Ceramic materials and wares, chemicals

Endpoint summary

Additional information

There are no studies available for “Reaction product of thermal process between 1000°C and 2000°C of mainly aluminium oxide and calcium oxide based raw materials with at least CaO+Al2O3+MgO >80% , in which aluminium oxide, magnesium oxide and calcium oxide in varying amounts are combined in various proportions into a multiphase crystalline matrix”. As this substance is an UVCB substance with aluminium oxide (AL2O3), calcium oxide (CaO) and magnesium oxide (MgO) as main constituents, data and justification based on these main components were taken into account by read across following a structural analogue approach.

 

Aluminium-compounds:

To place a proper perspective on the assessment of aluminium in soils we quote the Executive Summary of the USEPA EcoSSL (see attachment, Ecological Soil Screening Level) assessment for aluminium. 

"Aluminum (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 aluminum in soils is from 1 percent to 30 percent (10,000 to 300,000 mg Al kg-1) (Lindsay, 1979 and Dragun, 1988), with naturally occurring concentrations varying over several orders of magnitude.

EPA recognizes that due to the ubiquitous nature of aluminum, the natural variability of aluminum soil concentrations and the availability of conservative soil screening benchmarks (Efroymson, 1997a; 1997b), aluminum 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 aluminum solution that is added to test soils.

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

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

• Aluminum toxicity is associated with soluble aluminum.

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

• The oral toxicity of aluminum compounds in soil is dependent upon the chemical form (Storer and Nelson, 1968). Insoluble aluminum compounds such as aluminum oxides are considerably less toxic compared to the soluble forms (aluminum 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 aluminum oxide compared to 80 to 100% mortality in chicks fed soluble forms at 0.5% of the diet.

 

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

 

Calcium compounds:

Studies for terrestrial toxicity of calcium compounds are available for the following endpoints:

- Toxicity to soil macroorganisms – 2 studies

- Toxicity to terrestrial plants – 1 study

- Toxicity to soil microorganisms – 2 studies

The short-term toxicity of calcium dihydroxide on mortality and biomass of the earthworm Eisenia fetida (Friedrich, 2007b) was carried out according to OECD test guideline 207. The study is well documented, all validity criteria are fulfilled. As such a Klimisch 1 score was assigned to the study. After 14 days, no significant effect on both mortality and biomass was observed up to the highest tested dose (5000 mg Ca(OH)2 /kg dw)

The chronic study on the effect of calcium dihydroxide on the reproduction of the earthworm Eisenia fetida (Friedrich, 2007a), was carried out according to OECD test guideline 222. The study is well documented, all validity criteria are fulfilled. As such a Klimisch 1 score was assigned to the study. The study resulted in a 4w-EC50 of 4180 mg Ca(OH)2 /kg soil dw and a 4w-NOEC of 2000 mg Ca(OH)2 /kg soil dw.

One long-term study for toxicity to terrestrial plants is available for the read across substance calcium dihydroxide. This substance is structurally and compositionally related to calcium oxide, one main substance of the test material. The study (Friedrich 2007) was conducted according to OECD 208 with different plant species and resulted in LC 50 (21d) > 10 g/kg soil dw test mat. And NOEC (21d) of 1.08 – 2.27 g/kg soil dw test mat.

The chronic study on the effect of calcium dihydroxide on the nitrogen transformation in an agricultural loamy sand soil (Schulz, 2007a) was carried out according to OECD 216. The study is well documented, all validity criteria are fulfilled. As such a Klimisch 1 score was assigned to the study. Reported 96d-EC50 and 96d-NOEC values for nitrogen transformation equalled >12 g Ca(OH)2 /kg soil dw and ≥12 g Ca(OH)2 /kg soil dw, respectively.

The chronic study on the effect of calcium dihydroxide on the dehydrogenase activity in an agricultural loamy sand soil (Schulz, 2007b) was conducted according to German guidelines for testing of plant protection products (BBA VI, 1-1, 1990). The methods and results are well documented. As such a Klimisch 1 score was assigned to the study. Reported 96d-EC50 and 96d-NOEC values for dehydrogenase activity equalled 8.7 g Ca(OH)2 /kg soil dw and 4 g Ca(OH)2 /kg soil dw, respectively.

In the environment, lime substances rapidly dissociate or react with water. These reactions, together with the equivalent amount of hydroxyl ions set free when considering 100mg of the lime compound (hypothetic example), are illustrated below:

Ca(OH)2 <-> Ca2+ + 2OH-

100 mg Ca(OH)2 or 1.35 mmol sets free 2.70 mmol

CaO + H2O <-> Ca2+ + 2OH-

100 mg CaO or 1.78 mmol sets free 3.56 mmol

From these reactions it is clear that the effect of calcium oxide will be caused either by calcium or hydroxyl ions. Since calcium is abundantly present in the environment and since the effect concentrations are within the same order of magnitude of its natural concentration, it can be assumed that the adverse effects are mainly caused by the pH increase caused by the hydroxyl ions. Furthermore, the above mentioned calculations show that the base equivalents are within a factor 2 for calcium oxide and calcium hydroxide. As such, it can be reasonably expected that the effect on pH of calcium oxide is comparable to calcium hydroxide for a same application on a weight basis. Consequently, read-across from calcium hydroxide to calcium oxide is justified.

Magnesium oxide:

Magnesium oxide (MgO) is exempted from registration according to EC 1907/2006 Annex V Section 10.

 

References:

 

Efroymson, R.A., M.E. Will, and G.W. Suter II, 1997a,Toxicological Benchmarks for Potential Contaminants of Concern for Effects on Soil and Litter Invertebrates and Heterotrophic Process,ES/ER/TM-126/R2, Oak Ridge National Laboratory, Oak Ridge, TN.

 

Efroymson, R.A., M.E. Will, G.W. Suter II, and A.C. Wooten, 1997b,Toxicological Benchmarks for Screening Contaminants of Potential Concern for Effects on Terrestrial Plants: 1997 Revision, ES/ER/TM-85/R3,National Laboratory,,

 

Dragun, 1988.The Soil Chemistry of Hazardous Materials.Hazardous Materials Control Research Institute.,.

 

Lindsay, W.L. 1979.Chemical Equilibria in Soils.John Wiley & Sons,.

 

Press, F. and R. Siever. 1974.Earth. W. H. Freeman and Co.,.

 

Storer N.L.,Nelson T.S. 1968 The effect of various aluminum compounds on chick performance.Poult Sci.Jan; 47(1):244-7.