Ferrosilicon - reaction mass of iron and iron disilicide and iron silicide and silicon

Endpoint summary

Additional information

There are limited ecotoxicological test results available for these alloys but there are ecotoxicological data sets of individual constituents (metals/elements) of FeSi alloys. Depending of the element, these datasetscan be verydata-rich or scarce. Either way these datasets can be applied in this hazard assessment context as a supportive read across information in combination to dissolution test results.

 

In the case of sparingly soluble substances a dissolution protocol has to be followed instead of standard aquatic tests. The evaluation of the short term and long term aquatic toxicity of metals and sparingly soluble metal compounds is to be accomplished by comparison of (a) the concentration of the metal ion in solution, produced during transformation or dissolution in a standard aqueous medium with (b) appropriate standard ecotoxicity data as determined from soluble metal salt data. The method is published as annex X of the UN GHS system. How the results should be treated is given in annex 9 (A9.7) of the GHS.

 

Normally, the dissolved fraction in ecotoxicity tests refers to the fraction that passes through a filter of 0.45 μm. It should be noted, however, that this definition may not necessarily refer to the metals/elements in solution. In the range of 0.01- 0.45 μm colloid inert particles remain suspended. However, in the case of alloys, the saturation concept is a rather complex issue. It is hard to determine a saturation concentration for an alloy, and test guidelines do not sufficiently take into account issues in the preparation of test stock solution of slowly soluble alloy materials.

 

Dissolution test results for Ferrosilicon                                              

 

For sparingly soluble substances such as metals and metalloids, environmental hazard assessments can be performed using data on particle dissolution and metal release by using the OECD T/D (transformation/dissolution) protocol (OECD 2001). The principle of the T/D protocol is to determine the concentration of metal elements that are released from sparingly water soluble substances. These data are then compared with data that are already available for each of the elements to determine if the concentration released is above the concentration expected to cause an effect in the environment. In the following section, a short term T/D test in different artificial media and a screening approach is discussed followed by the results from full 7 and 28 day T/D tests performed according to OECD (2001).

 

The results from the T/D screening tests (Herting 2009) were assessed in Lillicrap et al. (2010) and from these results, FeSi high Ba was chosen for further evaluation with the full T/D tests.The T/D tests were performed as detailed in 4.1.1.1 and the results of the individual elements analysed in the solutions are presented in Tables 8a and 8b (7 and 28 day T/D tests).

 

7 day T/D tests

Comparing the data from the 7 day T/D tests with the limits recommended in the EU Risk Assessment Reports (RAR) as shown in Lillicrap (2010), the data indicated that FeSi High Ba requires no further ecotoxicity validation assessment as the concentration of the impurities are not likely to cause acute toxicity to aquatic organisms.

 

28 day T/D tests

A comparison of the 28 T/D test data with the data on the different elements from the RAR (Lillicrap, 2010) indicates that FeSi High Ba contained elements that were present at concentrations that might be likely to cause toxicity in the aquatic environment:

Cu = EU RAR: Lowest NOEC 6.0 μg/L (Juga plicifera), Pb = EU RAR: Lowest species mean NOEC 6.3 μg/L (Hyalella azteca) and NOEC 0.9 μg/L (Pimephales promelas) Zn = EU RAR: Lowest NOEC 17 μg/L (Algae).

 

Cu was present in the FeSi High Ba 28 T/D test solutions at a concentration of 10.33 μg/L (background control adjusted). The RAR report a NOEC value of 6.0 μg/L (Juga plicifera). The concentration of Cu measured in the solutions with FeSi High Ba exceeded this and effects may therefore be seen in the environment. However, this was only at a pH of 5.5 and not at 8.5. The conclusions of Lillicrap et al. (2010) was that a Daphnia magna chronic reproduction test would be recommended to verify the potential for chronic effects to aquatic organisms.