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Short-term toxicity to fish

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Description of key information

Based on the justification of the three main components of the test substance: 
Literary studies investigating the effects of aluminum in the aquatic environment have extensively used test solutions with aluminum concentrations above that of its solubility limit. Results of these studies are therefore limited for the investigation of intrinsic toxicity. The available 96-h LC50s from acute toxicity studies varied from 0.078 to > 218.6 mg Al/L, and 16-d LC50s ranged from 0.43 to 3.91 mg Al/L. The NOECs (96 h) varied from > 0.07 to > 50 mg Al/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: 

Many “acute” toxicity studies (i.e. <12 days) for aluminium compounds have been conducted with fish in acidic soft waters due to concern about aluminium leaching in environments sensitive to acid rain. Many of these experiments were conducted in flow-through systems to mimic the effects of mixing zones where some type of substance (i.e. lime) is added to increase the system pH. In the cases where effects due to transient forms of aluminium were investigated (i.e. Teien et al. 2004, 2006), fish were maintained in certain sections of a raceway, with a specified time of equilibration, or time after mixing. Most of the existing literature for fish focused on effects to Salmo salar since it is among the most sensitive fish species. Roy and Campbell (1997) showed that DOM had a protective effect against aluminium toxicity to S. salar. Gundersen et al. 1994 suggested just a minor effect of HA on aluminium toxicity with Oncorhynchus mykiss. It is possible that in some of the flow-through studies, aluminium toxicity is due to transient forms of aluminium, because transient forms may be present for the first several minutes after mixing in the flow-through diluter mixing chambers. While there are many studies that have investigated the toxicity of aluminium to fish, relatively few evaluated aluminium toxicity over a range of pH values. Roy and Campbell (1995) demonstrated that aluminium toxicity, on the basis of monomeric aluminium, decreased (less toxic) as pH decreased from 5.3 to 4.4. At weakly alkaline pH (i.e. pH 7.58 to 8.14), Gundersen et al. (1994) demonstrated very little effect of pH or hardness on aluminium toxicity to O. mykiss over higher pH ranges. Studies conducted at Norwegian Institute for Water Research (NIVA) (Figure 7.1.1.1.1-1, see attachment) show the effect of pH and other characteristics on survival at 190 hours; the results also demonstrate the effect of mixing time on mortality. From the literature, there were minimal studies that investigated the effect of water hardness on aluminium toxicity to fish. 

 

Thirteen acute toxicity studies for aluminium compounds to fish are provided. All the studies are for informational purposes with a total of seven fish species, and are presented for demonstrating the completeness of the literature review. The available 96-h LC50s varied from 0.078 to > 218.6 mg Al/L, and 16-d LC50s ranged from 0.43 to 3.91 mg Al/L. The NOECs (96 h) varied from > 0.07 to > 50 mg Al/L.

Calcium-compounds:

Two short-term studies for calcium dihydroxide with fish are provided. One of these both studies, the short-term toxicity study with the freshwater fish rainbow trout (Egeler et al., 2007), was executed according to OECD 203, resulting in a Klimisch 1 score. The biological findings (LC50 = 50.6 mg/L) were closely related to the initial pH of the test solutions. Therefore the initial high pH is considered to be the main reason for the effects of the test item on the fish. The other short-term toxicity study for calcium dihydroxide with the marine species Gasterosteus aculeatus Linnaeus (threespine stickleback) (Locke et al., 2009) was well described and a dose-response relationship was established (LC50 = 457 mg/L). However, the study was not carried out according to GLP, resulting in a Klimisch 2 score.

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.