Aluminium nitride

Endpoint summary

Description of key information

Aluminium nitride (99%) was tested negative for acute dermal irritating and corrosive properties in studies conducted according to OECD 431 and OECD 439. The substance caused no irritating effects in an acute eye irritation/corrosion study in rabbits conducted according to OECD 405. 

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2014-04-22 to 2014-07-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

other: human epidermis model: EpiSkin

Details on test animals or test system and environmental conditions:

Test system:
The test was carried out with the reconstituted three-dimensional human skin model EPISKIN-SM™ (SkinEthic). This skin model consists of normal (non-cancerous), adult human-derived epidermal keratinocytes (NHEK) which have been cultured to form a multilayered, highly differentiated model of the human epidermis. The NHEK are cultured on chemically modified, collagen-coated cell culture inserts. A highly differentiated and stratified epidermis model is obtained after 13-day culture period comprising the main basal, supra basal, spinous and granular layers and a functional stratum corneum.

Vehicle:

water

Controls:

not required

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 mg (26.3 mg/cm²) + 5 µL Aqua dest.

PREPARATION OF THE TEST ITEM:
Firstly, 5 μL distilled water (aqua dest.) were applied by a pipette to the epidermal surface in order to improve further contact between the powder and the epidermis. The water was gently spread with the pipette. Afterwards, approximately 10 mg (26.3 mg/cm²) of the powder were applied to the epidermis surface.

CONTROLS:
Controls were set up in parallel to the test item cultures in order to confirm the validity of the test.
Negative control: Phosphate Buffered Saline (PBS; Gibco, Cat. No. 14040-091, Lot No. 1528370).
Positive control: 5% sodium dodecyl sulfate (SDS; AppliChem, Art.-No. A7249,0250, CAS No.: 151-21-3, Lot No. 1X002858) in Aqua dest.

Duration of treatment / exposure:

15 ± 0.5 min.

Details on study design:

EXPERIMENTAL PROCEDURE
Upon receipt of the EPISKIN-SMTM, the tissues were transferred into 12-well plates containing 2 mL prewarmed maintenance medium per well. The 12-well plates were incubated in a humidified incubator at 37 ± 1 °C, 5.0% CO2 for at least 24 h.
After this pre-incubation the tissues were treated in triplicate, starting with the negative control. Start time was recorded with dosing of the first tissue. Then the tissues were incubated at room temperature for 15 ± 0.5 min. Afterwards, the tissues were washed with PBS to remove any residual test item. Excess PBS was removed by blotting bottom with blotting paper. The inserts were placed in a prepared 12-well plate containing 2 mL prewarmed fresh maintenance medium and post-incubated at 37 ± 1 °C, 5.0% CO2 for 42 ± 1 h.
After this incubation period the plates were placed for 15 ± 2 min. on a plate shaker. Then the inserts were transferred in a prepared 12-well plate containing 2 mL prewarmed MTT medium and further incubated for 3 h ± 5 min. at 37 ± 1 °C, 5.0% CO2.
After the 3 h MTT incubation period the tissues were placed on blotting paper to dry the tissues. Afterwards a total biopsy of the epidermis by using the special biopsy punch was performed and the epidermis was separated from the collagen matrix with the aid of forceps. Both parts (epidermis and collagen matrix) were transferred into suitable tubes and 500 μL of acidic isopropanol were added. Extraction was carried out protected from light over the weekend at 2 - 8°C.
At the end of the formazan extraction period the tubes were mixed by vortexing until solution colour became homogeneous.
If any visible cell/tissue fragments were in suspension, the tubes were centrifuged at 500 rpm to eliminate the fragments and avoid further possible interference with the absorbance readings.
Per each tissue 2 x 200 μL aliquots of the extract were transferred into a 96-well plate and OD was measured at 550 nm without reference wavelength in a plate spectrophotometer.

SCORING SYSTEM:
Irritant potential of the test item was predicted from the relative mean tissue viabilities compared to the negative control tissues concurrently treated with PBS. The test item is considered to be irritant to skin in accordance with regulation EC 1272/2008 and UN GHS Category 2 (17), if the tissue viability after 15 min of exposure and 42 h of post-incubation is less or equal to 50%. The test substance may be considered as non-irritant to skin in accordance with UN GHS No Category if the tissue viability after exposure and post-treatment incubation is higher than 50%.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

mean of three tissues

Value:

104.3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

mean of three tissues

Value:

25.6

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Pre-experiment:

The mixture of 10 mg test item per 2 mL MTT medium showed no reduction of MTT compared to the solvent. The mixture did not turn blue/purple.

The mixture of 10 mg of the test item per 90 μl aqua dest. showed no colouring detectable by unaided eye-assessment.

Results of the main experiment:

Table 1: Experimental Results

Name	Negative Control			Positive Control			Test Item
Tissue	1	2	3	1	2	3	1	2	3
Absolute OD550	0.780	0.761	0.727	0.260	0.158	0.288	0.751	0.946	0.774
	0.805	0.801	0.780	0.249	0.154	0.277	0.735	0.878	0.759
OD550(blanc corrected)	0.737	0.717	0.684	0.217	0.115	0.245	0.707	0.903	0.731
	0.762	0.758	0.736	0.206	0.111	0.233	0.692	0.835	0.716
Mean OD550of the duplicates (blanc corrected)	0.749	0.738	0.710	0.211	0.113	0.239	0.700	0.869	0.724
Total mean OD550of 3 replicate tissues (blanc corrected)	0.732*			0.188			0.764
SD OD550	0.029			0.060			0.085
relative tissue viability [%]	102.3	100.7	97.0	28.8	15.4	32.7	96.6	118.6	98.8
Mean relative tissue viability [%]	100.0			25.6**			104.3
SD tissue viability [%]***	2.7			9.1			12.5

*             corrected mean OD₅₅₀of the negative control corresponds to 100% absolute tissue viability.

**          mean relative tissue viability of the 3 positive control is ≤ 40%

***        The standard deviation (SD) obtained from the three tested tissues is ≤ 18%

 

Table 2: Quality Criteria

	value	Cut off	pass / fail
mean OD550 nmblank	0.043	< 0.1	pass
mean absolute OD550 nmNC	0.775	0.6 ≤ NC ≤ 1.5	pass
mean % viability PC	25.6	≤ 40%	pass
SD of viability	2.7 – 12.5%	≤ 18%	pass

 

Interpretation of results:

GHS criteria not met

Conclusions:

In this study under the given conditions the test item showed no irritant effects in an validated in vitro system (EPISKIN). The test item is classified as ‘non-irritant’ in accordance with UN GHS ‘No Category’.

Executive summary:

The potential for the test item to induce skin irritation was tested by using the three dimensional human skin model EpiSkin-SM^TM (SkinEthic) comprising a reconstructed human epidermis with functional stratum corneum. Ten (10) mg Aluminium nitride grade C was applied directly atop the EpiSkin-SM^TM tissue for 15 min. followed by 42 h post incubation period and immediate determination of cytotoxic effects via MTT reduction assay.

Irritant potential from the test item was predicted from the relative mean tissue viabilities obtained compared to the corresponding negative control tissues concurrently treated with PBS.

The test item showed no irritant effects. The mean relative tissue viability (% negative control) was ≥ 50% (104.3%) after 15 min treatment and 42 h post incubation.

The controls confirmed the validity of the study. The mean OD550 of the six blank values was < 0.1. The mean absolute OD550 of the three negative control tissues was ≥ 0.6 and ≤ 1.5. The mean relative tissue variability (% negative control) of the positive control was ≤ 40% (25.6%).

In this study under the given conditions the test item showed no irritant effects. The test item is classified as ‘non-irritant’ in accordance with UN GHS ‘No Category’.

Reference 2

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2014-01-10 to 2014-02-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Human Skin Model Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

other: in vitro: Human model skin (EPISKIN-SMTM tissue)

Details on test animals or test system and environmental conditions:

in vitro: Human model skin (EPISKIN-SMTM tissue)

Vehicle:

water

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 25 mg

VEHICLE
- Amount(s) applied (volume or weight with unit): 25 µL water

CONTROLS:
Negative control: distilled water
Positive control: 8 N Potassium Hydroxide

DOSE GROUPS:
Negative Control: 50 µL distilled water
Positive Control: 50 µL 8 N KOH
Test Item: 25 mg + 25 µL H20

Duration of treatment / exposure:

3 min and 60 min.

Details on study design:

TEST SITE
- Area of exposure: in vitro: Human model skin (EPISKIN)

REMOVAL OF TEST SUBSTANCE
- Washing (if done): about 20 times with PBS
- Time after start of exposure: 3min and 60 min

SCORING SYSTEM:
Corrosivity potential of the test item was predicted from the relative mean tissue viabilities obtained after 3min and 60min treatment compared to the negative control tissues concurrently treated with A. dest (=100%). A test item is classified corrosive in any case, if the relative tissue viability after 3min treatment is decreased below 50%. In addition, those test items with viability greater than 50% after 3min are classified as UN GHS subcategory 1B/C if the relative mean tissue viability after 60min treatment compared to the concurrent negative control tissues is decreased below 15%.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 minutes / mean of two replicates

Value:

94

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 minutes / mean of two replicates

Value:

97

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Pre-experiment:

The mixture of 25 mg test item per 1 mL MTT medium showed no reduction of MTT as compared to the solvent. The mixture did not turn blue/purple.

The mixture of 25 mg test item per 300 µL A. dest showed no clouring as compared to the solvent.

Results of the main experiment:

Table 1: 3 min

Name	Negative Control		Test Item		Positive Control
Tissue	1	2	1	2	1	2
Absolute OD550values	2.028	1.924	1.962	1.768	0.484	0.453
	2.001	1.914	1.906	1.737	0.471	0.446
	1.986	1.895	1.942	1.749	0.471	0.449
mean OD550(mean of 3 aliquots)	2.005	1.911	1.937	1.751	0.475	0.449
SD	0.021	0.014	0.028	0.016	0.007	0.003
Total mean OD550(mean of 2 replicate tissues)	1.958*		1.844		0.462
Mean relative tissue viability [%]	100		94		24**
Mean inter tissue viability difference [%]***	4.8		10.1		5.7

*             mean OD₅₅₀≥ 0.8

**          mean relative tissue viability of the 3 min. positive control ≤ 30%

***        inter tissue viability difference ≤ 30%

 

Table 2: 60 min

Name	Negative Control		Test Item		Positive Control
Tissue	1	2	1	2	1	2
Absolute OD550values	1.785	2.024	1.875	1.823	0.254	0.242
	1.751	2.013	1.855	1.799	0.252	0.243
	1.771	2.015	1.855	1.798	0.244	0.237
mean OD550(mean of 3 aliquots)	1.769	2.017	1.862	1.807	0.250	0.240
SD	0.017	0.006	0.012	0.014	0.005	0.003
Total mean OD550(mean of 2 replicate tissues)	1.893*		1.834		0.245
Mean relative tissue viability [%]	100		97		13
Mean inter tissue viability difference [%]***	13.1		3.0		4.1

*             mean OD₅₅₀≥ 0.8

***        inter tissue viability difference ≤ 30%

Table 3: Test Acceptance Criteria

	value	Cut off	Pass / fail
mean absolute OD550 nmNC (3 min. experiment)	1.958	≥ 0.8	Pass
mean absolute OD550 nmNC (3 min. experiment)	1.893	≥ 0.8	Pass
mean % viability PC (3 min. experiment)	24	≤ 30%	Pass
Max. inter tissue viability difference	3.0 – 13.1	≤ 30%	Pass

 

Interpretation of results:

GHS criteria not met

Conclusions:

The test item Aluminium nitride showed no corrosive effects in a validated in vitro test system (EPISKIN). The test item is classified as ‘non-corrosive’.

Executive summary:

The potential of Aluminium nitride to induce skin corrosion was tested by using the three-dimensional human skin model EpiDerm^TX, comprising reconstructed epidermis with a functional stratum corneum (OECD guideline 431). Aluminium nitride was applied topically to the EpiDerm^TX tissue for 3 min and 60 min periods followed by immediate determination of cytotoxic effects via MTT reduction assay. Distilled water served as negative control, corresponding to 100% tissue viability. The positive control did induce the appropriate response. The controls confirmed the validity of the study.

In this study under the given conditions the test item showed no corrosive effects. The relative mean tissue viability after 3 min treatment was ≥ 50% and after 60 min treatment ≥ 15%. Aluminium nitride is therefore classified as non-corrosive.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2014-05-23 to 2014-08-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2400 (Acute Eye Irritation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

rabbit

Strain:

New Zealand White

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: Charles River Deutschland, 97633 Sulzfeld, Germany
- Age at study initiation: 18 - 19 weeks old
- Weight at study initiation: > 2 kg
- Housing: ABS-plastic or Noryl rabbit cages, floor 4200 cm2, in an air-conditioned room
- Diet (e.g. ad libitum): ad libitum- Free access to autoclaved hay and to Altromin 2123 maintenance diet for rabbits (lot no. 0724), rich in crude fibre
- Water (e.g. ad libitum): ad libitum - Free access to tap water (drinking water, municipal residue control, microbiological controls at regular intervals)
- Acclimation period: at least 5 days under laboratory conditions

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 ± 3 °C
- Humidity (%): 55 ± 10%
- Air changes (per hr): at least 10 x / hour
- Photoperiod (hrs dark / hrs light): Artificial light, sequence being 12 hours light, 12 hours dark

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.1 g of the test item was applied to the test site

Duration of treatment / exposure:

single treatment

Observation period (in vivo):

72 hours, 24, 48 and 72-hours readings

Number of animals or in vitro replicates:

3 rabbits

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing (if done): At the end of the observation period the treated eyes were examined with the aid of a fluorescein solution and rinsed with physiological saline 0.9% NaCl after the examination.
- Time after start of exposure: 1 hour

SCORING SYSTEM: Grading System for Ocular Lesion

TOOL USED TO ASSESS SCORE: fluorescein

Irritation parameter:

conjunctivae score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0.67

Max. score:

3

Reversibility:

fully reversible within: 72 h

Remarks on result:

no indication of irritation

Irritation parameter:

cornea opacity score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

chemosis score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

iris score

Basis:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

2

Remarks on result:

no indication of irritation

Irritation parameter:

conjunctivae score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0.33

Max. score:

3

Reversibility:

fully reversible within: 48 h

Remarks on result:

no indication of irritation

Irritation parameter:

cornea opacity score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

chemosis score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

iris score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

2

Remarks on result:

no indication of irritation

Irritation parameter:

conjunctivae score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0.33

Max. score:

3

Reversibility:

fully reversible within: 48 h

Remarks on result:

no indication of irritation

Irritation parameter:

cornea opacity score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

chemosis score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

iris score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

2

Remarks on result:

no indication of irritation

Irritant / corrosive response data:

After the application into the eyes of three female NZW rabbits the test item produced slightly irritant but not corrosive effects in all animals (see Table 1 - Table 3). Neither mortalities nor significant clinical signs of toxicity were observed (see Table 4). Upon fluorescein examinations at the end of the observation period of 72 hours no corneal lesions were found in any animal. Conjunctival redness and discharge were observed in all animals and conjuntival chemosis was observed in 2 out 3 animals. Signs of eye irritation are individually described in Table 1 - Table 3.

Table 1: Eye Irritation Scores - Animal No. 1

Observation	Time Post-Application Animal 1
	1(1h)		2(24h)		3(48h)		4(72h)
	T	C	T	C	T	C	T	C	Average Score (24, 48 and 72 hours)
Redness	1	0	1	0	1	0	0	0	0.67
Chemosis	0	0	0	0	0	0	0	0	0.00
Iris	0	0	0	0	0	0	0	0	0.00
cornea	0	0	0	0	0	0	0	0	0.00

t= test item; c= control

  Table 2: Eye Irritation Scores - Animal No. 2

Observation	Time Post-Application Animal 2
	1(1h)		2(24h)		3(48h)		4(72h)
	T	C	T	C	T	C	T	C	Average Score (24, 48 and 72 hours)
Redness	1	0	1	0	0	0	0	0	0.33
Chemosis	1	0	0	0	0	0	0	0	0.00
Iris	0	0	0	0	0	0	0	0	0.00
cornea	0	0	0	0	0	0	0	0	0.00

  Table 3: Eye Irritation Scores - Animal No. 3

Observation	Time Post-Application Animal 3
	1(1h)		2(24h)		3(48h)		4(72h)
	T	C	T	C	T	C	T	C	Average Score (24, 48 and 72 hours)
Redness	1	0	1	0	0	0	0	0	0.33
Chemosis	1	0	0	0	0	0	0	0	0.00
Iris	0	0	0	0	0	0	0	0	0.00
cornea	0	0	0	0	0	0	0	0	0.00

Table 4: Clinical Signs

Animal No. 1	Time Post-Application	Systemic Findings	Local Findings(apart from effects in Table 1.)
	1 hour	nsf	discharge grade 1
	24 hours	nsf	Nsf
	48 hours	nsf	Nsf
	72 hours	nsf	Nsf
Animal No. 2	Time Post-Application	Systemic Findings	Local Findings(apart from effects in Table 2.)
	1 hour	nsf	discharge grade 1
	24 hours	nsf	Nsf
	48 hours	nsf	Nsf
	72 hours	nsf	Nsf
Animal No. 3	Time Post-Application	Systemic Findings	Local Findings(apart from effects in Table 3.)
	1 hour	nsf	discharge grade 1
	24 hours	nsf	nsf
	48 hours	nsf	nsf
	72 hours	nsf	nsf

 nsf: no specific findings

Table 5: Absolute Body Weights (kg)

BODY WEIGHT (kg)
Animal No.	1	2	3
Start of Study	3.9	3.8	3.4
End of Study	4.0	3.9	3.5

 

Interpretation of results:

not irritating

Conclusions:

In an in vivo acute eye irritation/corrosion study in Rabbits, Aluminium nitride Grade C was tested negative regarding irritation to the eye.

Executive summary:

In a primary eye irritation study 0.1 g of Aluminium nitride Grade C (99 % purity) was applied into the conjunctival sac of one eye of 3 female New Zealand White Rabbits, Crl: KBL (NZW). The undiluted test substance remained in the eye for 1 hour and was rinsed afterwards with physiological saline (0.9% NaCl). Control and treated Animals were observed for a period of 72 hours.

Under the conditions of the present study, a single ocular application of the test item to rabbits at a dose of 0.1 g produced slightly irritant effects in all animals, which were fully reversible within 72 hours in animal no. 1 and within 48 hours in animal no. 2 and no. 3. Neither mortalities nor significant clinical signs of toxicity were observed.

On the basis of the test results and in conformity with the criteria given in Annex I of Regulation (EC) 1272/2008, the substance should be not classified.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Aluminium nitride (99%) was tested negative for acute dermal irritating and corrosive properties according to OECD 439 and OECD 431. In a screening study for identifying ocular corrosives and severe irritants (OECD 437) no prediction could be made regarding the classification of aluminium nitride and further testing was required. Thus, an acute eye irritation study in vivo (OECD 405) was conducted in rabbits. Only slightly irritating effects (grade 1) were observed. These effects were fully reversible within 48 to 72 hours. Based on these results, aluminium nitride is considered to be not irritating to the skin and/or eye.

Justification for classification or non-classification

Aluminium nitride (99% purity) was tested negative for acute dermal irritating/corrosive and eye irritating properties in studies conducted according to OECD 431, OECD 439 and OECD 405. Therefore, no classification of the test item is warranted.