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Ecotoxicological information

Long-term toxicity to aquatic invertebrates

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Description of key information

Eight publications that report on chronic toxicity of iron to invertebrates are included in this dossier, but as for the findings reported on acute iron toxicity studies for this taxonomic group, the inherent physicochemical properties of iron make it virtually impossible to interpret the data in a way such that a meaningful PNEC could be identified.


Reported long-term no-effect levels were well above the solubility limit of ferrous/ferric ions: precipitation of iron in test media was reported by several authors (Birge et al, 1985 ; Randall et al, 1999). None of the studies provide a full characterization of the Fe-speciation during the test period. Due to the complexity and reactivity/solubility of Fe as a function of parameters like pH, redox-potential, dissolved organic carbon content, it is virtually impossible to properly qualify and quantify the time-dependent Fe-speciation profile during a chronic exposure testing period. Adverse effects could not be related to a specific Fe-species or to precipitates (intrinsic toxicity vs physical toxicity).

Key value for chemical safety assessment

Additional information

Intrinsic toxicity and bioavailability of metals is in general related to the free ion form. Due to the limited solubility of iron, the free ion concentration in test media will be within the range concentrations that are found in the environment at background/ambient concentration levels. It is thus reasonable to assume that organisms are adapted to the maximum concentrations of free iron that can be achieved in an aqueous solution. Therefore, adverse effects that may be observed at high exposure concentrations are not due to the intrinsic toxicity of iron.


Precipitation processes are most likely causing the toxicity, but only effects caused by the intrinsic toxicity of a chemical should be considered for derivation of a PNEC.