Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:10:p8
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 10 (pt 8/11)
Character Range: 2255894–2258992

of inorganic mercury compounds likely to be present in soil contamination. EA (2009) has adopted the lower guideline value (TC) available from WHO (2003) assuming its relevance to the assessment of inorganic mercury. This approach has been adopted, though it is noted that the derived HIL is essentially the same if the WHO TC value is adopted, compared with the HIL derived if the TDI for all routes of exposure is used.

10.4.2.2     Methyl Mercury
Long-term exposure to methyl mercury has induced renal tumours in mice, but only at doses at which significant nephropathy was also evident (WHO 2004). Review by the US EPA (IRIS) concluded that methyl mercury is not a potent genotoxic agent and that methyl mercury -nduced tumours in mice were likely to have a non-genotoxic mode of action. On this basis, a threshold approach is considered appropriate based on the most sensitive effect associated with methyl mercury exposure. The following threshold values are available from Level 1 Australian and International sources:

Source              Value                                               Basis/Comments
Australian
ADWG (NHMRC 2011)   TDI = 0.00047 mg/kg/day                             Current ADWG (NHMRC 2011) derived a guideline of 0.001 mg/L on the basis of a PTWI of 0.0033 mg/kg derived from the older JECFA evaluation (see below).
FSANZ (2003)        PTWI = 0.003 mg/kg/week (PTDI = 0.00047 mg/kg/day)  Value for total mercury referenced from older JECFA 1989, based on methyl mercury.
International
WHO (2011b)         Not established for methyl mercury                  The current WHO DWG (2011b) has derived a guideline for inorganic mercury in drinking water only.
JECFA (WHO 2004)    PTWI = 0.0016 mg/kg/week                            The most current evaluation by JECFA (WHO 2004) derived a PTWI of 0.0016 mg/kg based on a steady state intake of 1.5 µg/kg/day (from review of mercury in hair and blood, a benchmark dose approach to assess the relationship between maternal hair concentrations and foetal neurotoxicity and a pharmacokinetic model). This intake is estimated to represent the exposure that would be expected to have no appreciable adverse effects on children and applying an uncertainty factor of 6.4. The PTWI was considered to be sufficient to protect developing foetuses, the most sensitive subpopulation identified.
                    (PTDI = 0.00023 mg/kg/day)                          The previous evaluations by JECFA (WHO 2000a) identified a PTWI of 0.0033 mg/kg methyl mercury based on review of oral intakes of mercury and hair and blood mercury levels. Subsequent reviewed of the PTWI by JECFA in 2000 identified that the value may not be adequately protective of foetuses and infants, who are more sensitive than adults.
EA (2009)           PTWI = 0.0016 mg/kg/week                            Value adopted is referenced from JECFA for all routes of exposure.
                    (PTDI = 00023 mg/kg/day)
RIVM (2001)         TDI = 0.0001 mg/kg/day                              Derived on the basis of a NOAEL of 1.3 µg/kg/day for developmental