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EC number: 294-409-3
CAS number: 91722-09-7
Substance formed during processing of liquid steel or during production of iron castings. Consists primarily of fused silicates and trace elements as oxides as well as trace of alloying elements.
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
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
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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