Comparative toxicity and bioavailability of heavy fuel oils to fish using different exposure scenarios
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Heavy fuel oils (HFO) are produced from the refining of crude oils, and have high specific gravities and high viscosities. In recent years, spills of HFO have increased in the environment, and are of great concern because they are difficult to clean up. Spilled HFO is likely to become submerged, and can become stranded if fresh HFO coats benthic substrates or if weathered HFO sinks as tarballs. Conversely, lighter oils float on the surface and their components disperse and become diluted in the water column. There is a research need to assess the unique ecological risks of HFO that can sink and contaminate spawning shoals of fish. Chronic toxicity of HFO to fish embryos is correlated with exposure to polycyclic aromatic hydrocarbon (PAH) that become bioavailable from spilled HFO to identify under which spill conditions fish populations are at greatest risk. The results of this research demonstrate that: (1) Stranded HFO is a significant source of PAH to the receiving environment and causes chronic toxicity to embryonic fish; (2) Tarballs and weathered HFO cause less toxicity than fresh HFO, likely a consequence of physical limitations to PAH release; (3) HFO 7102 samples collected from an HFO spill in Wabamun Lake, Alberta, are less toxic than HFO 6303; (4) HFO is at least 2-fold more toxic than Medium South American (MESA), a well-studied reference crude oil, coincident with 3-fold higher concentrations of alkyl PAH, namely alkyl phenanthrenes.