This paper describes the last phase of a project sponsored by the American Petroleum Institute (API). Using risk communication methodologies, this project was designed to produce three dispersant issue papers as unbiased reference sources that present technical information and study results in non-scientific language for the layman. The third issue paper, currently in press, was designed to provide the decision maker and layman with an understanding of how spilled oil and chemically dispersed oil affect resources in the environment. Synopses of key sections of this paper are presented here.

Understanding exposure and effects is a complex task. Exposure to oil alone can cause a variety of adverse effects, including slowed growth, reduced reproduction, and death. Adding dispersants to spilled oil will change the way resources are affected. Today's dispersants are mixtures of solvents and surfactants and, although they can be toxic, are less dangerous than the dispersant products used in the 1960s and 1970s. How the addition of chemical dispersants to spilled oil will change the way resources are impacted has been a difficult question to answer.

Decision makers need to understand several concepts to evaluate how different resources will be affected by oil and chemically dispersed oil during a spill. These include understanding toxicity, what the different routes of exposure are for an organism, how resources from different areas (e.g., water column, water surface, bottom dwelling, or intertidal areas) typically are affected by oil exposure, and how the addition of dispersants changes their exposure to oil. These topics are addressed in this paper.

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