Dimolybdenum trizinc nonaoxide

Endpoint summary

Description of key information

Two reliable acute toxicity studies are available by the oral and inhalation routes of exposure. These were conducted in accordance with GLP and OECD Guidelines.

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 420 (Acute Oral Toxicity - Fixed Dose Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.1 bis (Acute Oral Toxicity - Fixed Dose Procedure)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

fixed dose procedure

Limit test:

yes

Species:

rat

Strain:

Wistar

Remarks:

RccHan:WIST

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Envigo RMS (UK) Limited
- Females (if applicable) nulliparous and non-pregnant: Yes
- Age at study initiation: 8 to 12 weeks
- Weight at study initiation: The bodyweight variation did not exceed +/- 20% of the mean bodyweight.
- Fasting period before study: Yes overnight fast before dosing and for approximately 3 to 4 hours after dosing.
- Housing: Suspended solid-floor polypropylene cages furnished with wood flakes.
- Diet (e.g. ad libitum): 2014C Teklad Global Rodent diet
- Water (e.g. ad libitum): Mains drinking water provided ad libitum.
- Acclimation period: At least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25°C
- Humidity (%): 30 to 70%
- Air changes (per hr): At least 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hour light/dark cycle

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 30 mg/mL (300 mg/kg) and 200 mg/mL (2000 mg/kg).
- Justification for choice of vehicle: Standard vehicle as per guidelines.

MAXIMUM DOSE VOLUME APPLIED: 10 mL/Kg

DOSAGE PREPARATION (if unusual): Prepared as a suspension in distilled water.

CLASS METHOD (if applicable)
- Rationale for the selection of the starting dose: In the absence of data regarding toxicity of the test substance, 300 mg/kg was chosen as the starting dose.

Doses:

300 and 2000 mg/kg bw

No. of animals per sex per dose:

1 female treated at 300 mg/kg followed by a total of 5 females treated at 2000 mg/kg.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days (or other?): 14 day observation period
- Frequency of observations and weighing: Clinical observations were made 30 minutes, 1, 2, and hours after dosing and then daily for the observation period. Individual bodyweights were recorded on the day of dosing and on Days 7 and 14.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight,organ weights, histopathology, other: None

Statistics:

Not a requirement of the study guideline

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

At both 300 and 2000 mg/kg no mortality was observed.

Clinical signs:

other: Tiptoe gait was noted in one animal on day 3 that received 2000 mg/kg. No other signs of toxicity were noted during the observation period and no signs were observed in the animal that received 300 mg/kg.

Gross pathology:

No abnormalities were noted at necropsy in any animals.

Interpretation of results:

GHS criteria not met

Conclusions:

The acute oral median lethal dose (LD50) of the test item in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Reliable OECD guideline, GLP study available. No effects observed at the limit dose of 2000 mg/kg.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 433 draft (Acute Inhalation Toxicity: Fixed Concentration Procedure) (not officially approved)

Version / remarks:

The guideline has been formally now been approved on 28 June 2018.

Deviations:

no

GLP compliance:

yes

Test type:

fixed concentration procedure

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

RccHan®:WIST

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Envigo RMS Limited
- Age at study initiation: 69 to 76 days
- Weight at study initiation: 280 to 300 g
- Fasting period before study: No
- Housing: The animals were housed five per cage, unless this number was reduced by mortality or isolation. The cages were made of a polycarbonate body with a stainless steel mesh lid.
- Diet (e.g. ad libitum): Free access to a standard rodent diet. The diet contained no added antibiotic or other chemotherapeutic or prophylatic agent.
- Water (e.g. ad libitum): Potable water taken from the public supply was freely available via polycarbonate bottles fitted with sipper tubes.
- Acclimation period: For at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 24°C
- Humidity (%): 40 to 70%
- Air changes (per hr): Not specified
- Photoperiod (hrs dark / hrs light): 12 hours light/dark cycle

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

2.7 µm

Geometric standard deviation (GSD):

>= 1.96 - <= 2.09

Remark on MMAD/GSD:

The mean MMAD value were within the ideal range of 1 to 4 microns (2.7 μm), indicating that the generated substance was respirable to the rat.

Details on inhalation exposure:

Exposure system:
The exposure system was composed of a flow-through nose only chamber. This was made from an aluminium alloy construction comprising a base unit, one animal exposure section with 20 exposure ports and a top section. The dimensions of the chamber give an internal volume of ca. 30L. Animals were restrained in a plastic nose-only restraint tube. Aerosol generation was performed by the use of a Wright Dust Feed Mechanism which is designed to produce and maintain test atmospheres containing dust by suspending material scraped from the surface of a compressed powder in a stream of dry air.
Inlet flow: from in-house compressed air system (breathing quality) at 19L/minute.
Extract airflow: Drawn by in-house vacuum system at 20L/minute.
Airflow monitoring: High quality tapered tube flowmeters and in-line flowmeters monitored continuously.

Concentration (aerosol samples collected as follows):
Sample type: Glass microfiber filter, held in an open face filter holder
Sample flow: 2 L/minute
Sample volume: Measured by wet-type gas meter
Sample frequency: Nine samples collected during Group 1 exposure and ten samples collected during Group 2 exposure
Sample location: Animal exposure port
Sample analysis: Gravimetric

Aerosol samples were collected at irregular intervals due to adjustments to operating conditions. A time-weighted average mean aerosol concentration was calculated in order to prevent undue biasing of repeat samples in the overall mean.

Particle size distribution:
Impactor type: Marple 290 Series Personal Cascade Impactor
Configuration: 298
Collection media: Stainless steel substrates and glass microfiber final stage filter
Sample flow: 2L/minute
Sample frequency: Two samples collected during each exposure
Sample location: Animal exposure port
Sample analysis: Gravimetric (MMAD and GSD derived)

Analytical verification of test atmosphere concentrations:

no

Duration of exposure:

4 h

Remarks on duration:

Standard as per OECD guidelines

Concentrations:

Group 1 (target 5 mg/L): Provided a TWA of 4.80 mg/L (SD 0.340).
Group 2 (target 1.0 mg/L): Provided a TWA of 1.06 mg/L (SD 0.0891)

The mean achieved aerosol concentration values were 96% and 106% of target, for groups 1 and 2 respectively.

No. of animals per sex per dose:

5 males per exposure group

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Rats were weighed at least once during the week prior to exposure and on Day 1 (prior to exposure) and on Days 2, 4, 8, 15 or at death. Clinical signs were recorded prior to exposure, at hourly intervals during exposure, immediately following exposure and then at 1 hour and 2 hours post-exposure. During the observation period, the animals were observed once in the morning and once toward the end of the experimental day. On the day of study termination there was one observation (morning only).
- Necropsy of survivors performed: yes

Statistics:

Not performed as not a guideline requirement

Sex:

male

Dose descriptor:

LC50

Effect level:

> 1.06 - < 4.8 mg/L air (nominal)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

All males exposed to 4.80 mg/L were found dead or euthanized after a single exposure. Two animals exposed to 4.80 mg/L were found dead on Day 2 and two animals exposed to 4.80 mg/L were euthanized on Day 2. The remaining animal exposed to 4.80 mg/L was euthanized on Day 3. No mortality was noted in animals exposed to 1.06 mg/L.

Clinical signs:

other: Following exposure at 4.80 mg/L, all animals were observed with clinical signs, including irregular and/or shallow breathing, wet rales, unsteady gait, closed/partially closed eyes, decreased activity and/or hunched posture. Two animals were found dead at

Body weight:

On the day following exposure at 1.06 mg/L, body weight losses were evident in all animals. Body weight gains were observed from Day 4 or Day 8, which continued to increase for the remainder of the observation period.

Gross pathology:

Decedents in Group 1 (4.8 mg/L)
Lungs and bronchi: Abnormal color (dark) and incomplete deflation was observed in all males exposed to 4.80 mg/L. Pale areas were observed in the two males exposed to 4.80 mg/L found dead on Day 2.
Stomach: Abnormal contents (blue) were noted in the stomach of four males exposed to 4.80 mg/L either found dead or euthanized on Day 2.

Group 2 (1.06 mg/L)
Lungs and bronchi: Pale areas were observed in the majority of animals exposed to 1.06 mg/L.

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

Under the conditions of this study, the LC50 (4 hour) of Zinc Molybdate is in excess of 1.06 mg/L (for male rats) but less than 4.80 mg/L where mortality was observed. This test item is Category 4 according to the Globally Harmonized System (GHS; UNITED NATIONS) and the EU CLP Regulation (EC No. 1272/2008, as amended).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Quality of whole database:

Reliable OECD guideline, GLP study available. Mortality was observed at 4.8 mg/L with no mortality observed at 1.06 mg/L. LC50 is between these values and accordingly no value for chemical safety assessment is included.

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The results of the acute oral toxicity study indicated no mortality was observed at the limit dose of 2000 mg/kg. As such, classification in accordance with the CLP Regulation (EC No. 1272/2008, as amended) is not warranted. In the acute inhalation study whole group mortality was observed in animals exposed to 4.80 mg/L whereas no mortality was observed in animals exposed to 1.06 mg/L. As the LC50 would fall between these values (i.e. the 1 and 5 mg/L band) classification as Category 4 (H332) is appropriate for this substance.