Benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH), is a known human carcinogen. In non-smoking adults greater than 95% of BaP exposure is through diet. The carcinogenicity of BaP is utilized by the U.S. EPA to assess relative potency of complex PAH mixtures. PAH relative potency factors (RPFs, BaP = 1) are determined from high dose animal data. We employed accelerator mass spectrometry (AMS) to determine pharmacokinetics of [<sup>14</sup>C]-BaP in humans following dosing with 46 ng (an order of magnitude lower than human dietary daily exposure and million-fold lower than animal cancer models). To assess the impact of co-administration of food with a complex PAH mixture, humans were dosed with 46 ng of [<sup>14</sup>C]-BaP with or without smoked salmon. Subjects were asked to avoid high BaP-containing diets and a 3-day dietary questionnaire given to assess dietary exposure prior to dosing and three days post-dosing with [<sup>14</sup>C]-BaP. Co-administration of smoked salmon, containing a complex mixture of PAHs with an RPF of 460 ng BaP<sub>eq</sub>, reduced and delayed absorption. Administration of canned commercial salmon, containing very low amounts of PAHs, showed the impacts on pharmacokinetics were not due to high amounts of PAHs but rather a food matrix effect.
