Synthetic Organic Chemical Presence in the Environment, and Impacts on Wildlife and Human Health

Abstract

Synthetic organic chemicals (SOCs) are ubiquitous in modern environments, yet long-term, multi-media assessments of their presence, transport, and implications for wildlife and human health remain relatively rare. This dissertation addresses this gap by evaluating SOC occurrence and risk across multiple environmental compartments and spatial scales, from national assessments of wild food safety to long-term monitoring of water, sediments, and fish in a major drinking water reservoir. Using a combination of statistical, geospatial, and risk-based approaches, this work examines four major contaminant classes (per- and polyfluoroalkyl substances (PFAS), phthalates, polycyclic aromatic hydrocarbons (PAHs), and pesticides) and their implications for public health. At the national scale, Perfluorooctanesulfonic acid (PFOS) concentrations in wild ungulates (deer and moose) were found to vary widely by tissue type, geography, and contamination source, with elevated concentrations observed in liver and the state of Maine, driven by industrial biosolids application. This study demonstrates that wild foods (often perceived as natural and safe) can represent a meaningful source of contaminant exposure. Estimated hazard quotients indicate that consumptive risk is generally low for ungulate muscle tissue but can be substantial for liver, particularly among subsistence consumers when conservative reference doses are assumed. At the watershed scale, a 26-year dataset from the Occoquan Reservoir shows that SOCs in surface water and sediments occur as dynamic mixtures dominated by phthalates and PAHs. Interannual variability is evident as well as long-term declines in overall contaminant burden. These declines coincide with management actions (e.g., implementation of stormwater best management practices) as well as broader voluntary and regulatory transitions that reduce contaminant inputs. SOCs in fish tissues do not exhibit these same trends. Although overall non-cancer risks from fish consumption are low, high concentration extremes for di(2-ethylhexyl) phthalate occasionally exceed hazard thresholds and other phthalates (e.g., diethyl phthalate) appear to increase over time. In both study domains there is cause for concern even though overall health risks are relatively low. Increasing trends in select phthalates in fish and the presence of high-concentration extremes warrant further attention in the Occoquan. Even relatively low concentrations of PFOS pose a risk to subsistence consumers of deer and moose, particularly for organ meats such as liver, and monitoring contaminants at these levels is difficult, complicating management efforts. These findings underscore the need for a proactive approach to managing contaminant exposure in wild foods. This study also draws attention to a multitude of unknowns that complicate risk assessment. For deer and moose, lack of attention to pristine reference sites in favor of sites with suspected contamination makes it difficult to fully characterize risk. For fish, improved understanding of food web dynamics and microplastics in the context of SOCs is needed to understand why risk might persist despite successful management of water and sediments. Further research in these areas will be essential for ensuring that environmental management translates into meaningful protection of human health across different environmental systems.