO2 size-related toxicities: 2 mg/L (~100 nm and ~ 200 nm suspensions).
Experiment 2 - examination of concentration- and exposure time-related toxicities: 0 (control), 0.5, 1, 2, 4 and 8 mg/L (~100 nm suspension).
Experiment 3 - nTiO2 dissipation from medium and photographic monitoring: Test concentrations: 0.5, 1, 2, 4, 8 mg/L
Experiment 4 - daphnia molting: 2 mg/L (test suspension: nTiO2, ~100 nm)

Details on test conditions:

TEST SYSTEM (experiments 1 and 2)
- Test vessel: 150 mL glass beakers
- Type (delete if not applicable): open
- Fill volume: 50 ml
- Aeration: no
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod:
- Light intensity:

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mobility after 24, 48, 72, and 96 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations:
- Results used to determine the conditions for the definitive study:

Duration:

24 h

Dose descriptor:

NOEC

Effect conc.:

8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: Experiment 2 - examination of concentration- and exposure time-related toxicities

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: Experiment 2 - examination of concentration- and exposure time-related toxicities

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

3.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: 95%, CI: 5.3–2.3; experiment 2 - examination of concentration- and exposure time-related toxicities

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.73 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: 95%, CI: 0.78–0.68; experiment 2 - examination of concentration- and exposure time-related toxicities

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.24 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Remarks:

nTiO2 ~ 100 nm

Basis for effect:

mobility

Remarks on result:

other: 95%, CI: 0.22–0.26; recalculation of 96-h EC50 based on findings of experiment 3

Details on results:

Experiment 1 - particle size dependency of TiO2 toxicity:
- No immobilisation after 24 and 48 h in test suspensions of ~100 nm and ~200 nm (test concentration: 2 mg/L)
- ~100 nm:
* 72 h: 66 % immobilisation
* 96 h: 100 % immobilisation
- ~200 nm:
* 72 h: 3 % immobilisation
* 96 h: 57 % immobilisation

Experiment 2 - Time and dose dependency of nTiO2 toxicity and dissipation
- Tendency for nTiO2 to form agglomerates and bind to organic and inorganic surfaces => dissipation from the water phase (see Experiment 3)

Experiment 3 - nTiO2 dissipation from medium and photographic monitoring
- Fast decline of measurable nTiO2 concentrations at all nominal concentrations
- Faster dissipation from the water phase with higher initial concentrations compared to lower concentrations

Experiment 4 - daphnia molting
a) Mechanism of toxicity – biological surface coating
- High tendency of nTiO2 to bind to organic surfaces => steadily growing layer of TiO2 on daphnids within the 96-h exposure period (= “biological surface coating”; TiO2 identified by SEM-EDX images)
- Visible within the first 24 h of exposure; complete disappearance with the first molting (shedding of shell)
- Biological surface coating reoccurred within 1 h after the first molting and continued steadily during the 96-h exposure period..
- Highest adhesion to filtering apparatus showed this particle adhesion phenomenon to a greater extent

b) Mechanism of toxicity – molting inhibition
- All animals (age ≤ 6 h at test start) completed the first molting within 36 h; no substantial differences between control and test animals (2 mg/L nTiO2,~100 nm)
- Control animals: second molting occurred in 100%, between 66 and 78 h after the start of the test
- Test animals: delay in molting and significantly (p = 0.0065) lower molting success of only 10%.

Reported statistics and error estimates:

Statistical analyses were carried out using the statistical software package R (version 2.10.1.). EC50 values were calculated using the drc package. Because the data from the size and molting experiments were not normally distributed, two sided Wilcoxon rank tests were performed, and a difference was considered to be statistically significant at p-values <0.05.

Validity criteria fulfilled:

yes

Conclusions:

No effects on daphnids at all concentrations tested after standard exposure duration of 48-h.

Executive summary:

A test according to OECD 202 was conducted with suspensions of non-nanosize TiO2 (~200 nm) and nanosize TiO2 (~ 100 nm) in order to investigate the effects on Daphnia magna in four different experiments. Experiments were conducted beyond the standard exposure duration of 48 h and effects were also investigated after 72h and 96 h.

In experiment 1 size-related toxicity of TiO2 was investigated. The test suspensions of ~200 nm and ~100 nm in mean diameter were applied at a single concentration of 2 mg/L for a total exposure duration of 96 h.

No immobilisation occurred after 24 and 48 h in both test suspensions of ~100 nm and ~200 nm. However, after 72 h and 96 h nanosize TiO2 particles (~ 100 nm) had a significantly higher effects on daphnids (66 % and 100 % immobilisation after 72 h and 96 h, respectively) compared to the ~200 nm suspension (3 % and 57 % immobilisation after 72 h and 96 h, respectively).

In experiment 2 concentration- and exposure time-related toxicities were evaluated. In this experiment the ~100 nm nano-TiO2 test suspension was used at concentrations of 0 (control), 0.5, 1, 2, 4 and 8 mg/L. Daphnids were exposed for up to 96 h.

No toxicity was observed at standard test durations at all test concentrations. Thus, the 48-h NOEC is 8 mg/L nano-TiO2. However, toxicity increases with increasing exposure duration. The calculated 72-h and 96-h EC50 values were 3.8 mg/L (95%; CI: 5.3–2.3) and 0.73 mg/L (95%; CI: 0.78–0.68), respectively.

Experiment 3 (see below) revealed the tendency for nano-TiO2 to form agglomerates and bind to organic and inorganic surfaces, resulting in dissipation from the water phase. Thus, the authors calculated time weighted average (TWA) values in the aqueous phase and recalculated the 96-h EC50 value of nano-TiO2 to be 0.24 mg/L (95%; CI: 0.22–0.26), based on measured aqueous-phase concentrations.

In the third experiment (experiment 3) the dissipation of nano-TiO2 from medium was investigated by analytical measurement accompanied by photographic monitoring. In this experiment the substance was again tested at concentrations of 0.5, 1, 2, 4, 8 mg/L. Triplicate samples from each concentration were taken after 0, 1, 2, 3, 6, 12, 24, 48, 72 and 96 h and were analyzed for the Ti concentration.

This experiment could demonstrate the tendency for nano-TiO2 to form agglomerates and bind to organic and inorganic surfaces, thus resulting in dissipation of TiO2 from the water phase. Measurable nano-TiO2 concentrations decline fast at all nominal concentrations, however, dissipation from the water phase with higher initial concentrations is faster than compared to lower initial concentrations.

In experiment 4 effects of nano-TiO2 (concentration: 2 mg/L) on molting daphnia were determined. The exposure period was 96 h.

Nano-TiO2 has a high tendency to bind to organic surfaces which results in steadily growing layers of TiO2 on the daphnids within the 96-h exposure period (= “biological surface coating”; TiO2 identified by SEM-EDX images). This biological surface coat completely disappeared with the first molting (shedding of shell) but reoccurred within 1 h after the first molting and continued steadily during the 96-h exposure period, causing a delay in molting and significantly (p = 0.0065) lower molting success of only 10% compared to the control.

Reference 15

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

ASTM guidelines study, well documented. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: American Society for Testing and Materials: Standard guide for conducting acute toxicity tests on test materials with fishes, macro invertebrates and amphibians.

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
* 10 mg TiO2 nanomaterial were added to 10 ml of ultrapure Milli-Q water (Millipore, Billerica, MA, USA) and then sonicated with a probe sonicator for six half-second pulses at an output of 6 W and 22.5 kHz.
* The required amounts of TiO2 nanometal suspensions were added to each test chamber by pipetting (volume of stock solution never exceeded 0.5% of total exposure volume).
* Test solutions were prepared immediately before use to avoid particle dissolution, aggregation, and sedimentation.

Test organisms (species):

Ceriodaphnia dubia

Details on test organisms:

TEST ORGANISM
- Common name: Cerodaphnia dubia
- Source: before the start of the test neonates were seperated from the adult daphnids and fed
- Age at study initiation (mean and range, SD): neonates (< 24 h)
- Feeding during test: none
- Amount and type of food: 7 ml YCT (yeast, cerophyll, trout chow) media and 7 ml of algae (P. subcapitata) per liter of invertebrate culture.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

Not applicable.

Hardness:

142 ± 2 mg/l as CaCO3

Test temperature:

25 °C

pH:

8.2 ± 1

Dissolved oxygen:

8.5 - 8.9 mg/l

Salinity:

not applicable

Nominal and measured concentrations:

nominal, up to 10 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 ml beakers
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 200 ml of test solution in filtered (pore size, 0.45 µm) test water.
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod and light intensity: ambient light

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Beakers were monitored daily and dead individuals were removed. Death was assessed by lack of movement or response to gentle prodding.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: based on the results of an initial study, an additional experiment was conducted spanning the relevant concentration range. For definitive experiments, five concentrations were tested: The estimated median lethal concentration (EC50) from the preliminary experiment and 0.6-, 0.36-, 1.67-, and 2.78-fold the estimated EC50.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- As nanoparticulate TiO2 did not show any toxic effects in the test the dissolved metal concentration was not determined.
- Aggregation increased mean particle diameter and much of the particle mass was present as larger aggregates (primary particle size distribution: 20.5 +/- 6.7 nm; major particle diameters observed in suspension: 687.5 nm).

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

EC50 values were calculated using the trimmed Spearman-Karber method.

Validity criteria fulfilled:

yes

Remarks:

all control survival was > 90 %

Conclusions:

Under the conditions of this test the EC50 was determined to be > 10 mg/L.

Executive summary:

The 48 hr acute toxicity of TiO2 nanoparticles (primary particle size distribution: 20.5 +/- 6.7 nm) to neonate Cerodaphnia dubia (< 24 h) was studied under semi-static conditions.  Cerodaphnids were exposed to 0 (control) and 10 mg/L nominal concentration. Major particle diameters observed in suspension were 687.5 nm. Immobilization was observed daily. 

The 48 hour EC₅₀ was > 10 mg/L (nominal concentration). 

The 48 hr NOEC based on immobilization was 10 mg/L (nominal concentration).

 

Reference 16

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

ASTM guideline study, well documented. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: American Society for Testing and Materials: Standard guide for conducting acute toxicity tests on test materials with fishes, macro invertebrates and amphibians.

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
* 10 mg TiO2 nanomaterial were added to 10 ml of ultrapure Milli-Q water (Millipore, Billerica, MA, USA) and then sonicated with a probe sonicator for six half-second pulses at an output of 6 W and 22.5 kHz.
* The required amounts of TiO2 nanometal suspensions were added to each test chamber by pipetting (volume of stock solution never exceeded 0.5% of total exposure volume).
* Test solutions were prepared immediately before use to avoid particle dissolution, aggregation, and sedimentation.

Test organisms (species):

Daphnia pulex

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia pulex
- Source: cultures were maintained continuously for six months
- Age at study initiation (mean and range, SD): adult
- Feeding during test: none
- Food type: YCT (yeast, cerophyll, trout chow) media;
- Amount: ad libitum
- Frequency: daily

ACCLIMATION
- Acclimation period: no data

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

Not applicable.

Hardness:

142 ± 2 mg/l as CaCO3

Test temperature:

25 °C

pH:

8.2 ± 1

Dissolved oxygen:

8.5 - 8.9 mg/l

Salinity:

not applicable

Nominal and measured concentrations:

nominal, up to 10 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 ml beakers
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 200 ml of test solution in filtered (pore size, 0.45 µm) test water.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 14:10
- Light intensity: no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Beakers were monitored daily and dead individuals were removed. Death was assessed by lack of movement or response to gentle prodding.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: based on the results of an initial study, an additional experiment was conducted spanning the relevant concentration range. For definitive experiments, five concentrations were tested: The estimated median lethal concentration (EC50) from the preliminary experiment and 0.6-, 0.36-, 1.67-, and 2.78-fold the estimated EC50.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- As nanoparticulate TiO2 did not show any toxic effects in the test the dissolved metal concentration was not determined.
- Aggregation increased mean particle diameter and much of the particle mass was present as larger aggregates (primary particle size distribution: 20.5 +/- 6.7 nm; major particle diameters observed in suspension: 687.5 nm).

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

EC50 values were calculated using the trimmed Spearman-Karber method.

Validity criteria fulfilled:

yes

Remarks:

all control survival was > 90 %

Conclusions:

Under the conditions of this test the EC50 was determined to be > 10 mg/L.

Executive summary:

The 48 hr acute toxicity of TiO2 nanoparticles (primary particle size distribution: 20.5 +/- 6.7 nm) to adult Daphnia pulex was studied under semi-static conditions.  Daphnids were exposed to 0 (control) and 10 mg/L nominal concentration. Immobilization were observed daily. Major particle diameters observed in suspension were 687.5 nm. The 48 hour EC₅₀ was > 10 mg/L (nominal concentration). 

The 48 hr NOEC based on immobilization was 10 mg/L (nominal concentration).

 

Reference 17

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Documentation insufficient for assessment. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Qualifier:

according to guideline

Guideline:

other: Daphotoxkit F(TM) magna SOP, 1996

GLP compliance:

not specified

Analytical monitoring:

no

Details on test solutions:

Stock solutions of 40 g/L were prepared in Milli-Q water and were sonicated for 30 min. Solutions were stored in the dark at +4 °C. Before toxicity testing, stocks were vortexed

Test organisms (species):

Daphnia magna

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

20 °C

pH:

7.3 - 7.8

Nominal and measured concentrations:

Nominal total concentrations: up to 20,000 mg/L (no further details reported).

Details on test conditions:

All test compound were diluted in synthetic freshwater.
Test plates were incubated for 48 h at 20°C in the dark.
The test were performed in four replicates.

Key result

Duration:

48 h

Dose descriptor:

other: EC60

Effect conc.:

ca. 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

20,000 mg nano TiO2/L induced 60% mortality. No toxicity could be observed at lower levels (incubation in the dark).
However, preliminary investigations (data not reported) demonstrated that illumination (8000 lux, cold white fluorescent lamp) during the test increased toxicity of nano TiO2 for daphnids about 30%.

Validity criteria fulfilled:

not specified

Conclusions:

20,000 mg nano TiO2/L induced 60% mortality. No toxicity could be observed at lower levels (incubation in the dark).

Executive summary:

The 48-h toxicity of nano TiO2 (25 -70 nm) to Daphnia magna was investigated according to Standard Operational Procedures of Daphtoxkit F TM magna (1996).

20,000 mg nano TiO2/L induced 60% mortality. No toxicity could be observed at lower levels (incubation in the dark).

Reference 18

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Documentation insufficient for assessment. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Qualifier:

according to guideline

Guideline:

other: Standard Operational Procedures Thamnotoxkit F TM (1995).

GLP compliance:

not specified

Analytical monitoring:

no

Details on test solutions:

Stock solutions of 40 g/L were prepared in Milli-Q water and were sonicated for 30 min. Solutions were stored in the dark at +4 °C. Before toxicity testing, stocks were vortexed

Test organisms (species):

other aquatic crustacea: Thamnocephalus platyurus

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

25 °C

pH:

7.3 - 7.8

Nominal and measured concentrations:

Nominal total concentrations: up to 20,000 mg/L (no further details reported).

Details on test conditions:

All test compound were diluted in synthetic freshwater.
Test plates were incubated for 48 h at 25°C in the dark.
The test were performed in three replicates.

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

ca. 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

No toxicity could be observed up to 20,000 mg/L (incubation in the dark).

Validity criteria fulfilled:

not specified

Conclusions:

20,000 mg nano TiO2/L induced no mortility in T. platyrus

Executive summary:

The 48-h toxicity of nano TiO2 (25 -70 nm) to T. platyrus was investigated according to Standard Operational Procedures of Thamnotoxkit F TM magna (1995). 20,000 mg nano TiO2/L induced no mortality.

Reference 19

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

No clear concentration-effect dependence. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

ISO 6341 (Water quality - Determination of the Inhibition of the Mobility of Daphnia magna Straus (Cladocera, Crustacea))

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

DIN EN 38412-30

GLP compliance:

no

Analytical monitoring:

no

Details on test solutions:

The particles were cleaned according to the recommendation of one of the producers, i.e. stirring 10 g of the particles in 500 ml of deionised H2O for 19h at room temperature. In addition to the recommendation, a second cleaning step was performed. After centrifugation for 1h at 20,000g, the pellet was dispersed again in 500 ml of water, stirred for 24h, centrifuged and dried at 55°C.
Before starting the test, the dispersion was illuminated with simulated sunlight (300-800 nm). Since daphnids are damaged by stirring, no daphnids were added to the dispersion before pre-illumination. Sub-samples were transferred to the test vessels.

Test organisms (species):

Daphnia magna

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

20 ± 2 °C

pH:

No data.

Dissolved oxygen:

No data.

Salinity:

Not applicable.

Nominal and measured concentrations:

nominal: 0, 1, 1.5, 2, 2.5 and 3 mg TiO2/l.

Details on test conditions:

TEST SYSTEM
- Test vessel: glass Petri dishes (d: 55 mm)
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 20 ml
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates):
- No. of vessels per control (replicates): 3-5
- No. of vessels per vehicle control (replicates): 3-5

TEST MEDIUM / WATER PARAMETERS: not reported

OTHER TEST CONDITIONS
- Photoperiod: Day/night: 16h/8h.
- Light intensity: Diffuse light.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

mainly anatase, particle-size 25 nm; non-illuminated

Basis for effect:

mortality

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

100 % anatase, particle size 100 nm, non-illuminated

Basis for effect:

mortality

Details on results:

In the control (illuminated), maximally 10% of the daphnids were immobilized at the end of the test.

Phototoxic effects have repeatedly been observed and reported for TiO2. As this effect is not known for TiC the results regarding ecotoxiclogical effects on daphnids from illuminated TiO2 solutions are not reported for the REACH registration of TiC.

Validity criteria fulfilled:

yes

Remarks:

Less than 10 % immobilization in control vessels.

Conclusions:

No clear concentration-effect dependence.

Executive summary:

The effects of nanoscale TiO2 particle (25 nm and 100 nm) on Daphnia magna was investigated in a 48 -h experiment according to OECD 202. TiO2 was used at nominal concentrations of 0, 1, 1.5, 2, 2.5 and 3 mg TiO2/l. Actual concentration were not verified by measurements.

A clear concentration-effect dependence could not be observed.

Reference 20

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

OECD and US EPA guideline. Methods and results generally well documented. Only one (1000 mg TiO2/L) concentration tested. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

other: U.S. Environmental Protection Agency (660/3-75-009), 1975: Methods for Acute Toxicity Tests with Fish, Macro-invertebrates and Amphibians

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

Not applicable.

Vehicle:

no

Details on test solutions:

Public drinking water passed through particle filters, activated charcoal filters an aged a minimum of 48 h in a 200 gallon polyethylene holding tank.
A 1000 mg TiO2/L suspension was prepared with an ultrasonic water bath, allowed to settle for 24 h and the supernatans solution was withdrawn for testing.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Source: First instar Daphnia magna reared from at least third generations past acclimation adults
- Age at study initiation (mean and range, SD): neonates
- Method of breeding: according to culture techniques described by Goulden et al.
- Feeding during test: no data
- Food type: no data
- Amount: no data
- Frequency: no data

ACCLIMATION. no data

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

50-65 ppm CaCo3

Test temperature:

20±1°C

pH:

6.8 - 7.0

Dissolved oxygen:

No data.

Salinity:

Not applicable.

Nominal and measured concentrations:

Nominal total, 1000 mg/l titanium dioxide.

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 glass beaker containing 100 ml of sample.
- Type (delete if not applicable): open
- Aeration: no
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: public drinking water, passed through particle filters, activated charcoal filters, and aged at minimum of 48 h in a 200 gallon PE holding tank

OTHER TEST CONDITIONS
- Adjustment of pH: no data
- Photoperiod: 16:8
- Light intensity: no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): immobilization

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Microscopic examinations of daphnids following exposure to TiO2 suspensions showed that the daphnids filtered the TiO2 particles, passing it to the gut.

Results with reference substance (positive control):

Not applicable.

Validity criteria fulfilled:

not specified

Conclusions:

Reliable study according to OECD 202 test guideline. Less than 50% effect was observed at the highest test concentration (1000 mg TiO2/L).

Executive summary:

In a study according to OECD Guideline 202 the 48 hr acute toxicity of TiO2 to Daphnia magna was studied under static conditions. Daphnids were exposed to 1000 mg/L TiO2 (nominal concentration) in two replicates and immobilization was observed. The 48 hour EC₅₀was > 1000 mg/L. 

Microscopic examinations of daphnids following exposure to TiO2 suspensions showed that the daphnids filtered the TiO2 particles, passing it to the gut.

Based on the results of this study, TiO2 would  be classified as non-toxic to Daphnia magna in accordance with the GHS classification system.

 

Reference 21

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Test according to USEPA 2024 but without detailed documentation; no data on water properties reported. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Qualifier:

according to guideline

Guideline:

other: U.S. EPA standard operating procedure 2024

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
See "Details on test material".

Analytical monitoring:

yes

Vehicle:

yes

Details on test solutions:

Titanium dioxide mixtures were prepared either by sonication or placement in tetrahydrofuran (THF) and filtration:

1. Sonication:
Particles were placed in deionized H2O and then a bath sonicator for at least 30 min in an attempt to break them into small particles. The average final particle size is 100-500 nm (measured).

2. THF and filtration:
- 20 mg of TiO2 were placed in 200 ml of THF. This solution was sparged with nitrogen and left overnight in the dark on a stir plate. The solution was then filtered through a 0.22 µm nylaflo filter and 200 ml of deionized water were added. The suspension was placed in a Büchi rotovapor to evaporate THF, then removed and pipetted into an Erlenmeyer flask. This procedure was repeated twice. The final solution was then filtered through a 0,22 µm nylaflo filter and stored until usage.
- Average final particle size 30 nm (measured)

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Source: no data
- Age at study initiation: juveniles (< 24 h):
- Method of breeding: Daphnia magna cultures were maintained in 500-ml beakers at 15°C and fed Selenastrum capricornutum and Alfalfa stock (General Nutrition, Pittsburgh, PA, USA). When an individual D. magna contained mature eggs, the female was placed in a 50-ml centrifuge until giving birth. Once this occurred, the female was placed in mass culture with other females that also had given birth. Subsequent offspring (second to sixth broods) were used for experimentation.
- Feeding during test: No

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

Not applicable.

Hardness:

Used water is moderately hard reconstituted water (MHRW).

Test temperature:

No data.

pH:

No data.

Dissolved oxygen:

No data.

Salinity:

Not applicable.

Nominal and measured concentrations:

Test 1 - Sonicated TiO2 samples: control 50, 200, 250, 300, 400 and 500 ppm (nominal/measured).
Test 2 - Filtered (THF) samples: control, 0.2, 1, 2, 5, 6, 8 and 10 ppm (nominal/measured)

Details on test conditions:

TEST SYSTEM
- Test vessel: no data
- Type (delete if not applicable): open
- Fill volume: 50 ml
- Aeration: no
- No. of organisms per vessel: 10 (juveniles < 24h)
- No. of vessels per concentration (replicates):
* sonicated test solutions: 5 replicates
* filtered /THF) trials: 4 replicates
- No. of vessels per control (replicates): 1-2 replicates (depending on number of offspring)
- No. of vessels per vehicle control (replicates): 1-2 replicates (depending on number of offspring)

TEST MEDIUM / WATER PARAMETERS
- No details reported.

OTHER TEST CONDITIONS
- No details reported.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mobility after 1, 24, and 48 hours of exposure.

TEST CONCENTRATIONS
- Range finding study: pre-tests were conducted at various concentrations to observe effects and to determine the concentration that caused 100% mortality.
- Test concentrations: see "Nominal and measured concentrations" above.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 500 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by sonication, particle size: 100-500 nm

Basis for effect:

mobility

Remarks on result:

other: 9 % effect at 500 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

1 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Remarks on result:

other: 6 % effect

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

2 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Remarks on result:

other: 9 % effect

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

5 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

10 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

TiO2 dispersed by tetrahydrofuran and filtered, particle size: 30 nm

Basis for effect:

mobility

Details on results:

Test 1 - Sonicated TiO2 samples:
None of the experiments involving sonicated TiO2 showed mortality greater than 9%. The control showed 2% mortality. The highest mortality occurred at a concentration of 350 ppm. The highest and lowest concentrations (500 and 50 ppm, respectively) both had 9% mortality. The lowest mortality was seen at a concentration of 300 ppm, at which fatalities were similar to those in the control (2%). The slope did not differ significantly from zero; therefore, the LOEC and NOEC were incalculable.

Test 2 - Filtered (THF) samples:
Exposure to filtered TiO2 concentrations ranging from 0 to 10 ppm caused an increase in mortality with an increase in concentration.
Test solutions containing filtered and THF-treated TiO2 particles and test solutions containing filtered and deionized H2O-treated TiO2 particles showed no statistical difference in survivability. Adding THF to MHRW and evaporating it out of solution did not significantly affect survival of daphnids.

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

Mortality was analysed regarding concentration using a probit method analysis (U.S. EPA Probit Analysis Program, Ver 1.5; Environmental Monitoring Systems Laboratory, Cincinnati, OH, USA). This allowed the median LC50 to be calculated. Mean and variance also were calculated among treatments using analysis of variance (ANOVA; SigmaStat Software, Ver 3.10; Systat Software; Point Richmond, CA, USA).
The LOEC and NOEC were then calculated using Dunnett's test (Sigma Plot, Ver 9.0; Systat Software).

Validity criteria fulfilled:

not specified

Conclusions:

Test 1 - Sonicated TiO2 samples:
Reliable study according to US EPA 2024 test guideline. Less than 50% effect was observed at the highest test concentration (500 mg TiO2/L).
Test 2 - Filtered (THF) samples:
Results are not considered relevant for environmnetal exposure due to the dispersion treatment of TiO2 before the toxicity test.

Executive summary:

In a study according to U.S. EPA standard operating procedure 2024 the 48 hr acute toxicity of TiO2 to Daphnia magna was studied under static conditions. Daphnids were exposed to different TiO2 samples in two tests. TiO2 mixtures were prepared either by sonication or placement in tetrahydrofuran (THF) and filtration.  

The way the particles were prepared, however, impacted their toxicity. Exposure to concentrations of unfiltered, sonicated TiO2 powder that contained both micro- and nanoparticles did not cause mortality like that of the filtered nanoparticle solutions. Instead, solutions of sonicated TiO2 caused very few fatalities. Concentrations of TiO2 that were 25- and 30-fold greater than the concentrations that caused mortality in trials with filtered particles showed no difference in mortality from that of the control. Even concentrations as high as 500 ppm caused only 9% mortality. The transmission-electron micrograph (TEM) images of the solutions show that the particles in the filtered solutions are not clumped like those in the sonicated solutions. In the filtered TiO2 solution, only the smaller particles were retained in the aqueous solution (filter size, 200 nm), and the average particle diameter was 30 nm. In the sonicated TiO2 solution, however, all sizes of clumped particles remained, ranging from 100 to 500 nm in diameter. If Daphnia magna encounter an individual nanoparticle, the reactivity may be greater than that of a nanoparticle reacting with many others in larger clumps.

The results obtained with the filtered (THF) TiO2 samples are not considered relevant for environmental exposure due to the dispersion treatment of TiO2 before the toxicity test.

Reference 22

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Documentation insufficient for assessment (no information on form of Ti added or Ti speciation in solution). Justification for read-across: Due to similar or lower transformation/dissolution results for titanium carbide (the target substance) than titanium (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Principles of method if other than guideline:

24 h prior to the start of the experiments asexual eggs of three rotifer species were collected from ovigerous asexual females grown at 25 °C in Petri dishes with EPA medium (U.S. EPA, 1985). The eggs were hatched by exposing them to 25 °C and continuous light for 24h. For the experiment 24-well polystyrene plates were used. Ten neonate females per well were exposed to the test chemical for total duration of 48h (endpopint mortility). The test volume per well is 0.5 ml.

GLP compliance:

no

Details on test solutions:

For the preparation of EPA they used deionized water obtained from a Water Pro PS deionization system (Labconco Co, U.S.A.).

Test organisms (species):

other: 1) Lecane hamata, 2) Lecane luna, 3) Lecane quadridentata

Details on test organisms:

TEST ORGANISM
- Common name: 1) Lecane hamata, 2) Lecane luna, 3) Lecane quadridentata
- Source: collection of asexual females:
* 1) Lecane hamata: Bordo Milpillas, Calvillo, Aguascalientes, Mexico
* 2) Lecane luna: Los Arquitos Dam
* 3) Lecane quadridentata: Lake Chapala
-> 2 year continuous culture in the laboratory, food: Nannochloropsis oculata (UTEX strain LB2194) grown in Bold’s Medium (Nichols, 1973)
- Age at study initiation (mean and range, SD): < 1 day (asexual eggs of all three species were collected from ovigerous asexual females grown in Petri dishes (EPA medium, 25 °C) 24h prior to the test)
- Feeding during test: no

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

80 - 100 mg/l CaCO3

Test temperature:

25 °C

pH:

7.4 - 7.8

Dissolved oxygen:

No data.

Salinity:

Not applicable.

Nominal and measured concentrations:

Nominal (no definite concentrations reported).
In a pre-test five concentrations in a logarithmic series ranging from 1 x 10E−08 to 5 × 10E04 mg/L plus control were used. The highest concentration without mortality and the lowest concentration with 100% mortality were chosen as the lower and upper limits, respectively, for the definitive test. Three intermediate concentrations were included in the definitive test.

Details on test conditions:

TEST SYSTEM
- Test vessel: 24-well polystyrene plates (Costar Co, U.S.A.).
- Type (delete if not applicable): open
- Fill volume: 0.5 ml
- Aeration: no
- No. of organisms per vessel: 10 neonate females
- No. of vessels per concentration (replicates): 5


OTHER TEST CONDITIONS:
- Photoperiod: none, incubation in the dark
- Light intensity: not applicable

Reference substance (positive control):

yes

Remarks:

sodium dodecyl sulfate (SDS)

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 1) Lecane hamata

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

15.6 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

morphology

Remarks on result:

other: 1) Lecane hamata, 95% CI: 9.1 - 22.0 mg/l

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 2) Lecane luna

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

11.9 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

mortality

Remarks on result:

other: 2) Lecane luna, 95 % Cl: 7.0 - 18.1 mg/l

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

< 5 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 3) Lecane quadridentata

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

8.5

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ti

Basis for effect:

mortality

Remarks on result:

other: 3) Lecane quadridentata, 95% CI: 2.26 - 15.8 mg/l

Validity criteria fulfilled:

not specified

Conclusions:

The 48-h LC50 for Lecane hamata, Lecane luna, and Lecane quadridentata are 15.6 mg Ti/L, 11.9 mg Ti/L and 8.5 mg Ti/L, respectively.

Executive summary:

The authors investigated the influence of Ti (speciation not specified) to neonate females of three rotifer species.

24 h prior to the start of the experiments asexual eggs of three rotifer species Lecane hamata, Lecane luna, and Lecane quadridentata

were collected from ovigerous asexual females grown at 25 °C in Petri dishes with EPA medium (U.S. EPA, 1985). The eggs were hatched by exposing them to 25 °C and continuous light for 24h. For the experiment 24-well polystyrene plates were used. Ten neonate females per well were exposed to the test titanium (adsorption standard solution) for total duration of 48h (endpoint mortility). The test volume per well is 0.5 ml. Exact test concentrations were not reported. The 48-h LC50 (nominal concentrations) for Lecane hamata, Lecane luna, and Lecane quadridentata are 15.6 mg Ti/L, 11.9 mg Ti/L and 8.5 mg Ti/L, respectively, demonstrating different susceptibility to the test chemical.

Reference 23

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Documentation insufficient for assessment. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

The chydorid were exposed to nanoparticles for 48 h without feeding. The mortality of the chydorids was counted at t=0 and 48h.
In addition to the ecotoxicological experiments investigations regarding the actual particle size under test conditions were conducted (in Milli-Q water and natural pond water).

GLP compliance:

no

Analytical monitoring:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: dilution of the 10 % (w/w) dispersion in water; dilution was made with tap water

Test organisms (species):

other: Chydorus sphaericus

Details on test organisms:

TEST ORGANISM
- Common name: Chydorus sphaericus
- Source: no data
- Age at study initiation (mean and range, SD): no data
- Method of breeding: no data
- Feeding during test: no
- Food type: not applicable
- Amount: not applicable
- Frequency: not applicable

Test type:

not specified

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Post exposure observation period:

Not applicable.

Hardness:

No data.

Test temperature:

20 °C

pH:

no data

Dissolved oxygen:

no data

Salinity:

not applicable

Nominal and measured concentrations:

Measured concentration (spectrophotometry and ICP-MS): 100 mg TiO2/L

Details on test conditions:

TEST SYSTEM
- Test vessel: vials
- Material, size, headspace, fill volume: 1 mL
- Aeration: no
- No. of organisms per vessel: ca. 5
- No. of vessels per concentration (replicates): no data
- No. of vessels per control (replicates): no data


TEST MEDIUM / WATER PARAMETERS: tap water, no details reported


OTHER TEST CONDITIONS
- Adjustment of pH: no data
- Photoperiod: 17:7-h light/dark
- Light intensity: no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mortality of the invertebrates was counted using a an inverted microscope at t=0h and t=48h

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: particle size: 50-150 nm

Details on results:

- Toxic effects could not be observed, probably due to rapid aggregation and/or coagulation of TiO2 nanoparticles (aggregation/coagulation was confirmed by analytical measurements).
- Dilution experiments demonstrate that formation of larger particles and settling of the lager particles under normal gravitation or centrifugation occurred to a greater extent in natural (pond) water than in ultrapure (Milli-Q) water.

Validity criteria fulfilled:

not applicable

Conclusions:

TiO2 nanoparticle (50-150 nm) are not toxic to Chydorus sphaericus under the conditions of the Chydotox test (EC50 (48 h) > 100 mg TiO2/L).

Executive summary:

The toxicity of TiO2 nanoparticles (50 -150 nm) at 100 mg/L to Chydorus sphaericus was tested in a Chydotox test. Invertebrates were exposed to the test chemical for a total duration of 48 h without feeding. Moartility counts were conducted at t=0h and t=48h. During the test TiO2 nanoparticles aggregated and were present in form of relatively large particles.

Under the conditions of the Chydotox test no mortality was observed.

Reference 24

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

According to OECD 202 test guideline. No data on water characteristics reported and only one test chamber per concentration tested. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

one test chamber per concentration tested

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

No data.

Test organisms (species):

Daphnia magna

Details on test organisms:

Age at study initiation: < 24 h

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

Not reported.

Test temperature:

1) 20.1 - 20.3 °C (fine TiO2)
2) 20.0 - 20.2 °C (ultrafine TiO2)

pH:

Not reported.

Dissolved oxygen:

Not reported.

Salinity:

Not applicable.

Nominal and measured concentrations:

Nominal concentrations of fine TiO2 and ultrafine TiO2: 0 (control), 0.1, 1.0, 10, 100 mg TiO2/L

Details on test conditions:

TEST SYSTEM
- Test vessel: no data
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: no data
- Aeration: no
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates): not applicable

TEST MEDIUM / WATER PARAMETERS: no details reported

OTHER TEST CONDITIONS: no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mobility

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

fine TiO2 (particle size 380 nm)

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

sub-pigmentary TiO2 (particle size 140 nm)

Basis for effect:

mobility

Details on results:

48-h exposure of daphnids to fine or ultrafine TiO2 particle nominal concentrations of 0, 0.1, 1.0, 10, and 100 mg/L resulted in 0, 0, 0, 10, and 10% or 0, 0, 0, 10, and 0% immobility, respectively.

Results with reference substance (positive control):

Not applicable.

Validity criteria fulfilled:

yes

Remarks:

All water quality parameters were within acceptable limits

Conclusions:

Reliable study according to OECD 202 test guideline. All water quality parameters were within acceptable limits during the exposure (however no data on water characteristics reported). Only one test chamber per concentration tested. Less than 50% effect was observed at the highest test concentration (100 mg TiO2/L).

Executive summary:

Fine TiO2 (380 nm) and ultrafine TiO2 (140 nm) was tested in an acute toxicity study using Daphnia magna as test organisms. The tests was conducted in accordance with OECD Guideline 202. The test substance were used at nominal test concentrations of 0 (control), 0.1, 1.0, 10, 100 mg TiO2/L. Daphnids were exposed for 48 h.

The 48-h EC50 for both fine and ultrafine TiO2 were determined to be > 100 mg/L.

Description of key information

The acute toxicity to aquatic invertebrates was tested using titanium dioxide and titanium. Hence, for titanium carbide this endpoint is derived by read-across from titanium dioxide and titanium.
Reliable, publically available relevant data for TiO2 short-term toxicity to aquatic invertebrates do not report mortality in any of the species tested. These data are used in a weight-of-evidence approach. Due to similar or lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide and titanium (the source substances), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach.

Additional information

Griffitt et al. (2008) examined the effect of TiO₂ nanoparticles (primary particle size distribution: 20.5 +/- 6.7 nm) to adult Daphnia pulex as well as to neonate Cerodaphnia dubia (< 24 h). Test organisms were exposed for 48 h to nominal concentrations of 0 (control) and 10 mg/L. Major particle diameters observed in suspension were 687.5 nm. 10 mg TiO₂/L did not result in immobilisation in both species.

In a limit study according to OECD guideline 202 (Johnson et al., 1986) Daphnia magna was exposed to a single nominal concentration of 1000 mg TiO₂/L for 48 h. Microscopic examinations of daphnids following exposure to TiO₂ suspensions showed that the daphnids filtered the TiO₂ particles, passing them to the gut. Thus combined oral exposure and exposure via the aqueous phase did not result in 50 % mortality. The 48 hour EC₅₀ was > 1000 mg/L.

 

Apart from Johnson et al. (1986) also Wahrheit et al. (2007) investigated the effects of TiO₂ on Daphnia magna after 48 h. While the particle size of TiO₂ used in the test was not stated by Johnson et al. (1986), Wahrheit et al. (2007) used fine (defined as ~ 100 nm) and ultrafine (defined as < 100 nm) test material at nominal test concentrations of 0 (control), 0.1, 1.0, 10, 100 mg TiO₂/L. Actual particle size of ultrafine and fine TiO₂ was 140 nm and 380 nm, respectively. No toxic effects could be observed after exposure for 48 h.

 

This result is in agreement with the result of Lovern & Klaper (2006) who studied the short-term toxicity of TiO₂ to Daphnia magna (U.S. EPA standard operating procedure 2024) with different TiO₂ samples in two tests. TiO₂ mixtures were prepared either by sonication or placement in tetrahydrofuran (THF) and filtration. Sonicated TiO₂ samples were used at nominal test concentrations of 50, 200, 250, 300, 400 and 500 ppm, whereas lower concentrations of 0.2, 1, 2, 5, 6, 8 and 10 ppm were used for the assessment of filtered (THF) samples. The way the particles were prepared, however, influenced their toxicity: while unfiltered, sonicated TiO₂ samples did not cause mortality or only 9 % effects at 500 ppm, filtered (THF) samples had toxic effects. Transmission-electron micrograph (TEM) images of the solutions show that the particles in the filtered solutions (filter size 200 nm) had a mean particle diameter of 30 nm, while particle size of sonicated TiO₂ solution samples ranged from 100 to 500 nm. Thus, the study emphasises that the type of dispersion and size of the TiO₂ particles may influence toxicity. Lovern & Klaper (2006) suggested that particle aggregation likely is the reason for the absence of effects in unfiltered, sonicated TiO₂ samples.

The results obtained with the filtered (THF) TiO₂ samples are not considered relevant for real-world environmental exposure due to the dispersion treatment of TiO₂ before the toxicity test, and only the results for sonicated, unfiltered TiO₂ samples (48-h EC₅₀ > 100 ppm) are further considered in the assessment.

 

Short-term toxicity experiments with TiO₂ (particle size: 100 nm and 200 nm) conducted by Dabrunz et al. (2011) did not result in mortality of Daphnia magna after the standard exposure duration of 48 h at the maximum concentration tested (8 mg/L) in any of the experiments. However, prolonged exposure up to 96 h led to an increase in toxicity. In addition, in experiments with prolonged exposure duration smaller particle size resulted in higher toxicity. Besides, in a prolonged experiment up to 96 h the authors observed “biological surface coating” of neonate daphnids with TiO₂ particles. This biological surface coat completely disappeared with the first molting (shedding of shell) but reoccurred within 1 h after the first molting and continued steadily during the 96-h exposure period, causing a delay in molting and significantly lower molting success of only 10% compared to the control (p = 0.0065).

However, as the standard duration of short-term toxicity experiments with daphnids is 48 h, and substance assessment as well as classification and labelling are based on standard experiments with an exposure duration of 48 h, and toxic effects may mainly be attributed to physical effects, results obtained in the prolonged experiments are not carried forward to the effects assessment of titanium carbide. In addition, (eco-)toxicologically relevant release of Ti ions from titanium carbide is not expected as the concentration of soluble Ti ions was below the method detection limit (< 0.4 µg/L) in the T/D test. Thus, TiC is considered to be practically insoluble and the formation of insoluble Ti compounds due to Ti ion release form TiC with subsequent biological surface coating and physical effects is considered to be irrelevant.

 

Besides the publications considered as reliable (see above), additional publically available information of lower reliability is available on TiO₂/Ti short-term toxicity to aquatic invertebrates. These data are considered supporting information only and are not decisive for the substance assessment:

 

Heinlaan (2008) investigated the 48-h toxicity of nano TiO₂ (25–70 nm) to T. platyurus and D. magna according to Standard Operational Procedures “Thamnotoxkit F TM magna” (1995) and “Daphtoxkit F TM magna” (1996), respectively. Nanosize TiO₂ did not induce mortality in T. platyurus at 20,000 mg/L whereas the same concentration induced 60 % mortality in D. magna. No toxicity could be observed at lower levels (incubation in the dark).

Effects (48-h) of TiO₂ nanoparticles (50–150 nm) at 100 mg/L on Chydorus sphaericus were tested in a Chydotox test (Velzeboer et al., 2008). Under the conditions of the Chydotox test no mortality was observed.

Pérez-Legaspi and Rico-Martínez (2001) investigated the influence of Ti (speciation as well as test concentrations not specified) to neonate females of three rotifer species (Lecane hamata,Lecane luna, and Lecane quadridentata). Test organisms where exposed to the test substance for 48 h. The 48-h LC₅₀ (nominal concentrations) for Lecane hamata, Lecane luna, and Lecane quadridentata are 15.6 mg Ti/L, 11.9 mg Ti/L and 8.5 mg Ti/L, respectively, demonstrating different susceptibility to the test chemical.

Borgmann et al. (2005) conducted a one-week toxicity tests using the freshwater amphipod Hyalella azteca. The 7-d LC₅₀ of Ti (element) to Hyalella azteca was determined to be 0.979 mg Ti/L (nominal) or <0.272 mg Ti/L (measured).

 

The absence of ecotoxic effects in most of the experiments referenced in this section may at least partly be explained by low concentrations of small TiO₂ particles in suspension due to aggregation and agglomeration (Lovern & Klaper, 2006; Velzeboer, 2008; Wahrheit et al., 2007; Griffitt et al., 2008). It is assumed that the actual concentrations of nano-sized TiO₂ material in the tests were probably far lower than the nominal test concentrations applied. The results of Dabrunz et al. (2011) suggest that toxic effects that could be partly observed at very high concentrations and/or prolonged exposure duration is caused be physical effects.

Based on lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance) the resulting toxicity potential is also be expected to be lower. Therefore, the dose descriptors are expected to be sufficiently high for the target substance, and read-across to the source chemical is adequately protective. In fact, (eco-)toxicologically relevant release of Ti ions from titanium carbide is not expected as the concentration of soluble Ti ions was below the method detection limit (< 0.4 µg/L) in the T/D test. Thus, TiC in considered to be practically insoluble. Release of Ti ions to any ecotoxicologically relevant extent (and potential subsequent formation of soluble and/or insoluble Ti compounds) is not expected. Therefore, any toxic effects to aquatic invertebrates are not expected to arise from TiC.