Reaction mass of diiron carbide, diiron phosphide and triiron phosphide

Endpoint summary

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Additional information

No specific study was performed on the absorption/distribution/metabolism/excretion (ADME) of this substance (Fe₃P). However data are currently available from  in vivo  toxicology studies performed with this substance.

Ferrophosphorus (Fe₃P) is an inorganic compound with a molecular weight of 198.5 g/mol and low water solubility (≤ 1 mg/L). It is used as an additive for powder metallurgy. It is a dark powder containing 31% w/w particles smaller than 10 μm (inhalable particulate material). These physicochemical properties suggest that Fe₃P will not be readily absorbed across biological membranes.

 

Absorption

Oral route

The available data on the acute and repeated dose toxicity studies by the oral route does not indicate any systemic toxicity from Fe₃P; there were no obvious clinical signs specific to treatment with Fe3P, the weights of examined organs after at least 28 days repeated oral administration were unaffected by treatment and no gross or microscopic changes were observed. This suggests that either the compound is absorbed and not toxic or it is not absorbed via the gastric intestinal tract. The abnormal colour (black) of the faeces recorded in the acute oral toxicity study in rats suggests that Fe3P is not absorbed and is excreted via the faeces.

 

Dermal route

Fe₃P did not show the potential to induce skin sensitization. No other data is available on absorption after dermal application.Therefore it is not possible to conclude if Fe3P can or cannot be absorbed through the skin. However, the physicochemical properties of the compound suggest that dermal absorption is insignificant.

 

Inhalation route

Effects seen in an acute inhaled toxicity study were limited to the lungs and tracheobronchial lymph nodes, suggesting the possibility of a local effect. The increased lung weights are consistent with a quantity of residual test material remaining in the lungs at the end of the 14‑day recovery period and enlarged lymph nodes are likely to be indicative of the on-going removal of exogenous material; neither effect is indicative of a systemic toxic effect, and such findings could be expected of many powders of inhalable particle sizes. On this basis, it is considered that Fe₃P is not readily absorbed via the lungs and that the treatment-related effects observed in the acute inhalation study are not specific to Fe₃P, but rather just to particulate material of inhalable or near-inhalable size.

 

 

Distribution, Metabolism, Excretion

No data are available on distribution and metabolism in the existing toxicity studies. There is evidence to suggest that the substance is not readily absorbed by the gastrointestinal tract, through the lungs or the skin. Therefore it is expected that Fe3P will not be distributed systemically or greatly metabolised. Some metabolism may occur in the gastrointestinal tract, the lungs or the skin but the majority of the substance will be excreted/removed as such. The abnormal colour (black) of the faeces recorded in the acute oral toxicity study in rats suggests that the substance will be excreted via the faeces. When administered by inhalation, it is expected that the substance will transported out of the respiratory tract by macrophages to the throat where it will be swallowed.

 

Conclusion

There is good evidence that the test substance is not readily absorbed by the gastro intestinal tract, the skin or the lungs. Since it is not absorbed, it is not expected to be distributed to internal body tissues/organs or metabolised. It seems to be excreted via the faeces when orally administered. When inhaled, there is evidence that it is removed from the lungs probably involving by the mucocilliary mechanism.