Yttrium oxide

Endpoint summary

Description of key information

Oral Route:
A combined repeated dose toxicity study with the reproduction/ developmental toxicity screening has been conducted according to OECD 422 test guideline  using the oral exposure route on wistar rats. 
No classification for repeat-dose toxicity is warranted based on the absence of toxicologically relevant effects in this study, according to the criteria of Annex VI Directive 67/748/EEC or the 1272/2008 regulation -CLP). 
Under the conditions of this study, no adverse systemic effects were observed and the No Observed Effect Level (NOEL) in males and females was considered to be 1000 mg/kg/day.  
Inhalation Route:
A publication (Reece, 1967) fully describes a 30 days repeated inhalation of yttrium oxide on beagle dogs. 
According to the observation, an overall NOEL could not be established based on the absence of relevant changes in hematology, organ weights, macroscopic observations at necropsy and histopathology at the tested concentration (above 20.63 mg/m3).
No relevant systemic effects were observed during this study, exposing dogs 30 days to 20.63 mg/m3.
Dermal Route:
Based on the available data and in accordance with section 1 of REACH Annex XI, the repeated dose toxicity study via the dermal route does not need to be conducted if the study does not appear to be scientifically necessary. According to chapter R7c table R7.12.3 table: "The substance must be sufficiently soluble in water to partition from the stratum corneum into the epidermis. Therefore if the water solubility is below 1 mg/l, dermal uptake is likely to be low". Considering that yttrium oxide solubility is 0.7 mg/L the dermal uptake of the substance is likely to be low. A Klimisch 2 irritation study conducted on rabbit (lambert, 1993) and a Klimisch 1 sensitisation study conducted on guinea pig (Guillot, 1986) showed no effect of yttrium oxide. As the substance shows no local effect and is unlikely to be uptake by dermal route the test does not need to be conducted.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-06-21 to 2014-04-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study was conducted according to GLP and in compliance with agreed protocols, with no or minor deviations from standard test guidelines, which do not affect the quality of the relevant results.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

Remarks:

No relevant deviation from the standard guideline

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Details on animals:
Species/strain: Wistar rats, Crl: WI(Han) (Full Barrier)
Source: Charles River, 97633 Sulzfeld, Germany
Sex: male and female; the female animals were non-pregnant and nulliparous.
Age at the start of
the treatment period: males: 10-11 weeks old. females: 10-11 weeks old.
Body weight at the allocation of the animals to the experimental groups: males: 250 - 298 g (mean: 272.80 g, ± 20% = 218.24 – 327.36 g) - females: 162 - 199 g (mean: 183.13 g, ± 20% = 146.50 – 219.75 g)
The animals were derived from a controlled full-barrier maintained breeding system (SPF).

Housing and Feeding Conditions
- Full barrier in an air-conditioned room
- Temperature: 22 3°C
- Relative humidity: 55 10%
- Artificial light, sequence being 12 hours light, 12 hours dark
- Air change: 10 x / hour
- Free access to Altromin 1324 maintenance diet for rats and mice
- Free access to tap water (drinking water, municipal residue control, microbiological controls at regular intervals)
- The animals were kept individually in Individually Ventiled cages (except during the mating period when one female will be paired with one male), type III H, polysulphone cages on Altromin saw fibre bedding
- Adequate acclimatisation period (at least 5 days) under laboratory conditions

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Remarks:

0.5 %

Details on oral exposure:

Preparation of the Animals
Prior to the start of the treatment period a detailed clinical observation outside the home cage was made. Before the first administration all animals used for the study were weighed and assigned to the experimental groups with achieving a most homogenous variation in body weight throughout the groups of males and females.

Experimental Groups and Doses
According to the results of the dose range finding studyin which no overt toxicological changes were observed at 1000 mg/ kg body weight/ day, the following doses: 100 ; 300 and 1000 mg/kg bw were selected for the 3 dose groups (LD = low dose, MD = medium dose, HD = high dose) and 1 control group (C).

The test item and vehicle were administered at a single dose to the animals by oral gavage. The application volume for all groups was 5 mL/kg body weight. For each animal the individual dosing volume was calculated on the basis of the body weight.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Dose Formulation Analysis
Each dosing concentration was analyzed for nominal concentration by ICP - optical emission spectroscopy using a validated analytical procedure. Stability and homogeneity of the test item in the vehicle was analyzed for the LD, MD and HD dosing formulation.
Samples for the nominal concentration verification was taken in study week 1 (first week of pre mating period), 3 (first week of mating), 5 (gestation) and 7 (gestation/lactation) of control and all treatment groups.
Samples for homogeneity were taken from the top, middle and bottom of HD, MD, and LD preparation in study week 1 and 5.
All formulation samples were stored at -20 oC until the analysis.

Duration of treatment / exposure:

The animals were treated with the test item formulation or vehicle on 7 days per week for a period of 54 days, i.e. during 14 days of pre-mating and maximum 14 days of mating in both males and females, during the gestation period (approximately 21 to 23 days) and up to post-natal day 3 in females. Males were dosed after the mating period until the minimum total dosing period of 28 days (5 males from each group received dose administration for 28 days and the rest 5 animals from each group received dose administration for 29 days) was completed.
The animals in the control group were handled in an identical manner to the test group subjects and received the vehicle using the same dose volume

Frequency of treatment:

Once daily

Remarks:

Doses / Concentrations:
1000 mg/kg/day
Basis:
actual ingested

Remarks:

Doses / Concentrations:
300 mg/kg/day
Basis:
actual ingested

Remarks:

Doses / Concentrations:
100 mg/kg/day
Basis:
actual ingested

Remarks:

Doses / Concentrations:
0 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

10 animals per sex per dose.

Control animals:

yes, concurrent vehicle

Details on study design:

According to the results of the dose range finding study and in consultation with the sponsor three selected doses were tested for the 3 dose groups (LD = low dose, MD = medium dose, HD = high dose) and 1 control group (C).

Observations and examinations performed and frequency:

Body Weight and Food Consumption
The body weight of all animals were recorded once before the assignment to the experimental groups, on the first day of administration and weekly during the treatment period as well as at the end of the study. During pregnancy, females were weighed on gestation days (GD) 0, 7, 14 and 20 and within 24 hours of parturition (day 0 post-partum) as well as day 4 post-partum along with pups.
Food consumption was measured weekly on the corresponding days of the body weight measurements after the beginning of the dose administration. Food consumption was not measured during the mating period in males and females and the post-mating period in males. The food consumption in males were measured only for two week during premating period and not during the postmating period as the number of days during the postmating period are not uniform in all males due to difference in mating.

Mating
Mating was performed in a ratio of 1:1 (male to female). The vaginal smears of the females were checked every morning after the start of the mating period to confirm the copulation. The day of the vaginal plug and/or sperm was considered as day 0 of gestation.
The cages were arranged in such a way that possible effects due to cage placement were minimised.
Copulation index, fertility index and delivery index was calculated for each group. The calculations were made using the formula as below,
Copulation Index (%) = (No. of rats copulated / No.of pairs) X 100
Fertility Index (%) = (No. of females pregnant / No. of females copulated) X 100
Delivery Index (%) = (No. of dams with live newborns / No.of pregnant dams) X 100

Clinical Observations
General clinical observations were made once a day. Once before the first exposure, and once a week thereafter, detailed clinical observations were made in all animals outside the home cage in a standard arena. Clinical observations included spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoea, asphyxia, vocalization, diarrhea, changes in the skin and fur, eyes and mucous membranes (salivation, discharge), piloerection and pupil size, Changes in gait, posture, response to handling as well as the presence of clonic or tonic movements, stereotypes, difficult or prolonged parturition or bizarre behavior were recorded.

Functional Observations

Multiple detailed behavioral observations were made in the week before the first treatment and during the last week of the treatment in 5 selected males and on lactation days in 5 selected females (only lactating females were evaluated) of control and treated groups outside the home cage using a functional observational battery of tests :
Sensory reactivity to different modalities, grip strength and motor activity assessments and other behavioral observations as well as rearing supported and not supported, urination, defecation, startle/ auditory response, equilibrium reflex, positional passivity, visual placing, fore and hind limb grip strength, tail pinch response, toe pinch reflex, extensor thrust/limb tone, hind limb reflex, righting reflex on the ground, air righting reflex, pupil response, body temperature and ophthalmoscopy (anterior chamber of the eye and fundus of eye).

Litter Observations

The duration of the gestation was recorded and was calculated from day 0 of the pregnancy. Each litter was examined as soon as possible after delivery of the dam to establish the number and sex of pups, stillbirths, live births, runts and the presence of gross abnormalities.
The pre- and post- implantation losses were calculated using number of corpora lutea, number of implantation sites and number of live pups born on PND 0 for each dam. The formula used for the calculation are as follows,
Pre Implantation Loss (%) = (No. of corpora Lutea - No. of implantation site / No. of corpora Lutea) x 100
Post Implantation Loss (%) = (No. of implantation site – No. of live pups / No. of implantation site) x 100
Live pups were counted and sexed and weighed within 24 hours of parturition (day 0 post-partum) and on day 4 post-partum. Live pups were identified by tattooing. In addition to the observations of parent animals, any abnormal behavior of the offspring was recorded.

Haematology
Haematological parameters from five selected males and females of each group were examined at the end of the treatment.
Blood from the abdominal aorta of the animals was collected in EDTA-coated tubes.
The following haematological parameters were examined:
Ihaematocrit value (%)
haemoglobin content (g/dL)
red blood cell count (10^12/L)
mean corpuscular volume (fL)
mean corpuscular haemoglobin (pg/erythrocyte)
mean corpuscular haemoglobin concentration (g/dL)
reticulocytes (%)
platelet count (10^9/L)
white blood cells (10^9/L)
neutrophils (%)
lymphocytes (%)
monocytes (%)
eosinophils (%)
basophils (%)

Blood Coagulation

Coagulation parameters from five selected males and females of each group were examined at the end of the treatment.
Blood from the abdominal aorta of the animals was collected in citrate- coated tubes.
The following coagulation parameters were examined:
prothrombin time (sec)
activated partial thromboplastin time (sec)

Clinical Biochemistry
Parameters of clinical biochemistry from five selected males and females of each group were examined at the end of the treatment.
Blood from the abdominal aorta of the animals was collected in serum separator tubes.
The following parameters of clinical biochemistry were examined:
alanine aminotransferase (U/L)
aspartate-aminotransferase (U/L)
alkaline phosphatase (U/L)
creatinine (µmol/L)
total protein (g/L)
albumin (g/L)
urea (mmol/L)
total bile acids (U/L)
total cholesterol (mmol/L)
glucose (mmol/L)
sodium (mmol/L)
potassium (mmol/L)

Urinalysis

A urinalysis was performed with samples collected from 5 selected males of each group at necropsy. Additionally, urine colour/ appearance were recorded.
The following parameters were measured using qualitative indicators (Heiland Urine Stripes URI 10SL).
specific gravity
nitrite
pH-value
protein
glucose
ketone bodies
urobilinogen
bilirubin
blood
leukocytes

Sperm analysis
At necropsy (one day after the last administration) one epididymis and one testis from males of each group were separated and used for evaluation of sperm parameters. Epididymal sperm motility was evaluated in all male animals using Hamilton Thorn Sperm Analyser. The testicular sperm count could not be measured at the end of the study as the testes stored at -80°C were inadvertently taken out of the freezer before the scheduled measurement.

Sacrifice and pathology:

Gross necropsy
All male animals were sacrificed after the completion of the mating period (minimum dosing period: 28 days) on study day 29 or 30, while female animals were sacrificed on post-natal day 4 (maximum dosing period: 54 days) using an anaesthesia was used.
Females showing no sign of pregnancy was sacrificed on day 26 after the last day of the mating period.
All animals were subjected to a detailed gross necropsy which includes careful examination of the external surface of the body, all orifices and the cranial, thoracic and abdominal cavities and their contents.

Organ Weights
The wet weight of the organs of 5 males and 5 females selected from each group was recorded as soon as possible. Paired organs were weighed separately. In addition reproductive organs of all animals were weighed. The enclosed organs were weighed at necropsy:
liver
uterus with cervix
kidneys
thymus
adrenals
thyroid/parathyroid glands
testes
spleen
epididymides
brain
prostate. seminal vesicles and coagulating glands
pituitary gland
ovaries

The following tissues of the same selected animals from each group were preserved in 10 % neutral buffered formalin except eyes, testes and epididymides that were fixed in Modified Davidson’s Fixative for approximately 24 hours before they were transferred to 10 % neutral buffered formalin:
brain (cerebrum, cerebellum and pons)
ovaries (females)
spinal cord
uterus with cervix (females)
liver
vagina (females)
kidneys
testes (males)
adrenal glands
epididymides (males)
stomach
prostate and seminal vesicles with coagulating glands as a whole (males)
small and large intestines (including Peyer´s patches)
urinary bladder
thymus
lymphnodes (mesentric and axillary)
thyroid
peripheral nerve (e.g. sciatic nerve) with skeletal muscle
spleen
bone with bone marrow (sternum)
lung and trachea
pituitary gland
mammary glands
oesophagus
heart
gross lesions

Histopathology
All organs and tissues listed above were evaluated from five selected males and females of the control and high dose group:
Reproductive organs and macroscopic changes were evaluated in all study animals. For the testes, a detailed qualitative examination was made.

Statistics:

Evaluation of Results and Statistical Analysis
The findings of this study were evaluated in terms of the observed effects, the necropsy and the microscopic findings.
Parameters like body weight gain and food consumption were calculated for each animal as the difference in weight measured from one week to the next. Mean body weights are also presented as figures. The relative organ weights were calculated in relation to the body weight (measured at necropsy) and are presented as percentage.
A statistical assessment of the results of the body weight. food consumption, parameters of haematology, blood coagulation and clinical biochemistry, absolute and relative organ weights were performed for each gender by comparing values of dosed with control animals of the main groups using a one-way ANOVA and a post-hoc Dunnett Test. These statistics were performed with GraphPad Prism 5.01 software (p<0.05 was considered as statistically significant).

Clinical signs:

no effects observed

Description (incidence and severity):

see "Details on results".

Mortality:

no mortality observed

Description (incidence):

see "Details on results".

Body weight and weight changes:

no effects observed

Description (incidence and severity):

see "Details on results".

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

see "Details on results".

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

no effects observed

Description (incidence and severity):

see "Details on results".

Haematological findings:

no effects observed

Description (incidence and severity):

see "Details on results".

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

see "Details on results".

Urinalysis findings:

no effects observed

Description (incidence and severity):

see "Details on results".

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

see "Details on results".

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

see "Details on results".

Gross pathological findings:

no effects observed

Description (incidence and severity):

see "Details on results".

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

see "Details on results".

Details on results:

Clinical Observation:
There were no clinical signs recorded in male and female animals of treated groups that could be directly related to treatment. However, there were few clinical signs namely moving the bedding, nasal discharge (dark or reddish), salivation and piloerection seen occasionally and transiently during the study period in MD or HD group animals. These findings were considered to be due to local effect but not the systemic effect of the test item. These findings were considered not likely to be adverse. In addition, there was alopecia (on hindlimb, forelimb, thorax and abdominal region) noted in few isolated animals of MD or HD groups, which was assumed to be incidental in origin.
During the weekly detailed clinical observation, no significant changes or differences between the groups were found.
There were no ophthalmoscopic findings in any of the animals of this study.

Functional Observation:
No relevant effects of treatment were observed in any of the parameters of the functional observation battery before and at the end of the treatment period. There were no biologically relevant differences in body temperature between the groups.

Body Weight development:
In both males and females, no adverse treatment related changes were noted for body weight and body weight change during the study period. Statistically there were significant increase in body weight change in female HD group during 2nd week of premating period when compared to control. In addition, there was lower mean body weight gain noted between days 1-7 of premating when compared to control without attaining the statistical significance. But, this increase or decrease in weight gain did not correlate with food intake during the same period. Hence, the changes were not considered likely to be adverse. There was decrease in body weight gain noted in female MD and HD groups during lactation period when compared to control. This decrease had no statistical significance and was not likely to be adverse.

Food Consumption:
In both males and females, no treatment related changes were noted for treated group when compared to corresponding control. The statistical evaluation of the data revealed no significant changes in food intake in treated group animals when compared to control.

Haematology and Coagulation (tables 3 and 4)
No treatment related changes were noted for haematology and blood coagulation parameters measured at the end of treatment period in male and female animals. There were no statistically significant changes noted for haematological and coagulation parameters between the treated and control groups.

Clinical Biochemistry :
There were no treatment related changes considered for measured clinical biochemistry parameters of male and female treated groups when compared to corresponding control. However, there was statistically significant increase noted for mean potassium value in male MD group. In the absence of dose response pattern no relevance to treatment was considered.

Urinalysis:
The urinalysis performed in male animals revealed no considerable changes in treated groups when compared to the control.

Pathology:
At terminal sacrifice, macroscopic organ findings noted were few, and none of them was considered to be test item related.
Yellow spot(s) at the epididymis were observed without dose relationship in 2/10 control males, 1/10 male of LD group, 3/10 males of MD group and 2/10 males of HD group. They were not considered treatment related as histologically they were confirmed to represent spermatic granuloma, a finding known to occur spontaneously in untreated rats of this strain and age. In one isolated male of MD group small testes was noted at necropsy. Histopathologically this finding was considered to be spontaneous in nature and unrelated to the test item.

Organ Weight
There were no changes considered to be related to treatment noted for organ weight in both males and females when compared to corresponding control. However, there was statistically significant increase in relative weight of left kidney weight in male treated (LD, MD and HD) groups, but not total kidney weight. This change in left kidney weight, in the absence of histological changes was not considered to have toxicological relevance.

Histopathology:
Reproductive organs
No test item-related effects were noted on male and female reproductive organs in any of the treatment groups.
Histopathological findings noted in male reproductive organs were few and considered to be spontaneous in nature and unrelated to the test item, comprising multifocal atrophic tubules in the testis of each one male treated at 300 and 1000 mg/kg/day and subsequent epididymal changes in the same animals.
Reproductive organs of most study females showed histomorphological evidence of precedent pregnancy in the uterus. The number of large corpora lutea in the ovary was not essentially different between the groups.
Non pregnant animals showed physiological sexual cycling, and their unsuccessful mating was considered unrelated to the treatment.
Other organs
No test item-related histopathological findings were noted in the other organs evaluated in randomized males and females of the control and high dose group.
Histopathological changes seen at terminal sacrifice were considered to be incidental in origin and/or within the range of expected changes for rats of this age and strain kept under laboratory conditions.

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No systemic toxicity

Critical effects observed:

not specified

Conclusions:

In conclusion, the repeated dose administration of the Yttrium Oxide to the male (minimum 28 days) and female (maximum 54 days) Wistar rats at dosages of 100, 300 and 1000 mg/kg body weight/day revealed neither mortalities nor adverse findings of toxicological relevance in male and female animals. There were also no toxicologically relevant findings noted for reproductive and developmental parameters.

Based on the data generated from this “Combined Repeated Dose Oral Toxicity Study with the Reproduction/ Developmental Toxicity Screening Test with Yttrium Oxide”, the no observed adverse effect level (NOAEL) for both male and female animals for systemic toxicity was considered to be 1000 mg/ kg body weight/ day.

No classification for repeated-dose toxicity is warranted based on the absence of toxicologically relevant effects in this study, according to the criteria of Annex VI Directive 67/748/EEC or the 1272/2008 regulation -CLP).

Executive summary:

There was no mortality noted in treated (at 100, 300 and 1000 mg/kg bw/day) and control groups during the study period (at least 28 days for males and 54 days for females).

There were few clinical signs namely moving the bedding (1/10 females, HD group), nasal discharge-dark or reddish (3/10 males, HD group; 4/10 females, MD) , salivation (2/10 males, 2/10 females MD; 5/10 females, HD group) and piloerection (1/10 males, 4/10 females MD; 2/10 females HD) seen occasionally and transiently during the study period in MD or HD group animals. These findings were considered to be due to local effect but not the systemic effect of the test item. These findings were considered not likely to be adverse.

During the weekly detailed clinical observation of male and female animals from treated and control groups, no significant changes or differences between the groups were found.

There were no ophthalmoscopic findings in any of the animals of this study.

No relevant effects were observed in any of the parameters of the functional observation battery before and at the end of the treatment period. There were no biologically relevant differences in body temperature between the groups.

In both males and females, no adverse treatment related changes were noted for body weight and body weight change in treated groups when compared to control. There were no treatment related changes noted for food consumption in both male and female treated groups when compared to control.

The statistical evaluation of food consumption revealed no significant changes in food intake in treated group animals when compared to control.

There were no statistically significant changes noted nor for haematological and coagulation parameters nor for clinical biochemistry parameters of male and female treated groups when compared to corresponding control.

The urinalysis performed in male animals revealed no considerable changes in treated groups when compared to the control.

No test item related histopathological findings were seen in the other organs evaluated in selected males and females of the control and high dose group.

At terminal sacrifice, macroscopic organ findings noted were few in both males and females, and none of them was considered to be test item related. There were no changes considered to be related to treatment noted for organ weight in both males and females when compared to corresponding control.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Test was performed according to an international guideline and according to GLP.

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

other: Published results

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This publication described a 30 days repeated inhalation study of yttrium oxide on dogs and is fully described with respect to the experimental conditions and the results. However, the GLP are not stated and there is no reference to international guideline.

Principles of method if other than guideline:

18 beagles dogs were subjected to treadmill exercise and exposure to a chamber atmosphere of yttrium oxide. The exposure lasted 30 days (180 exposure hours) and treadmill exercise was given for 10 minutes a day throughout the experiment. Postexercise value of blood lactate concentration was determined 2 times a week and erythrocyte volume, plasma volume, hemoglobin concentration and leukocyte count were determined before the start and at the end of the exposure period.
Thoracic radiographs were done before the exposure to determine freedom from lung lesions and subsequent fitness for treadmill exercise.
Histologic examination was done on dogs after exposure period. Aerosol concentration, distribution and particles size have been determined.

GLP compliance:

not specified

Limit test:

no

Species:

dog

Strain:

Beagle

Sex:

male/female

Details on test animals or test system and environmental conditions:

3 separate experiments with 8 dogs (4 males and 4 females), 6 to 9 months, were used. The dogs were vaccined against canine distemper, infectious hepatitis and lesptospirosis, given a physical examination and treated for internal parasitic infestation. A negative result was obtained on the examination for Dirofilaria. A commercial dry dog feed was reasonably fed according to the recommendation of the manufacturer and water was available ad libitum.

The dogs were trained (4 to 5 weeks) to run on a treadmill before the 10-week experiment. Each dog was exercised on the treadmill for 10 minutes daily, each 5 days a week in a room maintained at 22 - 23 °C. The dogs were placed in individual cages, placed in a chamber environment each afternoon for 6 hours, 5 days a week for the 10-week experiment.

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: 0.393 +/- 0.345 µm

Details on inhalation exposure:

Preparation of aerosol:
The original pulverized powder of yttrium oxide (99.9 %) was reduced to a uniform particles size in a blender. Generation of the aerosol was accomplished with a Wright dust feed mechanism. Its operation was dependent on the removal, by a stream of air, of dust as it was scraped from a revolving cylinder tightly packed with yttrium oxide.

Exposure method:
While in the chambers the dogs were confined to individual cage were made with stainless steel, the top, bottom, sides and ends were constructed of expanded stainless steel fabric which permitted free passage of air.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

During the experiment three kind of controls were performed: particles size determination, aerosol distribution and mass distribution of the aerosol.
Particle Size determination: the chamber atmosphere was sampled with a point-to-plane electrostatic precipitator. The maximal diameter was analyzed by an electron photomicrograph with a particle size analyzer.

Aerosol concentration: the concentration of yttrium oxide during the exposure period was arbitrarily set at 15 mg/cu.m. To maintain this concentration, daily sampling was required and adjustments were made accordingly. A color-forming reagent was used for the quantitative determination of yttrium and rare earths concentration (according to Fritz et al.).

Mass distribution of aerosol: a Casella cascade impactor was used to determine the mass distribution of aerosol and the percentage of particles less than 1 µm. When distribution samples were collected, glass coverslips coated with stopcock grease were affixed to the stages. A filter retained particles not impinged at the stages. Samples were collected for 30 seconds. The size of the particles collected on the various stages was determined by electron microscopy. Electron microscopy girds were mounted in the line of deposition at each stage and particles were impinged directly on these girds and measured.

Duration of treatment / exposure:

The dogs were trained (4 to 5 weeks) to run on a treadmill before the 10-week experiment. Each dog was exercised on the treadmill for 10 minutes daily, each 5 days a week in a room maintained at 22 - 23 °C. The dogs were placed in individual cages, placed in a chamber environment each afternoon for 6 hours, 5 days a week for the 10-week experiment.
The dogs were in paired experiment in which the first 4 weeks comprised the control period and the next 6 weeks, the treatment period.

Frequency of treatment:

6 hours a day, 5 days a week during 6 weeks.

No. of animals per sex per dose:

Three groups of six dogs (male and female) were treated with the enclosed measured concentrations (expressed in mg Y2O3/m3) :
exp 8A: 20.63 +/- 3.03
exp 8B: 12.65 +/- 5.04
exp 8C: 16.88 +/- 3.88

Control animals:

yes, concurrent no treatment

Details on study design:

The dogs were trained (4 to 5 weeks) to run on a treadmill, then, the 10-week experiment was started. Each dog was exercised on the treadmill (between 10:00 and 12:00 a.m.) for 10 minutes daily for 5 days a week. The exercising was accomplished in a room where the temperature was maintained at 22 to 23°C. The dogs were placed in individual cages and the cages were placed in a chamber environment each afternoon for 6 hours, 5 days a week for the 10-week experiment.

The dogs were in a paired experiment in which the first 4 weeks comprised the control period and the next 6 weeks, the treatment period. During the control period, increases in receptivity and running ability were noticed. Also a treadmill speed was set for each dog in two groups of six dogs that appeared to obtain satisfactory work output and that correlated with a plateau of blood lactate concentration. In the third group of dogs, they were exercised at the same treadmill speed and it became apparent that the running abilities were not equal. Establishing a lactic acid plateau seemed logical in that any blood lactate increase which might be observed later would be relative to previous level.
With this design it was possible to establish normal values before yttrium oxide was introduced and to obtain a series of observations during the inhalation or treatment period.
The various responses could then be expressed as « change » over the treatment period. To provide for histologic comparisons, 1 male and 1 female dog from each group of 8 were placed in chambers in which yttrium oxide was not introduced during the 6 weeks treatment. The 2 dogs never became good runners and tended to hang back in the harness. Because of their poor performance, the corresponding blood lactate concentration and other values relative to exercise were not meaningful.

Positive control:

No data

Observations and examinations performed and frequency:

Several analysis have been realised after the exposure period:

1. Post exercise blood lactate concentration, obtained 2 times a week during the experiment
2. Erytrocyte volume measurement was performed on each dog before and after the end of the experiment.
3. Plasma Volume for each dog was determined before and at the end of the exposure period.
4. Other hematologic values: Leukocyte counts, packed cell volume and total hemoglobin concentration were determined before and at the end of the experiment.
5. Radiographic examination of thorax on each dogs were made before and at the end of the exposure period.
6. Necropsy was realised after the end of each experiment.

Sacrifice and pathology:

6. Necropsy
After the end of each experiment the dogs were euthanatized and necropsied. Portion of sternum, lungs, heart, liver, spleen, adrenal gland, kidneys, bronchial lymph nodes, gonad and mesenteric lymph nodes were obtained for histologic examination. These tissues were fixed in 10 M formalin and paraffin sections were cut at a thickness of 6 µm and stained with hematoxin-eosin stain

Other examinations:

1. Post exercise blood lactate concentration, obtained 2 times a week during the experiment
5 ml of blood was withdrawn from the right and left jugular vein approximately 30 sec after the treadmill exercise. The blood was withdrawn in a syringe containing crystalline ammonium fluoride to avoid coagulation.
The same day, the lactate concentration was determined by the method of Barker and Summerson.

2. Erythrocyte volume measurement
The erythrocyte volume of each dog was determine before and after the end of the experiment, using Na2CrO4 which is a modification of Sterling and Grey. Radioactivity was determined in a well-type, thallium actived NaI crystal scintillation counter.

3. Plasma Volume measurement
Plasma volume for each dog was determined before and at the end of the exposure period by a modification of the T-1824 dye dilution method of Gregerson as already described in the literature.

4. Other hematologic values
Leukocyte counts, packed cell volume and total hemoglobin concentration were determined before and at the end of the yttrium oxide exposure.

5. Radiographic examination of thorax
Thoracic radiographs of each dogs were made before and at the end of the exposure period to determine freedom of lung lesions and subsequent fitness for treadmill exercise. The occurrence of any increase in radiographic density due to the exposure was also observed.

Statistics:

The Student's test was used to determine the relevance of observed difference after exposure and/or exercise. A variance test was also conducted to determine any difference due to the sex of dogs.

Clinical signs:

not specified

Mortality:

not specified

Body weight and weight changes:

not specified

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

No effect on plasma volume & hemoglobin concentration. Significant increase of white blood cells & decrease of the erythrocyte volume which should indicated Y2O3 was being transported from the lungs to other tissues, having negative erythropoiesis effect.

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not specified

Details on results:

Histologic examination showed no effect on: heart, liver, spleen, mesenteric lymph nodes, testis or ovaries, kidneys, adrenal gland, and bone marrow.
Toraxic radiography showed subtle changes which are consistent with the slightly increased density at the hilus of the lung. Possibly the enlarged bronchial lymph nodes which contained numerous dust laden macrophages contributed to the slight increase in density.

Blood lactate concentration:
This parameter was obtained by subtracting a normal value before the exposure and after 30 days of exposure for the same dog.
Normal value was determined as the average of results for 4 determinations (2 made during the week before exposure and 2 during the weeks after exposure began).
The mean of the difference was + 5.00 mg/100 mL of blood. This difference was tested as relevant according to the Student’s test. It was assumed that, with repeated treadmill exercise under conditions of no exposure, post exercise blood lactate concentration would decrease. This decrease was demonstrated by Yoder and al.
A variance analysis showed no significant difference due to replication of test or sex of dog.

A highly positive increase occurred in 3 dogs, 1 from each experiment which indicated that some alteration had occurred in their ability to transfer, transport or utilize oxygen. Toward the end of the experiment, it became difficult to these dogs to complete their 10-minute exercise period. It was observed that certain dogs respond to treadmill exercising quite favorably, whereas others are more reluctant to increase work output. In an ideal situation only dogs responding favorably should be selected and subjected to a greater work task.

Erythrocyte volume: The overall mean of the difference was 3.9 mL/kg of body weight and was only significant at the 0.10 level. No difference was observed regarding replication or sex. The mean of this difference was negative. One might assume that with increased tissue demands for oxygen an increase in erythrocyte volume might occur. It is possible that enough yttrium oxide was being transported from the lungs to other tissues to have an inhibiting effect upon erythropoiesis. One might have observed a more significant decrease in erythrocyte volume if the period of exposure and exercise had been extended.

Plasma volume and hemoglobin concentration: the mean of the differences were no significant.

Leukocyte count: The overall mean of the difference is 2.333 leucocytes/cm3 of blood. This was significant increase an active response of the body the remove foreign material. Regarding the absence of difference observed in white blood cell counts by Davison if mice and guinea pigs were exposed to dust aerosols of neodymium, this result could be a peculiarity of species response.
A slightly significant decrease in circulating monocytes was seen at the end of the exposure period. This was significant at the 0.10 level.
No significant change in distribution of other white blood cell types was detected.

Necropsy results:
Lungs of exposed dogs were reddish grey instead of pink. Bronchial lymph nodes in exposed dogs were enlarges 8 to 10 times but other body lymph nodes were normal in size. With regards to gross appearance, all other organs were normal.

Results of histologic examination:
Many cellular elements were within the alveoli of lungs of exposed dogs. The most apparent histologic change occurring as a result of 30 day’s exposure to yttrium oxide was the presence of many macrophages and leukocytes in the alveaoli. According to Hatch & gross, these alveolar macrophages or “dust cells”. The extreme hypertrophy of alveolar epithelial cells prior to desquamation is shown.
The leukocytes were mainly neutrophils. Many had elongated nuclei and were nuclei and were probably in the process of diapedesis. Seemingly, a leukotactic substance was attracting many leucocytes to the lungs and this was reflected by the increases leukocyte count.
Examination of the lungs indicated no connective tissue increase.

Results of examination of bronchial lymph nodes from expected dogs indicated the presence of many dust-laden macrophages. These macrophages were seen after 30 days of exposure.

Radiographic examination: slight increase of the lung density probably due to the increase of dust-laden macrophages.

Dose descriptor:

NOEL

Effect level:

> 20.63 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No systemic toxicity

Critical effects observed:

not specified

Conclusions:

No relevant systemic effects were observed during this study, exposing dogs 30 days to 20.63 mg Y2O3/m3.
However, an overall NOEL could be established to be above 20.63 mg/m3, based on the absence of change in hematology, organ weights, macroscopic observations at necropsy and histopathology at the tested concentration.

No classification for repeat-dose toxicity is warranted based on the absence of toxicologically relevant effects in this study, according to the criteria of Annex VI Directive 67/748/EEC or the 1272/2008 regulation -CLP).

Executive summary:

- Gross Pathology: No effect

- Histopathology: no effect on hearth, liver, spleen, mesenteric lymph nodes, testis or ovaries, kidneys, adrenal gland and bone narrow

- Thoracic radiographs of each dog were made before and at the end of the exposure period to determine freedom of lung lesions and subsequent fitness for treadmill exercise. No relevant effect.

- Lungs exposed dogs were reddish gray and were firmer than the lungs of the controls. Bronchial lymph nodes in exposed dogs were enlarged 8 - 10 times; other body lymph nodes were normal in size. With regards to gross appearance, other organs were normal.

- Effect on plasma volume & hemoglobin concentration. Significant increase of white blood cells, dust-laden macrophages in the bronchial lymph nodes & decrease of the erythrocyte volume which should indicated Y2O3 was being transported from the lungs to other tissues, having negative erythropoiesis effect.

The observed effects were rather consistent with a local inflammatory response of lung following inhalation of poorly soluble particles of low toxicity, with no systemic effects and a limited relevance to the human occupational situation given the levels of exposure.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

subacute

Species:

dog

Quality of whole database:

The operational conditions, control and results are fully described in the publication.

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Oral Route:

 

A combined repeated dose toxicity study with the reproduction/developmental toxicity screening has been conducted according to OECD 422 test guideline using the oral exposure route on Wistar rats. This study was scored as reliability 1 according to Klimisch criteria.

 

The test item, yttrium oxide, was administered daily by oral gavage to male and female Wistar rats, 7 days per week with a maximum exposure of 54 days in total for females (at least 14 days of pre-mating, maximum 14 days of mating, 22 days of gestation and 4 days of post-partum) and minimum 28 days for males., at dose-levels of 100, 300 or 1000 mg/kg/day.

 

Animals were observed for mortality, clinical signs, Body weight and bodyweight gain and food consumption were measured, Ophthalmoscopic examination, hematologic analyses and urinalysis were done. Neurobehavioral comportment including FOB and organ weights were measured. At necropsy, gross pathology and histopathology on selected organs were done. Developmental toxicity parameters were also observed, measured and assessed but no effects were observed.

There was no mortality noted in treated animals. Few clinical signs were seen occasionally and transiently during the study period in medium dose (MD - 300 mg/kg bw/day) or high dose (HD - 1000 mg/kg bw/day) group animals but these findings were considered to be due to local effect but not the systemic effect of the test item and were considered not likely to be adverse. There were no ophthalmoscopic findings in any of the animals of this study as well as no effect of treatment on FOB parameters and on body temperature. In both males and females, no adverse treatment related changes were noted for body weight and body weight change and for food consumption. No statistically significant changes were noted for haematological and coagulation parameters nor for clinical biochemistry and urinalysis parameters. There were no changes considered to be related to treatment noted for organ weight in both males and females when compared to corresponding control. At terminal sacrifice, macroscopic organ findings noted were few in both males and females, and none of them was considered to be test item related and histopathological findings were seen in the organs evaluated.

 

Based on the experimental conditions of this study, the No Observed Adverse Effect Level (NOAEL) for systemic toxicity was considered to be 1000 mg/kg/day in female and male rats.

Inhalation Route:

A publication (Reece, 1967), quoted 2 according to Klimisch quotation, described a 30 days repeated inhalation study of yttrium oxide on dogs at concentration levels up to 20.63 mg/m3 and is fully described with respect to the experimental conditions and the results.

Several analysis have been realised after the exposure period: Post-exercise blood lactate concentration, obtained 2 times a week during the experiment, Erythrocyte volume measurement after the end of the experiment, Plasma Volume before and at the end of the exposure period, Leukocyte counts, packed cell volume and total hemoglobin concentration before and at the end of the experiment, radiographic examination of thorax before and at the end of the exposure period, necropsy after the end of each experiment and histopathology on hearth, liver, spleen, mesenteric lymph nodes, testis or ovaries, kidneys, adrenal gland and bone marrow.

The study showed no relevant effect on:

- Gross Pathology

- Histopathology: no effect on hearth, liver, spleen, mesenteric lymph nodes, testis or ovaries, kidneys, adrenal gland and bone marrow

- Thoracic radiographs of each dogs were made before and at the end of the exposure period

 

Lungs of exposed dogs were reddish gray and were firmer than the lungs of the controls. Bronchial lymph nodes in exposed dogs were enlarged 8 - 10 times; other body lymph nodes were normal in size. With regards to gross appearance, other organs were normal.

The study showed only significant increase of white blood cells, dust-laden macrophages in the bronchial lymph nodes & decrease of the erythrocyte volume which should indicated Y2O3 was being transported from the lungs to other tissues, having negative erythropoiesis effect.

 

No relevant systemic effects were observed during this study, exposing dogs 30 days to 20.63 mg Y2O3/m3.

However, an overall NOEL could be established to be above 20.63 mg Y2O3/m3, based on the absence of change in hematology, organ weights, macroscopic observations at necropsy and histopathology at the tested concentration.

Furthermore a subchronic toxicity (90-day repeated inhalation study) is available on cerium oxide (quoted Klimisch 2 as the substance tested as an analogous) and a subacute 28 days on neodymium oxide and praseodymium oxide that could be considered as analogous in a read across strategy based on similar physico-chemical, toxicological, ecotoxicological and environmental properties. Here below are reported the toxicological data on cerium, neodymium, praseodymium and yttrium oxide compounds for comparison.

Tests:	Cerium Oxide	Yttrium Oxide	Neodymium Oxide	Praseodymium Oxide
Density	7.20 g/cm^3at 20.3°C	4.85 g/cm^3at 20°C	7.24 g/cm^3at 20.3°C	6.9 g/cm^3at 20.3°C
Solubility	< 0.123 mg/L	0.7 mg/L	7.8 µg/L	1.27 mg/L
Granumometry	D50~16.56 µm	0.5 – 40 µm	2 – 8 µm	2 -50 µm
7.2.1 Acute toxicity: oral (rat)	Oral LD50 Combined male/female > 5000 mg/kg bw	Oral LD50 Combined male/female > 5000 mg/kg bw	Oral LD50 Combined male/female > 5000 mg/kg bw	Oral LD50 Combined male/female > 5000 mg/kg bw
7.2.2 Acute toxicity: dermal (rat)	Dermal LD50 > 2000 mg/kg bw   Substance not classified	Dermal LD50 > 2000 mg/kg bw   Substance not classified	No data on neodymium oxide	No data on Praseodymium Oxide
7.3.1 Skin Irritation / Corrosion (rabbit)	Irritation Score (Draize Method): 0   Cerium Oxide is not a dermal irritant.	Irritation Score (Draize Method): 0   Cerium Oxide is not a dermal irritant.	Irritation Score (Draize Meth.): 0.13   Neodymium Oxide is not a dermal irritant.	Irritation Score (Draize Method): 0   Praseodymium Oxide is not a dermal irritant.
7.3.2 Eye Irritation / Corrosion (rabbit)	Mean ocular irritation scores (Draize) were 9.33, 1.33 and 0.67 at 1 h after instillation and on days 1 and 2, respectively. All the irritation signs had reversed by day 3   Cerium oxide was not classified as irritant to the eye, according to the criteria of Annex VIRegulation 1272/2008/EC.	Draize scores: Unwashed: 13 (24h) ; 3.7 (48h) ; 0.7 (72h) Draize scores: Washed: 9 (24h) ; 2 (48h) ; 0 (72h)           Yttrium oxide is slightly irritant to the eye but not classified as irritant to eyes according to EU criteria.	Draize Scores: Unwashed: 11 (24h); 2.3 (48 h); 0.7 (72 h) Draize Scores: Washed : 6 (24 h); 2 (48 h); 0.7 (72 h)           Neodymium Oxide is slightly irritant to the eye but not classified as irritant to eyes according to EU criteria.	Draize Scores: Unwashed : 13 (24 h); 3.7 (48 h); 0.7 (72 h) Washed : 9 (24 h); 2 (48 h); 0 (72 h)           Praseodymium Oxide is slightly irritant to the eye but not classified as irritant to eyes according to EU criteria.
7.4.1 Skin Sensitisation	Cerium Oxide is not classified as skin sensitising according to Annex VI of the Regulation 1272/2008/EC.	Yttrium Oxide is not classified as skin sensitising according to Annex VI of the Regulation 1272/2008/EC.	Neodymium Oxide is not classified as skin sensitising according to Annex VI of the Regulation 1272/2008/EC.	Praseodymium Oxide is not classified as skin sensitising according to Annex VI of the Regulation 1272/2008/EC.
7.5.1 Repeated Dose Toxicity: Oral (rat)	NOEL = 1000 mg/kg   LD50 > 1000 mg/kg   Cerium Oxide is not classified as repeated-dose toxic according to Annex VI of the Regulation 1272/2008/EC.	NOEL / NOAEL > 1000 mg/kg LD50 > 1000 mg/kg   Yttrium Oxide is not classified as repeated-dose toxic according to Annex VI of the Regulation 1272/2008/EC.	Neodymium Oxide is not classified as repeated-dose toxic according to Annex VI of the Regulation 1272/2008/EC.	NOEL > 1000 mg/kg       Praseodymium Oxide is not classified as repeated-dose toxic according to Annex VI of the Regulation 1272/2008/EC.
7.5.2 Repeated Dose Toxicity: inhalation	A 413 OECD tested Cerium oxide by inhalation on rats has been conducted. Considering all observed effects, alveolar epithelial hyperplasia was considered to calculate LOAEC = 0.0505 mg/l (50.5 mg/m3) based on the incidence and severity of alveolar epithelial hyperplasia in the lungs.   Cerium Oxide is not classified as repeated-dose toxic according to Annex VI of the Directive 67/548/EEC.	No data available	No data available	No data available
7.6.1 Genotoxicityin vitro- Ames	No mutagenic effect at 5000 µg/plate   Cerium Oxide is considered to be non-mutagenic in this Salmonella typhimurium reverse mutation assay.	No mutagenic effect at 5000 µg/plate   Yttrium Oxide is considered to be non-mutagenic in this Salmonella typhimurium reverse mutation assay.	No mutagenic effect at 5000 µg/plate   Neodymium Oxide is considered to be non-mutagenic in this Salmonella typhimurium reverse mutation assay.	No mutagenic effect at 5000 µg/plate   Praseodymium Oxide is considered to be non-mutagenic in this Salmonella typhimurium reverse mutation assay.
7.6.1 Genotoxicityin vitro– Gen. Toxin vitroHPRT	Cerium Oxide did not induce gene mutations at the HPRT locus in V79 cells up to the concentration of 1800 µg/mL with or without S9.    No evidence of gene mutations at the HPRT locus in V79 cells up to the concentration of 1800 mg/mL of Cerium Oxide with or without S9	Yttrium Oxide did not induce gene mutations at the HPRT locus in V79 cells up to the concentration of 10 mM with or 7.5 mM without S9.   Yttrium Oxide did not induce gene mutations at the HPRT locus in V79 cells at the higher tested concentration.	Neodymium oxide did not induce gene mutations at the HPRT locus in Cho cells up to 1682.5 µg/mL with S9 or 3365 µg/mL without S9.   Neodymium Oxide is considered to be non-mutagenic to CHO cells at the HPRT locus at the higher concentration with or without S9.	In one of the two experiments, significant cyctotoxic effects were observed ≥ 1250 µg/mL without metabolic activation producing reductions in cloning efficiency 21 & 89%.   Praseodymium oxide is considered to be mutagenic to CHO cells at the HPRT locus with and without of metabolic activation.
7.8.1 Toxicity to reproduction	NOEL parent = 1000 mg/kg/day NOEL progeny = 1000 mg/kg/day. Substance not classified	NOEL parent > 1000 mg/kg/day NOEL progeny > 1000 mg/kg/day. Substance not classified	No Observed Effect Level (NOEL) for reproductive effects was considered to be 1000 mg/kg/day for both males and females.	No Observed Effect Level (NOEL) for reproductive effects was considered to be 1000 mg/kg/day for both males and females.

 

As the table above summaries these four rare earth oxides are showing the same harmlessness for acute, chronic , and geno – toxicity:

-         Absence of effect for acute toxicity by oral (for the four oxides), inhalation (for the four oxides) and dermal (for the two tested oxides) routes

-         Absence of effects as dermal irritant, nor sensitisating, slight irritation on eyes were observed but no classification required for the 4 substances

-         No relevant effects were noted during a combined repeated dose toxicity study with the reproduction /developmental toxicity screening test. NOEL for systemic and reproduction effects were all above the maximum tested concentration (1000 mg/kg/day) for the 3 oxides. Concerning Neodymium oxide, the NOAEL is 300 mg/kg bw/day based on kidney seen in 2/10 females only at the limit dose of 1000 mg/kg. No adverse effects were seen in males nor for systemic toxicity, nor for reproduction/development toxicity in both tested sexes at the limit dose of 1000 mg/kg bw/day. This study concluded on the absence of local effects.

-         No genotoxic effects were observed when all considered substances were tested with Ames and chromosomal aberration (in vitro or in vivo). Tree of the four tested substances gave also a negative result on HPRT test. Only praseodymium oxide gave a positive result for one of the two experiments done in a HPRT test.

These data reveal that these substances can be considered as analogous, considering chemical properties, acute (by all routes of exposure), chronic toxicity in the context of a read across approach. Also genotixicity results are very closed. Only a slight difference has been observed on one of the tree genotoxicity test which have been realized on the four oxides: HPRT test on praseodymium oxide but the tree others rare earth oxides presented the same negative results of genotoxicity. This slight difference has no impact on the read across approach as all the other assessed parameters these four substances present a high similarity of non-toxic profile.

Results obtained in sub-acute studies performed on cerium, neodymium, praseodymium and yttrium oxides were very similar and support the read across approach.

 

In addition to the NOEL for systemic and reproductive effects which are similar (> 1000 mg/kg/day for each oxide and 300 mg/kg/day on females tested with neodymium oxide for systemic toxicity), the absence of effects on the observed parameters during the whole study was very similar for each ones.

No relevant effects were observed on the four tested oxides for: mortality, clinical signs, body weight, body weight gain, food consumption, ophthalmoscopic examination, histopathology, gross pathology, gross necrosis, clinical biochemistry, hematology formulation, urinary organs, neurobehavioral comportment, mating and pregnancy performance, fertility, maternal care and pup performance (litter survival and pup weights).

 

 

A 90-day repeated dose toxicity study of cerium dioxide is available. This study was performed in the rat with the analogous substance (cerium dioxide) and is summarized below. This study was performed according to OECD 413 guideline and in agreement with GLP (Viau A., 1994).

 

Following nose-only inhalation for 90 days (6 hours/day, 5 days/week) at 0, 5, 50.5 or 505.7 mg/m3, no treatment-related deaths or clinical signs occurred during the study. There were no effects on ophthalmology, clinical chemistry, urinalysis at any dose level. No behavioral changes following both acute or sub-chronic exposure and no significant differences in motor activity were observed in treated groups in the Functional Observational Battery assessment. Treatment-related significant changes in segmented neutrophil counts, lung and spleen weights, lung and lymph node gross appearance at necropsy and lung, respiratory tract and lymphoreticular system histopathology, were noted in groups exposed to cerium dioxide.

No NOAEC was determined in the study report based on effects at the low concentration. This study identified a LOAEC of 5 mg/m3 in rats, based on the increased incidence of lymphoid hyperplasia in the bronchial lymph nodes of male and female rats.

However, considering that lymphoid hyperplasia in the bronchial lymph nodes may not represent a specific toxic effect, but rather a non-specific adaptive response to the overloading of the pulmonary alveolar macrophages by inorganic poorly soluble particles in rats, and considering that alveolar epithelial hyperplasia in the lungs represents a more sensitive indication of adverse effects, the concentration of 0.0505 mg/l (50.5 mg/m3) can be regarded as a LOAEC in rats based on the incidence and severity of alveolar epithelial hyperplasia in the lungs following exposure for 13 weeks.

No systemic toxic effects specific to cerium dioxide as such were observed in the rat following 13-week inhalation exposure.

 All the considered tests (realized according to GLP and OECD guidance) and summarized in the table above show the absence of relevant effect and justify the non-classification of the four discussed substances according to regulation 1272/2008/EC. Accordingly, none of these substances should be classified in any of the toxicological category.

 

Moreover, considering the absence of effect of Yttrium Oxide tested in a reproduction/ developmental toxicity screening study according to OECD 422 test guideline using the oral exposure route on rat (Klimisch 1), the absence of relevant effects of Yttrium Oxide on dogs treated by inhalation route during 30 days and considering a read across approach with tree analogous substances:

-         Even with a calculated NOAEL of 300 mg/Kg/d (effect on kidneys for two females) with Neodymium Oxide, OECD 422 studies on Neodymium and Praseodymium Oxides showed the absence effect in a subacute toxicity by oral route

-         Cerium Oxide, showed no effect nor in a subacute toxicity study by oral route nor in a subchronic toxicity (90-day repeated inhalation study quoted Klimisch 1) by inhalation, the repeated dose toxicity endpoint and a further 90-day study for Yttrium Oxide is regarded as unnecessary as the existing data is considered to be adequately addressed.

Additionally, as discussed in the toxicokinetic summary part of this dossier and based on its insoluble nature, low absorption and distribution potentials in organs, absence of obvious metabolism, and absence of systemic effects, it is probable that Yttrium Oxide which is will be mostly eliminated under an unmodified form and confers its harmlessness.

 

Consequently, in accordance with Section 1 of Annex XI a subchronic toxicity study, as required under Section 8.6.2 of Annex IX does not appear scientifically necessary.

 

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The only available study was performed according to the GLP and international guideline.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
This publication described a 30 days repeated inhalation study of yttrium oxide on dogs and is fully described with respect to the experimental conditions and the results. However, the GLP are not stated and there is no reference to international guideline.

Justification for classification or non-classification

No classification for repeat-dose toxicity is warranted based on the absence of toxicologically relevant effects in these two studies -OECD 422 by oral route on wistar rat and repeated inhalation of yttrium oxide on beagle dogs, according to the criteria of Annex VI Directive 67/748/EEC or the 1272/2008 regulation -CLP).