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EC number: 231-843-4
CAS number: 7758-94-3
A range of BCF and BAF values are available
from different species. In general, metals do not biomagnify unless they
are present as, or having the potential to be, in an organic form (e.g.
methyl mercury). According to ECHA (2008, p 12) „The PBT and vPvB
criteria of Annex XIII to the Regulation do not apply to inorganic
substances but shall apply to organo-metals.“ This is because some
organo-metals are lipid soluble, not metabolized, and efficiently
assimilated upon diet borne exposure. McGeer et al (2002) conclude
“Overall, the use of BCF and BAF-based criteria for the hazard
classification of metals is not useful. In terms of hazard
identification, the declining BCF and BAF values at elevated exposures
lead to the prediction of reducing impacts as concentration increases, a
conclusion that is contrary to all of the toxicological data. Using BCF
and BAF for metals and inorganic metal compounds ignores fundamental
physicochemical and toxicological properties associated with these
substances. Compared with diffusional uptake of neutral organics, metal
uptake is complex and includes a diversity of mechanisms, accumulation
of both essential and non-essential elements from natural background,
homeostatic control of accumulation, as well as internal detoxification,
storage and elimination.”
Biologically, iron is an essential trace
element for organisms including micro-organisms, plants and animals.
Iron plays an important role in biological processes, and iron
homeostasis is under strict control. Due the natural occurrence in
considerable amounts biota have mechanisms to cope with concentrations
of the iron species in equilibrium with the kations constituting the
submission item. Thus the criteria for assessing bioaccumulation were
replaced by the bioavailability considerations.
The existence of organic molecules containing
iron is obvious. Biota use iron to build functional molecules (e.g.
haemoglobin, myoglobin, cytochromes, ferredoxins, rubredoxins,
catalases, peroxidases, nitrogenase, ferritin, transferrin,
haemosiderine). Given the complex anabolism, abiotical spontaneous
formation of these molecules seems unlikely. As they are natural
constituents of every prey they will be metabolized and used due to
adaptation (evolutionary response to local conditions) and if required
acclimation (short-term physiological response to challenges) of the
predators. As these (macro)molecules are intensively used over a large
range of taxonomic groups it seems unlikely that they bioaccumulate.
More organic iron compounds exist in the environmental media as chelated
in organic iron complexes are formed abiotically. Hutchins et al (1999)
summarize as follows: “Dissolved iron is overwhelmingly (approximately
99 %) bound to organic ligands with a very high affinity for iron (Wu et
al 1995, Rue & Bruland 1995, Witter & Luther 1998). The origin, chemical
identity and biological availability of this organically complexed iron
is largely unknown (Hutchins 1995). The release into sea water of
complexes that strongly chelate iron could result from the inducible
iron-uptake systems of prokaryotes (siderophore complexes) (Wilhelm
1995, Butler 1998, Granger & Price 1999) or by processes such as
zooplankton-mediated degradation and release of intracellular material
(porphyrin complexes).” Iron from chelates seems generally less readily
bioavailable than free kations. Hutchins et al (1999) conclude on
competitive strategies in marine phytoplancton to make iron bound to
uses specific complexes. Lis & Shaked (2009) found the bioavailability
of iron bound to the model organic ligand desferrioxamine B (CAS
70-51-9, a naturally occurring chelating agent) reduced compared to
uncomplexed iron species. While iron shortage is typically for marine
waters, the available data on iron
concentrations in the environment show that organisms display adaptation
to the high background concentrations of iron. Despite its presence no
accumulation in wildlife biota is described in the literature. This
supports the suggestion of a low potential for bioaccumulation.
Iron is present in all environmental media
with large reservoirs in soils and sediments. Iron is the forth-most
abundant element in the Earth's crust (4.7 % by mass) occurring
naturally as almost as oxide and hydroxide. Although it is widely
distributed and present in all environmental media the highest levels
were in soil. Comparison of the environmental levels outlined in the
discussion on Environmental fate and pathways with the additional
release according to the exposure scenario shows clearly that these
additional releases contribute insignificantly. This even more as the
environmental fate processes will probably carry additional releases to
the soil and sediment reservoirs without any lasting increase of the
bioavailable species as the equilibrium times are short.
In result the iron species, which would result from the release of the
submission item to the environment, are assessed irrelevant with regard
to bioaccumulation factor based hazard classification.
In conclusion no effects and thus no
hazard are identified with regard to bioaccumulation and/or
In the light of the inverse relationships between water
concentration and BCF and/or the biological regulation of uptake and
elimination and/or the presence of all submission item constituents in
natural background concentrations, a lack of relevant enrichment is
assumed. Thus and due to and the low toxicity of the ions and salts, it
is not necessary to assess effects on predators by secondary poisoning
for these substances and no hazard is assumed.
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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