Diiron tris(sulphate)

PBT assessment

PBT assessment: overall result

PBT status:

PBT assessment does not apply

Justification:

Persistence

A formal PBT assessment should not apply as the submission item is inorganic. Therefore true degradation or mineralisation is not possible. Nonetheless there are reasons to assume the submission item treatable as if readily/rapidly biodegradable, as bioavailable iron forms get readily depleted form the water column and the omnipresent hydronium, hydroxyl and sulphate ions resulting after dissolution in water do not fall into the scope of PBT assessment.

Bioaccumulation (iron)

Inverse medium level - BCF relationship

Based on experimental BCF data a metal-typical inverse relationship was established between the water concentrations of dissolved iron and the corresponding BCF in freshwater fish (300 to 2 L/kg). The iron metabolism of many biota includes transformation and complexation steps but remains strictly controlled due to the essential nature of iron.

Biodilution with increasing trophic level

The existing information suggests not only that iron does not biomagnify, but rather that it tends to exhibit biodilution at higher trophic levels in the food chain. This is considered a result of metal regulation by the organisms.

Natural occurrence

Iron is a naturally occurring element which is in equilibrium between bound and bioavailable forms in waters, sediments and soils. Additional emissions integrate eventually to permanent sinks due to integration in the soil and sediment matrix. Iron is the forth-most abundant element in the Earth's crust (ca. 5 % by mass, see chapter on environmental fate and pathways). It is biologically essential and is actively taken up by organisms. Although the metal is widely distributed in the environment no accumulation in food chains of aquatic or terrestrial wildlife biota is described in the literature.

Environmental Toxicity levels

There is convincing evidence that chronic ecotoxicological threshold level of iron is clearly > 0.01 mg/L (> 10 µg/L). The natural background concentration is 66 µg iron species/L fresh water (see chapter on environmental fate and pathways). The environmental bioavailability depends on local geochemical conditions rather than emissions and acclimation/adaptation of local biota is a natural process.

Conclusion

In conclusion further PBT assessment is obsolete as no indication for the formation of lipophilic stable organometallic compounds exists and no relevant bioaccumulation occurs. Iron is thus considered “not B” and in consequence “not PBT” and “not vPvB”.

Likely routes of exposure:

Due to absence of PBT/vPvB properties the routes of exposure are of little relevance. Iron speciates once released readily and rapidly into naturally occurring forms, which are omnipresent in the environment. Thus humans and environmental organisms are exposed via the media water, sediment, suspended matter, soil and air.