Phosphorus

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

insufficient hazard data available (further information necessary)

Sediment (marine water)

Hazard assessment conclusion:

insufficient hazard data available (further information necessary)

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Conclusion on classification

Ferro phosphorus is considered under REACH as a special mixture or alloy type materials. This means that the environmental hazard identification would be based on the hazard classification and concentration of the components, unless Transformation Dissolution (TD) evidence on the alloy(s) would be available.

On the contrary to metal compounds, neither the CLP nor the GHS require a 24 h screening test on metallic forms in order to decide if further acute or chronic testing are necessary. However, the determination of the relevant test conditions (such as filtration efficiency, and pH that dissolves the highest soluble fraction) require a pre-evaluation to ensure that the right choices for the 7 and 28 days full tests are made. These test conditions were evaluated during a 24h transformation dissolution pre-test. This TD pre-test was different from a classical screening test because the shaking conditions were set as in a full TD test.

 

Test results and hazard ID conclusions from the 24 h pre-tests:

Conclusion: The results of the 24 h pre-test for both ferro phosphorus and Fe3P in powder forms are consistent and robust. Even after correcting for the actual surface exposed, ferro phosphorus has a much lower release rate than Fe3P. The results confirmed the relevance for continuing with a 7 d testing for both substances and 28 d at 1 mg/l for Fe3P to define the appropriate environmental hazard category.

 

Short and long term environmental hazard identification for ferro phosphorus and Fe3P

Both 7 d TD tests and the 28 d test on Fe3P were conducted in full accordance with the OECD Test Guidance n° 29 and provided robust and relevant evidence for the acute and long term environmental hazard identification.

 

Ferro phosphorus: The dissolution results for ferro phosphorus after 7 days at pH6 at the highest loading level (100 mg) demonstrated very low releases of iron, phosphorus and orthophosphate, actually below the RL. The values for Fe and orthophosphate were all around or below 1 µg/L which is in order of magnitude below any potential acute or long term reference toxicity values. The measured dissolved phosphorus levels were also very low (<1 up to 4 µg P/L, see graph) but a lack of evidence on the speciation of the phosphorus form (white phosphorus or other non toxic forms) does not allow to conclude on the potential for long term toxicity. Such evidence can only be provided by a fish test (most sensitive trophic level) in the obtained dissolution water.

 

Fe3P: The 7 days acute Transformation results demonstrated a peak in dissolution rate for the first 2 days followed by a rapid precipitation, reaching levels of respectively 4 to 12 µg Fe/L after 7 days. Such dissolution characteristics were equally noted for other Fe-based alloys and conforming the generic fate predictions by the Unit World Model. The equilibrium values after 7 days as well as the short term peak values were all "in order of magnitude” below the lowest toxicity reference values for Fe thereby concluding no acute hazard for the Fe component of the alloys.

While not precipitating like iron, the levels for orthophosphates are low (+/- 15-30 µg/L), remaining far below any short or long term toxicity reference values and seemingly independent of the dose used (1 or 10 mg/L).

Comparable dissolution levels were noted for “dissolved phosphorus” leading to the same conclusion as for ferro phosphorus namely : “The measured dissolved phosphorus levels were very low (<1 up to 4 µg P/L) but lack of evidence on the speciation of the phosphorus form (white phosphorus or other non toxic forms) does not allow to firmly conclude on the potential for long term toxicity. Such evidence can only be provided by a fish test (most sensitive trophic level) in the obtained dissolution water”.

 

The potential long term hazard ID was tested in a 28 d TD test at a 1 mg loading at pH 6. Iron levels remained very low (in the order of 10 µg/L) and far below any potential long term toxicity reference value. 

Contrary to Fe behaviour, the orthophosphate level remained increasing over time following a first order kinetic relationship up to 30 µg/l, after 28 days, again an order of magnitude below any long term toxicity reference values.

Dissolution releases at equal surface level

7 d TD evidence is available for both materials (ferro phosphorus and Fe3P) under comparable conditions for iron, dissolved phosphorus and orthophosphates. However, both materials were tested at different loading levels requiring a correction of the ferro phosphorus results. The table below compares for the pH 6 results the theoretical release rates for these elements at comparable loading (10 mg/L) to determine differences in dissolution kinetics at different and common surface area.

Material	Fe dissolution µgFe/L at 10 mg/l loading	Fe dissolution for a standard surface (0,2 m²/g) in µg/L	Orthophosphates in µg/L at 10 mg/L loading	Orthophosphates for a standard surface (0,2 m²/g) in µg/L	Dissolved phosphorus in µg/L at 10 mg/L loading	Dissolved phosphorus for a standard surface (0,2 m²/g) in µg/L
Fe-P	< 1*	<1*	0,4*	0,4*	0,3*	0,3*
Fe3P	12	2*	16	2,67*	34	5,67*

*calculated value

As for the pre-test these results demonstrate that Fe3P dissolves more quickly and to a greater extent than ferro phosphorus at equal surface area for all composing parameters of the materials.

 

Conclusions:

- The acute and long term Transformation Dissolution tests on ferro phosphorus and Fe3P demonstrate very low dissolution levels for Fe and orthophosphates, in order of magnitude below any acute or chronic toxicity reference values for both materials under 7 and 28d conditions.

- Dissolution rates of phosphorus contained in alloys are always and under all relevant environmental conditions lower than dissolution rates of Fe3P, allowing to use reliable aquatic ecotoxicity data of Fe3P as a safe and precautionary read across. reference.