What is Risk Characterization?
Risk characterization is the integration of information on how much dose was received (from the Exposure Assessment) with how much risk is associated with different doses (from the Dose Response Assessment) to estimate a probability of harm (that is, risk).
Risk characterizations range from simply plugging a dose into a dose response function to get a single "point estimate" of risk to more sophisticated efforts that consider uncertainty in model input parameters and variability across individuals and subpopulations. These more sophisticated methods are known as probabilistic risk assessment.
Risk assessments are usually conducted in an iterative fashion. One might start with a simple point estimate of the most likely value, then explore some point estimates of high and low risk, before proceeding to a probabilistic risk assessment. The sensitivity of risk estimates to different modeling inputs and assumptions can then be assessed. Those inputs and assumptions that are found to have the most impact on the results are then refined further and the risk assessment repeated. By starting with simple models and then adding complexity only where necessary we seek to balance the required detail of analysis against the available resources for the assessment effort.
Follow this link for a simple example of a point estimate of microbial risk.
Follow this link for an explanation of Uncertainty Propagation in Probabilistic Risk Assessment.