Aluminium nitride

Endpoint summary

Description of key information

In a 28-day repeated dose inhalation toxicity study (according to OECD 412) adverse local effects were seen after inhalation of the target substance at 10 mg/m³ and 70 mg/m³. No adverse systemic effects were reported up to the maximum attained concentration of 70 mg/m³. No repeated dose oral toxicity data is available for aluminium nitride. However, suitable data is available from the read across partner aluminium potassium sulfate. A subchronic repeated dose oral toxicity study in rats (similar to EU method B.26) and a chronic oral toxicity study in mice (similar to EU method B.33) were conducted using aluminium potassium sulfate. No adverse effects have been reported up to 100.000 ppm in the diet (15.000 mg/kg bw/day).

Key value for chemical safety assessment

Toxic effect type:

concentration-driven

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

chronic toxicity: oral

Remarks:

combined repeated dose and carcinogenicity

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Vehicle:

unchanged (no vehicle)

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

MORTALITY
The survival rates at the end of the dosing period were 73.3% (male) and 78.3% (female) in the control group, and 86.7%-95.0% (male) and 86.7-91.7% (female) in the treatment group.

BODY WEIGHT AND WEIGHT GAIN
Both the male and the female mice in the high dose level exhibited slight growth retardation compared with the control group after 1 month, and those in the 1.0 and 2.5 % dose groups exhibited a slight increase in body weight after 3 months. Both male and female mice receiving 5.0% test item showed growth similar to that in the control group

FOOD CONSUMPTION
Food consumption did not show any variation among the groups throughout the experimental period for either males or females

ORGAN WEIGHTS
A significant increase in the absolute organ weight was observed in the kidneys and heart in both sexes in the 1.0, 2.5 and 5.0% dose groups, in the pituitary in the males in the 2.5% dose group and the brain in the females in the 1.0% group compared with those in the control group. Additionally, there were significant decreases in the absolute organ weight of the liver in both sexes in the 5.0 and 10.0% dose groups, the heart and brain in both sexes in the high dose group and lungs in the males and spleen in the females in the 10% high dose group compared with those in the control group. There was a significant increase in the relative organ weight of the kidneys in the males in the 5.0% dose group and a significant decrease in the relative organ weight of the liver in both sexes in 5.0 and 10% groups and spleen in the females in the high dose group.

HISTOPATHOLOGY: NON-NEOPLASTIC
The incidence of myocardial eosinophilic cytoplasm showed a significant dose-dependent decrease in the male mice in the treatment groups. A comparison between the sexes revealed a significant decrease in the incidence of hepatocytic anisonucleosis, myocardial eosinophilic cytoplasm and acinar cell vacuolation of sumandibular gland in females; and lymphocyte infiltration in the renal cortex and pelvis, and vacuolation of cerebrellar white matter in the males

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
The incidence of the male tumour bearing mice was 40.9%, and 54.5, 36.5, 42.9 and 17.5% in the control group and 1.0, 2.5, 5.0 and 10.0% dose groups, respectively, while that of female tumour.bearing mice was 29.8, 23.6, 17.3, 11.5 and 13.5% respectively.

HISTORICAL DATA
The incidence of all tumours and non-tumorous changes was withinh the normal range reported for spontaneous changes in B6C3F1 mice.

Dose descriptor:

NOAEL

Effect level:

100 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects notified

Critical effects observed:

not specified

Conclusions:

In conclusion, the results of the present study indicate that long-term administration of a diet containing 10% (w/w) aluminium potassium sulfate does not exert tumorgenicity or any other toxic actions in male and female B6C3F1 mice. Thus, the NOAEL can be considered to be 100000 ppm (10 % w/w).

Executive summary:

In a chronic (20 months) combined repeated oral dose toxicity and carcinogenicity study (similar to EU method B.33) aluminium potassium sulfate dodecahydrate was administered orally via the diet to 60 male and female B6C3F1 mice at concentrations of 0, 10000, 25000, 50000 and 100000 ppm. The animals were treated with the test item 7 days per week for a period of 20 months. The treatment does not exert tumourgenicity or any other toxic action (mortality, food consumption, body weights, organ weights and histopathology) in any dose group investigated. Based on the results the chronic NOAEL for both sexes can be considered to be 100000 ppm which equals 15000 mg/kg bw/day.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

15 000 mg/kg bw/day

Study duration:

chronic

Species:

mouse

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-11-15 to 1994-12-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc. Kingston, NY.
- Age at study initiation: 8 weeks
- Diet (e.g. ad libitum): Purina Certified Rodent Chow #5002, ad libitum (except during exposure)
- Water (e.g. ad libitum): municipal tap water, ad libitum (except during exposure)
- Acclimation period: one week (subsequently acclimated eight times over approximately two weeks to periods of nose-only exposure device restraint)

ENVIRONMENTAL CONDITIONS
- Animals were placed in rooms designed to maintain adequate environmental conditions concerning temperature, relative humidity and photocycle for the specific species under test.

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

not specified

Remarks on MMAD:

MMAD / GSD: MMAD: 1.5 um
GSD: 1.6
84% of the AlN aerosol mass in particles less than 2.4 µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Animals were exposed to test material in ADG or ADG type nose-only chambers with ADG restrainer systems (ADG instruments, Inc., Codicote, England) under dynamic air flow conditions.
- System of generating particulates/aerosols: Aerosols of aluminum nitride were generated with a particulate aerosol generator. A stainless steel cup held approx. 50 grams of AIN, and a screw driven bladed cap was driven into the cup. Air ports in the bladed cap swept the test material into the airstream of the aerosol distribution system.
- Temperature, humidity, pressure in air chamber: 22 °C, humidity 40-60%, neutral pressure
- Air flow rate: 30 liters/minute, determined with a manometer
- Method of particle size determination: particle size distribution in each chamber was determined (at least) weekly with a six-stage cascade impactor (Model 266, Sierra Instruments, Carmel, CA).
- Treatment of exhaust air: A distributor exhaust line was used which vents AlN aerosol to a high efficiency filter. The air flow in this exhaust line was not determined and, therefore, the usage cannot be precisely related to chamber "nominal" concentration.

TEST ATMOSPHERE
- Brief description of analytical method used: The mass concentration of test material in the chamber was monitored with weighed filter samples, at least four samples per chamber per day (TE 36 filters, 0.45 µm pore size, Schleicher and Schuell, Keene, NH). A constant volume pump (Model 110, Sierra Instruments, Carmel, CA) was used to collect air samples for filters and cascade impactors at 3 liters/min

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- The mass concentration of test material in the chamber was monitoted with weighed filter samples, at least four samples per chamber per day
- Constant volume pump was used to collect air samples for filters and cascade impactors at 3 liters/min
- A TSI APS 33 laser velocimeter was used to help monitor the AIN concentration in the distribution system

Duration of treatment / exposure:

19 exposures during a 4-week study period

Frequency of treatment:

6 hours/day, 5 days/week

Remarks:

Doses / Concentrations:
0, 2, 12, and 60 mg/m3
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
0, 2, 10, and 70 mg/m3
Basis:
analytical conc.

No. of animals per sex per dose:

10/sex/dose

Control animals:

yes

Details on study design:

- Necropsies were conducted on five rats/sex/dose on the day after the last exposure. The remaining 5 rats/sex/dose were the satellite group and were housed for additional 10 weeks without additional exposure. Afterwards, necropsies were performed and tissues saved.

Positive control:

N.A.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations: overt signs of toxicity and changes in demeanor

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: prior to the start of the study and weekly thereafter
- Observations: evaluation of the skin and fur, eyes, mucous membranes, respiration nervous system and behaviour pattern. Observations for lethargy, tremors, convulsions, salivation, lacrimation, diarrhea and other signs/of altered central nervous system function

BODY WEIGHT: Yes
- Time schedule for examinations: on test days 1, 3, 5 ,8, 11 and weekly thereafter

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to the initial exposure.
- Dose groups that were examined: all animals

HAEMATOLOGY: Yes
- Time schedule for collection of blood: prioir to necropsy (at week 4 and 10)
- Anaesthetic used for blood collection: Yes, methoxyfurane
- Animals fasted: No data
- How many animals: all animals
- Parameters checked: hematocrit (HCT, equivalent to packed ceⅡ volume), hemoglobin (HGB), erythrocyte count (RBC), total leukocyte (WBC), platelet count (PLAT), the differential Ieukocyte count, and a morphologic examination. Slides of blood smears were prepared and saved for all animals

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the terminal sacrifice after 4 weeks.
- Animals fasted: No data
- How many animals: all animals
- Parameters checked: urea nitrogen (UN), alanine aminotransferase activity (ALT), aspartate aminotransferase activity (AST), alkaline pbosphatase activity (AP), glucose (GLUC), total protein (TP), albumin (ALB), globulin (GLOB, calculated), total bilirubin (TBILI), phosphorus (PHOS), calcium (CALC), sodium (Na), potassium (K) and chloride (CL)

URINALYSIS: Yes
- Time schedule for collection of urine: during the fourth week of exposure.
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters checked: color, character, bilirubin, glucose, ketones, blood, pH, protein, urobilinogen, specific gravity. Microscopic examination was performed on sediments of pooled samples by exposure group.

NEUROBEHAVIOURAL EXAMINATION: performed during clinical examinations

Sacrifice and pathology:

- Animals in the main group were necropsied the day following the last exposure. All animals fasted overnight prior to necropsy
- All animals were weighed, anesthetized with methoxyflurane, and humanely euthanized
- Organ weights were taken from brain, lungs, Iiver, kidneys, adrenals and testes, plus an in situ examination of the eyes by a glass-side technique with fluorescent illumination.
- All animals were examined for gross pathological alterations.
- Histophathological examination of tissues and all identified gross lesions of rats in the 0 and 70 mg/m³ group
- Microscopic examination of respiratory tract tissue from rats exposed to 2 and 12 (nominal) mg/m³ was conducted because exposure-related effects were noted in animals from the highest exposure group.
- Satellite group animals were necropsied 10 weeks after the last exposure according to the pathology procedure described above. Microscopic examination of the respiratory tract from control and 70 mg/m³ exposed rats was conducted.

Other examinations:

N.A.

Statistics:

- Descriptive statistics only (means and standard deviations) are reported for chamber concentration, temperature, relative humidity, airflow, WBC differential counts, and RBC indices
- All parameters examined statistically were first tested for equality of variance using Bartlett's test (if the results from Bartletts test were significant, then the data for the parameter were subjected to a transformation to obtain equality of the variances. When Bartlett's test was satisfied no further transformations were to be applied, or, if none of the transformations resulted in homogeneous variances, the transformed data or raw data with the lowest Bartlett's statistic was used. The selected form ofthe data was then subjected to the appropriate parametric analysis as described below.
- In-life body weights were evaluated using a three-way repeated measures analysis of variance (RM-ANOVA) for time, sex, and dose
- Terminal body weight, organ weight (absolute and relative, excluding ovaries and testes), hematologic parameters (excluding differential WBC and RBC indices), clinical chemistry parameters, and urine specific gravity were evaluated using a two-way ANOVA with the factors of sex and dose. For these parameters the first exmination was whether the sex-dose interaction was significant. If so, an one-way ANOVA was done separately for each sex.
- Comparisons of individual dose groups to the control group were made with Dunett's test only when a statisticaⅡy significant dose effect existed
- Results for ovaries and testes weight (absolute and relative) were analyzed using a one-way ANOVA.If significant dose effects were determined in the one way ANOVA, then separate doses were to be compared to controls using Dunnett's test.

Clinical signs:

no effects observed

Description (incidence and severity):

See details below

Mortality:

no mortality observed

Description (incidence):

See details below

Body weight and weight changes:

no effects observed

Description (incidence and severity):

See details below

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 specified

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

See details below

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

See details below

Urinalysis findings:

no effects observed

Description (incidence and severity):

See details below

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

See details below

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

See details below

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

See details below

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
There were no clinically observed exposure related effects. There were sporadic observations of fur soiling (no single animal was repeatedly soiled). This was considered to be a normal, occasional consequence of restraint in rats acclimated for the nose-only exposure.

BODY WEIGHT AND WEIGHT GAIN
There was a statistically significant difference in the 10 and 70 mg/m³ exposure groups, but no statistically significant difference when the satellite group animals only were compared. The statistical analysis apparently reflects the lower mean body weight of the control males during the 4-week exposure period, and the lower mean body weight of both the control and 2 mg/m³ exposed males after the exposure period. These statistical differences are not likely to be exposure-related and were not considered to be biologically significant in any case.

HAEMATOLOGY
The main effect on hematology was an increase in neutrophil to lymphocyte ratio, reflecting a pulmonary inflammatory response, which was observedalso histologically. The neutrophil:leukocyte ratios increased in an exposure-related manner, except for females in the 2 mg/m³ group after the 10-week post exposure period, there was a numeric decrease relative to controls. Since females held for a 10-week post exposure period tended to have the greatest histopathological response, the numeric changes in the ratio at 2 mg/m³ were not considered biologically significant. A statistical increase in white blood cells (WBC) of rats exposed to 70 mg/m³ group was thought to reflect neutrophilia, that was more accurately depicted by the differential count. There were no apparent effects on leukocyte, erythrocyte, or platelet morphology, although there was increased variability in erythrocyte morphology in all groups of male rats.

CLINICAL CHEMISTRY
There were minor differences in total protein and globulin values that were statistically identified in 0 vs 70 mg/m³ female groups only. These were not a primary significant AlN effect, and may not have been exposure-related at all. The 10 mg/m³ exposed group had significant histopathologic effects, but no changes in these clinical laboratory parameters. There were no other statistical effects on other clinical chemistry values.

URINALYSIS
No effects were seen on any urinalysis parameter examined.

ORGAN WEIGHTS
Organ weight effects were restricted to alterations related to lung weight. Lung weights were increased at 4 weeks in the 70 mg/m³ (both sexes) and in the 10 mg/m³ exposed females. Relative lung weight means were increased in the 70 mg/m³ exposure groups.
Ten weeks after exposure, there was a significant increase in mean lung weights of all exposed rats. Lung weight relative to body weight increased in females (2 mg/m³ and greater) and males (10 mg/m³ and greater). There was a more pronounced effect on lung weights after 10 weeks and a slight effect in 2 mg/m³ exposed rats. Females may be more sensitive than males.

PATHOLOGY
Main Group:
After 4 weeks, effects were seen in the lungs, mediastinal lymph nodes (see Table 1 & 2) and nasal tissues. Brown granular particulate material was seen in lung and lymphoid tissues. In the lungs of rats exposed to 70 mg/m³, approximately 25% of the test material was free-either unphagocytized or freed from dead macrophages- and there was a slight subacute inflammatory response in 80% of the lung. This response was characterized as proliferative pneumonitis because of the proliferation of alveolar type II cells lining affected alveoli. Rats exposed to 2 and 10 mg/m³ showed little or no evidence of inflammation.
At necropsy, the mediastinal lymph nodes were enlarged and pale in 4/5 high exposed females. This change correlated histologically with reactive hyperplasia and the presence of test material within aggregates of macrophages in the nodes of 70 mg/m³ of rats of both sexes.
In nasal tissues there was a slight goblet cell hyperplasia noted in all high dose rats. This was considered to be non-specific and of little toxicologic significance.
High dose male rats exhibited slight chronic inflammation of the larynx, versus one slight chronic inflammation in male controls.Inflammation was associated with focal areas of mineralization. These foci of mineralization are very common spontaneous findings in Fischer-344 rats. Slight epithelial hyperplasia was observed in 4/5 high dose males and none at lower doses. Laryngeal lesions was only increased coincident with exposure levels in males.

Ten-Week Post-Exposure Group:
Test material was not appreciably cleared and inflammatory reaction in the lungs and mediastinal lymph nodes intensified (see Table 1 & 2). Grossly, the lungs of high dose rats of both sexes had an accentuated lobular pattern. Microscopically, the pattern was defined by normal alveoli clustered nearer the bronchiole, while the more peripheral portions of acinar unit tended to be filled with proteinaceous material, cellular debris, macrophages, and a small number of neutrophils, and test material. Alveolar septal thickening was marked due to prominent alveolar type II cell proliferation and interstitial congestion and thickening. Reactive hyperplasia of bronchial associated lymphoid tissue was quite marked, with numerous aggregates of macrophages containing test material scattered within the tissue. Perivascular lymphoid tissue was moderately increased.
After 10 weeks, most of the test material was extracellular. 90% of the high dose group lung parenchyma was severely affected.
The 2 and 10 mg/m³ groups had similar effects, but to much smaller degrees. There was one important qualitative difference from the high exposure group: the test material was almost all within alveolar macrophages rather than free in alveolar spaces, although at 10 mg/m³ some macrophages laden with the test material were disintegrating. Tissue response was less intense at lower exposures. Pathological changes in mediastinal lymph nodes extended to lower exposure groups. Gross enlargement of nodes was observed in all 70 mg/m³ exposed rats and most 10 mg/m³ exposed rats. Gross lesions correlated histologicaⅡy with reactive hyperplasia and the presence of test material in aggregates of macrophages in all 70 and 10 mg/m³ rats, and one 2 mg/m³ female rat.
Nasal tissue changes resolved substantially. Slight goblet cell hyperplasia was seen only in two high exposed females. Focal very slight acute inflammation was seen in one high dose male. Laryngeal lesions were similar to that observed in the main group, but without correlation to exposure level or to sex.

Dose descriptor:

NOAEC

Remarks:

(local)

Effect level:

2 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Based on mild adverse effects in the lungs, but alveolar macrophages had engulfed aⅡ the foreign material, which is an important step in the clearance process.

Dose descriptor:

LOAEC

Remarks:

(local)

Effect level:

10 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Dose descriptor:

NOAEC

Remarks:

(systemic)

Effect level:

70 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Lack of adverse effects (besides effects in the lung) at the highest concentration tested.

Critical effects observed:

yes

Lowest effective dose / conc.:

10 mg/m³ air

System:

respiratory system: lower respiratory tract

Organ:

lungs

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

presumably yes

Table 1: Significant Lung Histopathology
SEX					M	M	M	M	F	F	F	F
AlN Conc. (mg/m³)					0	2	10	70	0	2	10	70
Number examined					5	5	5	5	5	5	5	5
Lungs, 4-week main study
Pneumonitis - proliferative				slight	0	0	0	5	0	0	0	5
Macrophages with Foreign Material (MFM)				very slight	0	5	0	0	0	5	0	0
				slight	0	0	5	0	0	0	5	0
Macrophages with Foreign Material and Free Foreign Material (MFM/FFM)				Severe	0	0	0	5	0	0	0	5
Lungs, 10-Week Post-Exposure
Pneumonitis - proliferative				very slight	0	4	0	0	0	5	0	0
				slight	0	1	0	0	0	0	0	0
				moderate	0	0	5	0	0	0	5	0
				severe	0	0	0	5	0	0	0	5
MFM				very slight	0	5	0	0	0	5	0	0
MFM/FFM				slight	0	0	5	0	0	0	5	0
				severe	0	0	0	5	0	0	0	5

Table 2: Mediastinal Lymph Node (L.N.) Significant Findings
SEX					M	M	M	M	F	F	F	F
AlN Conc. (mg/m³)					0	2	10	70	0	2	10	70
Number examined					5	5	5	5	5	5	5	5
Mediastinal L.N., 4-week main study
Hyperplasia -reactive					0	0	0	5	0	0	0	4
Macrophages with Foreign Material (MFM)				very slight	0	0	1	0	0	0	0	0
				slight	0	0	0	0	0	0	0	1
				moderate	0	0	0	5	0	0	0	4
Mediastinal L.N., 10-Week Post-Exposure
Hyperplasia -reactive					0	0	5	5	0	1	5	5
MFM				slight	0	1	0	0	0	1	0	0
				moderate	0	0	5	0	0	0	5	0
				severe	0	0	0	5	0	0	0	5

Conclusions:

Aluminum nitride elicits local effects in the lung at concentrations saturating the lung clearance in rats. No adverse systemic effects have been reported at the highest attained concentration of 70 mg/m³.

Executive summary:

In a subacute inhalation toxicity study, aluminium nitride (AlN) was administered to 10 Fischer 344 rats/sex/concentration by nose only exposure at concentrations of 0, 2, 10, and 70 mg/m³ for 6 hours/day for 5 days/week for a total of 19 exposures during a 4 week study. The average Mass Median Aerodynamic Diameter (MMAD) was 1.5 μm; 84% of the aerosol mass consisted of particles less than 2.4 μm. Five rats/sex/exposure concentration were evaluated by pathology immediately after the 4 week exposure period, and five more rats/sex/exposure concentration were held for approximately 10 weeks after the last exposure, and were then evaluated by pathology. In addition to gross and histopathologic evaluations, there were clinical observations and determinations of body weights, clinical chemistry, hematology, urinalysis, and organ weights. Because the only exposure-related effect were related to the respiratory system in rats evaluated at 4 weeks, evaluations were focused on rats that were held for 10 week post-exposure.

After four weeks, there was a mild inflammatory response in the lungs of rats exposed to 70 mg/m³. In the 2 and 10 mg/m³ groups, there was little or no evidence of a tissue reaction in the lungs, other than phagocytosis. At the lower exposure concentrations, virtually all of the visible foreign material in the lung parenchyma was contained within alveolar macrophages. This foreign material was presumably AlN or an AlN degradation product. At 70 mg/m³, approximately 25% of the foreign material was "free” either phagocytized or freed from dead macrophages.

Following the 10 week post-exposure period, histologic examination of lungs from rats in the 2 mg/m³ group indicated that foreign material was present within the alveolar macrophages, and there were widely scattered small areas of mild inflammation characterized by slight alveolar type II cell proliferation and occasional neutrophils. At 10 mg/m³, the changes described above were increased, and there were reactive changes in the bronchial associated lymphoid tissue (BALT). At 70 mg/m³, much of the foreign material was trapped within proteinaceous material filling many of the alveolar spaces.

Alveolar type II cell proliferation and the BALT reaction were marked. Lung weights and blood neutrophil:leukocyte ratios were increased in most groups with pulmonary inflammation. Overall the reaction was characterized as a proliferative pneumonitis.

In rats exposed to 70 mg/m³ and evaluated immediately after 4 weeks of exposure, there were signs of upper respiratory tract irritation which included slight goblet cell hyperplasia of the nasal turbinates. Effects on the upper respiratory tract were largely resolved at 10 weeks post-exposure, and there were no upper respiratory tract effects in rats exposed to 2 or 10 mg/m³.

Proliferative pneumonitis was more severe after the 10 week post-exposure period. Excessive exposure to AIN exceeded physiologic lung clearance mechanisms, as suggested by the free foreign material in pulmonary alveoli of rats exposed to this concentrations of AIN aerosol. This may in part account for the more pronounced effects at 10 weeks post-exposure.

Overall, AlN predominantly affected the alveolar macrophages. The NOAEC for male and female rats was 2 mg/m³ based on mild adverse effects in the lungs and observed alveolar macrophages engulfing foreign material, which is an important step in the clearing process. The adverse effects at higher concentrations are considered to justify CLP classification for specific target organ toxicity (STOT RE2, lung, local).

This sub-acute toxicity study in the rat is acceptable and satisfies the guideline requirement accordign to OECD 412 for a sub-acute inhalation study in the rat.  

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

70 mg/m³

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-11-15 to 1994-12-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc. Kingston, NY.
- Age at study initiation: 8 weeks
- Diet (e.g. ad libitum): Purina Certified Rodent Chow #5002, ad libitum (except during exposure)
- Water (e.g. ad libitum): municipal tap water, ad libitum (except during exposure)
- Acclimation period: one week (subsequently acclimated eight times over approximately two weeks to periods of nose-only exposure device restraint)

ENVIRONMENTAL CONDITIONS
- Animals were placed in rooms designed to maintain adequate environmental conditions concerning temperature, relative humidity and photocycle for the specific species under test.

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

not specified

Remarks on MMAD:

MMAD / GSD: MMAD: 1.5 um
GSD: 1.6
84% of the AlN aerosol mass in particles less than 2.4 µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Animals were exposed to test material in ADG or ADG type nose-only chambers with ADG restrainer systems (ADG instruments, Inc., Codicote, England) under dynamic air flow conditions.
- System of generating particulates/aerosols: Aerosols of aluminum nitride were generated with a particulate aerosol generator. A stainless steel cup held approx. 50 grams of AIN, and a screw driven bladed cap was driven into the cup. Air ports in the bladed cap swept the test material into the airstream of the aerosol distribution system.
- Temperature, humidity, pressure in air chamber: 22 °C, humidity 40-60%, neutral pressure
- Air flow rate: 30 liters/minute, determined with a manometer
- Method of particle size determination: particle size distribution in each chamber was determined (at least) weekly with a six-stage cascade impactor (Model 266, Sierra Instruments, Carmel, CA).
- Treatment of exhaust air: A distributor exhaust line was used which vents AlN aerosol to a high efficiency filter. The air flow in this exhaust line was not determined and, therefore, the usage cannot be precisely related to chamber "nominal" concentration.

TEST ATMOSPHERE
- Brief description of analytical method used: The mass concentration of test material in the chamber was monitored with weighed filter samples, at least four samples per chamber per day (TE 36 filters, 0.45 µm pore size, Schleicher and Schuell, Keene, NH). A constant volume pump (Model 110, Sierra Instruments, Carmel, CA) was used to collect air samples for filters and cascade impactors at 3 liters/min

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- The mass concentration of test material in the chamber was monitoted with weighed filter samples, at least four samples per chamber per day
- Constant volume pump was used to collect air samples for filters and cascade impactors at 3 liters/min
- A TSI APS 33 laser velocimeter was used to help monitor the AIN concentration in the distribution system

Duration of treatment / exposure:

19 exposures during a 4-week study period

Frequency of treatment:

6 hours/day, 5 days/week

Remarks:

Doses / Concentrations:
0, 2, 12, and 60 mg/m3
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
0, 2, 10, and 70 mg/m3
Basis:
analytical conc.

No. of animals per sex per dose:

10/sex/dose

Control animals:

yes

Details on study design:

- Necropsies were conducted on five rats/sex/dose on the day after the last exposure. The remaining 5 rats/sex/dose were the satellite group and were housed for additional 10 weeks without additional exposure. Afterwards, necropsies were performed and tissues saved.

Positive control:

N.A.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations: overt signs of toxicity and changes in demeanor

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: prior to the start of the study and weekly thereafter
- Observations: evaluation of the skin and fur, eyes, mucous membranes, respiration nervous system and behaviour pattern. Observations for lethargy, tremors, convulsions, salivation, lacrimation, diarrhea and other signs/of altered central nervous system function

BODY WEIGHT: Yes
- Time schedule for examinations: on test days 1, 3, 5 ,8, 11 and weekly thereafter

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to the initial exposure.
- Dose groups that were examined: all animals

HAEMATOLOGY: Yes
- Time schedule for collection of blood: prioir to necropsy (at week 4 and 10)
- Anaesthetic used for blood collection: Yes, methoxyfurane
- Animals fasted: No data
- How many animals: all animals
- Parameters checked: hematocrit (HCT, equivalent to packed ceⅡ volume), hemoglobin (HGB), erythrocyte count (RBC), total leukocyte (WBC), platelet count (PLAT), the differential Ieukocyte count, and a morphologic examination. Slides of blood smears were prepared and saved for all animals

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the terminal sacrifice after 4 weeks.
- Animals fasted: No data
- How many animals: all animals
- Parameters checked: urea nitrogen (UN), alanine aminotransferase activity (ALT), aspartate aminotransferase activity (AST), alkaline pbosphatase activity (AP), glucose (GLUC), total protein (TP), albumin (ALB), globulin (GLOB, calculated), total bilirubin (TBILI), phosphorus (PHOS), calcium (CALC), sodium (Na), potassium (K) and chloride (CL)

URINALYSIS: Yes
- Time schedule for collection of urine: during the fourth week of exposure.
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters checked: color, character, bilirubin, glucose, ketones, blood, pH, protein, urobilinogen, specific gravity. Microscopic examination was performed on sediments of pooled samples by exposure group.

NEUROBEHAVIOURAL EXAMINATION: performed during clinical examinations

Sacrifice and pathology:

- Animals in the main group were necropsied the day following the last exposure. All animals fasted overnight prior to necropsy
- All animals were weighed, anesthetized with methoxyflurane, and humanely euthanized
- Organ weights were taken from brain, lungs, Iiver, kidneys, adrenals and testes, plus an in situ examination of the eyes by a glass-side technique with fluorescent illumination.
- All animals were examined for gross pathological alterations.
- Histophathological examination of tissues and all identified gross lesions of rats in the 0 and 70 mg/m³ group
- Microscopic examination of respiratory tract tissue from rats exposed to 2 and 12 (nominal) mg/m³ was conducted because exposure-related effects were noted in animals from the highest exposure group.
- Satellite group animals were necropsied 10 weeks after the last exposure according to the pathology procedure described above. Microscopic examination of the respiratory tract from control and 70 mg/m³ exposed rats was conducted.

Other examinations:

N.A.

Statistics:

- Descriptive statistics only (means and standard deviations) are reported for chamber concentration, temperature, relative humidity, airflow, WBC differential counts, and RBC indices
- All parameters examined statistically were first tested for equality of variance using Bartlett's test (if the results from Bartletts test were significant, then the data for the parameter were subjected to a transformation to obtain equality of the variances. When Bartlett's test was satisfied no further transformations were to be applied, or, if none of the transformations resulted in homogeneous variances, the transformed data or raw data with the lowest Bartlett's statistic was used. The selected form ofthe data was then subjected to the appropriate parametric analysis as described below.
- In-life body weights were evaluated using a three-way repeated measures analysis of variance (RM-ANOVA) for time, sex, and dose
- Terminal body weight, organ weight (absolute and relative, excluding ovaries and testes), hematologic parameters (excluding differential WBC and RBC indices), clinical chemistry parameters, and urine specific gravity were evaluated using a two-way ANOVA with the factors of sex and dose. For these parameters the first exmination was whether the sex-dose interaction was significant. If so, an one-way ANOVA was done separately for each sex.
- Comparisons of individual dose groups to the control group were made with Dunett's test only when a statisticaⅡy significant dose effect existed
- Results for ovaries and testes weight (absolute and relative) were analyzed using a one-way ANOVA.If significant dose effects were determined in the one way ANOVA, then separate doses were to be compared to controls using Dunnett's test.

Clinical signs:

no effects observed

Description (incidence and severity):

See details below

Mortality:

no mortality observed

Description (incidence):

See details below

Body weight and weight changes:

no effects observed

Description (incidence and severity):

See details below

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 specified

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

See details below

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

See details below

Urinalysis findings:

no effects observed

Description (incidence and severity):

See details below

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

See details below

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

See details below

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

See details below

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
There were no clinically observed exposure related effects. There were sporadic observations of fur soiling (no single animal was repeatedly soiled). This was considered to be a normal, occasional consequence of restraint in rats acclimated for the nose-only exposure.

BODY WEIGHT AND WEIGHT GAIN
There was a statistically significant difference in the 10 and 70 mg/m³ exposure groups, but no statistically significant difference when the satellite group animals only were compared. The statistical analysis apparently reflects the lower mean body weight of the control males during the 4-week exposure period, and the lower mean body weight of both the control and 2 mg/m³ exposed males after the exposure period. These statistical differences are not likely to be exposure-related and were not considered to be biologically significant in any case.

HAEMATOLOGY
The main effect on hematology was an increase in neutrophil to lymphocyte ratio, reflecting a pulmonary inflammatory response, which was observedalso histologically. The neutrophil:leukocyte ratios increased in an exposure-related manner, except for females in the 2 mg/m³ group after the 10-week post exposure period, there was a numeric decrease relative to controls. Since females held for a 10-week post exposure period tended to have the greatest histopathological response, the numeric changes in the ratio at 2 mg/m³ were not considered biologically significant. A statistical increase in white blood cells (WBC) of rats exposed to 70 mg/m³ group was thought to reflect neutrophilia, that was more accurately depicted by the differential count. There were no apparent effects on leukocyte, erythrocyte, or platelet morphology, although there was increased variability in erythrocyte morphology in all groups of male rats.

CLINICAL CHEMISTRY
There were minor differences in total protein and globulin values that were statistically identified in 0 vs 70 mg/m³ female groups only. These were not a primary significant AlN effect, and may not have been exposure-related at all. The 10 mg/m³ exposed group had significant histopathologic effects, but no changes in these clinical laboratory parameters. There were no other statistical effects on other clinical chemistry values.

URINALYSIS
No effects were seen on any urinalysis parameter examined.

ORGAN WEIGHTS
Organ weight effects were restricted to alterations related to lung weight. Lung weights were increased at 4 weeks in the 70 mg/m³ (both sexes) and in the 10 mg/m³ exposed females. Relative lung weight means were increased in the 70 mg/m³ exposure groups.
Ten weeks after exposure, there was a significant increase in mean lung weights of all exposed rats. Lung weight relative to body weight increased in females (2 mg/m³ and greater) and males (10 mg/m³ and greater). There was a more pronounced effect on lung weights after 10 weeks and a slight effect in 2 mg/m³ exposed rats. Females may be more sensitive than males.

PATHOLOGY
Main Group:
After 4 weeks, effects were seen in the lungs, mediastinal lymph nodes (see Table 1 & 2) and nasal tissues. Brown granular particulate material was seen in lung and lymphoid tissues. In the lungs of rats exposed to 70 mg/m³, approximately 25% of the test material was free-either unphagocytized or freed from dead macrophages- and there was a slight subacute inflammatory response in 80% of the lung. This response was characterized as proliferative pneumonitis because of the proliferation of alveolar type II cells lining affected alveoli. Rats exposed to 2 and 10 mg/m³ showed little or no evidence of inflammation.
At necropsy, the mediastinal lymph nodes were enlarged and pale in 4/5 high exposed females. This change correlated histologically with reactive hyperplasia and the presence of test material within aggregates of macrophages in the nodes of 70 mg/m³ of rats of both sexes.
In nasal tissues there was a slight goblet cell hyperplasia noted in all high dose rats. This was considered to be non-specific and of little toxicologic significance.
High dose male rats exhibited slight chronic inflammation of the larynx, versus one slight chronic inflammation in male controls.Inflammation was associated with focal areas of mineralization. These foci of mineralization are very common spontaneous findings in Fischer-344 rats. Slight epithelial hyperplasia was observed in 4/5 high dose males and none at lower doses. Laryngeal lesions was only increased coincident with exposure levels in males.

Ten-Week Post-Exposure Group:
Test material was not appreciably cleared and inflammatory reaction in the lungs and mediastinal lymph nodes intensified (see Table 1 & 2). Grossly, the lungs of high dose rats of both sexes had an accentuated lobular pattern. Microscopically, the pattern was defined by normal alveoli clustered nearer the bronchiole, while the more peripheral portions of acinar unit tended to be filled with proteinaceous material, cellular debris, macrophages, and a small number of neutrophils, and test material. Alveolar septal thickening was marked due to prominent alveolar type II cell proliferation and interstitial congestion and thickening. Reactive hyperplasia of bronchial associated lymphoid tissue was quite marked, with numerous aggregates of macrophages containing test material scattered within the tissue. Perivascular lymphoid tissue was moderately increased.
After 10 weeks, most of the test material was extracellular. 90% of the high dose group lung parenchyma was severely affected.
The 2 and 10 mg/m³ groups had similar effects, but to much smaller degrees. There was one important qualitative difference from the high exposure group: the test material was almost all within alveolar macrophages rather than free in alveolar spaces, although at 10 mg/m³ some macrophages laden with the test material were disintegrating. Tissue response was less intense at lower exposures. Pathological changes in mediastinal lymph nodes extended to lower exposure groups. Gross enlargement of nodes was observed in all 70 mg/m³ exposed rats and most 10 mg/m³ exposed rats. Gross lesions correlated histologicaⅡy with reactive hyperplasia and the presence of test material in aggregates of macrophages in all 70 and 10 mg/m³ rats, and one 2 mg/m³ female rat.
Nasal tissue changes resolved substantially. Slight goblet cell hyperplasia was seen only in two high exposed females. Focal very slight acute inflammation was seen in one high dose male. Laryngeal lesions were similar to that observed in the main group, but without correlation to exposure level or to sex.

Dose descriptor:

NOAEC

Remarks:

(local)

Effect level:

2 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Based on mild adverse effects in the lungs, but alveolar macrophages had engulfed aⅡ the foreign material, which is an important step in the clearance process.

Dose descriptor:

LOAEC

Remarks:

(local)

Effect level:

10 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Dose descriptor:

NOAEC

Remarks:

(systemic)

Effect level:

70 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Lack of adverse effects (besides effects in the lung) at the highest concentration tested.

Critical effects observed:

yes

Lowest effective dose / conc.:

10 mg/m³ air

System:

respiratory system: lower respiratory tract

Organ:

lungs

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

presumably yes

Table 1: Significant Lung Histopathology
SEX					M	M	M	M	F	F	F	F
AlN Conc. (mg/m³)					0	2	10	70	0	2	10	70
Number examined					5	5	5	5	5	5	5	5
Lungs, 4-week main study
Pneumonitis - proliferative				slight	0	0	0	5	0	0	0	5
Macrophages with Foreign Material (MFM)				very slight	0	5	0	0	0	5	0	0
				slight	0	0	5	0	0	0	5	0
Macrophages with Foreign Material and Free Foreign Material (MFM/FFM)				Severe	0	0	0	5	0	0	0	5
Lungs, 10-Week Post-Exposure
Pneumonitis - proliferative				very slight	0	4	0	0	0	5	0	0
				slight	0	1	0	0	0	0	0	0
				moderate	0	0	5	0	0	0	5	0
				severe	0	0	0	5	0	0	0	5
MFM				very slight	0	5	0	0	0	5	0	0
MFM/FFM				slight	0	0	5	0	0	0	5	0
				severe	0	0	0	5	0	0	0	5

Table 2: Mediastinal Lymph Node (L.N.) Significant Findings
SEX					M	M	M	M	F	F	F	F
AlN Conc. (mg/m³)					0	2	10	70	0	2	10	70
Number examined					5	5	5	5	5	5	5	5
Mediastinal L.N., 4-week main study
Hyperplasia -reactive					0	0	0	5	0	0	0	4
Macrophages with Foreign Material (MFM)				very slight	0	0	1	0	0	0	0	0
				slight	0	0	0	0	0	0	0	1
				moderate	0	0	0	5	0	0	0	4
Mediastinal L.N., 10-Week Post-Exposure
Hyperplasia -reactive					0	0	5	5	0	1	5	5
MFM				slight	0	1	0	0	0	1	0	0
				moderate	0	0	5	0	0	0	5	0
				severe	0	0	0	5	0	0	0	5

Conclusions:

Aluminum nitride elicits local effects in the lung at concentrations saturating the lung clearance in rats. No adverse systemic effects have been reported at the highest attained concentration of 70 mg/m³.

Executive summary:

In a subacute inhalation toxicity study, aluminium nitride (AlN) was administered to 10 Fischer 344 rats/sex/concentration by nose only exposure at concentrations of 0, 2, 10, and 70 mg/m³ for 6 hours/day for 5 days/week for a total of 19 exposures during a 4 week study. The average Mass Median Aerodynamic Diameter (MMAD) was 1.5 μm; 84% of the aerosol mass consisted of particles less than 2.4 μm. Five rats/sex/exposure concentration were evaluated by pathology immediately after the 4 week exposure period, and five more rats/sex/exposure concentration were held for approximately 10 weeks after the last exposure, and were then evaluated by pathology. In addition to gross and histopathologic evaluations, there were clinical observations and determinations of body weights, clinical chemistry, hematology, urinalysis, and organ weights. Because the only exposure-related effect were related to the respiratory system in rats evaluated at 4 weeks, evaluations were focused on rats that were held for 10 week post-exposure.

After four weeks, there was a mild inflammatory response in the lungs of rats exposed to 70 mg/m³. In the 2 and 10 mg/m³ groups, there was little or no evidence of a tissue reaction in the lungs, other than phagocytosis. At the lower exposure concentrations, virtually all of the visible foreign material in the lung parenchyma was contained within alveolar macrophages. This foreign material was presumably AlN or an AlN degradation product. At 70 mg/m³, approximately 25% of the foreign material was "free” either phagocytized or freed from dead macrophages.

Following the 10 week post-exposure period, histologic examination of lungs from rats in the 2 mg/m³ group indicated that foreign material was present within the alveolar macrophages, and there were widely scattered small areas of mild inflammation characterized by slight alveolar type II cell proliferation and occasional neutrophils. At 10 mg/m³, the changes described above were increased, and there were reactive changes in the bronchial associated lymphoid tissue (BALT). At 70 mg/m³, much of the foreign material was trapped within proteinaceous material filling many of the alveolar spaces.

Alveolar type II cell proliferation and the BALT reaction were marked. Lung weights and blood neutrophil:leukocyte ratios were increased in most groups with pulmonary inflammation. Overall the reaction was characterized as a proliferative pneumonitis.

In rats exposed to 70 mg/m³ and evaluated immediately after 4 weeks of exposure, there were signs of upper respiratory tract irritation which included slight goblet cell hyperplasia of the nasal turbinates. Effects on the upper respiratory tract were largely resolved at 10 weeks post-exposure, and there were no upper respiratory tract effects in rats exposed to 2 or 10 mg/m³.

Proliferative pneumonitis was more severe after the 10 week post-exposure period. Excessive exposure to AIN exceeded physiologic lung clearance mechanisms, as suggested by the free foreign material in pulmonary alveoli of rats exposed to this concentrations of AIN aerosol. This may in part account for the more pronounced effects at 10 weeks post-exposure.

Overall, AlN predominantly affected the alveolar macrophages. The NOAEC for male and female rats was 2 mg/m³ based on mild adverse effects in the lungs and observed alveolar macrophages engulfing foreign material, which is an important step in the clearing process. The adverse effects at higher concentrations are considered to justify CLP classification for specific target organ toxicity (STOT RE2, lung, local).

This sub-acute toxicity study in the rat is acceptable and satisfies the guideline requirement accordign to OECD 412 for a sub-acute inhalation study in the rat.  

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

2 mg/m³

Study duration:

subacute

Species:

rat

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

In a 28-day repeated dose inhalation toxicity study (according to OECD 412) adverse local effects were seen after inhalation of the target substance with 10 mg/m³ and 70 mg/m³. At a concentration of 2 mg/m³ alveolar macrophages were noticed, which had engulfed all the foreign material. This concentration was considered the NOAEC (see section toxicological information).

No repeated dose oral toxicity data is available for aluminium nitride. However, suitable data is available from the read across partner aluminium potassium sulfate. Due to lower water solubility of aluminium nitride compared to the source substance the resulting bioavailability would also be expected to be lower. Therefore, the read-across to the source substance aluminium potassium sulfate is adequately protective. Details on the read-across rational are provided in section 13.

A subchronic repeated dose oral toxicity study in rats (similar to EU method B.26) and a chronic oral toxicity study in mice (similar to EU method B.33) were conducted using aluminium potassium sulfate. As no effects were seen for clinical signs of toxicity, mortality, histopathologic lesions, haematology or organ weights in the subchronic study, the NOAEL can be considered to be 30000 ppm. The results of the chronic toxicity study indicate that long-term administration (20 months) of a diet containing 0, 1.0, 2.5, 5.0 and 10.0% aluminium potassium sulfate (AlK(SO4)2*12H2O) does not exert tumorigenicity or any other toxic action (mortality, food consumption, body weights, organ weights and histopathology) in sixty B6C3F1 mice of each sex/dose. Therefore, the chronic NOAEL for both sexes can be considered to be 100.000 ppm in the diet which equals 15000 mg/kg bw/day (by applying a default conversion factor of 0.15 as recommended in an EFSA guidance document).

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Well documented chronic toxicity study with aluminium potassium sulfate (AlK(SO4)2*12H2O) used as read-across partner

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
GLP study conducted with the target substance in accordance with OECD 412

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
GLP study conducted with the target substance in accordance with OECD 412

Justification for classification or non-classification

Adverse (local) effects in the lung start at 10 mg/m³ and are more pronounced at 70 mg/m³ in a 28-day repeated dose inhalation toxicity study with aluminium nitride. Effects at 10 mg/m³ are not considered to be significant toxic after 4-week exposure and 10 weeks recovery. Effects at 70 mg/m³ are mild after 4-week exposure but more pronounced after the 10-week recovery period. In line with the guidance value proposed in CLP table 3.9.2, significant toxic effects at 20 – 200 mg/m³/6h/day (for a 90d study) and 60 – 600 mg/m³/6h/day (for a 28d study), respectively, warrant classification in category 2 (H373) for specific target organ toxicity after repeated exposure (STOT RE2).