This is the ninth of 10 lectures on toxicologic epidemiology. It has been prepared to provide students with a short course on health risk characterization (RC) in practice. Health risk assessment (RA) was demonstrated in earlier lectures to have close linkages with public health, toxicology, and epidemiology. RC is the final, integrative step of this assessment process.

Also discussed at some length in this lecture are the major issues pertaining to the uncertainties inherent in RC. Uncertainties associated with RC are enormous and complex, in that the integrative step is basically a process in which both the information from toxicity assessment (TA) and the information from human exposure assessment (HEA) are used to assess the risk at issue. HEA and TA are the other two key components of RA. Because there are many uncertainties involved in HEA and TA, RC is likewise complex, dynamic, and full of uncertainties. These uncertainties need to be addressed and characterized before the performance of a RC (and of a RA as well) can come to a closure.

The titles of the 10 lectures are: (1) Toxicology and Epidemiology; (2) Public Health and Risk Assessment; (3) Toxicology and Risk Assessment; (4) Epidemiology and Risk Assessment; (5) Toxicologic Side of Epidemiology; (6) Epidemiologic Side of Toxicology; (7) Human Exposure Assessment I; (8) Human Exposure Assessment II; (9) Characterization of Health Risk; and (10) Toxicologic Epidemiology.