Slags, phosphorus-manufg.

Endpoint summary

Additional information

There is very little information available to base the toxicokinetic assessment of P-slag on. No key studies are available, but a supporting study is included in the dossier concerning the biodurability of wollastonite. The available toxicity studies provide no or little information. Only a few physicochemical properties are available that can be used.

 

Physical/chemical properties

P-slag is a multi constituent substance containing inorganic mineral silicates with a fibrous particle structure. Therefore a Log-P and vapour pressure is not applicable. The water solubility is very low. A dissolution/transformation protocol study learned that after 7 days < 1% of some elements (Si, F) were solved. If the cristalline structure of P-slag would solve in water, the elements would be present as ions in solution.

Absorption

Based on the very low water solubility it is expected that absorption via oral and dermal exposure will be very limited.

Exposure through inhalation of P-slag particles is the main route of possible exposure. However, respiratory absorption will also be very limited. The deposition, clearance and uptake of inorganic particles in the lungs will depend on the particle size, location of deposition, mucus production and macrophage activity. The average percentage of particles with a diameter of < 63 μm in the test substance is 1,3 (m/m) %. So the particles can be inhaled, and a small portion will reach the thoracic region.

Distribution, metabolism and excretion

In a supporting study (Bellman, 1994) the bio durability of wollastonite, a main constituent of P-slag, has been studied. This study revealed that the elimination kinetics of wollastonite fibers from the lung were relatively fast, with half-times of 15 to 21 days. For the thoracic fraction of wollastonite, the elimination from the lung was as fast as for the respirable particulate fraction. This suggests that mechanical clearance mediated by macrophages could be only of minor importance for wollastonite, for which dissolution of fibers must be the important clearance process. This elimination rate must be considered as a rough indication of the elimination of P-slag since this rate may differ substantially between different shapes of wollastonite and wollastonite is only a constituent of P-slag.

There is no further information about the systemic distribution, metabolism, excretion, bioavailability and accumulation of P-slag.

 

Conclusion:

After respiratory exposure, the amount of absorption of P-slag will be limited, and elimination of from the lung is relatively fast. It is expected that P-slag is not absorbed via the oral and dermal route.