Titanium dioxide

Additional ecotoxological information

Administrative data

Endpoint:

additional ecotoxicological information

Remarks:

Mesocosm study including Rotifera, Cladocera, Copepoda, Phytoplankton, Macrophytes, Chironomids and fish

Type of information:

experimental study

Remarks:

mesocosm study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see ''remarks''

Remarks:

Biological stability not verified prior to main test; Due to multiple exposure and no chemical analytical verification of exposure concentration in the mesocosms, it is not possible to link the observed effects to a specific exposure concentration. Hence, no effect values can be derived from this study that can be used for the hazard assessment of TiO2. Fish insertion not recommended where zooplankton is affected (OECD 53, 2006), fish species and source not stated and loading rate (i.e. 9 -10 g/L) > 2 g/L; Lakes Eymir and Mogan (source of biota) were insufficiently described (contamination status unclear); Waterloss in mesocosm enclosures > 20 % during exposure (i.e. 30 %); source of fish and macrophytes not described

Data source

Reference

Reference Type:

publication

Title:

Food web effects of titanium dioxide nanoparticles in an outdoor freshwater mesocosm experiment

Author:

Jovanovic, B.et al.

Year:

2016

Bibliographic source:

Nanotoxicology 10, 902-912

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD 53, 2006

Deviations:

yes

Remarks:

biological stability of system not verified prior to main test; fish inserted (species not stated) although not recommended if zooplancton is most sensitive; fish loading rate not <=2 g/L (i.e. 9 - 10 g/L); no validation of pond exposure concentration

Principles of method if other than guideline:

Outdoor mesocosms (1350 L), which were situated on a pontoon platform in the middle of a lake in Turkey, were applied with the TiO2 material E171 five times a week to reach a TiO2 concentration of 0, 25 and 125 µg/L. Physicochemical parameters of the water, nutrient concentrations, and biomass of the taxa (phytoplankton, zooplankton, macroinvertebrates, macrophytes, and fish) were monitored over a testing period of 78 d.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Titanium dioxide

EC Number:

236-675-5

EC Name:

Titanium dioxide

Cas Number:

13463-67-7

Molecular formula:

O2Ti

IUPAC Name:

dioxotitanium

Test material form:

solid: bulk

Details on test material:

E171 commercial food grade TiO2 (C.I. 77891, manufactured by Fiorio Colori Spa of Italy and obtained through Pharmorgana GmbH Eppstein, Germany)
- Purity: 99%
- Crystalline phase (XRD): anatase
- Primary particle size (AFM): 167 +/- 50 nm
- Coating: no information
- BET specific surface area (m²/g): 6.137
- Pore volume/pore diameter: 0.123 cc/g; 2.968 nm
- Shape: no information
- Particle size distribution in test medium (DLS; in lake water at 25 and 250 µg TiO2/L): >1000 to > 10000 nm
- Surface charge in test medium (ELS; in lake water at 25 and 250 µg TiO2/L): zeta potentials (mV) in lake water ranged from -6.8 +/- 0.3 to -7.4 +/- 0.3 mV

Results and discussion

Any other information on results incl. tables

Sedimentation experiment:

- Average TiO2 concentrations were: 238.3 ± 13.8, 230.7 ± 18.0, 182.5 ± 9.5 and 128.8 ± 12.5 µg/L after 1, 4, 8, and 24 h, respectively.

- Exposure concentration only verified in an additional laboratory experiment at 250 µg TiO2/L at t=0 and t=24 h and not directly in the mesocosms, hence exposure concentration within the mesocosms was not analytically confirmed.

Physicochemical water parameters:

- no significant differences in any of the measured water parameters between tanks on Day 0

- no significant differences in following water parameters during the experiment between treatments and controls (dissolved oxygen, water temperature, salinity, conductivity, water tranparencey, pH, total dissolved solids and total suspended soldis)

- total water volume per mesocosm was reduced by ~30% toward the end of the experiment due to evaporation

- PAR light intensity increased only significantly by 5% on average throughout the water column in the TiO2 250 µg/L treatment compared to the control.

- TN, NH4 +-N, NO2 +NO3 and TP levels were unaffected by the treatments

- Dose-dependent reduction of SRP levels in TiO2 treatments compared to the control; The concentration was reduced by 15 and 23% in the 25 and 250 µg/L TiO2 treatments compared to the control.

Biological effects:

- No significant differences between controls and TiO2 treatments observed for, Chl-a, carotenoids concentrations, biomass of Cladocera or Copepoda, zooplankton grazing pressure on phytoplankton, macrophytes PVI%, biomass of mactrophytes, biomass of periphyton, biomass and abundance of Chironomids.

- two out of 72 fish died during the experiment, one each in the 250 µg/L TiO2 treatment group and in the controls; no visible signs of lesions or infections on any deceased of living fish, no difference in biomass between treatments and control.

- Significant reduction of the average biomass of all sampling points of Rotifera at 25 µg/L by 32% and 250 µg/L by 57% compared to the controls.

- Rotifer biomass (µg/L) at test start (day 0) in the controls and 25 and 250 µg/L TiO2 treatment groups was 2.12 ± 0.32, 3.37 ± 1.63 and 1.79 ± 0.41 µg/L, and thus was not comparable within the different mesocosms. Rotifer biomass in control and 25 µg/L TiO2 treatments increased up to around 10 µg/L (graphical estimate) and 6.5 µg/L until day 16 of exposure and declined to values below 2 µg/L at day 65. In comparison, rotifer biomass in the 250 µg/L treatment groups remained between 2 and 4 µg/L during the whole testing period.

Applicant's summary and conclusion

Conclusions:

Outdoor mesocosms (1350 L), which were situated on a pontoon platform in the middle of a lake in Turkey, were applied with the TiO2 material E171 five times a week to reach a TiO2 concentration of 0, 25 and 250 µg/L. Physicochemical parameters of the water, nutrient concentrations, and biomass of the taxa (phytoplankton, zooplankton, macroinvertebrates, macrophytes, and fish) were monitored over a testing period of 78 d.
In comparison to the control 25 and 250 µg TiO2/L caused significant reductions in available soluble reactive phosphorus by 15 and 23 %, respectively and significantly reduced the biomass of rotifera by 32 and 57 %, respectively. Other aquatic organisms and functions of the ecosysem stayed unaffected. Rotifiers are not considered as keystone species (Waltz, 1997) in freshwater plankton communities. None of the negative effects were significant enough to affect the overall function of the ecosystem, as there were no cascade effects leading to a major change in its trophic state or primary production. Due to multiple exposure and no chemical analytical verification of exposure concentration in the mesocosms it is not possible to link the observed effects to a specific exposure concentration. Hence, no effect values can be derived from this study that can be used for the hazard assessment of TiO2.