Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability

For all members of the category, stability in water is expected. Iron oxides are almost insoluble in water, although the hydrated form of iron oxide is relatively soluble and exists in significant quantities in anaerobic groundwater. After aeration it is converted to very insoluble ferric hydroxide or hydrated ferric oxide. In the atmosphere, iron oxide substances will exist solely in the particulate phase and may be removed from the air by wet and dry deposition.

Biodegradation

Biotic degradation does not need to be assessed, as all members of the category are inorganic. In the environment, the ratio of iron(II) oxides to iron(III) oxides will be influenced by the availability of oxygen, and will also depend on the presence of microorganisms, nutrients, organics and many other environmental factors.

Bioaccumulation

A study on bioaccumulation does not need to be conducted, based upon the low bioavailability of the category members.The substances are highly insoluble in water, out of toxic response to aquatic organisms, and based upon its physico-chemical properties the category members do not bind to biological ligands. The essentiality of Iron, the evidence of absence of biomagnification is demonstrated.

Transport and Distribution

Iron oxides exist in crystalline form as uncharged, solid substances and no adsorption to suspended solids and sediment is expected. Due to their high density, iron oxides will be deposited on the ground of environmental waters. The hydrated form of diiron trioxide exists in an amorphous form when being precipitated from iron hydroxide. This form crystallises after ageing and drying. For soluble forms of Iron (III) a mean log Kd of 4.9; 6.6 and 2.7 for sediment, suspended particles and soil, respectively, is reported. Additionally, a log Kd, observed range of 3.97-5.66 for sediment and a log Kd of 4.50 for sediment is reported. Those studies are not reliable or not sufficiently described and are not taken into account for assessment.

The Henry’s law constant (HLC) and the distribution of iron oxides in the environment are not calculated according to the Mackay fugacity model, because the substances are inorganic and have an extremely low vapour pressure at ambient temperature.

Iron oxides are not volatile from aqueous suspensions.

In the atmosphere, iron oxide substances will exist solely in the particulate phase and may be removed from the air by wet and dry deposition.