Studies of Polycyclic Aromatic Hydrocarbons in Dungeness Crabs: Biomonitoring, Physiologically Based Toxicokinetic Model, and Human Health Risk Assessment

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants released into the environment from the incomplete combustion of organic material and petrochemical sources. PAH are persistent molecules that partition into sediments and biota in the aquatic environment. PAH such as benzo[a]pyrene, are of concern because they are metabolised into potentially carcinogenic chemicals that can cause tumours in fish and mammals. The purpose of this research was three-fold, (1) to explore the use of the dungeness crab for monitoring PAH in the aquatic environment, (2) to adapt a physiologically based toxicokinetic (PBTK) model to describe the disposition of benzo[a]pyrene in the dungeness crab, and (3) to examine the lifetime cancer risk to humans associated with the consumption of PAH contaminated crabs. Kitimat Arm is an aquatic ecosystem in British Columbia, contaminated with PAH by industrial processes. Dungeness crabs were collected at several sites within this fjord, and concentrations of PAH were determined in the crabs by GCIMS. A synchronous fluorescence spectroscopy assay was adapted to screen crab haemolymph samples for pyrene and it's metabolites. PAH could be readily determined in the tissues of crabs and tissue concentrations decreased with distance from the source of the PAH contamination. Therefore, crabs were an effective tool for monitoring PAH contamination in the fjord. A PBTK model was adapted to describe the disposition of benzo[a]pyrene in the dungeness crab. The model was composed of seven compartments representing the major tissues of the crab. The flux of benzo[a]pyrene in each compartment was described by algebraic and mass-balance differential equations, coded into Visual Basic and solved numerically by an Excel spreadsheet. The model was implemented with parameters, calibrated, and validated using data obtained empirically. The model successfully predicted benzo[a]pyrene concentrations in the tissue compartments after simulated exposures to benzo[a]pyrene by intravascular, oral and water exposure routes. A human health risk assessment was conducted to evaluate the lifetime cancer risk associated with consumption of PAH contaminated crabs from Kitimat Arm. Deterministic and stochastic risk assessment models were implemented. There was an excess cancer risk associated with consumption of crabs from Hospital Beach, an area near the source of PAH contamination.