Aluminium nitride

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

1.98 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

1.98 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.2 µg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Conclusion on classification

Aluminium nitride (AlN) undergoes hydrolysis in contact with water, with a reaction half-life of 22 h. Hydrolysis results in formation of ammonia (NH₃) and aluminium hydroxide, which is very poorly soluble. However, incomplete precipitation of the aluminium released during hydrolysis leads to generation of dissolved aluminium ions, as demonstrated in a transformation/dissolution (T/D) test (OECD Series on Testing and Assessment No 29). A loading rate of 100 mg AlN/L results in a dissolved Al^{3 +} concentration of ca. 1 mg/L (exact value: 1087 µg/L) after 7 days. Concurrently, 2 mg NH₃/L were measured. Accordingly, both ionic aluminium and ammonia need to be considered for classifying aluminium nitride.

Classification for acute aquatic hazards

Soluble aluminium salts used for read-across of environmental effects (AlCl₃, Al₂(SO₄)₃, Al(NO₃)₃) are not classified for acute aquatic hazards. Therefore, classification of AlN acute aquatic hazards based on its aluminium content is not necessary.

Ammonia (CAS No 7664-41-7) has a harmonised classification for environmental hazards according to Annex VI of Regulation (EU) No 1272/2008 as “Aquatic Acute 1 (H400)” due to EC₅₀ values in acute aquatic toxicity tests of < 1 mg/L. From AlN, NH₃ is released relatively slowly, reaching a maximum concentration of 2 mg/L total NH₃ after 7 days in the T/D-test at the maximum loading rate of 100 mg/L. Information that would allow linking the classification of ammonia to concentration levels relevant for classification of AlN is not available. Therefore, and due to the relatively low release rate, classification of AlN for acute aquatic hazards based on the formation of NH₃ is not possible.

Test results on short-term effects to aquatic organisms by aluminium nitride itself are not available. Read-across from other aluminium salts and from ammonia, as detailed above, suggests that AlN need not be classified for acute aquatic hazards.

Classification for chronic aquatic hazards

The most conservative chronic no-observed effect concentration (NOEC) of aluminium ions (Al_³⁺) is 13 µg/L (0.013 mg/L). Back-calculated to aluminium nitride (M (Al) = 40.989 g/mol, M (N) = 26.982 g/mol), this results in a substance-based NOEC of 0.020 mg/L. Aluminium release from AlN may lead to dissolved Al^{_{3 +}} concentrations of up to 1 mg/L, which is above the NOEC. Aluminium, as an element, cannot be further degraded hence needs to be considered as not rapidly degradable. Therefore, the criterion of Regulation (EU) Mo 1272/2008 for classifying as “Aquatic Chronic 1, H410” is fulfilled (not rapidly degradable, chronic NOEC ≤ 0.1 mg/L)

For ammonia, there is no harmonised classification for chronic aquatic hazards. However, joint entries into the CLP inventory claim a classification as “Aquatic Chronic 2, H411”. This is based on presumed rapid degradability (NH₃, as a central element of the bio-geochemical nitrogen cycle, is constantly incorporated into biomass) and a lowest aquatic NOEC of 0.022 mg/L. Back-calculated to aluminium nitride (M (Al) = 40.989 g/mol, M (N) = 26.982 g/mol), this results in a substance-based NOEC of 0.05 mg/L. Ammonia release from AlN may lead to dissolved total NH₃concentrations of up to 2 mg/L, which is above the NOEC. Therefore, the criterion of Regulation (EU) Mo 1272/2008 for classifying as “Aquatic Chronic 2, H411” is fulfilled (rapidly degradable, chronic NOEC > 0.01 to ≤ 0.1 mg/L)

Overall, the available data on the hydrolysis products of AlN suggest that aluminium nitride should be classified as “Aquatic Chronic 1, H410” (very toxic to aquatic life with long lasting effects).