Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 5/18)
Character Range: 2983850–2986711

as metals. Young children are especially vulnerable to the ingestion of soil contaminants as they may have direct contact with soil and dust during play activities.

5.3.1.1         Incidental soil/dust ingestion rate
Based on a number of overseas tracer studies, enHealth (2012a) recommends default soil (comprising 50% outdoor soil and 50% indoor dust (derived from outdoor soil) as per enHealth (2012b) ingestion rates 100 mg/day for 05 year old children and 50 mg/day for adults. These values have been applied in the derivation of the HILs.

For residential HIL B, the ingestion rates have been taken to be 25% of the total average soil intake to represent ingestion of indoor dust as the main ingestion exposure pathway. This assumes that these residents do not have significant access to on-site communal play areas where ingestion of soil outdoors might be likely. If outdoor recreational/landscaped areas with accessible soil are present, then the more conservative HIL C should be considered for these areas.

Ingestion values for HIL C are calculated assuming that 50% of the total average soil ingestion comes from outdoor soil only.

Ingestion rate for HIL D is calculated assuming that 50% of the total daily soil ingestion occurs while at work on the contaminated site. This allows for a nominal 16-hour waking period during which ingestion occurs (since none occurs while sleeping), 8 hours of which is spent at work.

The HIL assumptions do not include allowance for the small number of children and adults who deliberately eat soil, a behaviour known as 'soil pica'. Soil pica is a behaviour characterised by repeated intentional soil ingestion and people with soil-pica behaviour may ingest large quantities of soil on a regular basis. Pica behaviour is the deliberate ingestion of non-nutritive substances, such as soil, and can occur in some small children as well as some older children and adults more commonly with severe or profound intellectual disabilities. A number of studies are available that address pica behaviours; however, most of these are associated with substances/materials other than soil such as sand, clay, paint, plaster, hair, string, cloth and paper (and some others). Pica (general) behaviour (incidence) appears to be higher in lower socioeconomic groups, in rural areas, pregnant women, individuals with poor nutritional status and in children and adults with mental illness. US EPA (2008) assumes a default soil ingestion rate of 1 g/day for children with soil pica. It is recommended that a site-specific risk assessment should be considered in situations where soil pica behaviour is likely to occur.

5.3.1.2         Ingestion of soil adhering to home-grown produce
The approach applied to estimate the ingestion rate of soil adhering to home-grown produce was derived from the methodology outlined by the UK