Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:13:p7
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 13 (pt 7/9)
Character Range: 2326124–2328864

the evaluation that there is a wide margin between nutritionally required amounts of zinc and toxic levels. Clinical studies in which up to 600 mg of zinc sulfate (equivalent to 200 mg elemental zinc) has been administered daily in divided doses for a period of several months, provides a basis for the evaluation.
RIVM (2001)         TDI = 0.5 mg/kg/day                                         TDI derived on the basis of a LOAEL (adjusted) of 1 mg/kg/day associated with haematological effects in a 1989 human study (from supplements) and a UF of 2.
ATSDR (2005)        MRL = 0.3 mg/kg/day                                         Chronic oral MRL derived based on a NOAEL of 0.83 mg/kg/day from the same study considered by RIVM (however interpretation of the study differed) and a UF of 3.
US EPA (IRIS 2012)  RfD = 0.3 mg/kg/day                                         RfD (last reviewed in 2005) based on a LOAEL of 0.91 of 0.015 mg/kg/day, identified as the point of departure associated with haematological effects from a number of oral human studies published from 1984 to 2000 (including the study considered by ATSDR and RIVM) and a UF of 3.

It would be relevant and consistent to consider potential exposures to zinc in soil on the same basis as considered by FSANZ (also noted in WHO 2011) where dietary intakes are addressed. However it is noted that the upper limit of zinc intakes identified for children by NHMRC (2006) is lower than that considered in the 20th Australian Total Diet Survey (FSANZ 2003), where an upper limit of 7 mg/day for children aged 13 years, equivalent to 0.5 mg/kg/day (based on a 15.5 kg child) is identified. This is the same as derived by RIVM (2001) and is lower than the upper limit recommended for adults of 40 mg/day, equivalent to 0.57 mg/kg/day (based on 70 kg adult). It is recommended that the lower value for children of 0.5 mg/kg/day recommended by NHMRC (2006) be adopted.

It is noted that for the derivation of a soil HIL, where young children are most sensitive, background intakes of zinc for young children (aged 2 years) of 0.4 mg/kg/day exceeds the threshold value derived by US EPA and ATSDR. Hence it would not be appropriate to adopt these threshold values for the derivation of a soil HIL.

There are no dermal or inhalation specific values available for zinc, so the TDI adopted is considered relevant for all intakes.

    13.4.3     Recommendation
On the basis of the discussion above, the following toxicity reference values (TRVs) have been adopted for zinc in the derivation of HILs:

13.5          Calculated HILs
On the basis of the above the following HILs have been derived for zinc (refer to Appendix B for equations used to calculate the HILs and Appendix C