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TEST MATERIAL: Slags, Ferromanganese manufacturing (EC Number 273-728-1; CAS Number 69012-28-8; common name: FeMn Slag

 

Physical and chemical description

The test material is an industrial by-product from the manufacture of ferromanganese alloy.

It is a solid grey/green material composed of a mixture of mainly metallic oxides present at varying concentrations. The test material exists in a solid physical state of varying sizes ranging from dust; 10 - < 1 cm (Butler and O’Connor 2009) to rocks (5.5 x 3 x 3 cm) (Anderson 2009). The major and minor crystalline phases of the test material consist of a variety of calcium silicates (LSM 2010). The X-ray diffraction (XRD) phase detection analysis identified several crystalline components including; diopside, aluminian, wollastonite, and gehlenite. Chemical analysis of a typical FeMn slag has shown that it consisted of a mixture of the following oxides; silicon (16-44%), manganese (10-44%), calcium (11-45%), aluminium (0-24%), magnesium (1-12%), barium (< 5%), potassium (< 3%), iron (< 2%) and titanium (<2%) (LSM 2010).

 

Absorption 

The test material, FeMn slag, is of low solubility in water (4.3 x 10-4g/L) (Butler & O’Connor 2009). For the FeMn slag test sample, in order to produce a worst-case scenario potential inhalation risk, the larger particles were removed and only the smaller particles and dust particles were sampled for particle size determination. From the sub-sample, the percentage of test material with a particle size of < 100 µm was determined to be 3.3% by sieve analysis. This indicates that the test material was of a particle size that was essentially non-inhalable.This indicates an extremely low potential for absorption via the respiratory route. Once any of the test material is absorbed, the potential for FeMn slag to become bioavailable is unlikely and the possibility of breakdown into its various components is minimal. This is confirmed in the very low percentage (0.024%) of manganese leaching out of the substance when exposed to artificial lung fluid in a bioaccessability study (Anderson 2009).

 

FeMn slag is not readily available for absorption via the gut due to its low solubility and due to the homeostatic control of manganese in the body. Although the level of Mn release was determined to be 24% following exposure to artificial gastric fluid in a bioaccessibility test (Anderson 2009), the uptake of manganese via the gastric route is very low in humans (<5%). It is not considered that the potential uptake via this route of any released manganese will make a substantial contribution over and above the normal daily nutritional requirement IOM (2002) that is homeostatically-controlled by the liver (IEH, 2004). The level of release determined in the bioaccessibility study may be artificially, and unrealistically high since the test material was ground to a fine powder prior to exposure; this is likely to have altered the physic-chemical nature of the substance, making it more susceptible to dissolution.

As the test material is of very low solubility in water, coupled with its physical inorganic nature, means that it is very unlikely to be absorbed through the skin. As such, the test material has an exceedingly low potential for any absorption by inhalation or dermal absorption. Any potential absorption via the oral route is likely to be extremely low, particularly, as noted above, that the uptake of manganese from the gut in humans is less that 5% (IEH, 2004). Consideration has been given to any inhaled material reaching the gut via the mucociliary escalator but, as described above, the test material is essentially non-inhalable, thus this potential contribution is thought to be negligible.

 

Metabolism, Distribution and Excretion

Since the test material has a low potential for absorption by the inhalation and dermal route, it means that the test material will not be readily bioavailable by these two principle routes of potential human exposure. Most test material that is ingested orally is likely to pass through the gastrointestinal tract unchanged and be excreted in the faeces. Some small amount of manganese from the test material that is absorbed by the gut will enter the essential manganese pool along with that is absorbed from the daily nutritional requirement of manganese and the circulating amount will be controlled by the normal homeostatic mechanism provided by the liver that controls the manganese balance. As noted above, although the test material is essentially non-inhalable, is likely that any inhaled (non-respiratory) particles will be cleared from the lungs by the mucociliary escalator into the gastrointestinal tract.

 

Further information

A comprehensive toxicokinetic assessment has been made on manganese and its inorganic compounds, the full report is attached to this endpoint summary (Bounds 2009).

 

References

Anderson, K. A. (2009). Bioaccessibility of manganese from manganese Materials in Gastric and Lung (Alveolar) Biofluids, Oregon State University.

Bounds, S.V.J (2009). A toxicokinetic assessment for the Registration, Evaluation and Authorisation of Chemicals, Regulation (EC) No. 1907/2006 (REACH), Manganese and it inorganic compounds, Bounds Consulting Ltd.

Butler, R. E. and J. B. O'Connor (2009). FeMn slag (Ferroatlantica): Determination of water solubility and particle size determination, Harlan Laboratories Ltd.

IEH (2004) Occupational Exposure Limits: Criteria Document for Manganese and Inorganic Manganese Compounds (Web Report W17), Leicester, UK, MRC Institute for Environment and Health

IOM (2002) Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc, Washington DC, USA, National Academy Press, available [December 2002] athttp://books. nap.edu/books/0309072794/html/394.html

LSM (2010) Certificate of Analysis for FeMn Slag