tungsten zirconium oxide

Endpoint summary

Description of key information

Acute oral toxicity

In an acute oral toxicity study with female rats (Klimisch 1, Appl, 2018) following the acute toxic class method in accordance with OECD guideline 423, the LD50 of tungsten zirconium (hydroxide) oxide was determined to be greater than 2000 mg/kg bw for female animals, observed over a period of 14 days after dosing. No mortality was observed during the test.

Acute toxicity inhalation

In an acute inhalation toxicity study with rats, performed according to OECD guideline 436 using the read across substance zirconium dioxide (Klimisch 1, Smith, 2010), an LC50 greater than 4.3 mg/L (actual exposure; maximum technically achievable concentration) was derived. No mortality was observed during the test.

Acute dermal toxicity

A key study is available for the oral and inhalation route of exposure. According to the REACH Regulation, for substances other than gases, only one additional route of exposure should be tested other than the oral route of exposure for acute toxicity (Annex VIII, Section 8.5, Column 2). Therefore, it is not necessary to perform an acute dermal toxicity study. Moreover, since the substance does not meet the criteria for classification as STOT SE by oral route and no systemic effects have been observed in the in vivo studies with dermal application (i.e. the GPMT study on skin sensitisation, Tarcai, 2018), no study is needed and the substance can be concluded not to be classified for acute dermal toxicity.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-08-22 to 2017-09-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Version / remarks:

17 Dec 2001

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.1 tris (Acute Oral Toxicity - Acute Toxic Class Method)

Version / remarks:

30 May 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

yes

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Controlled room temperature (15-25°C, below 70 RH%).
- Stability under test conditions: Analysis of stability, homogeneity and concentration of the test item under test conditions was not performed as part of this study.

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The formulation was homogenised to visually acceptable levels and was stirred up to finishing the treatment to ensure sufficient homogeneity. No correction was made for the purity/composition of the test item.

Species:

rat

Strain:

other: Crl:(WI)

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, D-97633 Sulzfeld, Germany
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation: 9 weeks old
- Weight at study initiation: 205 - 232 g. Body weight variation did not exceed +/- 20% of the sex mean.
- Fasting period before study: overnight
- Housing: Type II. polypropylene/polycarbonate cages, with Lignocel 3/4-S Hygienic Animal Bedding produced by J. Rettenmaier & Söhne GmbH + CO.KG (D-73494 Rosenberg, Germany) was available to animals during the study. Arbocel crinklets natural produced by J. Rettenmaier & Söhne GmbH + CO.KG (D-73494 Rosenberg, Germany) was available to animals during the study.
- Diet (e.g. ad libitum): Animals received ssniff® SM R/M "Autoclavable complete diet for rats and mice – breeding and maintenance" produced by ssniff Spezialdiäten GmbH, D-59494 Soest, Germany (Batch number: 262 21592, Expiry date: 31 January 2018), ad libitum.
- Water (e.g. ad libitum): Tap water from the municipal supply, as for human consumption from a 500-mL bottle, ad libitum.
- Acclimation period: At least 12 days before start of treatment under laboratory conditions.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.1 – 23.9 °C
- Humidity (%): 32 – 71 %
- Air changes (per hr): 15-20 air exchanges/hour
- Photoperiod (hrs dark / hrs light): Light-12 hours daily, from 6.00 a.m. to 6.00 p.m.

Route of administration:

oral: gavage

Vehicle:

methylcellulose

Remarks:

1%

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 200 mg/mL
- Amount of vehicle (if gavage): 10 mL/kg
- Justification for choice of vehicle: The selection of the vehicle was based on trial formulations with the test item. The test item was found to be insoluble in distilled water (the formulation separated immediately to different phases) at a concentration of 200 mg/mL. With 1% methylcellulose aqueous solution, the formulation (suspension) was found to be acceptable for oral gavage.
- Lot/batch no. (if required): 5115851

DOSAGE PREPARATION (if unusual): The test item was freshly formulated at a concentration of 200 mg/mL in the vehicle in the Pharmacy of Citoxlab Hungary Ltd. on the day of administration. The formulation container was magnetically stirred continuously up to the end of dose administration procedures. Formulations were used within 4 hours after preparation.

Doses:

A single dose of 2000 mg/kg bw.

No. of animals per sex per dose:

3 females per group, 2 groups

Control animals:

no

Details on study design:

- Procedure: A single dose of 2000 mg/kg bw was administered by oral gavage (using a stainless steel bulb tipped gastric feeding tube attached to a syringe) in the morning. - Food was withheld overnight for a maximum of 16 hours before treatment, and returned 3 hours after treatment.
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Clinical observations were performed on all animals at 30 minutes, 1, 2, 3, 4 and 6 hours after dosing and daily for 14 days thereafter. Individual observations were performed on the skin, fur, eyes, mucous membranes, respiratory, circulatory, autonomic and central nervous system, somatomotor activity and behaviour pattern. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhoea, lethargy, sleep and coma. The body weight was recorded on the day before treatment (Day -1), on the day of the treatment (Day 0), weekly thereafter (Day 7) and at necropsy (Day 14).
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, macroscopic observations

Statistics:

No statistical analysis was performed (the method used is not intended to allow the calculation of a precise LD50 value).

Preliminary study:

Initially, three female animals were treated with 2000 mg/kg bw of the test item. No mortality was observed, therefore further 3 animals were treated at the dose level of 2000 mg/kg bw. As no mortality was observed in this second dose group, further testing was not required according to the test guidelines

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

The test item did not cause mortality at a dose level of 2000 mg/kg bw in any animal.

Clinical signs:

other: All animals were symptom-free during the observation period at a dose level of 2000 mg/kg bw.

Gross pathology:

There was no evidence of macroscopic changes at a dose level of 2000 mg/kg bw in any animal.

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of this study, the acute oral LD50 value of the test item tungsten zirconium hydroxide oxide was found to be above 2000 mg/kg bw in female Crl:(WI) rats.
The substance is not classified according to the CLP Regulation.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Endpoint covered using a study performed with the read across substance zirconium dioxide. The read across justification is attached to IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Remarks on result:

other: Based on the results of the study from Smith (2010) with zirconium dioxide, it was concluded that tungsten zirconium oxide is not expected to present a hazard for acute inhalation toxicity either.

Reference 2

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 April 2010 - 31 May 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1300 (Acute inhalation toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class Method)

Deviations:

no

GLP compliance:

yes

Test type:

acute toxic class method

Limit test:

no

Species:

rat

Strain:

other: Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Raleigh, NC. Animals were received on 20 April 2010.
- Age at study initiation: approximately 11 weeks
- Weight at study initiation: Body weight values ranged from 316 g to 357 g for males and from 220 g to 238 g for females. Individual body weights at assignment were within ± 20% of the mean for each sex.
- Fasting period before study: during acclimation to restraint and during the exposure period
- Housing: Upon arrival, all animals were housed in individual suspended wire-mesh cages. The animals were maintained by the WIL Animal Husbandry staff in accordance with WIL standard operating procedures (SOPs). On the day of exposure, the animals were placed in nose-only exposure holding tubes in the animal room, transported to the exposure room, exposed for the requisite duration and then returned to their home cages.
- Diet (e.g. ad libitum): The basal diet used in this study, PMI Nutrition International, LLC, Certified Rodent LabDiet 5002, is a certified feed with appropriate analyses performed by the manufacturer and provided to WIL.
- Water (e.g. ad libitum): Municipal water supplying the facility is analysed for contaminants according to WIL SOP
- No contaminants were present in animal feed or water at concentrations sufficient to interfere with the objectives of this study. The basal diet and municipal water, delivered by an automatic watering system, were provided ad libitum, except during acclimation to restraint and the exposure period.
- Acclimation period: 5 days, the animals were observed twice daily for mortality and moribundity. The animals were subjected to restraint in the nose-only exposure holding tubes for 1 hour on 27 April 2010 prior to the start of exposure. Animals were held in restraint tubes for 35 minutes prior to initiation of exposure.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): The room temperature control was set to maintain environmental conditions of 71°F ± 5°F (22°C ± 3°C) and 50% ± 20% relative humidity. Room temperature was monitored using the Metasys DDC Electronic Environmental control system and schedule for data collection was on an hourly basis. Actual mean daily temperature ranged from 70.3°F to 72.1°F (21.3°C to 22.3°C).
- Humidity (%): The humidity control was set to maintain environmental conditions of 50% ± 20% relative humidity. Relative humidity was monitored using the Metasys DDC Electronic Environmental control system and as scheduled for data collection on an hourly basis. Mean daily relative humidity ranged from 49.2% to 55.9% during the study.
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 hours light/12 hours dark

IN-LIFE DATES: no data

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: air (for compressed air system) and deionised water (for humidified air system)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: the test substance was delivered using an auger-type feeder (Schenck AccuRate, INc., Whitewater, WI) which fed test substance at a constant rate to a jet mill air micronizer (model 00, Jet-O-Mizer, Fluid Energy Aljet, Hatfield, PA) operating as a particle size reduction and dispersion device.
- Exposure chamber volume: 7.9 L convential nose-only exposure system (designed and fabricated by WIL)
- Method of holding animals in test chamber: Animals were restrained in nose-only exposure holding tubes during exposure
- Source and rate of air: Using 2 regulators, dry compressed air was supplied to the micronizing and inlet ports of the jet mill. The resulting aerosol from the jet mill was delivered to the nose-only exposure system through 22-mm respiratory tubing. A glass cyclone was placed in-line after the jet mill to reduce particle size. A tee fitting was placed at the inlet of the exposure system to provide humidified air. Humidified air was added using a Coilhose Pneumatics regulator and controlled using a rotameter-type flowmeter. Dry compressed air passed through a muffler-type bubbler submerged in a 2-L Erlenmeyer flask filled with deionized water to produce humidified air. The airflows used for the animal exposure is as follows: inlet airflow rate = 28.5-29.2 L/minute, micronizing airflow rate is 18.6L/minute, humidified airflow rate is 7.6 L/minute and total airflow rate is 54.7-55.4 L/minute
- Method of conditioning air: see above (source and rate of air)
- System of generating particulates/aerosols: see above (source and rate of air)
- Method of particle size determination: Three aerosol particle size determinations were conducted for this exposure using a 7-stage stainless steel cascade impactor (model 02-140, In-Tox Products, Moriarty, NM). Pre-weighed, 23-mm stainless steel discs were used as the collection substrates. Samples were collected at approximately 1.8 L/minute for 0.25 minutes. The filters were re-weighed and the particle size calculated based on the impactor stage-cut-offs. The aerosol size was expressed as the mass median aerodynamic diameter (MMAD) and the geometric standard deviation (GSD).
- Treatment of exhaust air: Exhaust atmosphere was filtered using a Solberg filter (Solberg Manufacturing, Inc., Itasca, IL) prior to entering the in-house exhaust system with activated charcoal and HEPA-filtration.
- Temperature, humidity, pressure in air chamber: The room temperature and humidity controls were set to maintain environmental conditions of 71°F±5°F (22°C ± 3°C) and 50%±20% relative humidity. Room temperature and relative humidity were monitored using the Metasys DDC Electronic Environmental control system and were scheduled for data collection on an hourly basis. Actual mean daily temperature ranged from 70.3°F to 72.1°F (21.3°C to 22.3°C) and mean daily relative humidity ranged from 49.2% to 55.9% during the study

TEST ATMOSPHERE
- Actual exposure concentrations: Actual exposure concentrations were determined using standard gravimetric methods. Samples were collected on pre-weighed, 25-mm glass-fiber filters (type A/E, PALL Corporation, Ann Arbor, MI) held in an open-faced filter holder positioned in the animal breathing zone within the nose-only exposure system. Following sample collection, the filters were re-weighed and the concentration calculated as the filter weight difference divided by the sample volume. Samples were collected at approximately 2 L/minute for 0.5 mintues.


VEHICLE
- Composition of vehicle (if applicable): not applicable
- Concentration of test material in vehicle (if applicable): not applicable
- Justification of choice of vehicle: not applicable
- Lot/batch no. (if required): not applicable
- Purity: not applicable

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: Effective cut-off diameter: 5.27 µm for stage 1, 4.22 µm for stage 2, 3.20 µm for stage 3, 1.90 µm for stage 4, 1.07 µm for stage 5, 0.41 µm for stage 6 and 0.27 µm for stage 7
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): 2.00 µm (mean MMAD) and 1.75 (Mean GSD)

CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration: The target exposure concentration was based on toxicity data from similar compounds as outlined in the product MSDS. Under the generation and exposure conditions of this study and requirements for a particle size of 1 to 4 microns and maintenance of a stable concentration for the 4-hour exposure period, it was determined that the maximum obtainable concentration of zirconium dioxide as a dust aerosol was approximately 4.3 mg/L. Since no animals died following exposure to the maximum obtainable concentration of the test substance, additional exposure levels were not required.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

Actual exposure concentration: 4.3 mg/L (SD 1.39 mg/L), this is the maximum obtainable mean concentration for a 4-hour exposure. The nominal exposure concentration was 41.4 mg/L.

No. of animals per sex per dose:

3

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing:
Body weights were obtained immediately prior to exposure on study day 0 and on post-exposure days 1, 3, 7, and 14.
Mortality: each animal was observed for mortality at the approximate midpoint of exposure, immediately following exposure on study day 0, and twice daily thereafter for 14 days.
Clinical observations: each animal was observed immediately following exposure on study day 0 and once daily thereafter for 14 days.
- Necropsy of survivors performed: yes; animals at the scheduled necropsy were euthanized by isoflurane anesthesia followed by exsanguination. The major organ systems of the cranial, thoracic, and abdominal cavities were examined for all animals.

Statistics:

no data

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 4.3 other: mg/L (actual exposure concentration: maximum technically achievable concentration)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

None of the animals died during exposure or during the 14-day post-exposure observation period. Based on the data obtained, the LC50 of zirconium dioxide was found to be greater than 4.3 mg/L, the maximum obtainable mean concentration.

Clinical signs:

other: There were no toxicologically significant clinical signs immediately following exposure. Several animals were noted with clear material on the neck, forelimb(s), trunk, and urogenital area, red material around the nose and mouth, and/or yellow material ar

Body weight:

All animals lost weight (10 g to 39 g) from study day 0 to 1. One male lost weight (9 g) from study day 1 to 3. All animals surpassed their initial (study day 0) body weight by study day 14 and were considered normal.

Gross pathology:

There were no macroscopic findings for any animal at the scheduled necropsy.

Interpretation of results:

GHS criteria not met

Conclusions:

Based on the results of this study, the LC50 of zirconium dioxide was greater than 4.3 mg/L, the maximum obtainable mean concentration, when male and female albino rats were exposed to a dust aerosol of the test substance as a single, 4-hour, nose-only exposure.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance does not meet the criteria for classification as acute toxicity or STOT SE by the oral route and no systemic effects have been observed in in vivo studies with dermal exposure (e.g. skin irritation, skin sensitisation)

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Acute oral toxicity

In an acute oral toxicity study with female rats (Klimisch 1, Appl, 2018) following the acute toxic class method in accordance with OECD guideline 423, the LD50 of tungsten zirconium (hydroxide) oxide was determined to be greater than 2000 mg/kg bw for female animals, observed over a period of 14 days after dosing. No mortality was observed during the test.

Acute toxicity: inhalation

Since no data are available on tungsten zirconium oxide, a key study, performed with the read across substance zirconium dioxide, is included in the dossier (Smith, 2010). As no mortality occurred during the study, the 4-h LC50 was higher than 4.3 mg/L (i.e. the maximal technically achievable mean concentration) in male and female rats after nose-only inhalation exposure to a dust aerosol of zirconium dioxide.

Although the LC50 is lower than the classification cut-off value of 5 mg/L for category 4 classification (CLP), further testing was considered not feasible/necessary as no mortality occurred at the maximum technically achievable concentration. Therefore classification of zirconium dioxide for acute inhalation toxicity was deemed unnecessary. The results of the study are considered applicable for tungsten zirconium oxide as well. For justification of read across, see IUCLID Section 13.

Acute dermal toxicity

A key study is available for the oral and inhalation route of exposure. According to the REACH Regulation, for substances other than gases, only one additional route of exposure should be tested other than the oral route of exposure for acute toxicity (Annex VIII, Section 8.5, Column 2). Therefore, it is not necessary to perform an acute dermal toxicity study. Moreover, since the substance does not meet the criteria for classification as STOT SE by oral route and no systemic effects have been observed in the in vivo studies with dermal application (i.e. the GPMT study on skin sensitisation, Tarcai, 2018), no study is needed and the substance can be concluded not to be classified for acute dermal toxicity.

Justification for classification or non-classification

Based on the available data for the substance itself (oral) and the read across substance zirconium dioxide (inhalation), the substance does not need to be classified for acute toxicity after oral, dermal or inhalation exposure under the CLP Regulation.