Food Safety and Environmental Stewardship Program

Regulatory agencies are required to mitigate human and ecological exposure to toxic chemicals of concern. In order to meet this demand, chemical drivers of toxicity and accurate exposure pathways must be identified. Though mixtures are complex systems, it has been postulated that the bioavailable fraction of mixtures is linked to toxicity. Applying additional stressors to chemical mixtures will likely transform the composition of the bioavailable fraction and induce differential toxicological responses. In order to more accurately characterize exposure, regulatory agencies need experimental approaches that can determine the effect of natural/remediation processes on the bioavailable fraction of chemical mixtures and mixture toxicity.

Passive sampling devices (PSDs) readily sequester the bioavailable fraction of environmentally relevant mixtures, which includes polycyclic aromatic hydrocarbons (PAHs). We hypothesized that perturbations of PSD extracts via UV light exposure could reduce concentrations of PAHs and simultaneously increase concentrations of currently unmonitored oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs). PSD samples collected from the Portland Harbor Superfund Megasite and the waters of the Gulf of Mexico following the Deepwater Horizon oil disaster were exposed to UV light (λ = 313 nm) for 30 minutes at an irradiance roughly 30-40 times greater than a single sunny day in Northern US cities. Along with PSD samples, 1 ppm standard mixtures of 16 EPA priority pollutant PAHs were also exposed. PAHs and 22 oxy-PAHs were quantified in pre- and post-UV exposed samples using a recently expanded and validated GC-MS analytical method. It was found that the concentration of nearly half of the monitored PAHs were significantly reduced in standard mixtures following UV exposure, while levels of 9,10-anthraquinone and 7,12-benz[a]anthracenequinone were increased by roughly an order of magnitude relative to controls. Similar results were observed in environmentally relevant PSD samples. Combining PSD technology with other environmental stressors could provide a powerful approach for identifying emerging chemicals of concern, accurate exposure pathways, and chemical drivers of toxicity.