Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 2/6)
Character Range: 2097259–2100195

with a conservative assumption of 0.1% considered.
    * Inhalation of beryllium in dust has been considered outdoors and indoors, assuming a dust concentration of 100 µg/m3 and outdoor dust contributes 75% to indoor dust.
    * Soil criteria derived on the basis of inhalation cancer risk values available from US EPA were calculated to be higher than the HIL of 20 mg/kg for infants (adopting a risk level of 10-5).

2.3              Significance of Exposure Pathways
Ingestion of soil and dust is considered the most significant pathway of exposure for inorganics in soil. The consideration of bioavailability and inclusion of other exposure pathways in the derivation of a soil HIL has been further reviewed, as noted below.

    2.3.1         Oral Bioavailability
While oral bioavailability has been considered in the previous HIL, insufficient data is available to adequately define the bioavailability of beryllium in the range of contaminated sites that may need to be considered in Australia. On this basis, a default approach of assuming 100% oral bioavailability has been adopted in the derivation of an HIL. It is noted that a site-specific assessment of bioavailability can be undertaken where required.

    2.3.2         Dermal absorption
In humans and animals sensitised to beryllium, contact with beryllium and its soluble and insoluble compounds can cause dermatitis and skin granulomas. In general, the more soluble the compound the greater the sensitising potential. Dermal effects usually occur on abraded skin. Dermal absorption of beryllium is assumed to be poor and would not likely cause further systemic effects. While it is noted that absorption through damaged/injured skin is expected to be higher, review of dermal absorption of beryllium (Deubner et al. 2001) noted that absorption through intact skin is considered negligible (<<1%). Hence the assumption of 0.1% dermal absorption considered in the previous HIL is considered appropriate. The value is consistent with the default presented by RAIS (2010).

It is noted that US EPA (2004) has recommended the use of a gastrointestinal absorption factor (GAF) of 0.7%, based on consideration of the rat study (with water) used in the derivation of the oral RfD. The GAF is used to modify the oral toxicity reference value to a dermal value in accordance with the US EPA (2004) guidance provided.

    2.3.3         Inhalation of Dust
Beryllium is not volatile and inhalation exposures associated with particulates outdoors and indoors are expected to be of less significance than ingestion of soil. While likely to be negligible, potential inhalation exposures associated with dust have been considered in the HIL derived.

    2.3.4         Plant Uptake
Limited data is available on the potential for the uptake of beryllium into plants, in particular,  edible fruit and vegetable crops. Review by ATSDR (2002) notes that in plants the uptake of beryllium