Slags, elec. furnace smelting, iron silicate

Endpoint summary

Additional information

The main constituents of FeSi silicate/slag are oxidized silicon and iron, both very common elements in the environment. Most living organisms contain at least trace quantities of silicon and iron. Bioaccumulation of Si and Fe and other significant constituent elements is well-known (or at least sufficiently known) for hazard assessment purposes, and no specific reasons have emerged to study the issue further in this context.

For naturally occurring inorganic substances such as metals, bioaccumulation is a complex issue, and many processes are available to modulate both the accumulation and potential toxic impact. The issue becomes even more complex if the substance under evaluation is a mixture of metals/elements. Adaptation and mechanisms to handle these common metals at the systemic level exists to a certain extent. Most species tend to regulate internal concentrations of these metals through active regulation, storage, or a combination of active regulation and storage over a wide range of environmental exposure conditions.

Silicon has no tendency or a low intrinsic tendency for bioconcentration and bioaccumulation if taken up passively by organisms. Si compounds are so abundant in the environment that most living organisms contain at least trace quantities of silicon. For some species Si is an essential element taken up actively, while for others Si is not essential but it is still taken passively (Si transport and distribution follows that of water). In these cases it needs to be excreted or passivated in other ways. Many organisms such as diatom algae, radiolarians, flagellates and gastropods have silicate skeletal structures.

Iron is a biologically essential metal actively taken up and to some extent regulated by aquatic and terrestrial organisms. In one study, bioaccumulation factors of 2756 – 9622 were measured for the blue mussel (Mytilus edulis) when exposed to initial total iron concentration of 0.009 mg/l for 42 days at 10^oC (Pentreath, 1973). The results support a sequestering mechanism for active uptake of iron from seawater to the organism. In a study on ferrous sulfate heptahydrate, it was shown that BCF values were less than 20 for the fishCyprinus sp.in a 28-day study using flow-through (CERI, 2001).

References:

Pentreath, R.J., 1973. The accumulation from water of 65Zn, 54Mn, 58Co and 59Fe by the mussel, Mytilus edulis. Journal of the Marine Biological Association of the. 53:1 127-14.

CERI, Tokyo, 2005. SIDS dossier for 7782-63-0. NITE CHRIP (Public database). Nationalofand Evaluation. Chemicals Evaluation and Research Institute (CERI);.