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Toxicity to microorganisms

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Description of key information

Based on the justification of the three main components of the test substance: 
No effects were seen in one activated sludge respiration inhibition test for aluminium chloride up to the highest test concentration (1000 mg/L).
In the environment, lime substances rapidly dissociate or react with water. 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.
Magnesium oxide (MgO) is exempted from registration according to EC 1907/2006 Annex V Section 10.

Key value for chemical safety assessment

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:

Aluminium is amongst the most common elements in the earth’s crust and can be found in great abundance in both the terrestrial and sediment environments. The relative contributions of anthropogenic aluminium to the existing natural pools of aluminium in soils and sediments is therefore not relevant either in terms of added amounts or in terms of toxicity. Based on these exposure considerations additional sediment and/or 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, see attachment).

One activated sludge respiration inhibition test is reported with a soluble aluminium salt. This test was performed with aluminum chloride (CAS RN 7446-70-0) according to standard guideline. No effects were seen up to the highest test concentration of 1000 mg/l test material. The test substance contained 20 g Al/100 g and the test concentrations can be converted to mg/l Al. 1000 mg/l test material is equal to 200 mg/l Al.

 

Table D: Toxicity to aquatic micro-organisms

species

endpoint

set up

result (mg/l)

 

Aluminum chloride

Activated sludge, domestic

EC10-180min

static

> 200 

 Al

 

Calcium-compounds:

One study for toxicity to microorganisms is available for calcium dihydroxide. This substance is structurally and compositionally related to aluminium oxide, one main substance of the test material. The study (Egeler & Goth, 2007) was conducted according to OECD 209 with activated sludge and resulted in EC50 (3h) of 300.4 mg/L (nominal) based on respiration rate.

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.

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