Registration Dossier

Administrative data

Endpoint:
short-term repeated dose toxicity: inhalation
Type of information:
experimental study
Remarks:
study currently ongoing
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2019

Materials and methods

Principles of method if other than guideline:
5-day inhalation exposure with 21 days recovery group.
Ma-Hock L, Burkhardt S, Strauss V, Gamer AO, Wiench K, van Ravenzwaay B, Landsiedel R. 2009. Development of a short-term inhalation test in the rat using nano-titanium dioxide as a model substance Inhal Toxicol 21, 102-118
GLP compliance:
yes (incl. certificate)
Limit test:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH; 97633 Sulzfeld
- Age at study initiation: about 7 weeks
- Weight at study initiation (means):
- Housing: The rats were housed together (up to 5 animals per cage)
- Diet: Mouse/rat laboratory diet; ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24
- Humidity (%): 30 - 70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:
other: dust aerosol
Type of inhalation exposure:
nose/head only
Vehicle:
air
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Generator systems: Solid particle generators (brush-generator), Aerosol mixing tube (Stainless steel), Glass cyclonic separators
- Generation procedure: The test substance was used unchanged. By means of dust generators the substance to be tested is generated into dust aerosols using compressed air in a mixing stage, mixed with conditioned air and passed into the inhalation systems via cyclonic separators. For each concentration, a solid particle generator (brush-generator) was used for generating the dust. The concentration was adjusted by varying the piston feed and by varying the brush rotation. For each concentration the dust aerosol was generated with the dust generator and compressed air inside a mixing stage mixed with conditioned dilution air and passed via the cyclonic separator into the inhalation system.

EXPERIMENTAL PROCEDURE
- Head-nose exposure systems: The inhalation atmosphere was maintained inside aerodynamic exposure systems consisting of a cylindrical inhalation chamber made of stainless steel sheeting and cone-shaped outlets and inlets. The rats were restrained in glass exposure tubes. Their snouts projected into the inhalation chamber and thus they inhaled the aerosol. The exposure systems were located in exhaust hoods in an air conditioned room.
- Exposures: The head-nose exposure technique was preferably selected for this aerosol/dust/ inhalation study to minimize fur contamination of the animals with the substance, which cannot be avoided during whole-body exposure. Fur contamination may lead to an additional dermal and oral uptake (animals preen as their fur becomes contaminated). Thus an estimation of an nominal dose, taken up by the animals and its correlation to a toxic effect becomes more difficult. Furthermore, by using the dynamic mode of operation with a low-volume chamber, the equilibrium characteristic of this exposure technique is favorable: t99 (the time to reach 99% of the final target concentration) is shorter as compared to whole-body chambers with a higher chamber volume. A positive pressure was maintained inside the exposure systems by adjusting the air flow of the exhaust air system. This ensured that the aerosol in the breathing zones of the animals was not diluted by laboratory air. In order to accustom the animals to exposure they were treated with supply air under conditions comparable to exposure on two days before start of exposure (pre-exposure period). Then all test groups were exposed for 6 hours from Monday to Friday to reach 5 exposures. The animals did not have access to water or feed during the exposure.
- Measurements of the exposure conditions: The following exposure parameters were recorded: Supply air (conditioned), Supply air 2 (compressed), Exhaust air, Chamber humidity, Chamber temperature, Real time concentration surveillance. No surveillance of the oxygen content in the inhalation system was performed. The air change within the inhalation systems was judged to be sufficient to prevent oxygen depletion by the breathing of the animals and the concentrations of the test substance used could not have a substantial influence on oxygen partial pressure.

The air flows were constantly maintained in the desired range.
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
6 hours
Frequency of treatment:
daily, for five consecutive days
No. of animals per sex per dose:
3/dose/group (main group or recovery group for microscopic examination)
5/dose/group (main group or recovery group for blood sampling and BAL)
Control animals:
yes, concurrent vehicle
Details on study design:
On study day 4 after exposure and on study day 25, 3 animals per group and time point were sacrificed underwent gross necropsy. Selected organs were weighed, a broad set of organs and tissues were preserved, respiratory tract was examined histologically.
On study days 7 and 28, blood was sampled from 5 rats/group and time point. Clinical chemistry parameters, hematology parameters and acute phase proteins were examined in blood. After blood sampling the animals underwent bronchoalveolar lavage. Lavage fluid was examined for cytological and biochemical parameters including selected antigens.

Examinations

Observations and examinations performed and frequency:
MORTALITY: The animals were examined for evident signs of toxicity or mortality twice a day (in the morning and in the late afternoon) on working days and once a day (in the morning) on Saturdays, Sundays and public holidays.

CLINICAL OBSERVATIONS: The clinical condition of the test animals was recorded once daily during the pre-exposure period and on post-exposure observation days on working days. On exposure days, clinical observation was performed at least 3 times daily, before, during and after exposure. During exposure only a group wise examination was possible.

BODY WEIGHT: The body weight of the animals was determined at the start of the pre-exposure (day -4), and then, as a rule, twice a week (Monday and Friday), as well as prior to gross necropsy. As a rule, the animals were weighed at the same time of the day. Body weight change was calculated as the difference between body weights from Monday to Friday. The main reason for this type of calculation is to show body weight change of the exposure week without the exposure-free weekend. It enables detection of minor decrease of body weight gain, which may be overlooked because the animals recover during the weekend. Group means were derived from the individual differences.

CLINICAL PATHOLOGY: In the morning blood was taken from the retrobulbar venous plexus from fasted animals. The animals were anaesthetized using isoflurane (Isoba, Essex GmbH Munich, Germany). The blood sampling procedure and subsequent analysis of blood and serum samples were carried out in a randomized sequence. The examinations for haematology and clinical chemistry were carried out in 5 animals per test group.

HAEMATOLOGY: The following parameters were determined in blood with EDTA-K3 as anticoagulant using a particle counter (Advia 120 model; Bayer, Fernwald, Germany): Leukocyte count (WBC), Erythrocyte count (RBC), Hemoglobin (HGB), Hematocrit (HCT), Mean corpuscular volume (MCV), Mean corpuscular hemoglobin (MCH), Mean corpuscular hemoglobin concentration (MCHC), Platelet count (PLT), Differential blood count, Reticulocytes (RET). Clotting tests were carried out using a ball coagulometer (AMAX destiny plus model; Trinity biotech, Lemgo, Germany). Prothrombin time (Hepato Quick’s test) (HQT) was measured. Furthermore, blood smears were prepared and stained according to WRIGHT without being evaluated, because of non-ambiguous results of the differential blood cell counts measured by the automated instrument. (reference: Hematology: Principles and Procedures, 6th Edition, Brown AB, Lea & Febiger, Philadelphia, 1993, page 101).

CLINICAL CHEMISTRY: clinicochemical parameters: Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), Alkaline phosphatase (ALP), γ-Glutamyltransferase (GGT), Sodium (NA), Potassium (K), Chloride (CL), Inorganic phosphate (INP), Calcium (CA), Urea (UREA), Creatinine (CREA), Glucose (GLUC), Total bilirubin (TBIL), Total protein (TPROT), Albumin (ALB), Globulins (GLOB), Triglycerides (TRIG), Cholesterol (CHOL).
ACUTE PHASE PROTEINS IN SERUM: Rat α2-macroglobulin was measured with an ELISA . Rat haptoglobin was measured with an ELISA.

BRONCHOALVEOLAR LAVAGE FLUID (BAL): The animals designated for lung lavage were killed by exsanguination from aorta abdominalis and vena cava under Narcoren® anesthesia. The lung was lavaged by two instillations of physiologic saline. The following examinations were carried out in 5 male animals per test group.
- Cytology in BAL: Total cell counts were determined using a haematology analyzer. Cytocentrifuge preparations were stained according to Wright and evaluated microscopically. Parameters: Total cell count (BALTCN), Macrophages (BALMPH), Polymorphonuclear neutrophils (BALPMN), Lymphocytes (BALLY), Eosinophils (BALEO), Monocytes (BALMO), Atypical cells (BALATY).
- Total Protein and enzymes in BAL: An automatic analyzer was used to examine the humoral parameters in the bronchoalveolar lavage fluid. Parameter: γ−Glutamyltransferase (GGT), Protein (MTP), Lactate dehydrogenase (LDH), Alkaline phosphatase (ALP), N-acetyl-β-Glucosaminidase (NAG)
- Antigens in BAL: The antigens were measured with MTP ELISAs. The following antigens were measured in BALF: Rat monocyte chemoattractant protein-1 (rat MCP-1) level measured with an Instant ELISA , Rat cytokine-induced neutrophil chemoattractant-1 level (rat CINC-1/IL-8) measured with an ELISA, Macrophage colony stimulating factor (M-CSF) measured with a Quantikine Mouse M-CSF ELISA , Rodent osteopontin measured with an ELISA .
Sacrifice and pathology:
NECROPSY: All animals were sacrificed under pentobarbitone anesthesia by exsanguination from the abdominal aorta and vena cava. The exsanguinated animals were necropsied and assessed by gross pathology.

ORGAN WEIGHTS: The following weights were determined in all animals sacrificed on schedule: Adrenal glands, Brain, Epididymides, Heart, Kidneys, Liver, Lungs, Spleen, Testes, Thymus, Thyroid glands.

HISTOPATHOLOGY: The following organs or tissues were fixed in 4% buffered formaldehyde or modified Davidson’s solution: All gross lesions, Adrenal glands, Brain with olfactory bulb, Bone marrow (femur), Epididymides, Eyes with optic nerve and eyelids, Heart, Kidneys, Larynx/Pharynx, Liver, Lungs, Lymph nodes (tracheobronchial and mediastinal lymph nodes), Nose (nasal cavity), Oesophagus, Seminal vesicles, Spinal cord (cervical, thoracic and lumbar cords), Stomach (forestomach and glandular stomach), Spleen, Testes, Thyroid glands, Thymus, Trachea, Urinary bladder. From the liver, one additional slice of the Lobus dexter medialis and the Lobus sinister lateralis were fixed in Carnoy’s solution and embedded in paraplast. The testes were fixed in modified Davidson’s solution. Fixation was followed by histotechnical processing and examination by light microscopy. Tissues and organs to be examined histologically: All gross lesions (only affected animals), Nasal cavity (4 levels), Larynx (3 levels), Trachea, Lungs (5 lobes), Lymph nodes (tracheobronchial and mediastinal lymph nodes).

Results and discussion

Effect levels

Sex:
male
Remarks on result:
other: the study is currently ongoing

Target system / organ toxicity

Critical effects observed:
no

Applicant's summary and conclusion