Christine C. Ghetu

Alkylated polycyclic aromatic hydrocarbons (PAHs) are abundant constituents of many PAH mixtures and contribute to risk at contaminated sites. Despite their abundance, the movement of alkylated PAHs remains understudied relative to unsubstituted PAHs. In the present study, passive sampling devices were deployed in the air, water, and sediments at 11 locations across multiple seasons to capture spatial and temporal variability in the abundance and movement of alkylated PAHs at a Brownsfield creosote site in Oregon, USA. Freely dissolved concentrations of 18 alkyl homologous series were quantified by gas chromatography-triple quadrupole mass spectrometry. Alkylated PAHs were consistently more abundant than unsubstituted PAHs in all sampled media (sum PAH and APAH concentrations 43-96% alkyl PAHs). Models of diffusive and advective flux revealed abundant 2 and 3-ring alkyl PAHs exhibited seasonal differences in movement, particularly across the air-water interface. The novel application of these methods to freely dissolved alkylated PAH homologues revealed that, in many instances, alkylated PAHs, particularly C3 and C4 homologues, moved in the opposite direction as unsubstituted PAHs across both the air-water and sediment-water interfaces. These findings reinforce the need to characterize alkylated PAHs and seasonal variability and can inform future sampling at contaminated sites.

The global wildfire risk is predicted to rise due to contributing factors of historical fire management strategies and increases in extreme weather conditions. Thus, there is a need to better understand contaminant movement and human exposure to wildfire smoke. Vapor-phase polycyclic aromatic hydrocarbons (PAHs) are elevated during wildfires, but little is known about how these chemicals move during and after wildfire events for exposure risk assessment. Paired air and soil pore air passive samplers were deployed before, during, and after wildfires to determine diffusive flux of vapor-phase parent (p-PAH) and alkylated (a-PAH) PAHs in the Western United States. Naphthalene and 2-methylnaphthalene contributed to most of the volatilization and deposition (6.3-89%) before and after a wildfire. Retene (41%) and phenanthrene (27%) contributed substantially to deposition during a wildfire. During wildfires, the number of PAHs in deposition increased at sites with worse air quality. Most p-PAHs and a-PAHs were either depositing or near equilibrium after a wildfire, except for retene at several locations. A majority (≥50%) of PAHs had a 50% magnitude difference between flux before and after a wildfire. This study increases the understanding of PAH movement and exposure during each stage of the wildfire cycle.

There is a growing need to establish alternative approaches for mixture safety assessment of polycyclic aromatic hydrocarbons (PAHs). Due to limitations with current component-based approaches, and the lack of established methods for using whole mixtures, a promising alternative is to use sufficiently similar mixtures; although, an established framework is lacking. In this study, several approaches are explored to form sufficiently similar mixtures. Multiple data streams including environmental concentrations and empirically and predicted toxicity data for cancer and non-cancer endpoints were used to prioritize chemical components for mixture formations. Air samplers were analyzed for unsubstituted and alkylated PAHs. A synthetic mixture of identified PAHs was created (Creosote-Fire Mix). Existing toxicity values and chemical concentrations were incorporated to identify hazardous components in the Creosote-Fire Mix. Sufficiently similar mixtures of the Creosote-Fire Mix were formed based on (1) relative abundance; (2) toxicity values; and (3) a combination approach incorporating toxicity and abundance. Hazard characterization of these mixtures was performed using high-throughput screening in primary normal human bronchial epithelium (NHBE) and zebrafish. Differences in chemical composition and potency were observed between mixture formation approaches. The toxicity-based approach (Tox Mix) was the most potent mixture in both models. The combination approach (Weighted-Tox Mix) was determined to be the ideal approach due its ability to prioritize chemicals with high exposure and hazard potential.

Air quality impacts from wildfires are poorly understood, particularly indoors. As frequencies increase, it is important to optimize methodologies to understand and reduce chemical exposures from wildfires. Public health recommendations use air quality estimates from outdoor stationary air monitors, discounting indoor air conditions, and do not consider chemicals in the vapor phase, known to elicit adverse effects. We investigated vapor-phase polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air before, during, and after wildfires using a community-engaged research approach. Paired passive air samplers were deployed at 15 locations across four states. Twelve unique PAHs were detected only in outdoor air during wildfires, highlighting a PAH exposure mixture for future study. Heavy-molecular-weight (HMW) outdoor PAH concentrations and average Air Quality Index (AQI) values were positively correlated (p < 0.001). Indoor PAH concentrations were higher in 77% of samples across all sampling events. Even during wildfires, 58% of sampled locations still had higher indoor PAH air concentrations. When AQI values exceeded 140 (unhealthy for sensitive groups), outdoor PAH concentrations became similar to or higher than indoors. Cancer and noncancer inhalation risk estimates from vapor-phase PAHs were higher indoors than outdoors, regardless of the wildfire impact. Consideration of indoor air quality and vapor-phase PAHs could inform public health recommendations regarding wildfires.

Disaster research faces significant infrastructure challenges: regional and federal coordination, access to resources, and community collaboration. Disasters can lead to chemical exposures that potentially impact human health and cause concern in affected communities. Community-engaged research, which incorporates local knowledge and voices, is well-suited for work with communities that experience impacts of environmental exposures following disasters. We present three examples of community-engaged disaster research (CEnDR) following oil spills, hurricanes, and wildfires, and their impact on long-term social, physical, and technical community infrastructure. We highlight the following CEnDR structures: researcher/community networks; convenient research tools; adaptable data collection modalities for equitable access; and return of data.