Titanium diboride

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1300 (Acute inhalation toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Titanium diboride

EC Number:

234-961-4

EC Name:

Titanium diboride

Cas Number:

12045-63-5

Molecular formula:

B2Ti

IUPAC Name:

titanium diboride

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

Titanium Diboride BATCH NO 703M1, mass median diameter 3.44µm; Test item sponsored by Lead Registrant ESK Ceramics GmbH & Co. KG, purity see section 1.4

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS

Number of Animals: 10

Sex: 5 Males and 5 Females. The females assigned to test were nulliparous and non-pregnant.

Species/Strain: Rat/Sprague-Dawley derived, albino.

Age/Body weight: Young adult (11-12 weeks)/males 293-335 grams and females 226-234 grams at experimental start.

Source: Received from Harlan Laboratories, Inc. on March 21, 2012.

ENVIRONMENTAL CONDITIONS

Housing: The animals were singly housed in suspended stainless steel caging with mesh floors, which conform to the size recommendations in the most recent Guide for the Care and Use of Laboratory Animals (Natl. Res. Council, 2011). Litter paper was placed beneath the cage and was changed at least three times per week.

Animal Room Temperature and Relative Humidity Ranges: 21-23ºC and 42-57%, respectively.

Animal Room Air Changes/Hour: 13. Airflow measurements are evaluated regularly and the records are kept on file at Product Safety Labs.

Photoperiod: 12-hour light/dark cycle

Acclimation Period: 22 days

Food: Harlan Teklad Global 16% Protein Rodent Diet® #2016. The diet was available ad libitum, except during the exposure.

Water: Filtered tap water was supplied ad libitum by an automatic water dispensing system except during exposure.

Contaminants: There were no known contaminants reasonably expected to be found in the food or water at levels which would have interfered with the results of this study. Analyses of the food and water are conducted regularly and the records are kept on file at Product Safety Labs.

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

air

Details on inhalation exposure:

NOSE-ONLY EXPOSURE CHAMBER: A nose-only inhalation chamber with an internal volume of approximately 6.7 liters (Mini-Nose Only Inhalation Chamber, ADG Developments LTD) was used for exposure. Animals were individually housed in polycarbonate holding tubes which seal to the chamber with an “O” ring during exposure. The base unit terminates the chamber with a 0.5-inch diameter tube for discharged air.

AIR SUPPLY: Approximately 30.0 liters per minute (Lpm) of filtered air was supplied by an air compressor (Powerex Model: SES05) to the dust generator. An additional 6.0 Lpm of compressed mixing air, supplied by an air compressor (Powerex Model: SES05) which was introduced into the chamber to help uniformly distribute the test atmosphere by creating a vortex at the chamber inlet. Compressed airflow was measured with a Mass Flowmeter (Omega, Model #FMA-5613). Chamber airflow was monitored throughout the exposure period and recorded periodically. Total airflow was 36.0 Lpm. Based on the volume of the inhalation chamber, this airflow provided approximately 322 air changes per hour during the study.
.
AMBIENT CONDITIONS: The exposure tube temperature and relative humidity ranges during exposure were 20-21ºC and 15-16%, respectively. The room temperature and relative humidity ranges during exposure were 20-21ºC and 32-33%, respectively. In-chamber measurements and room conditions were measured with a Temperature-Humidity Monitor (Fisher Scientific, Model #11-661-18). Temperature and relative humidity values were recorded every 15 minutes for the first hour of exposure and every 30 minutes thereafter.

DUST GENERATION: The test substance was aerosolized using a modified Wright Dust Generator (Dayton, Model #4Z538A) driven by a variable speed motor D.C. speed control with 0-100 potentiometer. The test substance was packed into the dust container (Wright, Model DF183) and compressed to 1,000 lbs/in2 using a lab press (Carver, Model C). The container was then fitted with a stainless steel cutting head (Model DF194SS) and cutting blade (Model DF191SS). Compressed/mixing air was supplied to the dust generator at 30 psi. The aerosolized dust was then fed directly into the chamber through the dust outlet assembly

CHAMBER CONCENTRATION MEASUREMENTS: Gravimetric samples were withdrawn at six intervals from the breathing zone of the animals. Samples were collected using 37 mm glass fiber filters (GF/B Whatman) in a filter holder attached by ¼ inch Tygon tubing to a vacuum pump (Westech Vacuum Pump). Filter papers were weighed before and after collection to determine the mass collected. This value was divided by the total volume of air sampled to determine the chamber concentration. The collections were carried out for 1 minute at airflows of 4 Lpm. Sample airflows were measured using a Mass Flowmeter (Aalborg, Model #GFC-17).

PARTICLE SIZE DISTRIBUTION: An eight-stage ACFM Anderson Ambient Particle Sizing Sampler was used to assess the particle size distribution of the test atmosphere. Samples were withdrawn from the breathing zone of the animals at two intervals. The filter paper collection stages were weighed before and after sampling to determine the mass collected upon each stage. The aerodynamic mass median diameter and geometric standard deviation were determined graphically using two-cycle logarithmic probit axes.
- Particle size distribution: see table 1
- MMAD : 3.5 µm +- 0.08

EXPOSURE PERIOD: The animals were exposed to the test atmosphere for 4 hours and 1 minute. The exposure period was extended beyond 4 hours to allow the chamber to reach equilibrium (T99). The times for 90 and 99% equilibration of the chamber atmosphere were 0.4 and 0.9 minutes, respectively. At the end of the exposure period, the generation was terminated and the chamber was operated for a further 17 minutes with clean air. At the end of this period the animals were removed from the exposure tube. Prior to being returned to their cages, excess test substance was removed from the fur of each animal.

Analytical verification of test atmosphere concentrations:

yes

Concentrations:

see table 2

No. of animals per sex per dose:

5 male/ 5female

Details on study design:

Individual body weights of the animals were recorded prior to test substance exposure (initial) and on Days 1, 3, 7 and 14 (termination).

All animals were observed for mortality during the exposure period. The animals were examined for signs of gross toxicity, and behavioral changes upon removal from the exposure tube and at least once daily thereafter for 14 days. Observations included gross evaluation of skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous systems, somatomotor activity and behavior pattern. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhea, and coma.

All rats were euthanized via CO2 inhalation on Day 14. Gross necropsies were performed on all animals. Tissues and organs of the thoracic and abdominal cavities were examined.

Results and discussion

Preliminary study:

not applicable

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.05 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Mortality:

no mortalities

Clinical signs:

other: Following exposure, all animals exhibited abnormal respiration. However, the animals recovered from this symptom by Day 6 and appeared active and healthy for the remainder of the 14-day observation period.

Body weight:

Although all animals lost body weight by Day 1 and/or Day 3, all animals showed a continued weight gain thereafter through Day 14.

Gross pathology:

No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of this study, the single exposure acute inhalation LC50 of the test substance is greater than 5.05 mg/L in male and female rats. Based on the results of this study, Titanium Diboride has no labeling requirements for acute inhalation toxicity and is not classified.

Executive summary:

An acute inhalation toxicity test was conducted with rats to determine the potential for Titanium Diboride to produce toxicity from a 4-hour exposure via the inhalation (nose-only exposure) route. Under the conditions of this study, the single exposure acute inhalation LC₅₀ of the test substance is greater than 5.05mg/L in male and female rats. Based on the results of this study, Titanium Diboride has no labeling requirements for acute inhalation toxicity and is not classified.

After establishing the desired generation procedures during pre-test trials, ten healthy rats (5/sex) were exposed to the test atmosphere for 4 hours. Chamber concentration and particle size distributions of the test substance were determined periodically during the exposure period. The animals were observed for mortality, signs of gross toxicity, and behavioral changes at least once daily for 14 days following exposure. Body weights were recorded prior to exposure and again on Days 1, 3, 7 and 14 (termination). Necropsies were performed on all animals at terminal sacrifice.

The gravimetric chamber concentration was 5.05mg/L. Based on graphic analysis of the particle size distribution as measured with an ACFM Andersen Ambient Particle Sizing Sampler, the mass median aerodynamic diameter was estimated to be 3.5.

All animals survived exposure to the test atmosphere. Following exposure, all animals exhibited abnormal respiration. However, the animals recovered from this symptom by Day 6 and appeared active and healthy for the remainder of the 14-day observation period. Although all animals lost body weight by Day 1 and/or Day 3, all animals showed a continued weight gain thereafter through Day 14. No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period.