Alkylated polycyclic aromatic hydrocarbons in fish and risk to human health: Implications for ecological and human health risk assessements in the Alberta oil sands

The Alberta oil sands are one of the largest sources of naturally occurring bitumen in the world. Aromatics, specifically polycyclic aromatic hydrocarbons (PAHs), constitute the largest proportion of compounds found in bitumen. The risks of PAHs are well understood, they are known to contribute to cancer development in humans and alter early life stage development in fish inhabiting the Athabasca region, within the Alberta oil sands. However, the risks posed by alkyl substituted PAHs (A-PAHs) remain uncertain and are being neglected by decision makers like the Canadian Environmental Assessment Agency (CEAA). A-PAHs are potentially toxic to aquatic organisms, making them a concern in Ecological Risk Assessment (ERA) and are also potentially, mutagenic and carcinogenic, making them a particular concern in Human Health Risk Assessment (HHRA). Elevated loading of PAHs into ecosystems during snowmelt is a particular concern for fish within ecosystems, as snowmelt occurs during fish spawning periods. For these reasons the effects of A-PAHs derived from bitumen on fish health, and human health were targeted for this review paper. Though concrete evidence does not yet exist, information is becoming more available to evaluate the risks of A-PAH toxicity. Observations of retene provide evidence that A-PAHs can be more toxic and can potentially follow alternate metabolic pathways than parent compounds resulting in effects consistent with dioxin like compounds. The suggestion that A-PAHs may follow different metabolic pathways, and consequently, may have different toxic effects than parent compounds will potentially have implications in both HHRA and ERA. Human health effects associated with A-PAHs remain poorly understood.