Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:13:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 13 (pt 5/9)
Character Range: 2320549–2323725

for infants and children aged 2 months to 19 years range from 5.613 mg/day (from dietary intakes). For a 2-year-old child these intakes range from 0.40.9 mg/kg/day (80% to greater than 100% of the recommended TD). Based on mean intakes from Australian data, background intakes can be assumed to comprise up to 80% of the recommended oral TRV.

13.4          Identification of Toxicity Reference Values

    13.4.1     Classification
The International Agency for Research on Cancer (IARC) has not evaluated zinc with respect to human carcinogenicity.

It is noted that US EPA has evaluated zinc in the more recent 2005 review (available on IRIS). The evaluation notes 'there is inadequate information to assess carcinogenic potential of zinc' because studies of humans occupationally-exposed to zinc are inadequate or inconclusive, adequate animal bioassays of the possible carcinogenicity of zinc are not available, and results of genotoxic tests of zinc have been equivocal.

    13.4.2     Review of Available Values/Information
Insufficient information is available to adequately assess zinc for carcinogenicity. WHO (2001) notes that the weight of evidence supports the conclusion that zinc is not genotoxic or teratogenic. At high concentrations zinc can be cytotoxic. More recent reviews of genotoxicity studies for zinc by EU (2003) and US EPA (2005) are equivocal.  The EU (2003) review concluded that in vitro tests indicated that zinc has a genotoxic potential, while the in vivo studies as presented are inconclusive, with sometimes contradictory results. However, there are indications of some weak clastogenic, and possibly aneugenic effects following zinc exposure. The relevance of these findings needs to be clarified.

On the basis of the available information, the consideration of a threshold approach for the quantification of zinc intakes is considered reasonable. It is noted that since zinc is an essential element, a number of the threshold values available are associated with recommended dietary intakes (RDIs) or adequate intake (AI) and associated upper limits (ULs) based on available studies. It is noted that in reviewing the available information, threshold values such as TDIs or RfDs should lie between the RDI or AI and the UL established for zinc intakes. TDIs or RfDs that are lower than the RDI or AI are considered overly conservative and may lead to deficiency. The following quantitative values are available from Level 1 Australian and International sources:

Source              Value                                                       Basis/Comments
Australian
ADWG (NHMRC 2011)   No health-based guideline established                       The ADWG (NHMRC 2011) has not derived a health-based guideline for zinc, with the current guideline based on aesthetic considerations (taste).
FSANZ (2003)        TDI = 1 mg/kg/day                                           TDI noted to be derived from WHO (refer to comments provided below from JECFA).
NHMRC (2006)        Infants:                                                    The upper limit (UL) applies to total zinc intake from food, water and supplements (including fortified