Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 1/5)
Character Range: 2766528–2769464

2                   1,1,1-Trichloroethane

2.1              General
Several comprehensive reviews of 1,1,1-trichloroethane (1,1,1-TCA) in the environment and its toxicity to humans are available and should be consulted for more detailed information not presented in this summary (ATSDR 1997; ATSDR 2006; WHO 1990). The following provides a summary of the key aspects of 1,1,1-TCA that is relevant to the derivation of interim HILs.

1,1,1-TCA is a synthetic chemical that does not occur naturally in the environment. It is a colourless, volatile liquid, with a characteristic sharp, sweet odour, and a vapour that is denser than air. It is slightly soluble in water, and is found in a number of solvents in a variety of domestic and industrial uses. 1,1,1-TCA is typically non-flammable under normal conditions however, at higher vapour concentrations (10 %), it can burn when it contacts a spark (ATSDR 1997).

No natural sources of 1,1,1-TCA have been identified. 1,1,1-TCA is a chlorinated hydrocarbon which is manufactured from vinyl chloride by chlorination. 1,1,1-TCA had many industrial and household uses, however its production has been limited to essential industrial use and is to be phased out due to its effects on the ozone layer (ATSDR 1997). It is widely used as a cleaning solvent, and is used to clean electrical equipment, motors, electronic components, printed circuit boards, photographic film and various metal and plastic parts. It is also used as a lubricant in metal-cutting oils and as a component in inks, correction fluid and drain cleaners (NHMRC 2011).

2.2              Previous HIL
No previous HIL is available for 1,1,1-TCA (NEPC 1999).

2.3              Proposed Interim HIL
Review of available information in relation to the presence of 1,1,1-TCA 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 1,1,1-TCA in soil (relevant to other pathways of exposure) is presented.

2.4              Significance of Exposure Pathways

    2.4.1         Inhalation
1,1,1-TCA 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