Slags, ferronickel-manufg.

Toxicity to soil microorganisms

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. Chromium exists in its less toxic form of Cr(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).

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

5 500 mg/kg soil dw

Additional information

Data on the toxicity to soil microorganisms for slags, ferronickel-manufg. is not available for the whole substance. In order to avoid unnecessary testing, 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 microorganisms is available on some of the constituents of slags, ferronickel-manufg, mainly nickel. The tests were performed with the more soluble species of Nickel chloride, in order to have a good understanding of their toxicological effects. From these studies, it was concluded that nickel (in the form of nickel chloride) was more toxic and produced adverse effects. From these, a NOEC was derived for Ni, with a value of 33 mg Ni/kg soil dw, which corresponds to a NOEC of 5500mg slag/kg soil dw and it can be used for the derivation of a PNECsoil for ferronickel slags.

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. Chromium exists in its less toxic form of Cr(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)