Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 1/7)
Character Range: 2817124–2820061

5                   Vinyl Chloride

5.1              General
Several comprehensive reviews of vinyl chloride in the environment and its toxicity to humans are available and should be consulted for more detailed information not presented in this summary (ATSDR 2006; WHO 1999; IARC 2008). The following provides a summary of the key aspects of vinyl chloride that is relevant to the derivation of interim HILs.

Vinyl chloride is a colourless, flammable gas, with a characteristic slightly sweet odour. It has a high vapour pressure, a high value for Henry's Law constant, a relatively low solubility in water, and is heavier than air. It is also soluble in most organic solvents. Under pressure, vinyl chloride is easily liquefied, and is commonly stored and transported as a liquid and made into polyvinyl chloride (PVC) (ATSDR 2006).

Vinyl chloride is not known to occur naturally. Vinyl chloride is predominantly used in the plastics industry, in the production of polyvinyl chloride (PVC). PVC is used in numerous industries including packaging, building, electrical appliances, medical care, agriculture, automobiles and toys. Vinyl chloride is also used in limited quantities as a refrigerant and an intermediate in the production of chlorinated compounds (WHO 1999).

Vinyl chloride is a degradation product of PCE/TCE/1,2-DCE and 1,1-DCE and its presence in the environment may not be due to a primary source, but rather it may be due to degradation of other chlorinated sources.

5.2              Previous HIL
No previous HIL is available for vinyl chloride (NEPC 1999).

5.3              Proposed Interim HIL
Review of available information in relation to the presence of vinyl chloride in soil indicates that the vapour inhalation pathway is the most significant/important. This pathway should be assessed on the basis of measured vapour data, in particular, soil vapour data. There are significant limitations in the derivation of a soil HIL, in particular, the modelling of phase partitioning from soil to soil vapour and the field measurement of volatiles in soil. Hence, an interim HIL has been derived for soil vapour only.

The following presents the values adopted for the calculation of a soil vapour interim HIL. In addition, other information that is relevant to the assessment of vinyl chloride in soil (relevant to other pathways of exposure) is presented.

5.4              Significance of Exposure Pathways

    5.4.1         Inhalation
Vinyl chloride is a volatile compound and, as such, the derivation of the HIL has considered the vapour inhalation pathway. The approach adopted for the 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.

It is noted