Polycyclic aromatic hydrocarbons (PAHs) are a class of chemicals formed during the incomplete combustion of carbon fuels such as coal, wood, and petroleum. They are potentially cancer-causing compounds, and humans are exposed to them through the environment.

The way that people metabolize and break down those chemicals internally can impact how toxic they are. However, little data has been available from human studies. To learn more, David Williams and former SRP investigator Rick Corley, applied the exquisite sensitivity of an accelerator mass spectrometer at Lawrence Livermore National laboratory. This instrument is able to detect and quantify a tiny amount of a PAH and its major metabolites, the compounds PAHs break down into in human subjects. PAH metabolites can be either more or less toxic than the parent compound. That means it’s very important to understand these processes when assessing risk of toxicity and cancer.

This project, approved through the FDA, created the first data set to assess metabolite profiles and associated movement of a carcinogenic PAH in human volunteers at an environmentally relevant dose (5-10x lower than the average daily exposure in a non-smoking adult). It provided the data necessary to translate high-dose experiments with animal models into actionable information of human risk assessment. This human data set has proven to be a valuable addition to risk assessment paradigms.

So now, Dr. Williams is investigating how dietary interventions in human subjects, like adding more cruciferous vegetables (e.g cabbage, broccoli, kale) to their diet, could protect people from these common cancer-causing agents. All of this research will assist regulatory agencies, such as the Environmental Protection Agency, to set safe limits for human exposure. Current exposure limits have to rely on animal data typically employing a million-times the average real world exposure.