Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 4/14)
Character Range: 2693500–2696583

with PCBs in air noted to be slowly declining since the early 1980s. Based on these concentrations, intake of PCBs in air away from significant sources is approximately 0.3 ng/kg/day (the lower end of the range reported by WHO). Intakes estimated by RIVM (2001) are dominated by food (particularly where seafood dominates the diet), where the total intake is estimated to be 10 ng/kg/day. More recent review of intakes of PCBs from food by RIVM (2003) suggests that median lifelong intakes are estimated to be 5.6 ng/kg/day, similar to those estimated by Di Marco & Buckett (1993).

If the intakes estimated by WHO (2003) for air (away from significant sources) and water are considered relevant to current background intakes in Australia (where intakes from food are negligible), these comprise approximately 0.5 ng/kg/day, approximately 2.5% of the recommended oral TRV. These intakes are considered negligible.

1.4              Identification of Toxicity Reference Values

1.4.1         Classification
The International Agency for Research on Cancer (IARC 1987) has classified PCBs as Group 2A—probably carcinogenic to humans. This evaluation is based on limited evidence in humans (occupational studies) and sufficient evidence in experimental animals, where some PCBs (particularly those with greater than 50% chlorination) produced liver neoplasms in mice and rats after oral administration.

It is noted that US EPA has classified PCBs as Group B2—probable human carcinogen.

1.4.2         Review of Available Values/Information
PCBs have been associated with carcinogenic effects (in particular, hepatocarcinogenic effects have been seen in animals for PCBs with higher levels of chlorination) but the mode of action is of prime importance for determining the most appropriate doseresponse approach to adopt for establishing an HIL. Review by WHO (2003) notes that the results of in vitro and in vivo genotoxicity studies on PCB mixtures are generally negative and suggest that PCB mixtures do not pose a direct genotoxic threat to humans. Although the mechanistic basis of the hepatocarcinogenicity of PCB mixtures in rodents is not clearly understood, it apparently is not due to genotoxicity. This is consistent with information provided by ATSDR (2000) and RIVM (2001).

On the basis of the available information, it is considered appropriate that a threshold doseresponse approach be adopted for PCBs. The following are available from Level 1 Australian and International sources:
Source              Value                         Basis/Comments
Australian
ADWG                No evaluation available
OCS (2012)          No evaluation available
International
WHO (2003)          TDI = 0.00002 mg/kg/day       Derived on the basis of a LOAEL of 0.005 mg/kg/day for Aroclor 1254 associated with immunological effects in a 23‑month study in monkeys, and an uncertainty factor of 300. WHO considers this TDI relevant to mixtures of PCBs.
WHO (2011)          No evaluation available
RIVM (2001)         TDI = 0.00001 mg/kg/day       TDI based on a LOAEL of 0.005 mg/kg/day