With an increasing number of sites going to risk assessment, it is important that site investigators understand how a risk assessor will bridge off their data to understand and describe risks. Most regulatory standards assume that the total amount (i.e., 100%) of a contaminant measurable in environmental media is “bioavailable”. Broadly speaking, the term “bioavailability” is used to describe the fraction or percentage of a contaminant that is taken up by an organism that is actually absorbed and in systemic circulation. The extent to which a contaminant can be taken up by an organism is related to the adverse response, or risk.
This talk will discuss how people and critters “see” those concentrations that you measure in various environmental media. For both humans and ecological receptors, the common measures of bioavailability will be reviewed for various environmental media. Some measures that contribute to understanding bioavailability are simple (e.g., measuring pH and alkalinity) whereas others are contaminant- and situation-specific (e.g., physiologically based extraction technique, biotic ligand model). Participants will be encouraged to talk to risk assessors early in the process, so that measures of bioavailability can be selected and made at the appropriate time to streamline the risk management process.