Aluminium oxide

Toxicity to terrestrial plants

Link to relevant study record(s)

Reference

Endpoint:

toxicity to terrestrial plants: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Description of key information

Aluminium, aluminium powders and aluminium oxide are non hazardous (not classified for the environment). Aluminum (Al) is the most commonly occurring metallic element, comprising eight percent of the earth's crust (Press and Siever, 1974) and is therefore found in great abundance in both the terrestrial and sediment environments. Concentrations of 3-8% (30,000-80,000 ppm) are not uncommon.  The relative contributions of anthropogenic aluminium to the existing natural pools of aluminium in soils and sediments is very small and therefore not relevant either in terms of added amounts or in terms of toxicity. Based on these exposure considerations soil testing is not warranted. More information about exposure based waiving for aluminium in soil and sediments can be found in attached document (White paper on exposure based waiving for Fe and Al in soils and sediments final 15-03-2010. pdf).

Additional information

To place a proper perspective on the assessment of aluminium in soil, the Executive Summary of the USEPA EcoSSL (Ecological Soil Screening Level) assessment for aluminium is presented here.

 

"Aluminium (Al) is the most commonly occurring metallic element, comprising eight percent of the earth's crust (Press and Siever, 1974). It is a major component of almost all common inorganic soil particles, with the exceptions of quartz sand, chert fragments, and ferromanganiferous concretions. The typical range of aluminium in soils is from 1 percent to 30 percent (10,000 to 300,000 mg Al/kg) (Lindsay, 1979 and Dragun, 1988), with naturally occurring concentrations varying over several orders of magnitude.

 

EPA recognizes that due to the ubiquitous nature of aluminium, the natural variability of aluminium soil concentrations and the availability of conservative soil screening benchmarks (Efroymson, 1997a; 1997b), aluminium is often identified as a COPC for ecological risk assessments. The commonly used soil screening benchmarks (Efroymson, 1997a; 1997b) are based on laboratory toxicity testing using an aluminium solution that is added to test soils.

Comparisons of total aluminium concentrations in soil samples to soluble aluminum-based screening values are deemed by EPA to be inappropriate. The standard analytical measurement of aluminium in soils under CERCLA contract laboratory procedures (CLP) is total recoverable metal. The available data on the environmental chemistry and toxicity of aluminium in soil to plants, soil invertebrates, mammals and birds as summarized in this document support the following conclusions:

Total aluminium in soil is not correlated with toxicity to the tested plants and soil invertebrates.

Aluminium toxicity is associated with soluble aluminum.

Soluble aluminum and not total aluminum is associated with the uptake and bioaccumulation of aluminium from soils into plants.

The oral toxicity of aluminum compounds in soil is dependent upon the chemical form (Storer and Nelson, 1968). Insoluble aluminium compounds such as aluminium oxides are considerably less toxic compared to the soluble forms (aluminium chloride, nitrate, acetate, and sulfate). For example, Storer and Nelson (1968) observed no toxicity to the chick at up to 1.6% of the diet as aluminium oxide compared to 80 to 100% mortality in chicks fed soluble forms at 0.5% of the diet.

 

Because the measurement of total aluminium in soils is not considered suitable or reliable for the prediction of potential toxicity and bioaccumulation, an alternative procedure is recommended for screening aluminium in soils. The procedure is intended as a practical approach for determining if aluminium in site soils could pose a potential risk to ecological receptors. This alternative procedure replaces the derivation of numeric Eco-SSL values for aluminium. "