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EC number: 701-265-1 | CAS number: -
Ferrous slags are solid UVCB substances (substances of Unknown or Variable composition, Complex reaction products or Biological materials) that resemble natural rocks found in terrestrial and sediment systems. The physicochemical properties are almost identical among ferrous slags, and their benign toxicological and ecotoxicological profiles are very similar. Similarities comprise also the mineralogical composition of the ferrous slags. Importantly, all mineral components of ferrous slags are present in natural rocks; no new component is introduced during steel processing. Ferrous slags demonstrate low extractability in water as metals in slag were found to be generally resistant to leaching. Ferrous slags are virtually free of hazardous fibres. Overall, ferrous slags can be considered artificial volcanic rocks.
The ‘Ferrous Slag Category’ comprises the following 5 slag types: (1) ABS/GBS i.e., Slag, ferrous metal, blast furnace (air cooled or granulated), (2) BOS i.e., Slag, steelmaking, converter (converter slag), (3) EAF C i.e., Slag, steelmaking, elec. furnace (carbon steel production), (4) EAF S i.e., Slag, steelmaking, elec. furnace (stainless/high alloy steel production), and (5) SMS i.e., Slag, steelmaking. No significant hazard to environmental and ecological receptors has been anticipated for these slags.
The pathways of exposure quantitatively evaluated in this assessment were inhalation of suspended airborne ferrous slag particulates, incidental ingestion of ferrous slag, and dermal contact with ferrous slag.
From single-dose toxicity testing in animals via the oral, dermal and inhalation routes it can be concluded that ferrous slags are not acutely toxic. They do not need to be classified as oral, dermal and inhalation toxicants; neither a signal word nor hazard statement is required. Furthermore, ferrous slags exhibit no relevant irritant or sensitising potential, and does not show any mutagenic potential. Extensive testing in rat inhalation studies revealed that the biological responses to inhaled ferrous slag show no correlation to the course of pulmonary toxicity reported for amorphous silica (quartz); quartz dust served as positive control as it is well known to produce irreversible lung damage. Overall, ferrous slag in vivo data differ markedly from those reported for quartz in rats exposed at similar doses.
Supplemental in vitro testing also shows that ferrous slags, alike natural mineral samples, do not cause significant toxicity in cultured alveolar macrophages, nor does the slags induce major reactive oxygen species (ROS) formation and oxidative stress or trigger any inflammation in a biological system. On the contrary, the positive assay control quartz caused consistently evidence for an inflammation response in vitro associated with a significant secretion of the mature forms of pro-inflammatory cytokines from the cells, strong activation of the inflammasome pathway, and impaired phagocytosis functionality of alveolar macrophages.
Taken together the data generated in vivo and in vitro for ferrous slags it can be summarised that ferrous slags behave like natural rock, representing a rather inert category of UVCB substances. As expected biokinetics investigations in rats following inhalation exposure to high concentrations of ferrous slag particulates showed concentration-dependent lung burdens of persistent metals after inhalation exposure of rats to ferrous slags but there was no translocation to other organs of any metal investigated. The animal data suggest that the rat lung was able to get rid of the inhaled solid aerosol via physiological clearance mechanisms.
The toxicology programme for ferrous slags, as documented in the Chemical Safety Report (CSR) as part of the registration dossier of ferrous slags (CSR 2017), can be considered to fulfil information requirements for REACH (Registration, Evaluation, Authorisation and Restriction of Chemical substances) registration at the European Chemicals Agency (ECHA). There is sufficient, adequate and reliable information on hazardous properties for classification and risk assessment of ferrous slags.
The registrant makes use of Annex XI criteria regarding the scientific necessity of information, the technical possibility for testing, and exposure-based waiving to adapt the standard information requirements under REACH. These non-clinical studies are waived based on physico-chemical properties of ferrous slags that resemble natural rocks, mimicking the natural concentration of an element in the environment, and the low solubility in water, low extractability of components from ferrous slags, and lack of toxicological bioavailable fraction / systemic bioavailability of metals. Slag has been utilised in road construction for more than two centuries and wealth of humane experiences are available. Furthermore, ferrous slags have no PBT (persistent, bioaccumulative and toxic) or vPvB (very persistent and very bioaccumulative) properties. It is also of note that no toxicity effects of particular concern were observed in animal inhalation studies that is the likely route of human exposure, and results obtained from suitable in vitro studies demonstrate no certain dangerous property of ferrous slags. Finally, previous risk assessments of slags provide sufficient supporting evidence that toxicity can reliably be excluded.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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