Introduction
More than 30 years ago, scientists began measuring biochemical and molecular responses in organisms as a way to understand pathways of exposure to chemicals in the environment. These responses, termed biomarkers, help screen for the presence or absence of classes of chemicals (e.g., aromatic hydrocarbons, metals) and other stressors (e.g., temperature, oxidative stress). They can also indicate possible mechanisms or pathways of potential toxic outcomes and provide direction for additional, more detailed analysis of the effects of exposures.
Biomarkers have been used extensively in studies of oil spills (Anderson and Lee, 2006). Investigations following the Exxon Valdez spill considered biomarkers for many species, including sea otters (Enhydra lutris), river otters (Lontra canadensis), harlequin ducks (Histrionicus histrionicus), Barrow’s goldeneye (Bucephala islandica), black oystercatchers (Haematopus bachmani), pigeon guillemots (Cepphus columba), intertidal fish, rockfish (Sebastes spp.), bottom fish, pink salmon embryos (Oncorhynchus gorbuscha), and mussels (Mytilus spp.).
No biomarker has received more attention than the Cytochrome P450 1A (CYP1A) enzyme system. Tens of thousands of papers have been published on using the CYP1A system as evidence of exposure to aromatic hydrocarbons found in fossil fuels and industrial chemicals. However, there are conflicting opinions in the literature on using the CYP1A system as a measure of low-level oil exposure when multiple sources of aromatic hydrocarbons are present. There are also conflicting opinions on whether the CYP1A system can be used as an indicator of both exposure and of effect or injury.