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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
OECD guideline study adapted for TiO2 photocatalytic properties. No data on water characteristics. 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 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
The required light intensity of 6,000– 10,000 lux was exceeded during pre-illuminating the algae at 250 watts for 30 min. However, preliminary experiments could show that this did not adversely effect algal grwoth.
Qualifier:
according to guideline
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Qualifier:
according to guideline
Guideline:
other: DIN 38412-33
GLP compliance:
not specified
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Algae test medium was prepared according to the guideline and TiO2 was dispersed (ultrasonication) in the medium in a 50-fold concentration. The dispersion (50 ml in a 100 ml beaker) was irradiated, in a SUNTEST CPS+ Tabletop Xenon Exposure System, with simulated sunlight (intensity and duration of the irradiation were varied). 1 ml of the dispersion was 50-fold diluted with algae adjusted to a concentration of 10,000 cells/ml in test medium.
- This was repeated for every concentration tested
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
incubation of 96-well microtiter plates in a Multitrone shaker (Infors AG, Bottmingen, Switzerland)
Test temperature:
20±2 °C
Nominal and measured concentrations:
Nominal: control, 3.1, 6.25, 12.5, 25 and 50 mg TiO2/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 96-well microtiter plates
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 200 µl
- Aeration: no
- Initial cells density: 10000 cells/ml (control initial fluorescence: 1672 +/- 33)
- Control end cells density: 27117 +/- 2562 (fluorescence)
- No. of vessels per concentration (replicates): 8-12
- No. of vessels per control (replicates): 8

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: no data
- Adjustment of pH: no
- Photoperiod: no data
- Light intensity and quality: light source: "OSRAM L 36W/21-840 Plus Eco" lamps


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): algea growth was measured prior to and after 72-h incubation
- Determination of cell concentrations: fluorescence intensity (Spectrafluor plus microtiter plate reader of Tecan, Crailsheim, Germany)
Reference substance (positive control):
yes
Remarks:
potaasium dichromate (K2Cr2O7)
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
44 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm
Basis for effect:
other: yield
Remarks on result:
other: 95 % CI: 30-94 mg/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm, additionally cleaned
Basis for effect:
other: yield
Remarks on result:
other: 95 % CI: 20-82 mg/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
100% anatase, particle size 100 nm
Basis for effect:
other: yield
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
100% anatase, particle size 100 nm, additionally cleaned
Basis for effect:
other: yield
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: all particle sizes and treatments
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
9.9 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm
Basis for effect:
growth rate
Remarks on result:
other: -0.9833 - 20.85
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
11.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm, additionally cleaned
Basis for effect:
growth rate
Remarks on result:
other: -5.240 - 28.61
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
47 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 100 nm
Basis for effect:
growth rate
Remarks on result:
other: -11.90 - 105.7
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
42 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 100 nm, additionally cleaned
Basis for effect:
growth rate
Remarks on result:
other: -39.04 - 123.4
Details on results:
Effect of shading negligible (as tested with a "sandwich test"): no effect of shading by TiO2 solution without direct contact between algae and TiO2 particles.
Results with reference substance (positive control):
EC50 = 0.5 mg/L
Reported statistics and error estimates:
NOEC and EC50-values and statistical significance were determined using the ToxRat program (Toxrat Solutions GmbH; Alsdorf, Germany).
In addition, ErC50 were calculated using the R package DRC, log logistic model LL3 (results not reported by the authors but own calculation).

1 Elaboration of optimum irradiation conditions:

The standard test guideline does not foresee preincubations with sunlight, and sensitivity of Desmodesmus subspicatus to UV light was unknown. Therefore, irradiation conditions had to be elaborated that do not adversly effect algal growth. Only irradiation with 500 W for 30 min caused a reduction of growth compared to controls. Thus for the following main tests a pre-incubation with 250 W for 30 min was selected.

2 Investigation of potential shading effects

The presence of TiO2 particles did not reduce algal growth when algae and TiO2 particles were physically seperated (> no shading effects). This was independent of the TiO2 concentration. It could be concluded that the concentration dependent inhibition of algal fluorescence by TiO2 was unlikely to be caused by lowered light intensity.

3) Influence of preliminary irradiation

Illuminated and non-illuminated particles were tested in parallel. Pre-illumination did not cause additional effects. The authors attribute differences between both treatments to technical reasons and biological variability.

Validity criteria fulfilled:
yes
Remarks:
< 10 % immobile daphnids in control
Conclusions:
The 48-h EC50 values for commercial and additionally cleaned TiO2 at 25 nm were 44 and 32 mg TiO2/L, respectively. The 48-h EC50 for 100 nm size TiO2 (commercial and additionally cleaned product) were > 50 mg/L.
The 48-h ErC50 values (based on growth rate) for both products and treatments were calculated to be > 50 mg/L. Respective 48-h ErC10 values range between 9.9 mg/L and 47 mg/L.
Executive summary:

Nanosize TiO2 (25 nm and 100 nm; actual particle size distribution was not verified) was tested in an acute toxicity study using Desmodesmus subspicatus in a study that was conducted in accordance with OECD Guideline 201. Each particle size of the test substance was used at nominal test concentrations of 0 (control), 3.1, 6.25, 12.5, 25, and 50 TiO2/L. In addition, investigations were conducted with additionally cleaned TiO2 nanomaterial of both sizes.

The 48-h EC50 values (yield) for commercial and additionally cleaned TiO2 at 25 nm were 44 and 32 mg TiO2/L, respectively. The 48-h EC50 for 100 nm size TiO2 (commercial and additionally cleaned product) were > 50 mg/L.

The 48-h ErC50 values (based on growth rate) for both products and treatments were calculated to be > 50 mg/L. Respective 48-h ErC10 values range between 9.9 mg/L and 47 mg/L.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
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:
72 h
Dose descriptor:
EC50
Effect conc.:
44 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm
Basis for effect:
other: yield
Remarks on result:
other: 95 % CI: 30-94 mg/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm, additionally cleaned
Basis for effect:
other: yield
Remarks on result:
other: 95 % CI: 20-82 mg/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
100% anatase, particle size 100 nm
Basis for effect:
other: yield
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
100% anatase, particle size 100 nm, additionally cleaned
Basis for effect:
other: yield
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: all particle sizes and treatments
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
9.9 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm
Basis for effect:
growth rate
Remarks on result:
other: -0.9833 - 20.85
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
11.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 25 nm, additionally cleaned
Basis for effect:
growth rate
Remarks on result:
other: -5.240 - 28.61
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
47 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 100 nm
Basis for effect:
growth rate
Remarks on result:
other: -11.90 - 105.7
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
42 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
mainly anatase, particle size 100 nm, additionally cleaned
Basis for effect:
growth rate
Remarks on result:
other: -39.04 - 123.4
Details on results:
Effect of shading negligible (as tested with a "sandwich test"): no effect of shading by TiO2 solution without direct contact between algae and TiO2 particles.
Results with reference substance (positive control):
EC50 = 0.5 mg/L
Reported statistics and error estimates:
NOEC and EC50-values and statistical significance were determined using the ToxRat program (Toxrat Solutions GmbH; Alsdorf, Germany).
In addition, ErC50 were calculated using the R package DRC, log logistic model LL3 (results not reported by the authors but own calculation).

1 Elaboration of optimum irradiation conditions:

The standard test guideline does not foresee preincubations with sunlight, and sensitivity of Desmodesmus subspicatus to UV light was unknown. Therefore, irradiation conditions had to be elaborated that do not adversly effect algal growth. Only irradiation with 500 W for 30 min caused a reduction of growth compared to controls. Thus for the following main tests a pre-incubation with 250 W for 30 min was selected.

2 Investigation of potential shading effects

The presence of TiO2 particles did not reduce algal growth when algae and TiO2 particles were physically seperated (> no shading effects). This was independent of the TiO2 concentration. It could be concluded that the concentration dependent inhibition of algal fluorescence by TiO2 was unlikely to be caused by lowered light intensity.

3) Influence of preliminary irradiation

Illuminated and non-illuminated particles were tested in parallel. Pre-illumination did not cause additional effects. The authors attribute differences between both treatments to technical reasons and biological variability.

Validity criteria fulfilled:
yes
Remarks:
< 10 % immobile daphnids in control
Conclusions:
The 48-h EC50 values for commercial and additionally cleaned TiO2 at 25 nm were 44 and 32 mg TiO2/L, respectively. The 48-h EC50 for 100 nm size TiO2 (commercial and additionally cleaned product) were > 50 mg/L.
The 48-h ErC50 values (based on growth rate) for both products and treatments were calculated to be > 50 mg/L. Respective 48-h ErC10 values range between 9.9 mg/L and 47 mg/L.
Executive summary:

Nanosize TiO2 (25 nm and 100 nm; actual particle size distribution was not verified) was tested in an acute toxicity study using Desmodesmus subspicatus in a study that was conducted in accordance with OECD Guideline 201. Each particle size of the test substance was used at nominal test concentrations of 0 (control), 3.1, 6.25, 12.5, 25, and 50 TiO2/L. In addition, investigations were conducted with additionally cleaned TiO2 nanomaterial of both sizes.


 


The 48-h EC50 values (yield) for commercial and additionally cleaned TiO2 at 25 nm were 44 and 32 mg TiO2/L, respectively. The 48-h EC50 for 100 nm size TiO2 (commercial and additionally cleaned product) were > 50 mg/L.


The 48-h ErC50 values (based on growth rate) for both products and treatments were calculated to be > 50 mg/L. Respective 48-h ErC10 values range between 9.9 mg/L and 47 mg/L.


 


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).

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Test according to OECD 201 without detailed documentation; no control for potential shading effect. 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 201 (Alga, Growth Inhibition Test)
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Synthetic algal-assay procedure nutrient medium.
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
Test organisms were reviewed and approved by the Institutional Animal Care and Use Committee. The DuPont Haskell Laboratory animal program is fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
Not reported.
Test temperature:
23.8°C (range: 23.7-23.8°C)
pH:
No data.
Dissolved oxygen:
No data.
Salinity:
Not applicable.
Nominal and measured concentrations:
Nominal: control, 0.01, 0.1, 1, 10 and 100 mg TiO2/l.
Details on test conditions:
TEST SYSTEM
- Test vessel: no data
- Type (delete if not applicable): no data
- Material, size, headspace, fill volume: no data
- Aeration: no
- Shaking speed: 100 rpm
- Initial cells density: 10,000 cells/ml
- Control end cells density:
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2


GROWTH MEDIUM
- Standard medium used: yes (synthetic algal-assay procedure (AAP) nutrient medium)

OTHER TEST CONDITIONS
- Sterile test conditions: not reported
- Adjustment of pH: not reported
- Photoperiod: not reported
- Light intensity and quality: mean lighting intensity: 8938 lux (range: 8200-9500 lux).


EFFECT PARAMETERS MEASURED: cell count
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
16 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
fine TiO2 (particle size 380 nm)
Basis for effect:
cell number
Remarks on result:
other: 95% Cl: 12-22
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
61 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
fine TiO2 (particle size 380 nm)
Basis for effect:
growth rate
Remarks on result:
other: 95% Cl: 52-72
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
21 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
ultrafine TiO2 (particle size 140 nm)
Basis for effect:
cell number
Remarks on result:
other: 95% Cl: 16-26
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
87 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
ultrafine TiO2 (particle size 140 nm)
Basis for effect:
growth rate
Remarks on result:
other: 95% Cl: 83-91
Details on results:
no control for potential shading effects
Validity criteria fulfilled:
not specified
Conclusions:
72-h exposure of Pseudokirchneriella subcapitata to fine (380 nm) or ultrafine (140 nm) TiO2 particle at nominal concentrations of 0.01, 0.1, 1.0, 10, and 100 mg/L resulted in 0, 1, 0, 8, and 66 % or -3, -1, -2, 3, and 54 % inhibition of growth rate, respectively.
Executive summary:

Fine TiO2 (380 nm) and ultrafine TiO2 (140 nm) was tested in an acute toxicity study using Pseudokirchneriella subcapitata as test organisms. The tests was conducted in accordance with OECD Guideline 201. The test substance were used at nominal test concentrations of 0 (control), 0.01, 0.1, 1.0, 10, 100 mg TiO2/L.

The ErC50 for fine and ultrafine TiO2 for Pseudokirchneriella subcapitata was determined to be 61 and 87 mg/L, respectively.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
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:
72 h
Dose descriptor:
EC50
Effect conc.:
16 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
fine TiO2 (particle size 380 nm)
Basis for effect:
cell number
Remarks on result:
other: 95% Cl: 12-22
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
61 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
fine TiO2 (particle size 380 nm)
Basis for effect:
growth rate
Remarks on result:
other: 95% Cl: 52-72
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
21 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
ultrafine TiO2 (particle size 140 nm)
Basis for effect:
cell number
Remarks on result:
other: 95% Cl: 16-26
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
87 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
ultrafine TiO2 (particle size 140 nm)
Basis for effect:
growth rate
Remarks on result:
other: 95% Cl: 83-91
Details on results:
no control for potential shading effects
Validity criteria fulfilled:
not specified
Conclusions:
72-h exposure of Pseudokirchneriella subcapitata to fine (380 nm) or ultrafine (140 nm) TiO2 particle at nominal concentrations of 0.01, 0.1, 1.0, 10, and 100 mg/L resulted in 0, 1, 0, 8, and 66 % or -3, -1, -2, 3, and 54 % inhibition of growth rate, respectively.
Executive summary:

Fine TiO2 (380 nm) and ultrafine TiO2 (140 nm) was tested in an acute toxicity study using Pseudokirchneriella subcapitata as test organisms. The tests was conducted in accordance with OECD Guideline 201. The test substance were used at nominal test concentrations of 0 (control), 0.01, 0.1, 1.0, 10, 100 mg TiO2/L.


 


The ErC50 for fine and ultrafine TiO2 for Pseudokirchneriella subcapitata was determined to be 61 and 87 mg/L, respectively.


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).

Endpoint:
toxicity to aquatic algae and cyanobacteria
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:
Documentation insufficient for assessment. Exposure duration is too short: 4.5 h instead of 72 h. 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:
Pseudokirchneriella subcapitata was exposed to the test chemical for 4.5h. Subsequently the efficiency of photosynthesis was measured.
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:
not specified
Vehicle:
no
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
4.5 h
Post exposure observation period:
not applicable
Hardness:
not reported
Test temperature:
20 °C
pH:
not reported
Dissolved oxygen:
not reported
Salinity:
not applicable
Nominal and measured concentrations:
Nominal: seven dilutions of test substance, highest concentration: 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: no data
- Type (delete if not applicable): no data
- Material, size, headspace, fill volume: no data
- Initial cells density: no data

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dutch standard water (Milli-Q) with NaHCO3, KHCO3, CaCl2 * 2H2O, and MgSO4 * 7H2O

OTHER TEST CONDITIONS
- Sterile test conditions: no data
- Adjustment of pH: no data
- Photoperiod: continous light exposure
- Light intensity and quality: 100 µE/m²/s, 650 nm

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): efficiency of photosynthesis (PAM fluorometer)
Reference substance (positive control):
yes
Remarks:
Atrazine standard in 98% ethanol, concentration: 0.1311 mM
Key result
Duration:
4.5 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: efficiency of photosynthesis
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 specified
Conclusions:
Concentrations up to 100 mg TiO2/L did not effect the efficiency of photosynthesis of Pseudokirchneriella subcapitata after 4.5 h of exposure.
Executive summary:

Pseudokirchneriella subcapitata was exposed to the test chemical TiO2 (50-150 nm) at seven concentrations up to 100 mg/L for 4.5h. Subsequently the efficiency of photosynthesis was measured.

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).

Under the conditions of the test not effects on the efficiency of photosynthesis of Pseudokirchneriella subcapitata could be observed. The authors attribute the absence of ecotoxicologic effects to the rapid aggregation and/or coagulation of TiO2 nanoparticles resulting in (assumed) low bio-active concentrations of TiO2.

Endpoint:
toxicity to aquatic algae and cyanobacteria
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.
Key result
Duration:
4.5 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: efficiency of photosynthesis
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 specified
Conclusions:
Concentrations up to 100 mg TiO2/L did not effect the efficiency of photosynthesis of Pseudokirchneriella subcapitata after 4.5 h of exposure.
Executive summary:

Pseudokirchneriella subcapitata was exposed to the test chemical TiO2 (50-150 nm) at seven concentrations up to 100 mg/L for 4.5h. Subsequently the efficiency of photosynthesis was measured.


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).


Under the conditions of the test not effects on the efficiency of photosynthesis of Pseudokirchneriella subcapitata could be observed. The authors attribute the absence of ecotoxicologic effects to the rapid aggregation and/or coagulation of TiO2 nanoparticles resulting in (assumed) low bio-active concentrations of TiO2.


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

Endpoint:
toxicity to aquatic algae and cyanobacteria
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:
90 d
Dose descriptor:
NOEC
Effect conc.:
0.1 other: % (w/v)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth
Remarks on result:
other: 0.1 % (w/v) correspond to 6.5 mg Ti/L
Duration:
90 d
Dose descriptor:
LOEC
Effect conc.:
0.25 other: % (w/v)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth
Remarks on result:
other: 0.25 % (w/v) correspond to 16 mg Ti/L

TiCl3 inhibited growth of Chlorella vulgaris at concentrations lower than the critical value for pH of 0.5 %.

Validity criteria fulfilled:
not applicable
Conclusions:
The 90-d NOEC of TiCl3 for Chlorella vulgaris is 0.1 % (w/v) which corresponds to 6.5 mg Ti/L.
Executive summary:

Chlorella vulgaris was brought into test medium with different concentrations of TiCl3 and growth was observed by comparison with blank cultures. The observations were continued until the cultures were 3 to 4 months old. Both the highest as well as the lowest concentration preventing growth was registred.


The 90-d NOEC and LOEC of TiCl3 for Chlorella vulgaris are 0.1 % (w/v), corresponding to 6.5 mg Ti/L, and 0.25 % (w/v), corresponding to 16 mg Ti/L, respectively.


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).

Endpoint:
toxicity to aquatic algae and cyanobacteria
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. The author states that the results were also not completely reproducible and results can only be regarded as preliminary. Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium trichloride (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:
no guideline followed
Principles of method if other than guideline:
Chlortella vulgaris was brought into test medium with different concentrations TiCl3 and growth was observed by comparison with blank cultures. The observations were continued until the cultures were 3 to 4 months old. Both the highest as well as the lowest concentration preventing growth was registered.
GLP compliance:
no
Analytical monitoring:
no
Test organisms (species):
Chlorella vulgaris
Details on test organisms:
TEST ORGANISM
- Common name: Chlorella vulgaris
- Source (laboratory, culture collection): Laboratory of Microbiology, Technological University, Delft
- Age of inoculum (at test initiation): no data
- Method of cultivation: cultivation on agar slants
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
90 d
Remarks on exposure duration:
Exposure duration not exactly specified (> 3-4 months)
Post exposure observation period:
Not applicable
Hardness:
No data
Test temperature:
Room temperature
pH:
Basal medium: just below 7
Dissolved oxygen:
No data
Salinity:
Not applicable.
Nominal and measured concentrations:
Nominal concentrations in %: 0 (control), 0.0001, 0.0002, 0.0003, 0.0005, 0.001, 0 .002, 0.003, 0.005, 0.0075, 0.01, 0.02, 0.03, 0.05, 0.075, 0.1, 0.25, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 20, 24, and 30
Details on test conditions:
TEST SYSTEM
- Test vessel: 150 ml Erlenmeyer flasks, sterilized (110 °C for 20 min)
- Type (delete if not applicable): closed (stoppered with cotton plugs)
- Material, size, headspace, fill volume: 50 ml
- Aeration:
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density:
- Control end cells density:
- No. of organisms per vessel:
- No. of vessels per concentration (replicates):
- No. of vessels per control (replicates):
- No. of vessels per vehicle control (replicates):

GROWTH MEDIUM
- Standard medium used: yes/no
- Detailed composition if non-standard medium was used:

TEST MEDIUM / WATER PARAMETERS
- Basal medium (salts used were of analytical grade):
* 0.05 % K2HPO4
* 0.05 % KHH2O4
* 0.05 % (NH4)2SO4
* 0.05% KNO3
* copper-free distilled water of which 20 % was replaced by activated-carbon-treated tapwater or well-water;
* pH: just below 7


Source/preparation of dilution water:
- Total organic carbon:
- Particulate matter:
- Metals:
- Pesticides:
- Chlorine:
- Alkalinity:
- Ca/mg ratio:
- Conductivity:
- Culture medium different from test medium:
- Intervals of water quality measurement:

OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH:
- Photoperiod:
- Light intensity and quality: natural daylight (test vessele were situated at a window situated on the North)
- Salinity (for marine algae):

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
- Chlorophyll measurement:
- Other:

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:
Reference substance (positive control):
no
Key result
Duration:
90 d
Dose descriptor:
NOEC
Effect conc.:
0.1 other: % (w/v)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth
Remarks on result:
other: 0.1 % (w/v) correspond to 6.5 mg Ti/L
Duration:
90 d
Dose descriptor:
LOEC
Effect conc.:
0.25 other: % (w/v)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth
Remarks on result:
other: 0.25 % (w/v) correspond to 16 mg Ti/L

TiCl3 inhibited growth of Chlorella vulgaris at concentrations lower than the critical value for pH of 0.5 %.

Validity criteria fulfilled:
not applicable
Conclusions:
The 90-d NOEC of TiCl3 for Chlorella vulgaris is 0.1 % (w/v) which corresponds to 6.5 mg Ti/L.
Executive summary:

Chlorella vulgaris was brought into test medium with different concentrations of TiCl3 and growth was observed by comparison with blank cultures. The observations were continued until the cultures were 3 to 4 months old. Both the highest as well as the lowest concentration preventing growth was registred.

The 90-d NOEC and LOEC of TiCl3 for Chlorella vulgaris are 0.1 % (w/v), corresponding to 6.5 mg Ti/L, and 0.25 % (w/v), corresponding to 16 mg Ti/L, respectively.

Description of key information

The acute toxicity to aquatic algae was tested using titanium dioxide and titanium trichloride. Hence, for titanium carbide this endpoint is derived by read-across from titanium dioxide and titanium trichloride.
Titanium compounds are of low toxicity for algae. Due to the insolubility of titanium carbide, toxic effects for aquatic algae are not expected to arise from the substance.

Key value for chemical safety assessment

Additional information

Two reliable key studies for toxicity of titanium dioxide to aquatic algae are available. The first study was conducted by Wahrheit et al. (2007) who investigated the toxicity of fine TiO2 (380 nm) and ultrafine TiO2 (140 nm) to Pseudokirchneriella subcapitata in accordance with OECD guideline 201. The test substance were used at nominal test concentrations of 0 (control), 0.01, 0.1, 1.0, 10, 100 mg TiO2/L. The ErC50 for fine and ultrafine TiO2 in Pseudokirchneriella subcapitata was determined to be 61 and 87 mg/L, respectively.

 

This relatively low toxicity of TiO2 to algae is further supported by the second key study by Hund-Rinke & Simon (2006) who investigated toxic effects of nano-size TiO2 (25 nm and 100 nm) to Desmodesmus subspicatus in a test according to OECD 201. Both particle size materials were investigated as such and in form of additionally cleaned material. Actual particle size distribution was not verified. The 48-h ErC50 values for both products and treatments were calculated to be > 50 mg/L. Respective 48-h ErC10 values ranged between 9.9 mg/L and 47 mg/L.

In addition, the results referenced above are supported by a study investigating 90-d exposure of Chlorella vulgaris to different concentrations of TiCl3 (Den Dooren, 1965). This exposure resulted in a 90-d NOEC and LOEC of TiCl3 for Chlorella vulgaris of 6.5 mg Ti/L and 16 mg Ti/L, respectively.

 

Velzeboer et al. (2008) investigated the influence of 100 mg TiO2/L (50-150 nm) on the efficiency of photosynthesis of Pseudokirchneriella subcapitata after exposure for 4.5 h. TiO2 did not result in a decrease of photosynthesis by the algae.

 

Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide and titanium trichloride (the source substances), the resulting toxicity potential would 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 is 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, toxic effects for aquatic algae are not expected to arise from TiC.