PAHs, Cancer Potencies, and Potency Equivalence Factors

Carcinogenicity of PAHs, Cancer Potencies, and Potency Equivalence Factors 

Evaluations of the carcinogenicity of selected PAHs and PACs are summarized in Tables 10.13 and 10.14. Designations are defined in Box 10.7. 

Unless otherwise noted, we use IARC definitions and symbols for the carcinogenicity of a given agent for example, BaP and benzo[fi]fluoranthene (BbF) are 

Class 2A and 2B animal carcinogens and probable and possible human carcinogens, respectively. A note of caution is appropriate, however, regarding differences in the classification schemes. For example, the EPA classifications for BaP and BbF are both B2, sufficient evidence from animal studies.  

To assess both the relative and absolute contributions of various PAHs and PACs to health impacts, the potencies must be combined with concentrations of the individual PAHs and PACs in air. The levels of compounds other than BaP can be quite substantial and hence contribute significantly to the overall carcinogenicity and mutagenicity. For example, Allen and co-workers (1998) reported that, while the individual concentrations of the biologically active 6-ring PAHs identified and quantified in urban Boston air are relatively small (e.g., the concentration of dibenzo[a,e]pyrene was 0.133 ng m-3), their total concentration of 1.5 ng m-3 is comparable to the BaP present as a copollutant in the sample. 

---