Registration Dossier

Environmental fate & pathways

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Elemental phosphorus contained in alloys has a very low water solubility. Transformation dissolution testing of ferro-phosphorus in accordance with OECD guideline 29, demonstrated extremely low solubility levels of Fe and P at 7 days, pH 6 and 100 mg Fe-P dosing per litre (< 5 µg P/l and < 1 µg Fe/l).

Elemental phosphorus is thermodynamically unstable in the presence of water and oxygen, and white phosphorus will react very fast to produce higher oxidation states of phosphorus in water. The estimated half-life for hydrolysis at ambient temperature is around 84 hours. The estimated half-lifes of white phosphorus at ambient temperatures due to a combination of hydrolysis and oxidation reaction are around 42 hours in air-saturated water and 56 hours in non air-saturated water. Half-life of white phosphorus in distilled water varies between 0.85 hours and 20 hours.

The speciation of the released soluble phosphorus is critical but difficult to assess given the low levels of soluble phosphorus which are close to or even below the detection limit of classical analytical techniques. Range finding tests with the most sensitive trophic level conducted to clarify the potential speciation of the released P-form for WFD and local permit requirements, indicate that the released form does not correspond with the toxic white phosphorus form. Further investigations are ongoing and would be equally useful for the REACH registration to demonstrate the chemical species released from the alloys and confirming the relevance of the justification of the read across from phosphates (PO4).

In conclusion, the releases of phosphorus from the alloys are extremely low and are expected to transform in the environment into soluble phosphates. The environmental fate and ecotoxicity endpoints are consequently based on the non-toxic soluble phosphates form.