Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:8:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 8 (pt 1/5)
Character Range: 1679683–1682580

8                   Lead

8.1              Lead compounds considered
The following compounds were considered in deriving the SQGs for lead (Pb):
    * lead metal (CAS No. 7439-92-1)
    * lead oxide (CAS Nos 1317-36-8)
    * lead tetroxide (CAS No. 1314-41-6)
    * dibasic lead phthalate (CAS No: 69011-06-9)
    * basic lead sulphate (CAS No: 12036-76-9)
    * tribasic lead sulphate (CAS No: 12202-17-4)
    * tetrabasic lead sulphate (CAS No: 12065-90-6)
    * neutral lead stearate (CAS No: 1072-35-1)
    * dibasic lead stearate (CAS No: 12578-12-0)
    * dibasic lead phosphite (CAS No: 12141-20-7)
    * polybasic lead fumarate (CAS No: 90268-59-0)
    * basic lead carbonate (CAS No: 1319-46-6)
    * basic lead sulphite (CAS No: 62229-08-7).

8.2              Exposure pathway assessment
If the logarithm of the Kd (log Kd) of an inorganic contaminant is less than 3 then it is considered to have the potential to leach to groundwater (Schedule B5b). The log Kd reported by Commentuijn et al. (2000) for Pb was 3.28 L/kg so there is little potential for Pb to leach to groundwater. If this exposure pathway were considered important at a site, then the methodology for SQG derivation advocates that this be addressed on a site-specific basis as appropriate (Schedule B5b).

The bioconcentration, bioaccumulation and biomagnification of Pb in aquatic ecosystems have received considerable attention. There has also been considerable attention paid to bioconcentration in terrestrial ecosystems but the biomagnification work has been more limited and often restricted to only examining transfer from food to consumer and not subsequent steps up food chains. One hundred and one terrestrial bioaccumulation factor (BAF) values for Pb have been published (LDA 2008) and these range from 0.00 to 6.86 with a median value of 0.1 kgdw/kgww (where dw = dry weight and ww = wet weight). The EU ecological risk assessment for Pb (LDA 2008) followed the EU technical guidance document (EC 1996), which applies assessment factors to the lowest NOEC for oral exposure of birds and mammals to account for the potential of Pb to biomagnify. However, using this method led to the derivation of limits that were below the concentrations found in control foods (that is, food that would occur in soils with background concentrations of Pb). These limits therefore imply that food (animal or plant) grown in soils with background concentrations poses a risk, which is not consistent with real-world experience. They therefore used an SSD method to determine the predicted no-effect concentration (PNEC) for oral exposure of birds and mammals and obtained a soil limit of 491 mg/kg. This value was higher than the limit based on direct exposure of soil organisms of 333 mg/kg.

Thus, it is apparent that Pb does not pose a biomagnification risk to terrestrial ecosystems. This finding is consistent with the