Boehmite (Al(OH)O)

Endpoint summary

Description of key information

Based on read-across:
Oral LD50 (rat) > 2000 mg/kg bw
Inhalation LC50 (rat) >  2.3 mg/L

Additional information

There are no studies available on the acute toxicity of Boehmite by the oral, dermal or inhalation route. In terms of hazard assessment of toxic effects, available data on the acute toxicity of other aluminium compounds were taken into account by read-across following a structural analogue approach, since the pathways leading to toxic outcomes are likely to be dominated by the chemistry and biochemistry of the aluminium ion (Al³⁺) (Krewski et al., 2007; ATSDR, 2008).

Oral route: No mortality was established and confirmed among rats after oral administration of aluminium hydroxide at the limit dose 2000 mg/kg bw. According to the results (Aluminium hydroxide, acute oral toxicity study in rats, LABRes, 2009, OECD Test Guideline 423, Klimisch Score 2), the oral LD₅₀(rat) for aluminium hydroxide is above 2000 mg/kg bw.

Based on the available data, it is proposed that aluminium hydroxide and therefore Boehmite need not be classified for acute oral toxicity. 

 

Dermal route:There are no studies available for Boehmite (CAS No. 1318-23-6). Justification based on aluminium compounds were taken into account. Aluminium hydroxide, aluminium oxide, aluminium oxyhydroxide are insoluble in water. Due to their insolubility it can be assumed that the above mentioned aluminium compounds will not be absorbed via skin. Moreover Flarend et al., 2001 showed a negligible bioavailability of aluminium after dermal application. This allows the prediction that the dermal LD50 of Boehmite will be much greater than 2000 mg/kg bw.This predictability makes acute dermal toxicity testing unnecessary.

Inhalation route: Read-across from aluminium oxide

Animal Studies

The study by Cabot (1996) was conducted according to EPA Guidelines for Test Procedures Subdivision F, Series 81-3 and TSCA 40 CFR 798.1150. Five healthy male and five healthy female Wistar Albino rats were exposed to fumed alumina in an inhalation chamber for 4 hours. The number of animals used and the exposure duration were adequate according to the guidelines. The air concentration in the chamber, determined gravimetrically, was 2.3 mg/L.  Only one concentration was tested. The average mass median diameter was 2.58 µm with a geometric standard deviation of 3.10 µm (2.31 µm, GSD 2.97 in the first 30 second sampling period and 2.85 µm, GSD 3.22 in a second sampling period). Chamber airflow, temperature (20.7 – 23.3 ºC) and humidity (60 to 61%) were monitored throughout the exposure period. Animals were observed for signs of toxicity at approximately one hour intervals during exposure, at one hour post exposure and then daily during a 14 day exposure period. Body weights were recorded pre-test, weekly and at termination.  No deaths were observed during exposure or during the 14 day post-exposure period. All animals had closed eyes, wet nose/mouth areas and fur coated with the test materials during the exposure. Observations were normal during the 14-day post-exposure period. Weight gain was normal in all the male animals. Weight loss was observed in two females on day 7 of the post-exposure period and in another two females on day 14. Lungs that were darker than normal with red areas were observed in only one female on necropsy. Based on the results of this study, the LC₅₀ is greater than 2.3 mg/L.

 

Justification for classification or non-classification

Based on read-across from aluminium hydroxide and aluminium oxide as structural analogues, the available data on the acute toxicity of Boehmite are conclusive but not sufficient for classification according to DSD (67/548/EEC) and CLP (1272/2008/EC).