In the environment, it is the unbound fraction of chemical (Cfree) which is able to diffuse across environmental interfaces and biological membranes. It is therefore Cfree which drives many important biological-environmental processes including contaminant transport, bioaccumulation and toxicity. Passive sampling devices (PSDs) offer a simplified and more accurate approach for measuring Cfree compared to traditional methods. The chapters of this dissertation extend the applications of passive sampling for answering questions related to the transport, bioaccumulation, and toxicity of contaminants, specifically polycyclic aromatic hydrocarbons (PAHs). In Chapter 1, using PSDs, we measured the diffusive flux of PAHs between sediment, water, and air at the Portland Harbor Superfund site (PHSS). Data indicated that modern (atmospheric) sources of 2- and 3-ring PAHs were more significant than legacy (sediment) sources. Additionally, the data pointed toward PHSS sediments as potential atmospheric sources of 4-ring and larger PAHs through diffusion. This result may have significant health risk implications for those living near the PHSS and other contaminated sites. Ultimately, data generated by this study was used to make a regulatory decision at the McCormick and Baxter Superfund site, highlighting the growing acceptance and applicability of passive sampling devices. Transport of contaminants may lead to exposure and bioaccumulation in humans and organisms. When organisms are consumed by humans, measuring bioaccumulation of contaminants in those organisms is essential for assessing human health risk. This is especially true for subsistence consumers who have elevated ingestion rates including Native American tribes. Traditional predictive methods for bioaccumulation in benthic organisms are often inaccurate because of reliance on poorly characterized and understood site specific sediment characteristics. Passive sampling devices directly measure Cfree and therefore inherently account for these site specific differences. In Chapter 2, sediment PSDs were used to build a model for predicting PAH concentrations in traditionally harvested clams on Native American tribal land in the Puget Sound region of the Salish Sea. The model was able to predict PAH concentrations in butter clams (Saxidomus giganteus) within a factor of 1.9 ± 0.2. This model will provide a more accurate and simplified method to monitor PAH concentrations in clams without having to remove clams from the environment. Additionally, data from this study highlighted spatial differences in carcinogenic risk associated with the consumption of clams and was used to inform local communities. Bioaccumulation of PAHs may result in health effects if the PAHs are toxic. In the environment PAHs exist as mixtures and it is therefore essential to consider the toxicity of relevant environmental PAH mixtures. There is growing evidence for developmental effects (morphological and neurological) from PAH exposure. In Chapter 4, data from passive sampling devices deployed in surface water at the PHSS was used to construct a surrogate mixture of the 10 most abundant PAHs (Supermix10). Using the zebrafish model, we assessed the developmental toxicity of Supermix10 (SM10), its toxic (Supermix3) and non-toxic (Supermix7) sub-fractions, and the 10 individual PAHs. Data indicated that the general additivity model may be sufficient for explaining the overall developmental effects caused by these PAH mixtures. However, we showed that individual PAH toxic endpoints may not be predictive of the toxic endpoints in PAH mixtures. Finally, SM10 caused behavioral effects in adult fish following exposure during development at concentrations below those which caused overt morphological effects. Ultimately the work in this dissertation advances the application of passive sampling technologies toward a better understanding of PAH transport, bioaccumulation, and toxicity.