Hexacalcium hexaoxotris[sulphato(2-)]dialuminate(12-)

Toxicity to soil macroorganisms except arthropods

Description of key information

Ettringite is not expected to have a detrimental effects on terrestrial organisms.  See discussion in this section.

Additional information

There are no studies available on terrestrial organisms for Ettringite.

Due to its chemical nature Ettringite is not stable under natural environmental conditions. The main degradation products are calcium sulfate (dihydrate) with limited solubility resulting in free calcium and sulfate ions and insoluble aluminium hydroxides and insoluble aluminium oxides (at neutral pH range).

The relevant compound to consider with regard to terrestrial toxicity of Ettringite is aluminium. Nevertheless, aluminium is the most abundant metallic element in the Earth's crust. Based on its ubiquitous occurrence the present natural background concentration far outweighs anthropogenic contributions of aluminium to the terrestrial environment. As detailed in the endpoint summary on terrestrial toxicity in general further toxicity testing on terrestrial organisms is considered unjustified and waiving based on exposure consideration is applied.

However, for reasons of completeness existing data on the terrestrial toxicity of aluminium are provided in addition and summarised here. Based on an analogue approach data are read across to aluminum chloride, aluminum oxide, and aluminum sulphate. Although different aluminium compounds are used as source for testing aluminium, results and concentrations are based on total aluminum and thus facilitate comparison. van Gestel & Hoogerwerf (2001) conducted three range finding studies with the three aforementioned substances. Worms belonging to the species Eisenia andrei were exposed for 14 days in parallel test series to soils treated with different concentrations of Al and under different pH regimes. For AlCl3 these authors found an increasing toxicity with decreasing pH values with the following LC50 values determined in mg Al/kg soil dw: >1000 at pH 6.70 - 4.37, >359 at pH 4.38 - 3.69, and 316 at pH 3.52 - 3.21. The same trend was found with Al2(SO4)3. Respective LC50 values found are >4000 mg Al/kg soil dw at pH values in the range of 7.39 - 4.32 and 457 mg Al/kg soil dw at pH 3.24. Additionally EC50 values for reproduction were determined for the latter substance. Reproduction was least affected at near neutral pH (7.22 ± 0.17) with an EC50 of 883 mg Al/kg soil dw. Effects were strongest around pH 4.86 with an EC50 of 197 mg Al/kg soil dw. However, at lower pH of 3.24 Al was less toxic to reproduction reflected by the higher EC50 of 330 mg Al/kg soil dw. For Al2O3 no toxicity to earthworms was found at any pH tested (7.14 - 2.30) up to 5000 mg Al/kg soil dw.

A chronic study was carried out by the same authors. Earthworms were exposed for 6 weeks to soils treated with Al2(SO4)3. Survival, growth and cocoon production was followed. Although not as distinct as in the range finding study, a similar pattern of toxicity can be seen with aluminium exhibiting stronger toxicity at pH 3.4 than at higher pH values.As in the range finding study this substance was most toxic at the lowest pH (3.4) and mortality resulted in a LC50 of 589 mg Al/kg soil dw. Effects on growth of worms and production of cocoons did not follow the same trend when exposed to different Al concentrations at different pH. At the lowest pH of 3.4, growth and cocoon production were significantly reduced at 320 mg Al/kg dry soil, while at 1000 mg Al/kg dry soil all earthworms died. At pH 4.3 and 7.3 survival was not affected by 1000 mg Al/kg soil dw. At the same pH and concentration growth and cocoon production was significantly reduced, cocoon production also at a concentration of 320 mg/kg soil dw. At pH 7.3 aluminum affected cocoon production only at 320 and 1000 mg Al/kg dry soil, whereas growth under same conditions was significantly increased, which might be explained by a trade-off between growth and reproduction. The following EC50 and NOEC values (as mg Al/kg soil dw) were determined for these 6 weeks experiments (pH values in parentheses): (a) EC50 growth: >1000 (4.3 and 7.3), 189 (3.4); NOEC growth: 320 (4.3), 100 (3.4 and 7.3), (b) EC50 reproduction: 291 (7.3), 529 (4.3), 294 (3.4); NOEC 100 (3.4, 4.3, and 7.3).

Phillips & Bolger (1998) also used Al2(SO4)3 as test substance and exposed Eisenia fetida for 30 days to different Al concentrations and different pH values. Responses of earthworms to aluminum were followed in terms of survival, growth, cocoon production and cocoon viability. Results obtained show no clear relation between toxicity exhibted by aluminum and pH range. At pH 4.2 the lethal dose was determined to be between 2000 - 4000 mg Al/kg soil. High levels of aluminum inhibited cocoon production at any pH between 4 and 7, whereas intermediate aluminum levels stimulated cocoon production at pH 6 to 7 and low levels of aluminum inhibited hatching and juvenile production at low pH. Cocoon viability in terms of numbers of juveniles hatched from cocoons was stimulated when parents were kept at intermediate levels of aluminum at pH 6 to 7.

A further long-term study is available on AlCl3 by Rundgren & Nilsson (1997). These authors examined effects of different aluminum concentrations and different pH values in soils to Dendrodrilus rubidus in two consecutively conducted tests. This species of earthworm was chosen in order to better reflect natural conditions since Eisenia, as a recommended test species by e.g. OECD guidelines, is not a true soil dwelling organism. At first activity, survival and reproduction was studied in the parent generation exposed for 16 weeks and then hatching, survival and growth in the filial generation exposed for another 48 weeks. In order to determine whether effects were caused by aluminum itself or only by varying pH, a parallel pH series was run without exposure of earthworms to aluminum. It was observed that aluminum had no significant effects on the parameters followed for the parent generation in comparison to controls. For the filial generation, however, responses were observed. Reproduction was significantly affected and a marked drop in reproduction occurred from an average of 12.4 cocoons per surviving adult over the four month period at pH 4.6 to 4.7 cocoons at pH 4.5. A second drop occurred when pH was further lowered from pH 4.5 to 4.2. In the test series with aluminum similar results were obtained. As the concentrations was increased from 100 to 200 mg Al/kg soil, cocoon production decreased from 8.3 to 4.4 cocoons per survivor. Hatchability at 200 mg Al/kg soil significantly decreased. After 26 weeks of incubation all juveniles produced in the first month and maintained in soils of the two highest Al-concentrations had died. Only a few juveniles hatched from cocoons produced in the second month in soils of 200 mg Al/kg soil. All juveniles hatched in soils of 100 mg Al/kg soil (dw) were dead at the end of experiment. In summary, this investigation shows that lowered pH in itself affects D. rubidus and the presence of aluminum does not increase the strength of the response. Lowered pH alone is followed by decreased activity, slightly enhanced weight loss of ageing adult individuals, lowered individual production of cocoons, lowered hatching success of cocoons produced late during the reproductive period, and hampered juvenile growth. Some of these effects might be related, e.g. lowered activity might affect feeding activity and following from this lowered cocoon production and decreasing number of hatchlings.