Iron dichloride

Endpoint summary

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).

Environmental iron levels

Values for the Chemical Safety Assessment

The following table summarizes the levels considered as background concentrations in the present assessment. These background concentrations can be used in the environmental risk assessment.

Table: Environmental medium concentrations (upper level) of iron used for Chemical Safety Assessment (CSA)

Urban air		Marine water		Surface freshwater, dissolved		Freshwater sediment		Soil
[ng Fe/m³]	Reference	[µg Fe/L]	Reference	[µg Fe/L]	Reference	[g Fe/kg dw]	Reference	[g Fe/kg dw]	Reference
6000	WHO 2003	ca.5*	OECD 2007	66	Gaillardet et al 2003	20	Vangheluwe et al 2010	20	Vangheluwe et al 2010

* calculated from ca. 10 µg/L, as hydroxide

It should be noted that some of the figures may deviate from those in table A3.1 of the SIAR (SIDS Initial Assessment Report, OECD 2007) document, which are given below. Nonetheless the above listed environmental levels are in comparable ranges.

Table: Summary of background concentrations & levels in biota from SIAR (OECD 2007, Table A3.1)

Matrix or organism	Typical concentration (order of magnitude only)
Earth’s crust	5 %
Soil	Approx. 5 %*
Atmosphere – background	1 ng/m³
Atmosphere - urban	6000 ng/m³
Sediment – fresh water and marine	4.5 % d.w.*
River water – background	Approx. 1 mg/L (total)
Sea water – background	Approx. 10 µg/L, as hydroxide
Plants – roots	4000 mg/kg d.w.
Plants	200 mg/kg d.w.
Marine sediment organisms	Up to approx. 500 mg/kg d.w.
Marine algae	Up to approx. 500 mg/kg d.w.
Marine crustacean	Up to approx. 500 mg/kg d.w.
Gastropods	Up to approx. 500 mg/kg d.w.
Marine fish	5 – 30 mg/kg d.w.
Terrestrial animals	Typically up to 600 mg/kg d.w.

* Values deviate from those to be used in the chemical safety assessment given above

Natural occurrence of iron

Iron is the fourth most abundant element in the Earth's crust accounting for approximately 5 % by weight (Wildermuth 2004). Iron is found in various minerals (as ferric chloride, ferrous chloride, ferric sulphate, ferrous sulphate and their mixtures, oxides and sulphides) and in nearly all soils, sediments and mineral waters. Iron levels range from 0.01 mg/L in seawater up to 0.1 – 10 mg/L in fresh water, 0.5 – 5 % in soil and 1 – 9 % in sediments (Drever 1982, Hem 1970, Horne 1978, Kabata-Pendias & Pendias 1984, Khalid et al 1977, Lindsay 1979, Morel 1993, Stumm & Morgan 1981). Overall, the data show that iron is present naturally in abundance in all environmental compartments, apart from water, where solubility of the hydroxide and oxides is a limiting factor. The dissolved concentrations of iron tend to be low whereas sediment concentrations can be high.

Mobilization of natural iron from soils

Johnson et al (2007) summarize the mobilization of iron from soils with reference to Schnitzer (1969) as follows: “Hydrous iron(II) oxides [FeO(OH)] are generally red–brown gels and are the major constituents of soil. The major iron ores found in nature are haematite (Fe2O3), magnetite (Fe3O4), limonite [FeO(OH)] and siderite (FeCO3). Iron in crustal rocks is mobilized by weathering of iron silicates and carbonates. The weathering products are oxidized and hydrolyzed to insoluble ferric hydroxides and hydrous oxides that are then transported within the aquatic environment.”

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