Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:9:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 9 (pt 1/7)
Character Range: 2219208–2222172

9                   Manganese

9.1              General
Several comprehensive reviews of manganese in the environment and its toxicity to humans are available and should be consulted for more detailed information (ATSDR 1997 and 2008; WHO 1999 and 2004; Health Canada 2008). The following provides a summary of the key aspects of manganese that are relevant to the derivation of a soil HIL.

Manganese (Mn) is the 12th most abundant element and comprises approximately 0.01% of the Earth's crust. Manganese does not occur naturally in its elemental state and is most commonly found in mineral form as oxides, carbonate and silicates. Elemental manganese is a steel-gray coloured solid at room temperature. Manganese can exist in a relatively wide range of oxidation states from -3 to +7. The most common oxidation state of manganese is Mn (IV), the form associated with manganese dioxide (MnO2) (ATSDR 2008).

Manganese is used to increase stiffness, hardness and strength in a range of alloys including carbon steel, stainless steel, high-temperature steel, cast iron and super-alloys. Manganese is additionally used in the manufacture of dry cell batteries, matches, fireworks, porcelain, brick colourant, glass, animal feed, and plant fertilisers. Strongly oxidising forms of manganese, such as potassium permanganate are used as a disinfectant, an anti-algal agent, a water purifying agent, for metal cleaning, tanning and as bleach (ATSDR 2008).

Manganese is a dietary essential element that is required in several important processes including bone mineralisation, energy metabolism, metabolic regulation, and the formation of glycosaminoglycans (ATSDR 2008). As it is an essential element ,adverse effects can occur as a result of deficiency as well as toxicity associated with excess intake from contamination.

9.2              Previous HIL
The derivation of the previous HIL (HIL A = 1500 mg/kg) for manganese is presented by Lindon & Sabordo (1996). In summary, the HIL was derived on the basis of the following:
    * Intakes of manganese from other sources were estimated with dietary intakes considered most significant for the general population. Intakes presented were based on data from WHO, where dietary intakes for young children were approximately 2.22.5 mg/day. Intakes from water were estimated to be low, less than 2% of total manganese intake.
    * No toxicity threshold was identified for inorganic compounds of manganese and hence the HIL was derived on the basis of an incremental flux of manganese associated with ingestion of soil. The value of 1500 mg/kg was based on an incremental exposure of 10% over an adequate manganese intake received from food and water.

9.3              Significance of Exposure Pathways
Ingestion of soil and dust is considered the most significant pathway of exposure for inorganics in soil. The consideration of bioavailability and inclusion of other exposure pathways in the derivation of a soil HIL