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Short-term toxicity to aquatic invertebrates

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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
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Titanox 1000
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Tronox CRX
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Tioxide R-FC6
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Tiona RCL-69
Basis for effect:
mobility
Details on results:
24h EC50: > 1000 mg/L
Reported statistics and error estimates:
EC50 computed using the probit analysis
Validity criteria fulfilled:
not specified
Conclusions:
Dispersions of four different micro sized TiO2 materials did not affect the mobility of Daphnia magna (< 24 h old) in an acute toxicity test according to US EPA (660/8-87/011; 1987) and ASTM (Standard E729, 1986) guidelines. 48 h-EC50 values of >1000 mg TiO2/L (nominal) were derived for all materials, including Tronox CRX (TiO2) which was described to have remained in the water phase for 48 h.
The same EC50 values are predicted for the structural analogue titanium oxide (Ti3O5) based on its similar low water solubility and the fact that any free titanium released will react to TiO2 when in contact with oxygen.
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
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Titanox 1000
Basis for effect:
mobility
Validity criteria fulfilled:
not specified
Conclusions:
The dispersion of the micro sized TiO2 material Titanox 1000 (particle size: 5-6 µm) did not affect the mobility of first instar Daphnia magna in an acute toxicity test, which was performed according to OECD 202 and US EPA (660/8-87/011; 1987) guidelines. The determined 48 h-EC50 value was > 1000 mg TiO2/L (nominal).
The same EC50 values are predicted for the structural analogue titanium oxide (Ti3O5) based on its similar low water solubility and the fact that any free titanium released will react to TiO2 when in contact with oxygen.
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
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
3.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: test A), SW
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: all other tests
Validity criteria fulfilled:
yes
Remarks:
according to OECD guideline
Conclusions:
Daphnia magna (< 24 h old) were exposed to dispersions of nano-TiO2 material (uncoated, anatase/rutile 70:30, primary particle size: 20-30 nm), which were prepared with different dispersion techniques using either artificial or natural waters in an acute toxicity test according to the OECD 202 guideline. All experiments revealed 48 h-EC50 values > 100 mg TiO2/L (nominal). 48 h EC10 values < 100 mg/L were only determined in well-spring water (48 h-EC10: 3.7 mg/L) and M4 medium (48 h-EC10: 76.4 mg/L). Exposure concentrations were not measured.
Experiments, which were performed in M4 medium are not considered to be relevant for hazard assessment purposes of nano-TiO2, because M4 medium contained EDTA.
The same ECx values are predicted for the structural analogue titanium oxide (Ti3O5) based on its similar low water solubility and the fact that any free titanium released will react to TiO2 when in contact with oxygen.
Executive summary:

During all acute toxicity tests the measured pH of the test dispersions remained within the range of 7.1 and 8.7 and did not vary by more than 1.0 unit in any given test. During the chronic toxicity study the pH remained within the range of 7.8 and 8.4. The temperature ranged from 20.0 to 21.0°C during all acute tests and from 19.3 to 21.3 °C during the chronic toxicity study. The oxygen content of the test dispersions in all acute toxicity tests was above >= 3mg/L.

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
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks:
in SW medium
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
13.8 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks:
in SW medium
Details on results:
Test in M4 medium:
48 h-EC50 (mobility): > 100 mg/L
48 h-EC10 (mobility): 91.2 mg/L
Results with reference substance (positive control):
Reference acute toxicity tests using potassium dichromate were performed regularly at intervals of 1–2 months, whereby the median effective concentration (EC50) after 24 h ranged from 0.6 to 1.4 mg/L during the last 10 months, thus meeting the validity criterion according to the OECD guideline.
Reported statistics and error estimates:
Effective concentrations (EC10 and EC50 values) for the parameter immobilization were calculated with the help of the results obtained from the 48-h acute toxicity tests. The dose–response curve was fitted via the probit model according to Finney (1971). If the goodness-of-fit test Pearson Chi-Square was significant (p 6 0.05), high or low doses were excluded from the evaluation. This analysis was only performed, if interpolation was possible. In those cases were extrapolation was necessary the EC10 or EC50 were given as >100 mg/L. All calculations were done withthe help of Microsoft Excel 2000.

During all acute toxicity tests the measured pH of the test dispersions remained within the range of 7.1 and 8.7 and did not vary by more than 1.0 unit in any given test. During the chronic toxicity study the pH remained within the range of 7.8 and 8.4. The temperature ranged from 20.0 to 21.0°C during all acute tests and from 19.3 to 21.3 °C during the chronic toxicity study. The oxygen content of the test dispersions in all acute toxicity tests was above >= 3mg/L.

Validity criteria fulfilled:
yes
Remarks:
according to OECD guideline
Conclusions:
Daphnia magna (< 24 h old) were exposed to dispersions of a pigment grade TiO2 material either in artificial (M4 medium) or natural water in an acute toxicity test according to the OECD 202 guideline. Determined 48 h-EC50 values were > 100 mg TiO2/L (nominal) in both media, and 48 h-EC10 values were 13.8 mg/L (nominal) and 91.2 mg/L (nominal) in either natural or artifical water. Exposure concentrations were not measured. Results of experiments, which were performed in M4 medium are not considered to be relevant for hazard assessment purposes of nano-TiO2, because M4 medium contained EDTA.
The same ECx values are predicted for the structural analogue titanium oxide (Ti3O5) based on its similar low water solubility and the fact that any free titanium released will react to TiO2 when in contact with oxygen.
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
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
AEROXIDE TiO2 P25
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
AEROXIDE TiO2 P25
Basis for effect:
mortality
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.62 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
AEROXIDE TiO2 P25
Basis for effect:
mobility
Remarks on result:
other: 95 % CL: 0.87 - 2.45; Results are not reliable as the organisms were not fed during the testing period.
Duration:
72 h
Dose descriptor:
LC50
Effect conc.:
2.02 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
AEROXIDE TiO2 P25
Basis for effect:
mortality
Remarks on result:
other: 95 % CL: 1.22 - 2.86; Results are not reliable as the organisms were not fed during the testing period.
Reported statistics and error estimates:
Endpoint estimation:
The 48 and 72 h EC50 (immobilization), and LC50 (mortality) values as well as their associated 95% confidence intervals (95% CI) were calculated using a probit method (US EPA Probit Analysis Program, Ver. 1.5, http://www.epa.gov/nerleerd/stat2/probit.zip).

Statistical analysis:
All experiments were repeated three times independently, and data were recorded as the mean with standard deviation (SD). Linear regression was used to determine Michaelis–Menten constants. For toxicity tests, a one-way analysis of variance (ANOVA) with Tukey’s multiple comparisons was used to detect significant differences between the control and treated groups. In all data analyses, a p-value < 0.05 was considered statistically significant.

Characterisation of nanomaterials according to Zhang et al. (2997):
For the TiO2 concentrations, the mean values were calculated from the three replicates and expressed with standard deviation (n = 3). The homogenicity of variance was checked out and a one-way analysis of variance (ANOVA) was then performed to assess the significance of differences observed TiO2 nanoparticles. All statistical analyses were conducted at a significance level of 0.05.
Validity criteria fulfilled:
not specified
Remarks:
Control mortality after 48 h < 10%; Oxygen content not reported
Conclusions:
Daphnia magna (age, < 24 h) exposed to dispersion of the nano sized TiO2 material P25 (21 nm) in an acute toxicity assay according to OECD 202 did not show immobilisation after a standard exposure period of 48 h (48 h EC50 of > 100 mg n-TiO2/L, nominal). Effects observed after 72 hours cannot be considered reliable as the organisms were not fed during testing, which might have increased their sensitivity.
The same EC50 values are predicted for the structural analogue titanium oxide (Ti3O5) based on its similar low water solubility and the fact that any free titanium released will react to TiO2 when in contact with oxygen.

Description of key information

No acute toxicity (<50%) of TiO2 powder or nanoforms on Daphnia magna was observed at 100 mg/L based on weight of evidence of 5 studies. The same conclusions are taken forward for the structural analogue titanium oxide (Ti3O5) based on its similar low water solubility and the fact that any free titanium released will react to TiO2 when in contact with oxygen in water or air.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
100 mg/L

Additional information