Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:9:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 9 (pt 4/7)
Character Range: 2227182–2230295

(2003). These background concentrations comprise (based on average concentrations) approximately 15% of the recommended inhalation TRV. A conservative background of 20% of the inhalation TRV could be assumed for intakes from air.

9.4              Identification of Toxicity Reference Values

    9.4.1         Classification
The International Agency for Research on Cancer (IARC) has not classified manganese. US EPA has classified manganese as Group D—not classifiable.

    9.4.2         Review of Available Values/Information
Insufficient data is available to assess wither manganese is carcinogenic to humans. Some in vitro and in vivo assays are available for manganese, with studies providing conflicting results. Overall review of the data shows that some chemical forms of manganese have mutagenic potential, but most results are inconsistent and hence no overall conclusion as to the genotoxic potential associated with exposure to manganese can be determined (ATSDR 2008). On this basis, a threshold approach is considered appropriate, based on the most sensitive effect associated with manganese exposure (CNS effects).

The following threshold values are available from Level 1 Australian and International sources:
Source                Value                                 Basis/Comments
Australian
ADWG (NHMRC 2011)     Safe level of 10 mg/day               The ADWG (NHMRC 2011) derived a health based guideline of 0.5 mg/L based on a level of 10 mg/day, which is the amount of manganese that can be safely consumed from all sources, referenced from WHO 1973 evaluation.
International
WHO (2011)            TDI = 0.05 mg/kg/day                  The current WHO DWG (2011) has not established a guideline for drinking water, as the compound is not considered to be of health concern at the levels found in drinking water. The review notes that a health-based guideline of 0.4 mg/L can be derived based on the upper range value of manganese intake of 11 mg/day from dietary studies (IOM 2002) and an uncertainty factor of 3 (to allow for the increased bioavailability of manganese from water), which results in a TDI of 0.05 mg/kg/day for a 70 kg adult. The guidance also notes that the presence of manganese in drinking water will be objectionable (water discolouration) above 0.05 mg/L.
WHO (1999)            TC = 0.00015 mg/m3                    Tolerable concentration or guideline value derived by WHO on the basis of the same study considered by the US EPA (IRIS 2012) and ATSDR (2008), with the guideline value derived on the basis of a NOAEL of 0.03 mg/m3 for neurotoxicological effects from a benchmark dose (BMD) analysis, adjustment for continuous exposure (5/7 x 8/24) and an uncertainty factor of 50. The value derived is similar to that from ATSDR (2008) with the main difference being the application of the BMD model.
                                                            No oral guideline value was provided.
Health Canada (2008)  RfC = 0.00005 mg/m3                   RfC derived based on most sensitive benchmark dose analysis associated with neurotoxicological effects in