Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 2/7)
Character Range: 2819822–2822698

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.

It is noted that there is the potential for vinyl chloride to undergo biodegradation within the soil profile. Available data (Scheutz 2002) suggests that the degradation of vinyl chloride is complex, involving both anaerobic and aerobic processes. Vinyl chloride is rapidly degraded in the presence of oxygen and is considered one of the least stable chlorinated chemicals in soil gas. NJ DEP (2005) notes that, due to these processes, vinyl chloride is seldom found in soil gas above a contaminated source. Hence, while the potential for vapour migration to be significant has been modelled and considered in the HILs, due to the potential for degradation, this approach is expected to be conservative for vinyl chloride.

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

    5.4.2         Dermal absorption
Insufficient data is available on the dermal absorption of vinyl chloride 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).

    5.4.3         Plant Uptake
No data is available on the potential for vinyl chloride to be taken up by home-grown produce. It is noted that vinyl chloride can be absorbed by produce packaged in PVC plastic. Concentrations reported in these products are not associated with plant uptake from soil. Given the volatility of this compound, the potential for plant uptake is expected 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 vinyl chloride.

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.

    5.4.4         Intakes from Other Sources – Background
As vinyl chloride is highly volatile and not persistent, background intakes will be dominated by inhalation exposures. Concentrations of vinyl chloride in industrial, urban and regional areas are available in Australia. Data collected in NSW (DEC 2003) from urban and regional areas in NSW