Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 5/14)
Character Range: 2696331–2699263

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 for Aroclor 1254 associated with immunological effects in a 23‑month study in monkeys, and an uncertainty factor of 270 (approx. 300). An additional factor of 2 has been applied that relates the TDI derived from Aroclor 1254 to that relevant to PCB mixtures, where the seven indicator PCBs are present in Aroclor 1254 between 40 and 50%. Hence the assessment of mixtures has been undertaking by assuming 50% of the TDI for Aroclor 1254.
                    TC = 0.0005 mg/m3             TC is based on a LOAEC (adjusted) of 0.3 mg/m3 for Aroclor 1254 associated with marginal effects in experimental animals, and an uncertainty factor of 300. The additional 50% factor noted above is also applied to the Aroclor TC.
ATSDR (2000)        Oral MRL = 0.00002 mg/kg/day  Chronic oral MRL based on the same study as considered by RIVM and WHO (2003), with no additional adjustment for PCB mixtures.
                                                  No inhalation MRL has been derived.
US EPA (IRIS 2012)  RfD = 0.00002 mg/kg/day       US EPA RfD (last reviewed in 1994) derived on the same basis as that presented by ATSDR and WHO (2003).
                                                  US EPA also presents a non‑threshold oral slope factor for PCBs which is not considered relevant in this assessment.

All the currently available oral threshold values for PCBs, based on Aroclor 1254, are derived from the same study with the only difference being the application of an additional factor by RIVM (2001) to address PCB mixtures. WHO (2003) considers that the available TDI for Aroclor 1254 is adequate to address PCB mixtures with no further adjustment. Hence the value derived by WHO (2003), also adopted by ATSDR and US EPA, is recommended for use in the derivation of a soil HIL.

Few inhalation‑specific studies are available, with RIVM deriving an inhalation‑specific value based on limited data. No dermal or inhalation‑specific studies or data are available. As the data is limited and does not suggest the toxicity of PCBs is significantly different via inhalation, the oral TDI is recommended for the assessment of all pathways of exposure.

1.4.3         Recommendation
On the basis of the discussion above, the following toxicity reference values (TRVs) have been adopted for PCBs in the derivation of HILs

1.5              Calculated HILs
On the basis of the above, the following HILs have been derived for PCBs (refer to Appendix B for equations used to calculate the HILs and Appendix C for calculations):
HIL Scenario            HIL (mg/kg)                      Percentage Contribution from Exposure Pathways
Ingestion of Soil/Dust  Ingestion of Home‑grown Produce