Polycyclic aromatic hydrocarbons (PAHs), from incomplete combustion of carbon (coal, diesel, auto
exhaust, wood smoke, etc.) are 3 of top 10 chemicals of concern for ATSDR. In rodent models, PAHs
are potent lung carcinogens and there is ample epidemiological evidence also for humans. Lung cancer
is the #1 cause of cancer deaths worldwide (160,000 in U.S. for 2016). Diagnosis occurs in late stages
emphasizing the need for prevention. Benzo[a]pyrene (BaP), the most widely-studied PAH lung
carcinogen, is a class 1 known human carcinogen (IARC). The current EPA IRIS cancer risk slope
factor for BaP (lifetime exposure) is 7 mg/kg/day-1, assuming linearity over orders of magnitude from
rodent tumor studies. Collaborating with Lawrence Livermore National Laboratory we can employ
ULPC-accelerator mass spectrometry (AMS) to conduct human ADME studies at doses below average
daily dietary exposure. Our overarching premise is: for accurate PK analysis and risk assessment
humans are the best model for humans. Conducted under an FDA IND, we will perform 3 novel
studies with BaP providing a unique dataset for regulatory agencies charged with providing the most
accurate risk assessment possible for BaP (PAH) exposure.
1. Determine the impact of dose (50-250 ng) over a range at or below average daily exposure for a
non-smoking U.S. adult. Utilizing ULPC interfaced with AMS determine the impact of dose on metabolic
profiles (bioactivation and detoxication) in plasma and urine. Working with our long-term collaborators
at Pacific Northwest National Laboratory incorporate these data into their PBPK and risk assessment
models.
2. Assess the impact of another PAH, phenanthrene, commonly found in environmental PAH mixtures,
on the ADME of BaP. What components of ADME are impacted? Is the effect additive, inhibitory or
perhaps synergistic? The answer is critical for risk assessment and testing assumptions of the Relative
Potency Factor approach to risk assessment for PAH mixtures currently considered by most regulatory
agencies.
3. Test the chemoprevention potential of cruciferous vegetables/supplement, effective in preclinical
cancer models and human populations, in humans at environmentally relevant exposure levels of
BaP. What is the impact and does it involves alterations in absorption, metabolism and/or excretion?
This study will, for the first time, determine the efficacy, potency and mechanism of a whole food,
compared to a supplement, with respect to chemoprevention in healthy humans exposed to a dietary
chemical carcinogen at a defined environmentally relevant dose.
