Proposed Procedure for Derivation of Regulatory Values for Carcinogenic Airborne Polycyclic Aromatic Hydrocarbons (PAHs) Based on Coal Tar Pitch (CTP) Volatiles
A procedure for estimating upper bound lifetime human cancer risk from air levels of 6 common carcinogenic PAHs, termed "PAHs of concern", is proposed. These PAHs are benzo(a)pyrene, benz(a)anathracene, benzo(k)flouranthene, indeno(1,2,3-c,d)pyrene and chrysene. In application, this proposed procedure would regard any given air level obtained for a "PAH of concern" to originate from a standard mixture of coal tar pitch (CTP). The given air level for the "PAHs of concern" is then related to a corresponding air level of CTP and then to an inhalation unit cancer risk calculated for CTP. Reference values for the procedure are the relative and absolute PAH composition of a CTP standard (SRM-1597) and the inhalation unit cancer risk. Qualitative characterization of the results are a vital part of the procedure especially when more than on "PAH of concern" is being considered. Toxic equivalency factors (TEFs) may be used as an evaluative tool in characterization of the procedure and outcome. Limitations of this proposed procedure include the uneven database for the reference values and the inability to consider air samples inclusive of another common carcinogenic PAHs, dibenz(a,h)anthracene due to its lack of documentation in CTP and high TEF.