Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 2/13)
Character Range: 2369053–2372349

over the last two decades. The most recent (published final) review of TEF and their basis, presented by CCME (2008), suggests the use of TEF recommended by the World Health Organization (WHO 1998), with minor modifications. This is a scheme based on the order-of-magnitude cancer potency.

Any finer-scale assertions about relative potency for more generic application are hard to justify given the current state of knowledge and confounding influences such as the route of exposure or non-additive effects in complex PAH mixtures. It is not currently possible to develop different relative potency schemes across different exposure routes (oral, dermal, inhalation), owing to a lack of data. Hence the TEFs adopted have been applied for all routes of exposure for the carcinogenic PAHs assessed. Application of the TEFs is relevant to the assessment of PAHs that are considered to be carcinogenic. Other PAHs that are not carcinogenic should be assessed separately on an individual basis.

The following table presents a summary of the TEFs adopted for the assessment of carcinogenic PAHs (CCME 2008):

PAH                     IARC Classification  US EPA Classification  TEF
Benzo(a)anthracene      2B                   B2                     0.1
Benzo(a)pyrene          1                    B2                     1
Benzo(b+j)fluoranthene  2B                   B2                     0.1
Benzo(k)fluoranthene    2B                   B2                     0.1
Benzo(g,h,i)perylene*   3                    D                      0.01
Chrysene                2B                   B2                     0.01
Dibenz(a,h)anthracene   2A                   B2                     1
Indeno(1,2,3-cd)pyrene  2B                   B2                     0.1

Notes: 1/A= Human Carcinogen, 2A/B2= Probable Human Carcinogen, 2B/C=Possible Human Carcinogen, 3/D= Not classifiable.
* Benzo(g,h,i)perylene included due to positive findings in genotoxicity studies (WHO 1998). Note there is insufficient data available to determine carcinogenicity.

The toxic effects of different PAH compounds in a mixture are additive. Experimental evidence suggests that this is a fair assumption (Fitzgerald 1991; Fitzgerald 1998; CCME 2008).

The following relates to the approach used to assess BaP in the derivation of HILs (which can be used for the assessment of BaP alone or for carcinogenic PAHs using the above TEFs).

1.2              Previous HIL
The derivation of the previous HIL (HIL A = 1 mg/kg) for BaP is presented by Fitzgerald (1991) and NEPC (1999). In summary, the HIL was derived on the basis of the following:
    * Intakes associated with daily exposure by children and adults living near or on soil containing 1 mg/kg BaP were assessed on the basis of:
             + Dermal absorption, with 1% BaP absorbed via the skin

             + Ingestion, with 100% bioavailability assumed

             + Inhalation, over 24 hours, with 100% bioavailability assumed.

    * In comparison to background intakes of BaP, intakes from soil at 1 mg/kg are low but higher intakes may be nearing a significant contribution. Adoption of 1 mg/kg was considered appropriate also due to the potential for further review by S EPA where reference values for BaP may change.
Further review of BaP (and PAHs using TEFs)