Slags, ferronickel-manufg.

Toxicity to soil macroorganisms except arthropods

Description of key information

In general, it can be said that Slags, ferronickel manufg. do not contain substances that are toxic to the terrestrial environment. Iron, Calcium, Aluminium and Magnesium are common elements that have no toxicity towards terrestrial organisms.Chromiumexistsin its less toxic formofCr(III). A study on the speciation of Chromium in Ferronickel slags using alkaline digestion and colorimetric analysis (EPA 3060A and EPA 7196A respectively) showed that no hexavalent Chromium species were present up to the limit of detection of the analytical method (20mg/kg) so all Cr in the substance is considered to be in trivalent form(NTUA 2011c). 
The read-across approach for the available studies has shown that Nickel is the constituent of highest concern, but its toxicity for terrestrial organisms is much lower than its aquatic toxicity. 
Additionally, the substance has very low solubility in water (ref.), therefore it poses no risk for plant life and soil microorganisms. Its most soluble components, Calcium and Magnesium, are common nutrients. Other terrestrial organisms that feed directly from the ground are more exposed, but the lack of solubility of the slags in water does not allow them to pass to tissues and cause toxicity. The coarse form of the material’s particles (see granulometry studies) decrease the bioavailability (and the solubility) of the substance to other soil macroorganisms (such as earthworms). 
The various constituents of the slags are chemically bound in the mineral matrix of the substance and they do not dissociate readily into ionic form. Ionic forms of elements are more water soluble and, in general, more toxic (locally or systemically) to living organisms. Very low concentrations of nickel and chromium in ionic form indicate that toxicity is highly unlikely. 

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil macroorganisms:

16 667 mg/kg soil dw

Additional information

Data on the toxicity to soil macroorganisms for slags, ferronickel-manufg. is not available for the whole substance. In order to avoid unnecessary testing to animals, it was attempted to identify possible adverse effects based on data for its recognised constituents, even though the results cannot be applied directly, due to the way the constituents are bound in the matrix of the substance and are not as bioavailable as the free substances that are examined. So, the results must be taken into consideration with care.

Data on studies on earthworms is available on some of the constituents of slags, ferronickel-manufg, mainly aluminium oxide and nickel.

Iron Oxides

Iron 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 iron to the existing natural pools of iron in soils and sediments is therefore not relevant either in terms of added amounts or in terms of toxicity (ARCHE, 2010).

Calcium Oxide

CaOeffect on soil is mainly the increase of alkalinity. However land spreading of CaO usually is of insignificant effect due to the large neutralizing capacity of the soil. Furthermore, Calcium Oxide is bound in the mineral matrix of the slags which reduces significantly its reactivity.This has been verified in the acute oral and inhalation toxicity experiments of CS (see respective sections) as well as in the skin and eye irritation experiments. It is concluded that CaO is of negligible toxicity inferronickel slags.

Chromium (III)

Sivakumar and Subbhuraam (2005) examined the effects of trivalent and hexavalent Chromium substances on earthworms (E.fetida). For Cr(III) they resulted in a NOEC of 1635 -1902mg/kg soil, which is significantly high so as to assume that no toxic effect is expected on soil macroorganisms from trivalent Cr species.

Nickel

Nickel (in the form of nickel chloride) is the more toxic constituent and produced adverse effects in a number of experiments. From these, a NOEC was derived for Ni, with a value of 100mg Ni/kg soil dw, which corresponds to a NOEC of 16667mg slag/kg soil dw.

Aluminium Oxide

The tests that were performed with these studies were with their more soluble species, in order to have a good understanding of their toxicological effects. From these studies, it was concluded that aluminium oxide (a constituent of the slag) showed no toxic effects even at the highest concentration of 5000mg/kg dw (at a range of pH values).