Since the metabolic capabilities of vertebrates are generally higher than those of invertebrates, potential toxicity from activated PAHs in vertebrates is higher than in that for invertebrates. PAH metabolites are commonly found in fish bile within 1 day of exposure. Common oil exposure biomarkers such as cytochrome P450 isozyme activity and formation of DNA adducts are generally induced after 1 week of initial exposure, but toxic manifestations in different species of fish are very different. Therefore, it is difficult to extrapolate toxicological data from one species to another based on these indicators. Numerous studies on pink salmon embryos following the Exxon Valdez oil spill suggest that toxicity was mainly from dissolved PAHs which partitioned from oiled substrates. However, since the salmon eggs were exposed to oiled gravel directly, PAHs were most likely directly absorbed by the eggs, leading to both high mortality and developmental abnormalities. Intergenerational toxicity in pink salmon was also suggested, as some studies reported an increased mortality of embryos exposed to oiled stream substrates years after the spill.
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