Diiron titanium pentaoxide

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is highly insoluble in water, hence indicating that aquatic toxicity is unlikely to occur

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

For Read-Across Justification please refer to Section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: luminescence inhibition

Duration:

30 min

Dose descriptor:

NOEC

Effect conc.:

> 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: luminescence inhibition

Reference 3

Endpoint:

toxicity to microorganisms, other

Remarks:

Flash assay with Vibrio fisheri

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

not specified

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Principles of method if other than guideline:

A Flash Assay was performed. In this assay the luminescence inhibition to V. fischeri kinetic was assessed taking into account the color and turibidity (measured using a Luminometer controlled by Multiuse software). The luminescence was measured every 0.05 g under continuous mixing at ambient temperature (20℃). The test item was diluted and tested in 2% NaCl.

GLP compliance:

not specified

Specific details on test material used for the study:

- Name of test material (as cited in study report): Titanium dioxide (bulk)
- Substance type: particle
- Source: Riedel-de Haen

Analytical monitoring:

not specified

Details on sampling:

Not specified

Vehicle:

not specified

Details on test solutions:

Not specified

Test organisms (species):

Vibrio fisheri

Test type:

other: Flash assay

Water media type:

not specified

Limit test:

no

Total exposure duration:

30 min

Post exposure observation period:

Not applicable

Hardness:

Not specified

Test temperature:

Not specified

pH:

Not specified

Dissolved oxygen:

Not specified

Salinity:

Not specified

Conductivity:

Not specified

Nominal and measured concentrations:

Not specified

Details on test conditions:

Not specified

Reference substance (positive control):

not specified

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: luminescence inhibition

Duration:

30 min

Dose descriptor:

NOEC

Effect conc.:

> 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: luminescence inhibition

Details on results:

The test item suspension was not acutely toxic up to and including 20 g/L level.

Results with reference substance (positive control):

Not specified

Reported statistics and error estimates:

EC50 values were calculated using Biotox software (Thermo Lab systems, Helsinki, Finland)

Table 1. The toxicity (30min EC50 and NOEC) of titanium dioxide to Vibrio fischeri.

Chemical	Toxicity to Vibrio fischeri
TiO2	EC50+/- SD	NOEC
	>20000	>20000

Validity criteria fulfilled:

not specified

Conclusions:

The 30-min EC50 and NOEC were determined to be higher than 20 g/L in nominal.

Executive summary:

In a Flash assay with Vibrio fischeri the 30-min EC50 and NOEC were determined to be higher than 20000 mg/L (nominal).

Reference 4

Endpoint:

activated sludge respiration inhibition testing

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

For Read-Across Justification please refer to Section 13.

Reason / purpose for cross-reference:

read-across source

Dose descriptor:

EC50

Effect conc.:

>= 500 - <= 1 000 other: ppm

Basis for effect:

growth inhibition

Remarks:

B. subtilis

Remarks on result:

other: not further specified

Dose descriptor:

EC50

Effect conc.:

> 2 000 - <= 5 000 other: ppm

Basis for effect:

growth inhibition

Remarks:

E. coli

Remarks on result:

other: not further specified

Reference 5

Endpoint:

toxicity to microorganisms, other

Remarks:

not further specified

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

not specified

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Principles of method if other than guideline:

Petri dishes filled with liquid MD media were supplemented with nanoparticle suspensions (final volume of 5 mL). The plates were inoculated with cultures of B. subtilis or E.coli and incubated overnight. Control plates containing MD medium and bacteria were sealed with Parafilm. Cultures were diluted to achieve cell concentration of approximately 103 CFU/mL, spread onto LB plates (in duplicates, three test runs), and left to grow at 36℃ for 14-20h. Colonies were counted and compared to control plates to calculate percentage growth inhibition.

GLP compliance:

not specified

Specific details on test material used for the study:

- Name of test material: Titanium dioxide
- Particle size: 44 µm (powder)
- Purchase: Sigma-Aldrich (St. Louis, MO, USA)

Analytical monitoring:

not specified

Details on sampling:

not specified

Vehicle:

not specified

Details on test solutions:

not specified

Test organisms (species):

other: Bacillus subtilis and Escherichia coli

Details on inoculum:

not applicable

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

20 h

Remarks on exposure duration:

14-20h

Post exposure observation period:

None

Hardness:

not applicable

Test temperature:

23℃

pH:

not specified

Dissolved oxygen:

not applicable

Salinity:

not applicable

Conductivity:

not applicable

Nominal and measured concentrations:

not specified

Details on test conditions:

- Sunlight for 6h(9 AM to 3 PM)-UV Index 6-7

Reference substance (positive control):

not specified

Dose descriptor:

EC50

Effect conc.:

>= 500 - <= 1 000 other: ppm

Basis for effect:

growth inhibition

Remarks:

B.subtilis

Remarks on result:

other: not further specified

Dose descriptor:

EC50

Effect conc.:

> 2 000 - < 5 000 other: ppm

Basis for effect:

growth inhibition

Remarks:

E. coli

Remarks on result:

other: not further specified

Table 1. Percentage growth inhibition to B. subtilis and E. coli at various concentrations.

Treatment	Percentage growth inhibition at various concentrations
	10ppm		50 ppm	100 ppm	500 ppm	1000 ppm	2000 ppm	5000 ppm
B.subtilis	TiO2330nm	n.d	0	0	0	75 +/-6.6	99 +/-0.9	n.d
E.coli	TiO2330nm	n.d	0	0	15 +/-4.2	44 +/-7.0	46 +/-11.3	72 +/-9.4

n.d: not determined

Validity criteria fulfilled:

not specified

Conclusions:

The EC50 for B. subtilis and E. coli were determined to be 500~1000 and 2000-5000 ppm, respectively.

Description of key information

The study on toxicity to microorganisms with diiron titanium pentaoxide does not need to be conducted because the substance is highly insoluble in water, hence indicating that aquatic toxicity is unlikely to occur (study scientifically not necessary). However, by applying an analogue approach the EC50 for the target substance was determined to be 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

Non submission justification for diiron titanium pentaoxide

Data on toxicity of Diiron titanium pentaoxide to aquatic microorganisms is not available. The substance was assessed in three guideline studies to be highly insoluble in water (references 4.8-2, 4.8-3 and 4.8-1). In a worst case approach the water solubility of the test item was determined to be 2.715 µg/L at a temperature of 20 °C (please refer to the endpoint summary in IUCLID section 4.8). Toxic effects to aquatic microorganisms are hence unlikely. Therefore, in accordance with the criteria given in column 2 of Annex VIII to Regulation (EC) No 1907/2006 (REACH), the study on toxicity to aquatic microorganisms is considered scientifically not necessary and was waived.

Nevertheless, available data for the read across source substances titanium dioxide (CAS 13463-67-7) and diiron trioxide (CAS 1309-37-1) are summarized below.

Titanium dioxide

In a Flash assay with Vibrio fischeri the 30-min EC50 and NOEC were determined to be higher than 20000 mg/L (nominal) (reference 6.1.7 -1).

In another in vitro test the EC50 for Bacillus subtilis and Escherichia coli were found to be 500~1000 and 2000-5000 ppm, respectively (reference 6.1.7 -2).

Key information on toxicity to microorganisms provided in public ECHA REACH dossiers for the read across substances titanium dioxide and diiron trioxide

Titanium dioxide

According to the public ECHA REACH dossier on titanium dioxide (last accessed on: 18 March 2020) dispersions of nano- and microsized titanium dioxide do not inhibit microbial respiration in activated sewage sludge up to 1000 mg/L.

Diiron trioxide

In the public ECHA REACH dossier on diiron trioxide (last accessed on: 18 March 2020) a 3-hour EC50 of > 10000 mg/L was used as key value regarding the toxicity to aquatic microorganisms.

Conclusion

Based on the physico-chemical properties of diiron titanium pentaoxide a test on toxicity to aquatic microorganisms is scientifically not justified in accordance with column 2 of Annex VIII to Regulation (EC) No 1907/2006 (REACH). Moreover, the source substances titanium dioxide (CAS 13463-67-7) and diiron trioxide (CAS 1309-37-1) are found to be non-toxic to aquatic microorganisms. Target and source substance are metal-containing inorganic oxides. The target substance diiron titanium pentaoxide is a mixed oxide of titanium dioxide and diiron trioxide. The source substances share the common atoms Ti, O and Fe with the target substance and have very similar physicochemical properties (for further information please refer to the read across justification attached to IUCLID section 13). Therefore, by applying an analogue approach, diiron titanium pentaoxide is not considered to be toxic to aquatic microorganisms and additional studies are scientifically not necessary. Following a weight of evidence approach the EC50 of the target substance is determined to be 1000 mg/L.