Ceramic materials and wares, chemicals

Toxicity to soil macroorganisms except arthropods

Description of key information

Based on the justification of both main components, it can be concluded:
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.
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.

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 >80% , in which aluminium 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) and calcium oxide (CaO) as main constituents, data and justification based on both main components were taken into account.   

Aluminium-compounds:

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 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 short-term and one long-term study with Eisenia andrei are reported using soluble aluminium salts (Van Gestel and Hogerwerf, 2001). The studies are presented for completeness, but are not considered relevant for assessing the aluminium compounds being assessed in the dossier. In the short-term study, three aluminum salts were tested with an exposure period of 14 days. Three pH (KCl) levels were assessed, namely 3.3, 4.4 and 6.7. Aluminum chloride was most toxic and showed higher toxicity with lower pH levels. At pH (KCl) 4.4 the LC50 was 316 mg/kg dw (Al). Al2O3 did not affect survival at concentrations of 5000 mg/kg dw Al at pH levels of 2.4 and 7.1.

The long-term study was performed with Sulfuric acid, aluminium salt (3:2), octadecahydrate (CAS RN 7784-31-8). The effect on reproduction was assessed in artificial soil. In the main test, earthworms were exposed for 6 weeks to soils treated with Al2(SO4)3. As in the range-finding test, aluminium sulfate was most toxic at a pH of 3.4 with an LC50 of 589 mg/kg dw (Al). At this pH, growth and cocoon production of earthworms were significantly reduced at 320 mg/kg dw (Al), while at 1000 mg/kg dw (Al) all earthworms died. Survival was not affected by 1000 mg/kg dw (Al) at pH 4.3 and 7.3. At pH 4.3, growth was significantly reduced at 1000 mg/kg dw (Al) and cocoon production at 320 and 1000 mg/kg dw (Al). At pH 7.3, aluminium only affected cocoon production at the two highest exposure levels. At the highest two exposure levels at pH 7.3, growth was significantly increased, suggesting a trade-off between growth and reproduction.

Table E: Toxicity to soil macroorganisms

species	endpoint	set up	pH(KCl)	result (mg/kg dw)
Aluminum chloride
Eisenia andrei	LC50-14d	Artificial soil	3.3 4.4 6.7	316 359 >1000	Al
Sulfuric acid, aluminium salt (3:2), octadecahydrate (CAS 7784-31-8)
Eisenia andrei	LC50-14d	Artificial soil	3.3 4.4 6.7	457 >4000 >4000	Al
Eisenia andrei	NOEC-42d	Artificial soil	3.4	100	Al

Calcium-compounds:

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.

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.

References:

Van Gestel, Hogerwerf G (2001) Influence of soil pH on the toxicity of aluminium for Eisenia andrei in an artificial soil substrate. Pedobiologia 45: 385-395.