The toxicity of oil sands process-affected water (OSPW): A critical review

Large volumes of oil sands process-affected water (OSPW) are produced by the surface-mining oil sands industry in Alberta. Both laboratory and field studies have demonstrated that the exposure to OSPW leads to many physiological changes in a variety of organisms. Adverse effects include compromised immunological function, developmental delays, impaired reproduction, disrupted endocrine system, and higher prevalence of tissue-specific pathological manifestations. The composition of OSPW varies with several factors such as ore sources, mining process, and tailings management practices. Differences in water characteristics have confounded interpretation or comparison of OSPW toxicity across studies. Research on individual fractions extracted from OSPW has helped identify some target pollutants. Naphthenic acids (NAs) are considered as the major toxic components in OSPW, exhibiting toxic effects through multiple modes of action including narcosis and endocrine disruption. Other pollutants, like polycyclic aromatic hydrocarbons (PAHs), metals, and ions may also contribute to the overall OSPW toxicity. Studies have been conducted on OSPW as a whole complex effluent mixture, with consideration of the presence of unidentified components, and the interactions (potential synergistic or antagonistic reactions) among chemicals. This review summarizes the toxicological data derived from in vitro and in vivo exposure studies using different OSPW types, and different taxa of organisms. In general, toxicity of OSPW was found to be dependent on the OSPW type and concentration, duration of exposures (acute versus sub chronic), and organism studied.