Rutile (TiO2)

Endpoint summary

Description of key information

No reliable results are available for repeated dose toxicity of synthetic rutile. Therefore, read-across is proposed to available data on TiO2.
Titanium dioxide did not show adverse effects in a chronic oral repeated dose toxicity study in rats with a NOAEL of 3500mg/kg bw/day.
Titanium dioxide is not absorbed to any relevant extent through human skin, thus no toxic effects can be expected via the dermal route of exposure.
Synthetic rutile is not inhalable at any relevant extent, thus conduct of repeated dose toxicity studies via the inhalation route is considered dispensable.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Study period:

2005-09-14 to 2006-01-18

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented study. However, only one sex and one dose were used.

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

limit test dose is 24 times higher than in guideline, only one sex was used

GLP compliance:

not specified

Limit test:

yes

Species:

rat

Strain:

other: Crl:CD (SD)IGS BR

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, North Carolina
- Age at study initiation: between 6 and 8 weeks of age
- Weight at study initiation: 211 to 214 g
- Housing: All animals were housed singly in stainless steel, wire-mesh cages suspended above cage boards. Each cage rack contained only animals of one sex.
- Diet: All rats were fed PMI® Nutrition International, LLC Certified Rodent LabDiet® 5002 ad libitum.
- Water: ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-26
- Humidity (%): 30-70
- Photoperiod: 12 hour light/dark cycle

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The test substance was suspended in NANOpure water and the dosing suspensions were prepared daily.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses to address homogeneity/concentration verification and stability were not done during this study.

Duration of treatment / exposure:

The rats were dosed by intragastric intubation for 29 consecutive days.

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
24,000 mg/kg
Basis:
other: nominal

No. of animals per sex per dose:

5 male animals per dose

Control animals:

yes

Details on study design:

- Dose selection rationale: Under the conditions of a previously conducted study, the no-observed-effect level (NOEL)a for H-27201 and H-27203 was 24,000 mg/kg/day for male rats, based on the lack of any adverse effects at this dose.
- Rationale for animal selection: Rats were selected for use on study on the bases of adequate body weight gain and freedom from clinical signs of disease or injury. They were distributed by computerised, stratified randomisation into study groups as designated in the study design, so that there were no statistically significant differences among group body weight means.

Positive control:

no

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily throughout the study
- Cage side observations checked: Detection of moribund or dead rats and abnormal behaviour and/or appearance among rats.
Each rat was individually handled and examined for abnormal behaviour and appearance (careful clinical observations ) daily approximately 1 -2 hours after receiving the final daily dose. Any abnormal clinical signs were recorded.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Day 0 and weekly thereafter
At every weighing, each rat was individually handled and examined for abnormal behaviour and appearance. Detailed clinical observations in a standardized arena were also evaluated on all rats. The detailed clinical observation included (but were not limited to ) evaluation of fur, skin, eyes, mucous membranes, occurence of secretions and excretions, autonomic nervous systemactivity (lacrimation, piloerection, and unusual respiratory pattern), changes in gait, posture, response to handling, presence of clonic, tonic, stereotypical, or bizarre behaviour. Any abnormal clinical signs noted were recorded.

BODY WEIGHT: Yes
- Time schedule for examinations: Day 0 and weekly thereafter

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Time schedule for examinations: weekly

FOOD EFFICIENCY: Yes

WATER CONSUMPTION AND COMPOUND INTAKE : No data

OPHTHALMOSCOPIC EXAMINATION: see below (sacrifice and pathology)

HAEMATOLOGY: Yes, blood samples for hematology were collected from the orbital sinus/abdominal vena cava of each animal.
- Time schedule for collection of blood: A clinical pathology evaluation was conducted on all surviving rats on test day 29.
- Anaesthetic used for blood collection: Yes, the animals were under carbon dioxide anesthesia.
- Animals fasted: Yes, animals were fasted after 3 p.m. for at least 15 hours.
- Parameters checked: red blood cell count, absolute reticulocyte count, hemoglobin, platelet count, hematocrit, white blood cell count, mean corpuscular (cell) volume, differential white blood cell count, mean corpuscular (cell) hemoglobin, microscopic blood smear examination, mean corpuscular (cell) hemoglobin concentration, red cell distribution width, prothrombin time and activated partial thromboplastin time

CLINICAL CHEMISTRY: Yes, blood samples for clinical chemistry measurements were collected from the orbital sinus of each animal.
- Time schedule for collection of blood: A clinical pathology evaluation was conducted on all surviving rats on test day 29.
- Animals fasted: Yes, animals were fasted after 3 p.m. for at least 15 hours.
- Parameters checked: aspartate aminotransferase, glucose, alanine aminotransferase, total protein, sorbitol dehydrogenase, albumin, alkaline phosphatase, globulin, total bilirubin, calcium, urea nitrogen, inorganic phosphorus, creatinine, sodium, cholesterol, potassium, triglycerides and chloride

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER: Bone marrow smears were prepared at sacrifice from all surviving animals. Bone marrow smears were stained with Wright-Giemsa stain, but analysis was not necessary to support experimental findings.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
After approximately 28 days on study (test day 29), the surviving rats were sacrificed and necropsied for evaluation of repeated dose toxicity. The order of sacrifice for scheduled deaths was stratified among treatment groups. Rats were euthanised by carbon dioxide anesthesia and exsanguination. Gross examinations were performed on all rats. Final body weights and organ weights were recorded.
The following tissues were collected from all (15/15) rats: digestive system (liver, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, salivary glands, pancreas), urinary system (kidneys, urinary bladder), respiratory system (lungs, trachea, nose, larynx/pharynx), cardiovascular system (heart, aorta), hematopoietic system(spleen, thymus, mandibular lymph node, mesenteric lymph node, bone marrow (collected with the femur and sternum), Peyer's patches (collected from sections of the digestive tract)), endocrine system (pituitary gland, thyroid gland, parathyroid glands, adrenal glands), nervous system (brain (three sections; including cerebrum, cerebellum, medulla/pons), spinal cord (three levels; cervical, mid-thoracic, lumber) sciatic nerve), musculoskeletal system (skeletal muscle, femur/knee joint, sternum), reproductive system male (testes, epididymides, prostate, seminal vesicles) and miscellaneous (skin, eyes (including retina and optic nerve), gross observations.
The following tissues were weighed from rats sacrificed by design at the end of the 28-day repeated dose toxicity study: liver, kidneys, adrenal glands, thymus, brain, spleen, heart, testes, and epididymides. Organ weight ratios (% final body weight, % brain weight) and group mean values were calculated.

HISTOPATHOLOGY: Yes
All tissues collected from all rats were processed to slides and evaluated microscopically.
Testes, epididymides, and eyes were fixed in modified Davidson’s solution. All other tissues were fixed in 10% neutral buffered formalin. Processed tissues were embedded in paraffin, sectioned approximately 5-6 microns thick, stained with hematoxylin and eosin (H&E), and examined microscopically by a veterinary pathologist.

Other examinations:

no

Statistics:

Significance was judged at p < 0.05. Statistical comparisons were made between the control group (group I) and H-27201 (group III) and H-27203 (group V). Statistical comparison was performed between the two treatment groups H-27201 (group III) and H-27203 (group V).

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
No test substance-related signs were noted on daily or weekly clinical observations during the 28-day oral gavage study. Some non-specific clinical observations were noted in some animals but were not test substance related. These observation which included a neck wound, misshapen ears and hair loss. These types of clinical signs are commonly reported among rats of this sex and age group. One animal, number 305 (H-27201), was found dead at the end of the first week. During the second week, animal number 505 (H-27203) was observed to have breathing noises and was sacrificed. The necropsy report indicated both deaths were attributed to trauma from gavage. The remaining 13 male rats survived until the scheduled sacrifice (test day 29).

BODY WEIGHT AND WEIGHT GAIN
No statistically significant test substance related effects were observed on mean body weight or body weight gains in the two treatment groups when comparison was made between the groups and when each group was compared to the control.

FOOD CONSUMPTION AND FOOD EFFICIENCY
There were no statistically significant differences in food consumption and food efficiency in the two treatment groups when compared against each other, and when compared to the control.

HAEMATOLOGY
There were no statistically significant or treatment-related changes in hematologic parameters in male rats exposed to 24,000 mg/kg TiO2 particles in either group when compared against each other or when compared to the control.
There were no statistically significant or treatment-related changes in coagulation parameters in male rats.

CLINICAL CHEMISTRY
There were no statistically significant or treatment-related changes in clinical chemistry parameters in male rats.

ORGAN WEIGHTS
There were no test substance-related effects on organ weights. All individual and mean organ weight differences were considered to be spurious and unrelated to test substance administration.

GROSS PATHOLOGY
There were no test substance-related deaths. Of the 15 rats on study (5 males/dose group), two died before the terminal sacrifice, both due to dosing accidents. Gross examination demonstrated perforation of the esophagus in both rats.
There were no test substance-related gross observations in the treatment or the control groups. All gross observations at the terminal necropsy were consistent with normal background lesions in rats of this age and strain.

HISTOPATHOLOGY: NON-NEOPLASTIC
Microscopic examination of the two rats that died before the terminal sacrifice revealed several lesions associated with esophageal trauma and morbidity (e.g., rupture-associated inflammation, splenic and thymic lymphoid depletion, bone marrow hyperplasia, centrilobular liver necrosis, esophageal reflux and pulmonary aspiration).
There were no test substance-related adverse microscopic findings in the treatment or the control groups.
The observation of gavage material in macrophages within the mesenteric lymph nodes and Peyer’s patches of rats given the test substance was considered to be the expected disposition of a non-toxic particulate. There was no evidence of an adverse cellular response to the presence of the phagocytised particulates. The observation of these particulates was facilitated by their optical birefringence.
Inflammation in the nose of 3/5 Group III rats and 2/5 Group V rats was the result of gastro-esophageal reflux in all but one rat (Group III). This latter rat had minimal focal inflammation in the turbinate mucosa that was interpreted to be incidental. Three of the remaining four rats with evidence of reflux had esophageal perforations identified either by gross or microscopic examination. The remaining rat had minimal gavage material and inflammation and no identified esophageal lesion. All cases of gastro-esophageal reflux and associated inflammation were interpreted to be dosing related and not test substance related.
All other microscopic findings were consistent with either the normal background lesions in rats of this age and strain or were the result of a dosing accident.

Dose descriptor:

NOEL

Effect level:

24 000 mg/kg bw/day (nominal)

Sex:

male

Critical effects observed:

not specified

Conclusions:

Male rats were exposed by oral gavage for 29 days to 24,000 mg/kg TiO2 particles H-27201, H-27203, or the vehicle. Under the conditions of this study, the no-observed-effect level (NOEL) for H-27201 and H-27203 was 24,000 mg/kg/day for male rats, based on the lack of any adverse effects at this dose.

Endpoint conclusion

Dose descriptor:

NOAEL

3 500 mg/kg bw/day

Study duration:

chronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Read across concept

Synthetic rutile consists primarily of a titanate phase (solid solution) most of which is titanium in an oxidised form. Upon ingestion, a low rate of dissolution in the GI tract is assumed, based on the experimental verified inertness of the material. Any material being released from Synthetic rutile under physiological conditions will be in the form of ionic titanium, which is similarly the case for titanium dioxide, thus read-across from repeated dose oral toxicity data on titanium dioxide is considered feasible without any restrictions.

Furthermore, transformation/dissolution testing according to “OECD 29 Environmental Health and Safety Publications, Series on testing and assessment, Guidance document on transformation/ dissolution of metals and metal compounds in Aqueous media” has shown that synthetic rutile compared to titanium dioxide has a similar release rate of titanium ions (please refer to the respective entry under the endpoint water solubility).

 

Repeated dose toxicity, oral

Male and female F344 rats (8-weeks old, 50 animals per group) were fed a diet containing 2% corn oil and 25,000 or 50,000 ppm titanium dioxide for 103 weeks (7 days per week). Groups of male and female B6C3F1 mice (36 days old, 50 animals per group) were fed analogously. With the exception of white faeces, there was no other clinical sign that was judged to be related to titanium dioxide exposure (for detailed information please refer to the endpoint study records reported under section carcinogenicity).

In a 28 -days study male rats were exposed by oral gavage for 29 days to 24,000 mg/kg titanium dioxide particles (test items: H-27201, H-27203), or the vehicle. Under the conditions of this study, the no-observed-effect level for titanium dioxide was 24,000 mg/kg/day for male rats, based on the lack of any adverse effects at this dose.

Repeated dose toxicity, dermal

Titanium dioxide was tested in various percutaneous absorption tests which have been reviewed by the Scientific Committee on cosmetic products and non-food products (SCCNFP/0005/98, 2000) and which concluded “extensive tests for percutaneous absorption, mostly in vitro, indicate that absorption does not occur, either with coated or uncoated material; one experiment found some evidence that a little of the material could be found in the openings of the follicles. [...] The toxicological profile of this material does not give rise to concern in human use, since the substance is not absorbed through the skin. In view, also, of the lack of percutaneous absorption, a calculation of the margin of safety has not been carried out.”

Repeated dose toxicity, inhalation

The conduct of a repeated dose toxicity study via inhalation is unjustified as inhalation of the substance is considered negligible, based on the outcome of the dustiness testing according to method EN 15051/ DIN 33897-2, as reported under section particle size distribution (granulometry). The results demonstrate that synthetic rutile has a limited ability to be inhaled by humans: 0.025 % of airborne material is estimated to be inhalable, whereas about 0.002 % or less of inhaled material is predicted to be deposited in the pulmonary region (PU), i.e. respirable fraction. The material deposited in the tracheobronchial (TB) and the extrathoracic region (Head) may be assumed to be cleared to the GI tract (i.e., by mucociliary escalation and subsequent swallowing).

For the reasons presented above, the conduct of a repeated dose toxicity study via inhalation is considered dispensable.

Justification for classification or non-classification

Repeated dose toxicity, oral

The reference National Cancer Institute (1979) is considered as the key study for repeated dose toxicity via oral application and will be used for classification. Rats were dosed at 3500 mg/kg bw/day orally via feed. Based on the lack of any adverse effects, the no observed adverse effect level (NOAEL) via oral application for titanium dioxide was established at 3500 mg/kg bw/day

(for detailed information please refer to the endpoint study records reported under section carcinogenicity).

The classification criteria according to regulation (EC) 1272/2008 as specific target organ toxicant (STOT) – repeated exposure, oral are not met since no reversible or irreversible adverse health effects were observed immediately or delayed after exposure and the no observed adverse effect level (NOAEL) via oral application is above the guidance value for a Category 1 classification of 10 mg/kg bw/day and above the guidance value for a Category 2 classification of 100 mg/kg bw/day. For the reasons presented above, no classification for specific target organ toxicant (STOT) – repeated exposure, oral is required.

It is considered that these conclusions can be read across to Synthetic Rutile.

 

Repeated dose toxicity, dermal

Titanium dioxide was tested in various percutaneous absorption tests which have been reviewed by the Scientific Committee on cosmetic products and non-food products (SCCNFP/0005/98, 2000) and which concluded “extensive tests for percutaneous absorption, mostly in vitro, indicate that absorption does not occur, either with coated or uncoated material; one experiment found some evidence that a little of the material could be found in the openings of the follicles. [...] The toxicological profile of this material does not give rise to concern in human use, since the substance is not absorbed through the skin. In view, also, of the lack of percutaneous absorption, a calculation of the margin of safety has not been carried out.”

For the reasons presented above, no classification for specific target organ toxicant (STOT) – repeated exposure, dermal is required.

It is considered that these conclusions can be read across to Synthetic Rutile.

Repeated dose toxicity, inhalation

The conduct of a repeated dose toxicity study via inhalation is unjustified as inhalation of the substance is considered negligible, based on the outcome of the dustiness testing according to method EN 15051/ DIN 33897-2, as reported under section particle size distribution (granulometry). The results demonstrate that synthetic rutile has a limited ability to be inhaled by humans: 0.025 % of airborne material is estimated to be inhalable, whereas about 0.002 % or less of inhaled material is predicted to be deposited in the pulmonary region (PU), i.e. respirable fraction. The material deposited in the tracheobronchial (TB) and the extrathoracic region (Head) may be assumed to be cleared to the GI tract (i.e., by mucociliary escalation and subsequent swallowing).

For the reasons presented above, the conduct of a repeated dose toxicity study via inhalation is considered dispensable.

It is considered that these conclusions can be read across to Synthetic Rutile.