In this lecture, students will first learn about the principles and applications of hazard identification and dose-response assessment, which are now consolidated into a single process called toxicity assessment (TA). That is, nowadays human exposure assessment (HEA), TA, and health risk characterization (RC) are the three key components of health risk assessment (RA). As mentioned in the notespage to the first slide, RC is the final, integrative step of RA. Yet in its simplest technical term, RC is a process comparing a human exposure dose estimated in HEA to a level determined in TA as insignificant.

Students will then learn about the dozen or more measures that are used to quantify health risk. They will also be introduced to the numerous ways in which an estimated exposure level can be compared to a level pre-established as safe.

Finally, student will learn that as a quantitative process, RC involves a great deal of uncertainties. The main task of TA is to identify and determine the toxic endpoints of concern and to quantify their significance level. The issues involved in TA are complex and full of uncertainties because direct, quantifiable toxicity data from human studies are almost always unavailable. HEA, which was discussed extensively in the last two lectures, involves principally the estimation of human exposure to environmental contaminants. The issues involved in HEA are likewise enormous and even more overwhelming, given that its overall framework is more vulnerable.