Iron dichloride

Sediment toxicity

Description of key information

No relevant effects

Additional information

This endpoint is covered by the category approach for soluble iron salts (please see the section for physical and chemical properties for the category justification/report format). Testing for this endpoint has been waived in accordance with column 2 and Annex XI, part 3, restrictions.

Data describing long-term toxic effects on epibenthic and sediment-dwelling organisms exposed via sediment are absent. Short- and long-term test data for a range of organisms exposed via the aqueous phase to iron salts do show effects but only at concentrations that significantly exceed the solubility of the iron species that is present under the test conditions; typically high pH and high dissolved oxygen concentration.

Absence of toxicity to aquatic species and EPM

The assessment on aquatic effects indicates no relevant toxicity of the submission item category member soluble iron salts to the aquatic life in the foreseen uses. Therefore and due to the assigned ready biodegradability the submission category belongs to the lowest “soil hazard category 1” (according to ECHA 2008, Chapter R.7c, Table R.7.11 -2, p 131) and thus the straight forward application of the EPM according to the TGD (ECB 2003, part II, p 112) is possible to derive PNECs for sediments, but as no aquatic PNECs were derived this is obsolete.

• ECB European Chemicals Bureau (2003). Technical Guidance Document in support of Commission Directive 93/67/EEC on Risk Assessment for new notified substances, Commission Regulation (EC) No 1488/94 on Risk Assessment for existing substances and Directive 98/8/EC of the European Parliament and of the Council concerning the placing of biocidal products on the market. Parts I to IV. Self-published, Ispra, Italy.
• ECHA European Chemicals Agency (2008). Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance. Self-published, Helsinki, Finland, May 2008. 235 p.

Exposure considerations

Iron compounds may represent about 2 % mass of the sediment dry weight (see section on Environmental fate and pathways). It can therefore be assumed that the contribution of additional iron species due to human activity will be low compared to these levels. Moreover the iron species are involved in intense readily transformation to different species and any additional release would probably not result in an increase of bioavailable species but contribute to the anyhow large sediment sinks/reservoirs.

Straightforward testing technically not feasible, existing data not relevant/adequate

Furthermore, although effects can be observed in some laboratory studies with sediment dwelling organisms, the lowest concentrations at which they have been found to occur are well below natural background concentrations, to which natural sediment organisms are adapted. Laboratory test data indicating effects at concentrations below background therefore have no practical significance for setting PNECs. The chemical species reaching environmental sediments as consequence of the supported uses of the submission item will be equilibrated to the naturally occurring almost insoluble and biounavailable forms. Testing of sediments freshly spiked with soluble iron salts would not reflect relevant environmental exposure. Exposure to iron-amended sediments via ingestion might result in additional uptake of iron as a consequence of the conditions prevailing in the gut of the organism. Therefore and due to the secondary effects of speciation such as flocculation, oxygen consumption due to oxidation from ferric to ferrous forms, precipitation and fouling the results from such experiments cannot show intrinsic toxicity. This is a violation of Hill criterion 3 (Specificity, see section on Ecotoxicological information) and no mono-causation of the observed effects is assured. Therefore the existing data are of little relevance for the assessment of intrinsic toxicity. Nonetheless the use of aged, equilibrated test item could be performed, but regarding the significant high natural background concentrations this will not be insightful.

Anoxic and low pH conditions in sediments may result in higher concentrations of the more toxic ferrous iron forms but such conditions are only conducive to supporting specialist species. Experiments with test organisms that are adapted to conditions of low pH and anoxia might be justified, but only to investigate specific exposure scenarios.