Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:7:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 7 (pt 1/5)
Character Range: 2536559–2539501

7                   Hexachlorobenzene (HCB)

7.1              General
Several comprehensive reviews of HCB in the environment and its toxicity to humans are available and should be consulted for more detailed information (ATSDR 2002; WHO 1997). The following provides a summary of the key aspects of HCB that are relevant to the derivation of a soil HIL.

HCB is a fully chlorinated aromatic hydrocarbon. In its pure state HCB is a stable, white crystalline solid, which is insoluble in water but is soluble in fats and organic solvents. HCB has low flammability but when heated, it decomposes and emits toxic fumes. HCB was originally manufactured primarily for use as a pesticide to prevent fungal disease in seeds and grains but its use in the agricultural industry was discontinued in most countries in the mid-1960s to 1970s (WHO 1997; ATSDR 2002). HCB was also used in the manufacturing of fireworks, ammunition and synthetic rubber, and as a fluxing agent in the manufacture of aluminium. Given the concerns regarding HCB's effect on human health and the environment, its intentional uses in commerce are limited (ATSDR 2002).

On the basis of the potential for long-range transport, persistence in air, water, soil and sediment, bioaccumulation, toxicity and ecotoxicity, HCB meets the UN-ECE Persistent Organic Pollutant (POP) criteria (UN-ECE 1998). HCB is listed under Schedule X within the National Strategy for the Management of Scheduled Waste. In addition, HCB has a National Waste Management Plan endorsed by ANZECC in 1996.

7.2              Previous HIL
No previous HIL is available for HCB (NEPC 1999).

7.3              Significance of Exposure Pathways

7.3.1         Oral Bioavailability
Insufficient data is available to adequately define the bioavailability of HCB hence 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.

7.3.2         Dermal absorption
Insufficient data is available on the dermal absorption of HCB from soil. Hence the default value of 0.1 (10%) suggested by US EPA (1995) for pesticides has been adopted in the derivation of HILs.

7.3.3         Inhalation of Dust
HCB is not considered sufficiently volatile to be of significance 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.

7.3.4         Plant Uptake
The few studies that are available with respect to the potential for plant uptake of HCB relate to the application of the product in solution (as a product), or from fresh applications where some volatilisation has occurred (not considered relevant where HCB products are no longer used), rather than uptake from soil. HCB has