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 2/5)
Character Range: 2769215–2772127

quantification of potential vapour migration to outdoor air and intrusion indoors is outlined in Schedule B7. It is noted that the derived HIL is dominated by the assessment of these pathways of exposure. Due to limitations with the vapour modelling approach adopted, the HILs derived are considered interim.

The inhalation of particulates outdoors and indoors is considered essentially insignificant, compared with vapour inhalation.

    2.4.2         Dermal absorption
Insufficient data is available on the dermal absorption of 1,1,1-TCA from soil. Given the volatility of the compound, dermal absorption is expected to be low though, as there is insufficient data available to further assess dermal absorption from soil, a default value of 0.03 (3%) has been adopted for the volatile organic compounds (US EPA 1995).

    2.4.3         Plant Uptake
No data is available on the potential for 1,1,1-TCA to be taken up by home-grown produce. Given the volatility of this compound, the potential for plant uptake is expected to be similar to that of TCE, which was considered to be limited. As with the assessment presented for TCE, the use of the more commonly adopted equations for quantifying plant uptake (as presented in the text of Schedule B7) that do not address uptake of volatiles (from air) rather than the root or transformations within the plant, are not considered appropriate and relevant for the assessment of 1,1,1-TCA.

It is expected that the potential for plant uptake will be of less significance in the derivation of an HIL, when compared with the assessment of vapour inhalation, and given the limitations involved in providing a meaningful evaluation of plant uptake, it has not been considered in the derivation of HILs.

    2.4.4         Intakes from Other Sources – Background
As 1,1,1-TCA is highly volatile and not persistent, background intakes will be dominated by inhalation exposures. TCA has been reported in sampling undertaken in urban, suburban and industrial areas in NSW (DEC 2003) where the average concentration reported was 0.1 ppbv (0.5 μg/m3) and the maximum reported in Beresfield was 0.3 ppbv (1.6 μg/m3).  Concentrations of 1,1,1-TCA in industrial air in Brisbane (Hawas et al. 2001) were similar (mean of 0.15 ppbv and maximum of 0.4 ppbv). These concentrations are lower than the average urban concentration assumed by ATSDR (2006) of 1 ppbv. Indoor air sources may also be significant; however, there are no estimates of exposure or intake from these sources.

Based on the recommended inhalation TRV for 1,1,1-TCA, these concentrations are essentially negligible.

It is noted that other sources found indoors (from a wide range of common products) are likely to be present and may contribute more significantly to background exposures. These sources need to be addressed on a site-specific basis.

2.5              Identification of Toxicity Reference Values