Alkyl-phenanthrenes are a class of compounds present in crude oil and toxic to developing fish. Most research on alkyl-phenanthrenes has focused on retene (7-isopropyl-1-methyl-phenanthrene), but little is known about the chronic toxicity of related congeners to the early life stages of fish. This project is the first to describe the chronic toxicity of a series of alkyl-phenanthrenes to the embryos of Japanese medaka (Oryzias latipes) using the partition-controlled delivery (PCD) method of exposure and is the first to establish a relationship between toxicity of alkyl-phenanthrenes and log P. With PCD, test concentrations were maintained by equilibrium partitioning of test chemicals from polydimethylsiloxane (PDMS) films containing various concentrations of C1 to C4 phenanthrenes. Log film:solution partition constants (log K(fs)) and aqueous solubility limits were determined for each alkyl-phenanthrene. The prevalence of abnormalities in fish embryos increased in an exposure-dependent manner, with median effective concentration (EC50) values lower than experimental solubility limits of the compounds, and typical of environmental concentrations. Alkyl-phenanthrenes were more toxic to medaka embryos than unsubstituted phenanthrene, with effects resembling those of dioxin and indicating a specific receptor-based mechanism of toxicity. These results extend conclusions for the Exxon Valdez oil spill, suggest a specific mechanism of toxicity for alkyl-phenanthrenes, and provide a model for assessing the risks of mixture toxicity.
Pearl dace (Semotilus margarita) and brook stickleback (Culaea inconstans) were collected from tributaries of the Athabasca River (Alberta, Canada), upstream (reference site) and downstream of oil sands deposits where fish were expected to be exposed to naturally occurring oil sands constituents. The objective was to determine if fish collected from these sites exhibited differences in the prevalence or intensity of infection by parasites or in gill histology. Dace did not display significant differences in these parameters. Alternately, upstream stickleback were predominantly infected by complex life history parasites, while downstream fish were primarily infected by parasites with simpler life histories. Moreover, downstream stickleback exhibited significantly more clubbing and aneurysms in secondary gill lamellae relative to upstream fish. This suggested a difference in habitat quality between upstream and downstream sites. However, based on basic body condition parameters of the fish, it would appear that any impacts upon the health of the fish due to the presence of naturally occurring oil sands associated chemical constituents would have been minor.
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