Dipraseodymium trioxide

Endpoint summary

Description of key information

Oral Toxicity: Read-across performed with structurally similar substance (Praseodymium (III,IV) Oxide)

The oral LD50 (males and females) was >2000 mg/kg bw and therefore the test material is not classified for acute oral toxicity based on the results of this study according to EU criteria.

Oral Toxicity: Read-across performed with structurally similar substance (Praseodymium Tricarbonate)

The acute oral median lethal dose (LD50) of the test material in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight and as such requires no classification in accordance with EU criteria.

Inhalation Toxicity: Read-across performed with structurally similar substance (Praseodymium (III,IV) Oxide)

The 4 hour LC50 was determined to be > 5.21 mg/L, the test material therefore requires no classification in accordance with EU criteria.

Inhalation Toxicity: Read-across performed with structurally similar substance (Praseodymium Tricarbonate)

The 4 hour LC50 was therefore determined to be > 5.25 mg/L, the test material therefore requires no classification in accordance with EU criteria.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 March 1994 to 16 March 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Read-across performed with structurally similar substance.

Reason / purpose for cross-reference:

other: read-across target

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: approximately 6 weeks
- Weight at study initiation: 165 ± 7g for the males, 159 ± 6 g for the females
- Fasting period before study: 18 hours before treatment; food was replaced approximately 4 hours after treatment.
- Housing: The animals were housed in groups of 4 to 7 animals of the same sex in polycarbonate cages (48 x 27 x 20 cm) during the acclimatisation period and groups of 5 animals of the same sex during the study. Each cage contained graded, dust-free sawdust.
- Food consumption (e.g. ad libitum): ad libitum; AO4 C pelleted diet (U.A.R., 91360 Villemoisson-sur-Orge, France).
- Water consumption (e.g. ad libitum): ad libitum filtered water contained in bottles.
- Acclimation period: 5 days during which they were observed daily.
- Source: Iffa Crédo, 69210 L'Arbresle, France.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 50 ± 20 % relative humidity
- Air changes (per hr): 13 cycles/hour of non-recycled and filtered air
- Photoperiod (hrs dark / hrs light): 12hr/12hr

In-life dates: From 02 to 16 March 1994

Route of administration:

oral: gavage

Vehicle:

methylcellulose

Details on oral exposure:

VEHICLE
The vehicle used was an aqueous solution of methylcellulose at 0.5 % (batch No. 73H0365 Prolabo, 75526 Paris, France)
Water for injections (batch No. 7860 Biosédra, 92240 Malakoff, France)

MAXIMUM DOSE VOLUME APPLIED: 10 mL/kg

DOSAGE PREPARATION:
On the day of the treatment, the test material was ground using a mortar and pestle, then was suspended in the vehicle.

Doses:

2000 mg/kg bw

No. of animals per sex per dose:

5 animals per sex per dose

Control animals:

no

Details on study design:

DETAILS ON STUDY DESIGN
- Duration of observation period following administration: 14 days
- Frequency of observations: the animals were observed frequently after administration of the test material and at least once a day for clinical signs and at least twice a day for mortality.
- Frequency of weighing: Animals were weighed just before administration of the test material and then on days 5, 8 and 15. The body weight of the animals treated with the test material was compared to laboratory historical control data for animals dosed by the oral route.
- Necropsy of survivors performed: yes (day 15)
- Other examinations performed: macroscopic examination at necropsy (digestive tract, heart, kidneys, liver, lungs, pancreas, spleen and any other organ with obvious abnormalities).

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No deaths occured during the observation period.

Clinical signs:

other: No clinical signs were observed during the study.

Gross pathology:

The macroscopic examination of the main organs of the animals sacrificed at the end of the study revealed no apparent abnormalities.

Interpretation of results:

other: Not classified in accordance with EU criteria

Conclusions:

Under the experimental conditions of this study, the oral LD50 of the test material was > 2000 mg/kg in rats. No signs of toxicity were observed at this dose and the test material requires no classification in accordance with EU criteria.

Executive summary:

An acute oral toxicity limit test was conducted to assess the test material in accordance with the standardised guideline OECD 401 under GLP conditions.

Groups of fasted, 6 week old Sprague-Dawley rats (5 per sex) were given a single oral dose of the test material in an aqueous solution of methylcellulose at 0.5 % at a dose of 2000 mg/kg bw (dose volume 10 mL/kg) and observed for 14 days.

No mortality and no clinical sign were observed during the study. The body weight gains of the treated rats were normal. No gross abnormalities were observed at necropsy.

The oral LD50 (males and females) was >2000 mg/kg bw and therefore the test material is not classified for acute oral toxicity based on the results of this study according to EU criteria.

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material

Justification for type of information:

Read-across performed with structurally similar substance.

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Reference 3

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 September 2012 to 25 October 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Read-across to structurally similar substance.

Reason / purpose for cross-reference:

other: read-across target

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

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Strain: RccHan:WIST
- Age at study initiation: 8 - 12 weeks.
- Weight at study initiation: The bodyweight variation did not exceed ± 20 % of the bodyweight of the initially dosed animal.
- Fasting period before study: The animals were fasted overnight immediately before dosing and for approximately three to four hours after dosing.
- Housing: The animals were housed in groups of up to four in suspended solid-floor polypropylene cages furnished with woodflakes.
- Diet: ad libitum.
- Water: ad libitum access to mains drinking water.
- Acclimation period: at least 5 days.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 25 °C
- Humidity (%): 30 - 70 %
- Air changes (per hr): at least 15
- Photoperiod (hrs dark / hrs light): lighting was controlled by a time switch to give twelve hours continuous light (0600 to 1800) and twelve hours darkness.

IN-LIFE DATES:
From: 25 September 2012
To: 25 October 2012

Route of administration:

oral: gavage

Vehicle:

arachis oil

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 200 mg/mL
- Justification for choice of vehicle:The test material was prepared as a suspension in arachis oil BP because it did not dissolve/suspend in distilled water.

MAXIMUM DOSE VOLUME APPLIED: 10 mL/kg

Doses:

2000 mg/kg

No. of animals per sex per dose:

5 female animals were dosed.

Control animals:

no

Details on study design:

SIGHTING STUDY
In the absence of data regarding the toxicity of the test material, 300 mg/kg was chosen as the starting dose.
A single female animal was treated at a dose level of 300 mg/kg (concentration 30 mg/mL, dose volume 10 mL/kg). No toxicity was observed.
In the absence of toxicity at a dose level of 300 mg/kg, an additional female animal was treated at 2000 mg/kg.

MAIN STUDY
No toxicity was observed in the animal treated at 2000 mg/kg, therefore a further 4 animals were treated, bringing the number treated at this dose level to 5.
All animals were dosed once by gavage, using a metal cannula attached to a graduated syringe. The volume administered to each animal was calculated according to the fasted bodyweight at the time of dosing. Treatment of animals was sequential. Sufficient time was allowed between each dose level to confirm the survival of the previously dosed animals.

- Duration of observation period following administration: 14 days.
- Frequency of observations and weighing: Clinical observations were made 0.5, 1, 2, and 4 hours after dosing and then daily for fourteen days. Morbidity and mortality checks were made twice daily. Individual bodyweights were recorded on Day 0 (the day of dosing) and on Days 7 and 14.
- Necropsy of survivors performed: yes. At the end of the observation period, the animals were killed by cervical dislocation. All animals were subjected to gross necropsy. This consisted of an external examination and opening of the abdominal and thoracic cavities. The appearance of any macroscopic abnormalities was recorded. No tissues were retained.

Preliminary study:

In the single animal dosed at 300 mg/kg, no mortality was observed and no signs of systemic toxicity were present. The animal showed expected bodyweight gain throughout the observation period. No abnormalities were detected at necropsy.

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was observed.

Clinical signs:

other: No signs of systemic toxicity were noted throughout the observation period.

Gross pathology:

No abnormalities were noted at necropsy.

Interpretation of results:

other: Not classified in accordance with EU Criteria

Conclusions:

The LD50 of the test material in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight and as such requires no classification in accordance with EU criteria.

Executive summary:

The acute oral toxicity of the test material was assessed in the Wistar strain rat in accordance with the standardised guidelines OECD 420 and EU Method B.1 bis, using the fixed dose method.

In the absence of toxicological information, a single fasted female was dosed at 300 mg/kg bw. In the absence of toxicity, a further sighting test was conducted by administering a dose of 2000 mg/kg to one fasted female. Following this, a further group of four fasted females was given a single oral dose of the test material as a suspension in arachis oil BP at a dose level of 2000 mg/kg bodyweight.

No mortality occurred and no signs of systemic toxicity were seen throughout the study. All animals showed expected gains in bodyweight and no abnormalities were noted at necropsy.

The acute oral median lethal dose (LD50) of the test material in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight and as such requires no classification in accordance with EU criteria.

Reference 4

Endpoint:

acute toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material

Justification for type of information:

Read-across to structurally similar substance.

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Quality of whole database:

Two guideline studies are available on structurally similar substances. Both studies were conducted under GLP conditions. The quality of the database is good.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 July 2012 to 21 September 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Read-across performed with structurally similar substance.

Reason / purpose for cross-reference:

other: read-across target

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

see below

Principles of method if other than guideline:

The mean mass median aerodynamic diameter (MMAD), which was 4.90, is outside the range given in test guidelines (1-4 µm). This deviation is considered to be due to the physical characteristics of the test material and is not considered to have affected the validity of the study.

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Strain: RccHan:WIST
- Age at study initiation: approximately 8 to 12 weeks
- Weight at study initiation: 200 to 350 g
- Fasting period before study: no
- Housing: The animals were housed in groups of up to three by sex in solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes and provided with environmental enrichment items: wooden chew blocks and cardboard “fun tunnels”.
- Diet (e.g. ad libitum): With the exception of the exposure period, free access to food was allowed; Harlan 2014C Rodent Diet, Harlan Laboratories UK Ltd., Oxon, UK.
- Water (e.g. ad libitum): ad libitum with the exception of the exposure period.
- Acclimation period: at least 5 days
- Source: Harlan Laboratories UK Ltd., Oxon, UK. 

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 25 °C
- Humidity (%): 30 - 70 %
- Air changes (per hr): at least 15 per hour
- Photoperiod (hrs dark / hrs light): the lighting was controlled to give twelve hours continuous light and twelve hours darkness.

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

clean air

Details on inhalation exposure:

ATMOSPHERE GENERATION
A dust atmosphere was produced from the test material using an SAG 410 Solid Aerosol Generator located adjacent to the exposure chamber. The SAG 410 was connected to a metered compressed air supply.
A particle separator was introduced before the aerosol entered the exposure chamber during the sighting study in order to remove large particles and thereby increase the inhalable portion of the generated aerosol. This could not be utilised during the main study exposure as the target concentration could not be achieved with the particle separator attached to the generation equipment. The test material was ground in a Llytron mini grinder prior to use in the main study.
Compressed air was supplied by means of an oil free compressor and passed through a water trap and respiratory quality filters before it was introduced to the SAG 410.
The cylindrical exposure chamber had a volume of approximately 30 litres (dimensions: 28 cm diameter x 50 cm high). The concentration within the chamber was controlled by adjusting the test material feed rate from the SAG 410. The extract from the exposure chamber passed through a ‘scrubber’ trap and was connected with a high efficiency filter to a metered exhaust system. The chamber was maintained under negative pressure.

Prior to the start of the study, test material atmospheres were generated within the exposure chamber. During this characterisation period test material input rates and the generation system were varied in order to achieve the required atmospheric conditions.

EXPOSURE PROCEDURE
Prior to the day of exposure each rat was acclimatised (for approximately 2 hours) to a tapered polycarbonate restraining tube. During the day of exposure, each rat was individually held in a tapered, polycarbonate restraining tube fitted onto a single tier of the exposure chamber and sealed by means of a rubber ‘O’ ring.
A target concentration of 5.0 mg/L was used for the exposure. The mean achieved concentration was 104 % of target.

EXPOSURE CHAMBER TEMPERATURE AND RELATIVE HUMIDITY
The temperature and relative humidity inside the exposure chamber were measured by an electronic thermometer/humidity meter located in a vacant port in the animals’ breathing zone of the chamber and recorded every thirty minutes.

EXPOSURE CHAMBER OXYGEN CONCENTRATION
Oxygen levels within the exposure chamber were measured by an electronic oxygen analyser located in a port in the animals' breathing zone. The test atmosphere was generated to contain at least 19 % oxygen.
The MMAD was 4.90 µm, resulting in an inhalable fraction (% <4 µm) of 41.1. The geometric standard deviation was 2.50.

EXPOSURE CHAMBER ATMOSPHERE CONCENTRATION
The actual chamber concentration was measured at regular intervals during the exposure period. The gravimetric method used glass fibre filters placed in a filter holder. The holder was temporarily sealed in a vacant port in the exposure chamber in the animals’ breathing zone and a suitable, known volume of exposure chamber air was drawn through the filter using a vacuum pump.
Each filter was weighed before and after sampling in order to calculate the weight of collected test material. The difference in the two weights, divided by the volume of atmosphere sampled, gave the actual chamber concentration.
The nominal chamber concentration was calculated by dividing the mass of test material used by the total volume of air passed through the chamber.
The nominal concentration is 889 % of the actual mean achieved atmosphere concentration and shows that keeping the aerosol airborne was difficult.

PARTICLE SIZE DISTRIBUTION
The particle size of the generated atmosphere inside the exposure chamber was determined three times during the exposure period using a Marple Personal Cascade Impactor. This device consisted of six impactor stages (9.8, 6.0, 3.5, 1.6, 0.93 and 0.52 µm cut points) with stainless steel collection substrates and a back up glass fibre filter, housed in an aluminium sampler. The sampler was temporarily sealed in a sampling port in the animals’ breathing zone and a suitable, known volume of exposure chamber air was drawn through it using a vacuum pump.
The collection substrates and backup filter were weighed before and after sampling and the weight of the test material, collected at each stage, calculated by the difference.
The mean amount for each stage was used to determine the cumulative amount below each cut-off point size. In this way, the proportion (%) of aerosol less than 9.8, 6.0, 3.5, 1.6, 0.93 and 0.52 µm was calculated.
The resulting values were converted to probits and plotted against Log10 cut-point size. From this plot, the Mass Median Aerodynamic Diameter (MMAD) was determined (as the 50 % point) and the geometric standard deviation was calculated. In addition the proportion (%) of aerosol less than 4 µm (considered to be the inhalable fraction) was determined.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

The test atmosphere was sampled seventeen times during the exposure period and the actual concentration of the test material calculated.

Duration of exposure:

4 h

Concentrations:

5.21 mg/L

No. of animals per sex per dose:

3 animals per sex per dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: all animals were observed for clinical signs at hourly intervals during exposure, immediately on removal from the restraining tubes at the end of exposure, one hour after termination of exposure and subsequently once daily for up to 14 days. Any evidence of overt toxicity was recorded at each observation.
- Frequency of weighing: Individual bodyweights were recorded on arrival, prior to treatment on the day of exposure and on Days 1, 3, 7 and 14.
- Necropsy of survivors performed: yes. At the end of the 14 day observation period the animals were killed by intravenous overdose of sodium pentobarbitone. All animals were subjected to a full external and internal examination, and any macroscopic abnormalities were recorded. The respiratory tract was subjected to a detailed macroscopic examination for signs of irritancy or local toxicity.

Preliminary study:

SIGHTING EXPOSURE
During characterisation, a group of two rats (one male, one female) were exposed to an atmosphere of the test material at a mean achieved atmosphere concentration of 2.26 mg/L for approximately four hours. Increased respiratory rate was the only significant observation noted in both animals during exposure, on removal from the chamber and one hour post-exposure, red/brown staining around the snout was also noted in both animals on removal. One day post-exposure, both animals exhibited increased respiratory rate and hunched posture only. Both animals recovered quickly to appear normal on Day 3 or Day 4 post-exposure.

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.21 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

There was no mortality during the study.

Clinical signs:

other: In addition to the observations considered to be due to the restraint procedure (such as hunched posture, pilo-erection, wet fur and fur staining due to the test material), increased respiratory rate was noted in all animals during exposure, on removal fr

Body weight:

All animals exhibited bodyweight losses or showed no bodyweight gain on the first day post-exposure. All animals exhibited bodyweight gains during the remainder of the observation period, with the exception of one female animal which showed no bodyweight gain from Days 1 to 3 post-exposure.

Gross pathology:

Four animals (all males and one female) exhibited dark patches on the lungs at necropsy.

Table 1: Exposure Chamber Atmosphere Concentrations

Duration of Exposure (minutes)	Net Weight of Sample (mg)	Volume of Air Sampled (L)	Chamber Flow Rate (L/min)	Atmosphere Concentration (mg/L)
5	9.81	2	60	4.91
15	10.56	2	60	5.28
29	10.72	2	60	5.36
45	10.17	2	60	5.09
60	10.05	2	60	5.03
75	10.74	2	60	5.37
90	10.31	2	60	5.16
105	11.94	2	60	5.97
120	10.18	2	60	5.09
135	10.46	2	60	5.23
150	10.32	2	60	5.16
165	10.76	2	60	5.38
181	9.80	2	60	4.90
195	10.09	2	60	5.05
210	10.66	2	60	5.33
225	10.67	2	60	5.34
235	9.84	2	60	4.92

Mean achieved atmosphere concentration: 5.21 mg/L (standard deviation 0.26)

 

Nominal Concentration

- Test material used: 714 g

- Air flow: 60 L/min

- Total generation time: 257 minutes*

- Nominal concentration: 46.3 mg/L

 

* Test atmospheres were generated for a total of 17 minutes prior to animal insertion to ensure that the test material concentration was being achieved.

 

Table 2: Particle Size Distribution - Cascade Impactor Data

Impactor Stage Number	Cut Point (µm)	Amount Collected (mg) Per Sample Number			Mean Amount Collected (mg)
		1	2	3
3	9.8	0.69	0.82	0.54	0.68
4	6.0	0.67	0.84	0.55	0.69
5	3.5	0.76	0.93	0.54	0.74
6	1.6	0.53	0.67	0.57	0.59
7	0.93	0.34	0.43	0.29	0.35
8	0.52	0.02	0.09	0.12	0.08
Back-up filter	<0.52	0.00	0.05	0.02	0.02

Total mean amount of test material collected: 3.15 mg

 

Table 3: Particle Size Distribution - Calculation

Cut Point (µm)	Log10 Cut Point	Mean Cumulative Amount Less Than Cut Point
		(mg)	(%)	Probit
9.8	0.991	2.47	78.4	5.79
6.0	0.778	1.78	56.5	5.16
3.5	0.544	1.04	33.0	4.56
1.6	0.204	0.45	14.3	3.93
0.93	-0.032	0.10	3.18	3.14
0.52	-0.284	0.02	0.635	2.51

MMAD: 4.90 µm

Geometric standard deviation: 2.50

Predicted amount <4 µm: 41.1 %

Table 4: Individual Bodyweights

Animal Number and Sex	Bodyweight (g) on Day:						Increment (g) During Days:
	-9	0	1	3	7	14	-9 to 0	0 to 1	1 to 3	3 to 7	7 to 14
1 Male	241	288	280	297	312	319	47	-8	17	15	7
2 Male	229	263	254	264	270	290	34	-9	10	6	20
3 Male	236	271	266	271	283	294	35	-5	5	12	11
4 Female	191	226	219	229	236	245	35	-7	10	7	9
5 Female	199	228	228	234	238	250	29	0	6	4	12
6 Female	187	218	216	216	221	224	31	-2	0	5	3

Interpretation of results:

other: Not classified in accordance with EU criteria

Conclusions:

The 4 hour LC50 was determined to be > 5.21 mg/L, therefore the test material requires no classification under the conditions of this study in accordance with EU criteria.

Executive summary:

An acute inhalation study was conducted to assess the toxicity potential of the test material in accordance with the standardised guideline OECD 436.

Male and female RccHan:WIST strain rats (3 per sex) were exposed (nose only) for 4 hours to a dust atmosphere containing the test material at a mean concentration of 5.21 mg/L, with a MMAD of 4.90 µm.

Following exposure, the animals were observed for 14 days for signs of mortality and toxicity. At the end of the observation period, all animals were subjected to necropsy.

No deaths occurred throughout the study and the 4 hour LC50 was therefore determined to be > 5.21 mg/L. The test material requires no classification under the conditions of this study in accordance with EU criteria.

Reference 2

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material

Justification for type of information:

Read-across performed with structurally similar substance.

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.21 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Reference 3

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 August 2012 to 20 September 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Read-across to structurally similar substance.

Reason / purpose for cross-reference:

other: read-across target

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

see below

Principles of method if other than guideline:

The mean mass median aerodynamic diameter (MMAD), which was 4.92, and the GDS, which was 3.35, are outside the range given in test guidelines (1-4 µm and 1.5 - 3.0, respectively). This deviation is considered to be due to the physical characteristics of the test material and is not considered to have affected the validity of the study.

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Strain: RccHan:WIST
- Age at study initiation: approximately 8 - 12 weeks
- Weight at study initiation: 200 - 350 g
- Fasting period before study: no
- Housing: The animals were housed in groups of up to three by sex in solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes and provided with environmental enrichment items: wooden chew blocks and cardboard “fun tunnels”.
- Diet (e.g. ad libitum): With the exception of the exposure period, free access to food was allowed.
- Water (e.g. ad libitum): ad libitum with the exception of the exposure period.
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 25 °C
- Humidity (%): 30 - 70 %
- Air changes (per hr): at least 15 per hour
- Photoperiod (hrs dark / hrs light): the lighting was controlled to give twelve hours continuous light and twelve hours darkness.

IN-LIFE DATES:
From: 30 August 2012
To: 20 September 2012

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

clean air

Details on inhalation exposure:

TEST MATERIAL TREATMENT
In order to facilitate aerosolisation and reduce particle size, the test material was ground using a small amount of diethyl ether in a Retsch Planetary Ball Mill (Retsch (UK) Ltd., Leeds, UK) and the solvent was removed via evaporation prior to use.

ATMOSPHERE GENERATION
A dust atmosphere was produced from the test material using an SAG 410 Solid Aerosol Generator located adjacent to the exposure chamber. The SAG 410 was connected to a metered compressed air supply.
Compressed air was supplied by means of an oil free compressor and passed through a water trap and respiratory quality filters before it was introduced to the SAG 410.
The cylindrical exposure chamber had a volume of approximately 30 litres (dimensions: 28 cm diameter x 50 cm high). The concentration within the chamber was controlled by adjusting the test material feed rate from the SAG 410. The extract from the exposure chamber passed through a ‘scrubber’ trap and was connected with a high efficiency filter to a metered exhaust system. The chamber was maintained under negative pressure.

Prior to the start of the study, test material atmospheres were generated within the exposure chamber. During this characterisation period test material input rates and the generation system were varied in order to achieve the required atmospheric conditions.

EXPOSURE PROCEDURE
Prior to the day of exposure each rat was acclimatised (for approximately 2 hours) to a tapered polycarbonate restraining tube. During the day of exposure, each rat was individually held in a tapered, polycarbonate restraining tube fitted onto a single tier of the exposure chamber and sealed by means of a rubber ‘O’ ring.
A target concentration of 5.0 mg/L was used for the exposure. The mean achieved concentration was 105 % of target.

EXPOSURE CHAMBER TEMPERATURE AND RELATIVE HUMIDITY
The temperature and relative humidity inside the exposure chamber were measured by an electronic thermometer/humidity meter located in a vacant port in the animals’ breathing zone of the chamber and recorded every thirty minutes.

EXPOSURE CHAMBER OXYGEN CONCENTRATION
Oxygen levels within the exposure chamber were measured by an electronic oxygen analyser located in a port in the animals' breathing zone. The test atmosphere was generated to contain at least 19 % oxygen.
The MMAD was 4.92 µm, resulting in an inhalable fraction (% <4 µm) of 43.2. The geometric standard deviation was 3.35.

EXPOSURE CHAMBER ATMOSPHERE CONCENTRATION
The actual chamber concentration was measured at regular intervals during the exposure period. The gravimetric method used glass fibre filters placed in a filter holder. The holder was temporarily sealed in a vacant port in the exposure chamber in the animals’ breathing zone and a suitable, known volume of exposure chamber air was drawn through the filter using a vacuum pump.
Each filter was weighed before and after sampling in order to calculate the weight of collected test material. The difference in the two weights, divided by the volume of atmosphere sampled, gave the actual chamber concentration.
The nominal chamber concentration was calculated by dividing the mass of test material used by the total volume of air passed through the chamber.
The nominal concentration is 348 % of the actual mean achieved atmosphere concentration and confirms that keeping the aerosol airborne was moderately difficult.

PARTICLE SIZE DISTRIBUTION
The particle size of the generated atmosphere inside the exposure chamber was determined three times during the exposure period using a Marple Personal Cascade Impactor. This device consisted of six impactor stages (7.8, 5.8, 3.6, 1.4, 0.74 and 0.34 µm cut points) with stainless steel collection substrates and a back up glass fibre filter, housed in an aluminium sampler. The sampler was temporarily sealed in a sampling port in the animals’ breathing zone and a suitable, known volume of exposure chamber air was drawn through it using a vacuum pump.
The collection substrates and backup filter were weighed before and after sampling and the weight of the test material, collected at each stage, calculated by the difference.
The mean amount for each stage was used to determine the cumulative amount below each cut-off point size. In this way, the proportion (%) of aerosol less than 7.8, 5.8, 3.6, 1.4, 0.74 and 0.34 µm was calculated.
The resulting values were converted to probits and plotted against Log10 cut-point size. From this plot, the Mass Median Aerodynamic Diameter (MMAD) was determined (as the 50 % point) and the geometric standard deviation was calculated. In addition the proportion (%) of aerosol less than 4 µm (considered to be the inhalable fraction) was determined.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

The test atmosphere was sampled seventeen times during the exposure period and the actual concentration of the test material calculated.

Duration of exposure:

4 h

Concentrations:

5.25 mg/L

No. of animals per sex per dose:

3 animals per sex per dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: all animals were observed for clinical signs at hourly intervals during exposure, immediately on removal from the restraining tubes at the end of exposure, one hour after termination of exposure and subsequently once daily for up to 14 days. Any evidence of overt toxicity was recorded at each observation.
- Frequency of weighing: Individual bodyweights were recorded on arrival, prior to treatment on the day of exposure and on Days 1, 3, 7 and 14.
- Necropsy of survivors performed: yes. At the end of the 14 day observation period the animals were killed by intravenous overdose of sodium pentobarbitone. All animals were subjected to a full external and internal examination, and any macroscopic abnormalities were recorded. The respiratory tract was subjected to a detailed macroscopic examination for signs of irritancy or local toxicity.

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.25 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

There was no mortality during the study.

Clinical signs:

other: In addition to the observations considered to be due to the restraint procedure (such as hunched posture, pilo-erection, wet fur), increased respiratory rate was noted in all animals during exposure, on removal from the chamber and one hour post-exposure.

Body weight:

All male animals and two female animals exhibited bodyweight losses or showed no bodyweight gain on the first day post-exposure. All animals exhibited bodyweight gains during the remainder of the recovery period, with the exception of two female animals which exhibited slight bodyweight losses from Days 1 to 3 post-exposure.

Gross pathology:

No macroscopic abnormalities were detected amongst animals at necropsy.

Table 1: Exposure Chamber Atmosphere Concentrations

Duration of Exposure (minutes)	Net Weight of Sample (mg)	Volume of Air Sampled (L)	Chamber Flow Rate (L/min)	Atmosphere Concentration (mg/L)
5	9.49	2	60	4.75
15	10.15	2	60	5.08
30	10.04	2	60	5.02
45	9.66	2	60	4.83
60	9.90	2	60	4.95
75	9.50	2	60	4.75
90	9.92	2	60	4.96
105	12.45	2	60	6.23
120	10.36	2	60	5.18
135	11.99	2	60	6.00
150	11.67	2	60	5.84
165	10.54	2	60	5.27
181	11.15	2	60	5.58
195	10.15	2	60	5.08
210	11.08	2	60	5.54
225	10.38	2	60	5.19
238	10.11	2	60	5.06

Mean achieved atmosphere concentration: 5.25 mg/L (standard deviation 0.44)

 

Nominal Concentration

- Test material used: 290 g

- Air flow: 60 L/min

- Total generation time: 264 minutes*

- Nominal concentration: 18.3 mg/L

 

* Test atmospheres were generated for a total of 24 minutes prior to animal insertion to ensure that the test material concentration was being achieved.

 

Table 2: Particle Size Distribution - Cascade Impactor Data

Impactor Stage Number	Cut Point (µm)	Amount Collected (mg) Per Sample Number			Mean Amount Collected (mg)
		1	2	3
3	7.8	0.27	0.20	0.14	0.20
4	5.8	0.33	0.14	0.20	0.22
5	3.6	0.38	0.24	0.18	0.27
6	1.4	0.05	0.07	0.07	0.06
7	0.74	0.02	0.04	0.03	0.03
8	0.34	0.03	0.01	0.02	0.02
Back-up filter	<0.34	0.07	0.01	0.04	0.04

Total mean amount of test material collected: 0.84 mg

 

Table 3: Particle Size Distribution - Calculation

Cut Point (µm)	Log10 Cut Point	Mean Cumulative Amount Less Than Cut Point
		(mg)	(%)	Probit
7.8	0.892	0.64	76.2	5.71
5.8	0.763	0.42	50.0	5.00
3.6	0.556	0.15	17.9	4.08
1.4	0.146	0.09	10.71	3.76
0.74	-0.131	0.06	7.14	3.54
0.34	-0.469	0.04	4.76	3.33

MMAD: 4.92 µm

Geometric standard deviation: 3.35

Predicted amount <4 µm: 43.2 %

 

Table 4: Individual Bodyweights

Animal Number and Sex	Bodyweight (g) on Day:						Increment (g) During Days:
	-22	0	1	3	7	14	-22 to 0	0 to 1	1 to 3	3 to 7	7 to 14
1 Male	231	320	320	335	348	360	89	0	15	13	12
2 Male	222	318	307	312	322	334	96	-11	5	10	12
3 Male	221	332	305	312	324	340	111	-27	7	12	16
4 Female	198	226	223	216	223	228	28	-3	-7	7	5
5 Female	204	225	226	230	235	244	21	1	4	5	9
6 Female	201	223	222	220	225	229	22	-1	-2	5	4

Interpretation of results:

other: Not classified in accordance with EU Criteria

Conclusions:

The 4 hour LC50 was determined to be > 5.25 mg/L, therefore the test material requires no classification under the conditions of this study in accordance with EU criteria.

Executive summary:

An acute inhalation study was conducted to assess the toxicity potential of the test material in accordance with the standardised guideline OECD 436, under GLP conditions.

Male and female RccHan:WIST strain rats (3 per sex) were exposed (nose only) for 4 hours to a dust atmosphere containing the test material at a mean concentration of 5.25 mg/L, with a MMAD of 4.92 µm.

Following exposure, the animals were observed for 14 days for signs of mortality and toxicity. At the end of the observation period, all animals were subjected to necropsy.

No deaths occurred throughout the study and the 4 hour LC50 was therefore determined to be > 5.25 mg/L. The test material requires no classification under the conditions of this study in accordance with EU criteria.

Reference 4

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material

Justification for type of information:

Read-across to structurally similar substance.

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.25 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

5 mg/m³ air

Quality of whole database:

Two guideline studies are available on structurally similar substances. Both studies were conducted under GLP conditions. The quality of the database is good.

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:

other:

Additional information

Oral Toxicity: Read-across performed with structurally similar substance (Praseodymium (III,IV) Oxide)

An acute oral toxicity limit test was conducted to assess the test material in accordance with the standardised guideline OECD 401 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Groups of fasted, 6 week old Sprague-Dawley rats (5 per sex) were given a single oral dose of the test material in an aqueous solution of methylcellulose at 0.5 % at a dose of 2000 mg/kg bw (dose volume 10 mL/kg) and observed for 14 days.

No mortality and no clinical sign were observed during the study. The body weight gains of the treated rats were normal. No gross abnormalities were observed at necropsy.

The oral LD50 (males and females) was >2000 mg/kg bw and therefore the test material is not classified for acute oral toxicity based on the results of this study according to EU criteria.

Oral Toxicity: Read-across performed with structurally similar substance (Praseodymium Tricarbonate)

The acute oral toxicity of the test material was assessed in the Wistar strain rat in accordance with the standardised guidelines OECD 420 and EU Method B.1bis,using the fixed dose method under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

In the absence of toxicological information, a single fasted female was dosed at 300 mg/kg bw. In the absence of toxicity, a further sighting test was conducted by administering a dose of 2000 mg/kg to one fasted female. Following this, a further group of four fasted females was given a single oral dose of the test material as a suspension in arachis oil BP at a dose level of 2000 mg/kg bodyweight.

No mortality occurred and no signs of systemic toxicity were seen throughout the study. All animals showed expected gains in bodyweight and no abnormalities were noted at necropsy.

The acute oral median lethal dose (LD50) of the test material in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight and as such requires no classification in accordance with EU criteria.

Inhalation Toxicity: Read-across performed with structurally similar substance (Praseodymium (III,IV) Oxide)

An acute inhalation study was conducted to assess the toxicity potential of the test material in accordance with the standardised guideline OECD 436.

The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Male and female RccHan:WIST strain rats (3 per sex) were exposed (nose only) for 4 hours to a dust atmosphere containing the test material at a mean concentration of 5.21 mg/L, with a MMAD of 4.90 µm.

Following exposure, the animals were observed for 14 days for signs of mortality and toxicity. At the end of the observation period, all animals were subjected to necropsy.

No deaths occurred throughout the study and the 4 hour LC50 was therefore determined to be > 5.21 mg/L. The test material requires no classification under the conditions of this study in accordance with EU criteria.

Inhalation Toxicity: Read-across performed with structurally similar substance (Praseodymium Tricarbonate)

An acute inhalation study was conducted to assess the toxicity potential of the test material in accordance with the standardised guideline OECD 436, under GLP conditions.

Male and female RccHan:WIST strain rats (3 per sex) were exposed (nose only) for 4 hours to a dust atmosphere containing the test material at a mean concentration of 5.25 mg/L, with a MMAD of 4.92 µm.

Following exposure, the animals were observed for 14 days for signs of mortality and toxicity. At the end of the observation period, all animals were subjected to necropsy.

No deaths occurred throughout the study and the 4 hour LC50 was therefore determined to be > 5.25 mg/L. The test material requires no classification under the conditions of this study in accordance with EU criteria.

Dermal Toxicity: Waiver

In accordance with the column 2 adaptation of REACH Annex VIII, the acute dermal toxicity study (required in section 8.5.3) is not considered scientifically justified as the oral and inhalation exposure routes are the most appropriate to assess the acute toxicity hazard presented by the substance based on its physico-chemical characteristics and use pattern. Furthermore, dermal exposure of the substance is considered unlikely.

Justification for classification or non-classification

In accordance with the criteria for classification as defined in Annex I, Regulation (EC) No 1272/2008, the substance does not require classification with respect to acute oral, dermal and inhalation toxicity.